Journal articles: 'Anionic transport'

1

Uchino, Hiroshi, Ikumi Tamai, Hikaru Yabuuchi, Kayoko China, Ken-ichi Miyamoto, Eiji Takeda, and Akira Tsuji. "Faropenem Transport across the Renal Epithelial Luminal Membrane via Inorganic Phosphate Transporter Npt1." Antimicrobial Agents and Chemotherapy 44, no. 3 (March 1, 2000): 574–77. http://dx.doi.org/10.1128/aac.44.3.574-577.2000.

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ABSTRACT We previously showed that the mouse inorganic phosphate transporter Npt1 operates in the hepatic sinusoidal membrane transport of anionic drugs such as benzylpenicillin and mevalonic acid. In the present study, the mechanism of renal secretion of penem antibiotics was examined by using a Xenopus oocyte expression system. Faropenem (an oral penem antibiotic) was transported via Npt1 with a Michaelis-Menten constant of 0.77 ± 0.34 mM in a sodium-independent but chloride ion-sensitive manner. When the concentration of chloride ions was increased, the transport activity of faropenem by Npt1 was decreased. Since the concentration gradient of chloride ions is in the lumen-to-intracellular direction, faropenem is expected to be transported from inside proximal tubular cells to the lumen. So, we tested the release of faropenem from Xenopusoocytes. The rate of efflux of faropenem from Npt1-expressing oocytes was about 9.5 times faster than that from control water-injectedXenopus oocytes. Faropenem transport by Npt1 was significantly inhibited by β-lactam antibiotics such as benzylpenicillin, ampicillin, cephalexin, and cefazolin to 24.9, 40.5, 54.4, and 26.2% of that for the control, respectively. Zwitterionic β-lactam antibiotics showed lesser inhibitory effects on faropenem uptake than anionic derivatives, indicating that Npt1 preferentially transports anionic compounds. Other anionic compounds, such as indomethacin and furosemide, and the anion transport inhibitor 4,4′-diisothiocyanostilbene-2,2′-disulfonic acid significantly inhibited faropenem uptake mediated by Npt1. In conclusion, our results suggest that Npt1 participates in the renal secretion of penem antibiotics.

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2

Lo, I. M. C., H. M. Liljestrand, J. Khim, and Y. Shimizu. "Clay liner materials for land disposal of hazardous non-metal wastes." Water Science and Technology 33, no. 8 (April 1, 1996): 71–77. http://dx.doi.org/10.2166/wst.1996.0154.

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Simple land disposal systems for hazardous and mixed wastes contain heavy metal cationic species through precipitation and ion exchange mechanisms but typically fail by releasing soluble organic and inorganic anionic species. To enhance the removal of anions from leachate, clays are modified with coatings of iron or aluminium cations to bridge between the anionic surface and the anionic pollutants. A competitive surface ligand exchange model indicates that surface coatings of 10 meq cation/gm montmorillonite under typical leachate conditions increase the inorganic anion sorption capacity by at least a factor of 6 and increase the intrinsic surface exchange constants by more than a factor of 100. Similarly, metal hydroxide coatings on montmorillonite increase the organic anion sorption capacity by a factor of 9 and increase the intrinsic surface exchange constants by a factor of 20. For historical concentrations of non-metal anions in US hazardous and mixed waste leachate, sorption onto natural clay liner materials is dominated by arsenate sorption. With cation coatings, anion exchange provides an effective removal for arsenate, selenate, phenols, cresols, and phthalates. Engineering applications are presented for the use of modified clays as in situ barriers to leachate transport of anionic pollutants as well as for above ground treatment of recovered leachate.

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3

Garlid, K. D., M. Jaburek, and P. Jezek. "Mechanism of uncoupling protein action." Biochemical Society Transactions 29, no. 6 (November 1, 2001): 803–6. http://dx.doi.org/10.1042/bst0290803.

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Two competing models of uncoupling protein (UCP) transport mechanism agree that fatty acids (FAs) are obligatory for uncoupling, but they disagree about which ion is transported. In Klingenberg's model, UCPs conduct protons. In Garlid's model, UCPs conduct anions, like all members of this gene family. In the latter model, UCP transports the anionic FA head group from one side of the membrane to the other, and the cycle is completed by rapid flip-flop of protonated FAs across the bilayer. The head groups of the FA analogues, long-chain alkylsulphonates, are translocated by UCP, but they cannot induce uncoupling, because these strong acids cannot be protonated for the flip-flop part of the cycle. We have overcome this limitation by ion-pair transport of undecanesulphonate with propranolol, which causes the sulphonate to deliver protons across the membrane as if it were an FA. Full GDP-sensitive uncoupling is seen in the presence of propranolol and undecanesulphonate. This result confirms that the mechanism of UCP uncoupling requires transport of the anionic FA head group by UCP and that the proton transport occurs via the bilayer and not via UCP.

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4

Salhany, James M. "Anion binding characteristics of the band 3 / 4,4'-dibenzamidostilbene-2,2'-disulfonate binary complex: Evidence for both steric and allosteric interactions." Biochemistry and Cell Biology 77, no. 6 (December 1, 1999): 543–49. http://dx.doi.org/10.1139/o99-061.

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A novel kinetic approach was used to measure monovalent anion binding to better define the mechanistic basis for competition between stilbenedisulfonates and transportable anions on band 3. An anion-induced acceleration in the release of 4,4prime-dibenzamidostilbene-2,2prime-disulfonate (DBDS) from its complex with band 3 was measured using monovalent anions of various size and relative affinity for the transport site. The K1/2 values for anion binding were determined and correlated with transport site affinity constants obtained from the literature and the dehydrated radius of each anion. The results show that anions with ionic radii of 120-200 pm fall on a well-defined correlation line where the ranking of the K1/2 values matched the ranking of the transport site affinity constants (thiocyanate < nitrate equivalent to bromide < chloride < fluoride). The K1/2 values for the anions on this line were about 4-fold larger than expected for anion binding to inhibitor-free band 3. Such a lowered affinity can be explained in terms of allosteric site-site interactions, since the K1/2 values decreased with increasing anionic size. In contrast, iodide, with an ionic radius of about 212 pm, had a 10-fold lower affinity than predicted by the correlation line established by the smaller monovalent anions. These results indicate that smaller monovalent anions have unobstructed access to the transport site within the band 3 / DBDS binary complex, while iodide experiences significant steric hindrance when binding. The observation of steric hindrance in iodide binding to the band 3 / DBDS binary complex, but not in the binding of smaller monovalent anions, suggests that the stilbenedisulfonate binding site is located at the outer surface of an access channel leading to the transport site.Key words: band 3, anion transport, membrane protein structure, red cell membrane.

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5

El-Sheikh, Azza A. K., Rosalinde Masereeuw, and Frans G. M. Russel. "Mechanisms of renal anionic drug transport." European Journal of Pharmacology 585, no. 2-3 (May 2008): 245–55. http://dx.doi.org/10.1016/j.ejphar.2008.02.085.

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6

Matos, C. T., S. Velizarov, J. G. Crespo, and M. A. M. Reis. "Removal of bromate, perchlorate and nitrate from drinking water in an ion exchange membrane bioreactor." Water Supply 5, no. 5 (December 1, 2005): 9–14. http://dx.doi.org/10.2166/ws.2005.0033.

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The presence of anionic micropollutants, such as bromate, perchlorate and nitrate, in drinking water supplies represents a risk for public health. This work evaluates the applicability of the ion exchange membrane bioreactor (IEMB) concept for their removal. The IEMB concept combines the transport of anionic pollutants, through a dense mono-anion permselective membrane, with their simultaneous biodegradation to harmless products by a suitable microbial culture in a separated biocompartment. The transport of the pollutant counter-ions (anions) is governed by the Donnan equilibrium principle and, therefore, it is possible to enhance it by using a more concentrated driving counter-ion (e.g. chloride) added to the biocompartment. The IEMB process proved to selectively remove nitrate and perchlorate to concentrations below the recommended levels of 4 ppb for ClO4− and 25 ppm of NO3−, from a model polluted stream containing 100 ppb of ClO4− and 60 ppm of NO3−. Transport studies, made under Donnan dialysis conditions, showed bromate fluxes comparable to those obtained for nitrate under similar experimental conditions. However, the rate of biological reduction of bromate was about one order of magnitude slower than that of nitrate.

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7

Muller, M., and P. L. Jansen. "Molecular aspects of hepatobiliary transport." American Journal of Physiology-Gastrointestinal and Liver Physiology 272, no. 6 (June 1, 1997): G1285—G1303. http://dx.doi.org/10.1152/ajpgi.1997.272.6.g1285.

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Generation of bile flow is a regulated, ATP-dependent process and depends on the coordinated action of a number of transporter proteins in the sinusoidal and canalicular domains of the hepatocyte. Dysfunction of any of these proteins leads to retention of substrates, with conjugated hyperbilirubinemia or cholestasis as a result. In recent years many of the transport proteins involved in bile formation have been identified, cloned, and functionally characterized. The hepatocyte sinusoidal membrane contains transport proteins for the hepatic uptake of organic anions and cations and for the uptake of bile acids. The multispecific organic anion transporting polypeptide (OATP) mediates the hepatic uptake of organic anions and a variety of organic amphiphilic compounds, including organic cations. The organic cation transporter OCT1 more specifically transports small organic cations. NTCP is the Na(+)-bile acid cotransporting protein that mediates the hepatic uptake of bile acids. The canalicular transport proteins are able to transport endogenous and exogenous metabolites into the bile against steep concentration gradients. Most of these transporters are members of the large ATP-binding cassette (ABC) superfamily, and their transport function directly depends on the hydrolysis of Mg2+/ATP. At least five ABC transporter proteins have been characterized so far: 1) the human multidrug resistance protein MDR1 mediates the excretion of hydrophobic, mostly cationic, metabolites; 2) MDR3 is involved in phosphatidylcholine secretion; 3) the canalicular bile acid transporter cBAT mediates secretion of monovalent bile salts and provides the molecular basis of bile acid-dependent bile flow; 4) SPGP, product of the P-glycoprotein sister gene, is exclusively expressed in the liver but its function is currently unknown; and 5) the human multidrug resistance protein MRP2 mediates the excretion of multivalent anionic conjugates.

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8

Hosseinioun, Ava, Pinchas Nürnberg, Monika Schönhoff, Diddo Diddens, and Elie Paillard. "Improved lithium ion dynamics in crosslinked PMMA gel polymer electrolyte." RSC Advances 9, no. 47 (2019): 27574–82. http://dx.doi.org/10.1039/c9ra05917b.

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Ionic transport was investigated in a PMMA gel electrolyte by electrochemical, Raman, PFG-NMR, e-NMR spectroscopies and ab initio calculations. The presence of the PMMA matrix reduces anionic mobility and decorrelates cationic and anionic transport.

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9

Russel, Frans G. M., Rosalinde Masereeuw, and Rémon A. M. H. van Aubel. "Molecular Aspects of Renal Anionic Drug Transport." Annual Review of Physiology 64, no. 1 (March 2002): 563–94. http://dx.doi.org/10.1146/annurev.physiol.64.081501.155913.

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10

Allred, Barry, and Glenn O. Brown. "ANIONIC SURFACTANT TRANSPORT CHARACTERISTICS IN UNSATURATED SOIL." Soil Science 161, no. 7 (July 1996): 415–25. http://dx.doi.org/10.1097/00010694-199607000-00001.

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11

Zelikovic, I., E. Stejskal-Lorenz, P. Lohstroh, A. Budreau, and R. W. Chesney. "Anion dependence of taurine transport by rat renal brush-border membrane vesicles." American Journal of Physiology-Renal Physiology 256, no. 4 (April 1, 1989): F646—F655. http://dx.doi.org/10.1152/ajprenal.1989.256.4.f646.

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The anionic requirements and the stoichiometric relationships of Na+-taurine cotransport into rat renal brush-border membrane vesicles (BBMV) were evaluated. External Cl- (100 mM) or Br- (100 mM) gradients supported the full overshoot of Na+-taurine symport and yielded similar high-affinity transport systems for taurine uptake. No active uptake of taurine was evident in the presence of external (100 mM) NaF, NaI, Na gluconate, or Na p-aminohippurate (PAH). Na+:taurine stoichiometry was 2.18:1 in the presence of Cl- and 1.60:1 in the presence of Br-. When the external anion gluconate was employed, Na+-dependent taurine uptake was negligible over the whole range of Na+ concentrations examined. Cl-:taurine and Br-:taurine stoichiometries in the presence of external Na+ were 0.97:1 and 0.81:1, respectively. External furosemide (1 mM) or bumetanide (1 mM) did not change taurine accumulation and kinetic parameters. The anionic transport inhibitors 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (5 x 10(-4) M), N-(4-azido-2-nitrophenyl)-2-aminoethylsulfonate (10(-3) M) and p-chloromercuribenzoate (5 x 10(-4) M) significantly decreased initial rate of taurine uptake by 48, 31, and 31%, respectively. These data suggest that Na+-taurine cotransport into rat renal BBMV is Cl- or Br- dependent and probably operates by means of 2 Na+:1 Cl- or Br-:1 taurine carrier complex. Na+-taurine symport across the rat renal brush-border membrane surface is not affected by diuretics that influence NaCl cotransport but is affected by selected anionic transport inhibitors. An intact anionic binding site may be needed for this translocation process.

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12

Heijn, M., R. P. Oude Elferink, and P. L. Jansen. "ATP-dependent multispecific organic anion transport system in rat erythrocyte membrane vesicles." American Journal of Physiology-Cell Physiology 262, no. 1 (January 1, 1992): C104—C110. http://dx.doi.org/10.1152/ajpcell.1992.262.1.c104.

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The uptake of oxidized glutathione (GSSG) into inside-out membrane vesicles of Wistar rat erythrocytes was studied. Uptake was ATP dependent, into an osmotically active space, and saturable. Analysis of saturable ATP-dependent GSSG uptake showed two affinities for GSSG [concentration for half-maximal velocity (K1/2 1), 26 microM; K 1/2 2, 4 mM; maximum transport rate (Vmax 1), 100 pmol.mg-1.min-1; Vmax 2, 360 pmol.mg-1.min-1]. Interactions of the high-affinity system with different organic compounds were studied. Leukotriene C4, bromosulfophthalein-S-glutathione, and 2,4-dinitrophenyl-S-glutathione were effective inhibitors. In addition, anionic nonglutathione conjugates, like indocyanine green, rose bengal, dibromosulfophthalein, and sulfated or glucuronidated (divalent) bile acids inhibited GSSG transport. Monovalent bile acids had no influence on GSSG transport. Inhibition by 2,4-dinitrophenyl-S-glutathione [inhibition constant (Ki) = 2.6 microM] and sulfated glycolithocholic acid (Ki = 2.9 microM) was purely competitive. The use of adenosinetriphosphatase (ATPase) inhibitors suggested a resemblance with E1E2-type ATPase. Vesicles of erythrocytes isolated from the TR- rat, a mutant rat strain with a defective biliary secretion of organic anions, have an impaired uptake of GSSG (Vmax was decreased 2-fold). In conclusion, erythrocytes have an ATP-dependent organic anion transport system that can be inhibited by a broad range of organic anions. This system is very similar if not identical to the hepatocanalicular ATP-dependent organic anion transporter.

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13

Zaki, Laila. "Inhibition of anion transport in the red blood cell membrane by anionic and non-anionic arginine-specific reagents." Journal of Biosciences 15, no. 3 (September 1990): 179–85. http://dx.doi.org/10.1007/bf02703882.

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14

Janarthanan, Rajeswari, James L. Horan, Benjamin R. Caire, Zachary C. Ziegler, Yuan Yang, Xiaobing Zuo, Matthew W. Liberatore, Michael R. Hibbs, and Andrew M. Herring. "Understanding anion transport in an aminated trimethyl polyphenylene with high anionic conductivity." Journal of Polymer Science Part B: Polymer Physics 51, no. 24 (September 14, 2012): 1743–50. http://dx.doi.org/10.1002/polb.23164.

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15

Sen, Arindam, Ya-Li Zhao, and Sek Wen Hui. "Saturated Anionic Phospholipids Enhance Transdermal Transport by Electroporation." Biophysical Journal 83, no. 4 (October 2002): 2064–73. http://dx.doi.org/10.1016/s0006-3495(02)73967-2.

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Sen, Arindam, Yali Zhao, Lei Zhang, and Sek Wen Hui. "Enhanced transdermal transport by electroporation using anionic lipids." Journal of Controlled Release 82, no. 2-3 (August 2002): 399–405. http://dx.doi.org/10.1016/s0168-3659(02)00164-5.

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17

Brown, Warren, Maksim Kvetny, Juan Liu, and Gangli Wang. "Cationic and Anionic Transport through Single Quartz Nanopipettes." ECS Transactions 33, no. 19 (December 17, 2019): 1–8. http://dx.doi.org/10.1149/1.3552605.

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18

Novak, Donald, Forrest Quiggle, Carlos Artime, and Mark Beveridge. "Regulation of glutamate transport and transport proteins in a placental cell line." American Journal of Physiology-Cell Physiology 281, no. 3 (September 1, 2001): C1014—C1022. http://dx.doi.org/10.1152/ajpcell.2001.281.3.c1014.

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We utilized HRP.1 cells derived from midgestation rat placental labyrinth to determine that the primary pathway for glutamate uptake is via system X[Formula: see text], a Na+-dependent transport system. Kinetic parameters of system X[Formula: see text]activity were similar to those previously determined in rat and human placental membrane vesicle preparations. Amino acid depletion caused a significant upregulation of system X[Formula: see text] activity at 6, 24, and 48 h. This increase was reversed by the addition of glutamate and aspartate but not by the addition of α-(methylamino)isobutyric acid. Immunoblot analysis of the three transport proteins previously associated with system X[Formula: see text] activity indicated a trend toward an increase in GLT1, EAAC1, and GLAST1 immunoreactive protein contents by 48 h; cell surface expression of the same was enhanced by 24 h. Inhibition analysis suggested key roles for EAAC1 and GLAST1 in basal anionic amino acid transfer, with an enhanced role for GLT1 under conditions of amino acid depletion. In summary, amino acid availability as well as intracellular metabolism regulate anionic amino acid uptake into this placental cell line.

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19

Ghosh, P. S., A. Arya, G. K. Dey, N. Kuganathan, and R. W. Grimes. "A computational study on the superionic behaviour of ThO2." Physical Chemistry Chemical Physics 18, no. 46 (2016): 31494–504. http://dx.doi.org/10.1039/c6cp05794b.

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This study reports DFT and MD study of lattice dynamical, mechanical and anionic transport behaviour of ThO2 in the superionic state. Softening of B1u phonon mode is a precursor to the dynamical disorder of the oxygen sublattice and 〈001〉 is the easy direction for anion migration in the superionic state.

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20

Van Aubel, Rémon A. M. H., Rosalinde Masereeuw, and Frans G. M. Russel. "Molecular pharmacology of renal organic anion transporters." American Journal of Physiology-Renal Physiology 279, no. 2 (August 1, 2000): F216—F232. http://dx.doi.org/10.1152/ajprenal.2000.279.2.f216.

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Renal organic anion transport systems play an important role in the elimination of drugs, toxic compounds, and their metabolites, many of which are potentially harmful to the body. The renal proximal tubule is the primary site of carrier-mediated transport from blood to urine of a wide variety of anionic substrates. Recent studies have shown that organic anion secretion in renal proximal tubule is mediated by distinct sodium-dependent and sodium-independent transport systems. Knowledge of the molecular identity of these transporters and their substrate specificity has increased considerably in the past few years by cloning of various carrier proteins. However, a number of fundamental questions still have to be answered to elucidate the participation of the cloned transporters in the overall tubular secretion of anionic xenobiotics. This review summarizes the latest knowledge on molecular and pharmacological properties of renal organic anion transporters and homologs, with special reference to their nephron and plasma membrane localization, transport characteristics, and substrate and inhibitor specificity. A number of the recently cloned transporters, such as the p-aminohippurate/dicarboxylate exchanger OAT1, the anion/sulfate exchanger SAT1, the peptide transporters PEPT1 and PEPT2, and the nucleoside transporters CNT1 and CNT2, are key proteins in organic anion handling that possess the same characteristics as has been predicted from previous physiological studies. The role of other cloned transporters, such as MRP1, MRP2, OATP1, OAT-K1, and OAT-K2, is still poorly characterized, whereas the only information that is available on the homologs OAT2, OAT3, OATP3, and MRP3–6 is that they are expressed in the kidney, but their localization, not to mention their function, remains to be elucidated.

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21

VIEIRA, Lita L., Esther LAFUENTE, Francisco GAMARRO, and Z. Ioav CABANTCHIK. "An amino acid channel activated by hypotonically induced swelling of Leishmania major promastigotes." Biochemical Journal 319, no. 3 (November 1, 1996): 691–97. http://dx.doi.org/10.1042/bj3190691.

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Leishmania promastigotes accumulate amino acids (AAs) by an uphill transport mechanism that is dependent on membrane potential. The accumulated AAs provide the cell with an osmotic reservoir that can be utilized for osmoregulation. Exposure of Leishmania promastigotes to hypotonic media induced a rapid release of AAs that was proportional to the imposed osmotic gradients and independent of the ionic strength or the presence of Cl-, K+, Na+ or Ca2+ in the medium. The hypotonically activated AA release pathway was of relatively low chemical specificity. The solutes released included most of the zwitterionic and anionic AAs, predominantly alanine, hydroxyproline, glycine and glutamic acid, whereas cationic AAs were virtually excluded. AA release was markedly blocked by classical anion transport inhibitors such as the disulphonic stilbene 4,4´-di-isothiocyanostilbene-2,2´-disulphonate (DIDS) and its dihydro derivative H2DIDS and others, by restoration of isotonicity or by lowering the temperature (4 °C). The temperature profile of AA release showed a low energy of activation (Ea 46±1.3 (S.E.M.) kJ/mol) in the range 15-30 °C and a very high Ea (147±8 kJ/mol) in the range 4–15 °C. Parasites exposed to hypotonic media containing AAs also showed a hypotonically stimulated AA uptake under favourable solute concentration gradients. This uptake was analogous for L- and D-isomers of threonine. After hypotonic exposure, cells underwent a depolarization that was largely prevented by anion transport blockers. On the basis of all these results we propose that after hypotonic stress Leishmania promastigotes restore their internal volume by a regulated release of AAs, which involves activation of channels that allow the passage of both neutral and anionic AAs and possibly other anionic substances.

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22

Schnabolk, Gloriane W., Geri L. Youngblood, and Douglas H. Sweet. "Transport of estrone sulfate by the novel organic anion transporter Oat6 (Slc22a20)." American Journal of Physiology-Renal Physiology 291, no. 2 (August 2006): F314—F321. http://dx.doi.org/10.1152/ajprenal.00497.2005.

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Recently, a novel Slc22 gene family member expressed in murine olfactory mucosa was identified and based on sequence homology proposed to be an organic anion transporter [Oat6 ( Slc22a20); J. C. Monte, M. A. Nagle, S. A. Eraly, and S. K. Nigam. Biochem Biophys Res Commun 323: 429–436, 2004]. However, no functional data for Oat6 was reported. In the present study, we demonstrate that murine Oat6 mediates the inhibitable transport of estrone sulfate using both Xenopus oocyte expression assay and Chinese hamster ovary (CHO) cells stably transfected with mOat6 (CHO-mOat6). Uptake was virtually eliminated by probenecid and the anionic herbicide 2,4-dichlorophenoxyacetate. The organic anions ochratoxin A, salicylate, penicillin G, p-aminohippurate, and urate inhibited mOat6-mediated accumulation to varying degrees. Transport of estrone sulfate by mOat6 was demonstrated to be saturable, and Kmestimates of 109.8 ± 22.6 μM in oocytes and 44.8 ± 7.3 μM in CHO-mOat6 cells were obtained. Inhibitory constants for 2,4-dichlorophenoxyacetate (15.7 ± 2.0 μM), salicylate (49.0 ± 4.4 μM), probenecid (8.3 ± 2.5 μM), and penicillin G (1,450 ± 480 μM) were also determined. Accumulation of estrone sulfate mediated by mOat6 was significantly trans-stimulated by glutarate, indicating that mOat6 functions as an organic anion/dicarboxylate exchanger. These data demonstrate for the first time that the novel murine gene Oat6 ( Slc22a20) encodes a functional organic anion transporter and mOat6 is indeed the newest member of the OAT gene family.

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Romanova, O. B., Sergei S. Aplesnin, A. M. Vorotynov, G. I. Makovetskii, O. F. Demidenko, and K. I. Yanushkevich. "Peculiarities of Transport, Resonance and Optical Properties of the Anion-Substituted Manganese Chalcogenides." Solid State Phenomena 233-234 (July 2015): 447–50. http://dx.doi.org/10.4028/www.scientific.net/ssp.233-234.447.

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The transport, resonance and optical properties of anion-substituted manganese chalcogenides MnSe1-xTex in the 77-300 K temperature range in magnetic fields up to 1T are studied. The magnetoresistance effect with the maximum value in the vicinity of the Neel temperature for the composition x = 0.1 is revealed. EPR data indirectly indicate the type of the current carriers – lattice polarons. The changes in electron structure occurring due to the anionic substitution are studied using the optical methods.

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Uvarov, N. F., A. A. Iskakova, A. S. Ulihin, N. N. Medvedev, and A. V. Anikeenko. "Ion transport in salts orientationally disordered in anionic sublattice." Solid State Ionics 188, no. 1 (April 2011): 78–82. http://dx.doi.org/10.1016/j.ssi.2010.10.014.

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25

Chao, A. C., and W. M. Armstrong. "Cl(-)-selective microelectrodes: sensitivity to anionic Cl- transport inhibitors." American Journal of Physiology-Cell Physiology 253, no. 2 (August 1, 1987): C343—C347. http://dx.doi.org/10.1152/ajpcell.1987.253.2.c343.

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Cl(-)-selective microelectrodes, containing Corning code 477315 or 477913 liquid ion exchangers, are often used to measure extra- and intracellular Cl- activities in the presence of Cl- transport inhibitors such as furosemide, bumetanide, and the stilbene sulfonic acid derivative 4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS). Because these inhibitors are anions in the physiological pH range and have relatively high lipid solubilities, they would be expected to interfere with the response to Cl- of these microelectrodes. Preliminary reports have confirmed this expectation. We examined the effect of furosemide, bumetanide, and SITS on the Cl(-)-selective barrels of double-barreled microelectrodes containing Corning code 477315 liquid anion exchanger and suitable for impaling small cells (e.g., epithelial cells). The results showed that at pH 8.2 in pure solutions of furosemide and bumetanide, these microelectrodes gave linear responses to the logarithm of furosemide or bumetanide concentrations ranging from 1 X 10(-2) to 1 X 10(-4) M. In the physiological pH range both these inhibitors (in concentrations of 0.1 mM) interfered significantly with the response of the microelectrodes to Cl- (in concentrations ranging from 100 to 1 mM). Calculated electrode sensitivities, relative to Cl-, were approximately 150 for both these compounds. Microelectrodes of this type appeared to be approximately 1,000 times as sensitive toward SITS as they were toward Cl-.

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26

Bartosz, G., H. Sies, and T. P. M. Akerboom. "Organic anions exhibit distinct inhibition patterns on the low-Km and high-Km transport of S-(2,4-dinitrophenyl)glutathione through the human erythrocyte membrane." Biochemical Journal 292, no. 1 (May 15, 1993): 171–74. http://dx.doi.org/10.1042/bj2920171.

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The low-Km and high-Km components of S-dinitrophenyl-glutathione (DNPSG) uptake by inside-out vesicles of human erythrocytes show different pH profiles and inhibition properties with organic anions. Both components are competitively inhibited by various polyvalent anions, including glutathione conjugates, conjugated steroid hormones and bile salts, and bilirubin ditaurate. A variety of monovalent anions, including glucuronidated and sulphated drugs and taurocholate, inhibit the high-Km system only. Taurocholate is taken up by the erythrocyte vesicles in an ATP-dependent manner. The anionic dyes fluorescein, Indocyanine Green and bromosulphophthalein inhibit the low-Km system competitively and the high-Km system non-competitively. The study shows that interactions between different types of biologically occurring conjugates can occur at the level of the transport step out of erythrocytes. The kinetic properties suggest overlapping substrate specificities for the two systems, in which the low-Km component is physiologically more important for transport of glutathione conjugates and polyvalent organic anions, whereas the high-Km component is of significance for transport of monovalent organic anions. Low- and high-Km transport of DNPSG is also observed in plasma membrane vesicles from rat, pig and bovine erythrocytes.

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Shin, H. C., Y. Kato, T. Yamada, K. Niinuma, A. Hisaka, and Y. Sugiyama. "Hepatobiliary transport mechanism for the cyclopentapeptide endothelin antagonist BQ-123." American Journal of Physiology-Gastrointestinal and Liver Physiology 272, no. 5 (May 1, 1997): G979—G986. http://dx.doi.org/10.1152/ajpgi.1997.272.5.g979.

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The hepatobiliary transport of an anionic cyclopentapeptide endothelin antagonist, BQ-123, was studied in rats. Biliary excretion of [3H]BQ-123 was extensive in vivo (approximately 75% of intravenous infusion rates). Liver-to-plasma and bile-to-liver concentration ratios at steady state were approximately 3 and 200, respectively, suggesting that hepatic uptake and biliary excretion are concentrative processes. The biliary excretion clearance exhibited a saturation at a hepatic concentration of > 100 nmol/g liver and was markedly reduced in Eisai hyperbilirubinemic rats, which have a hereditary defect of canalicular multispecific organic anion transporter. An ATP-dependent and saturable uptake of BQ-123 by isolated canalicular membrane vesicles was observed in vitro. Impaired transport of BQ-123 was also confirmed in canalicular membrane vesicles prepared from Eisai hyperbilirubinemic rats. These results demonstrate that the biliary excretion process is ATP-driven primary active transport. It is proposed that a canalicular multispecific organic anion transporter is mainly responsible for the biliary excretion of BQ-123.

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Niinuma, Kayoko, Yukio Kato, Hiroshi Suzuki, Charles A. Tyson, Valorie Weizer, Jack E. Dabbs, Ritchie Froehlich, Carol E. Green, and Yuichi Sugiyama. "Primary active transport of organic anions on bile canalicular membrane in humans." American Journal of Physiology-Gastrointestinal and Liver Physiology 276, no. 5 (May 1, 1999): G1153—G1164. http://dx.doi.org/10.1152/ajpgi.1999.276.5.g1153.

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Biliary excretion of several anionic compounds was examined by assessing their ATP-dependent uptake in bile canalicular membrane vesicles (CMV) prepared from six human liver samples. 2,4-Dinitrophenyl- S-glutathione (DNP-SG), leukotriene C4(LTC4), sulfobromophthalein glutathione (BSP-SG), E3040 glucuronide (E-glu), β-estradiol 17-(β-d-glucuronide) (E2–17G), grepafloxacin glucuronide (GPFXG), pravastatin, BQ-123, and methotrexate, which are known to be substrates for the rat canalicular multispecific organic anion transporter, and taurocholic acid (TCA), a substrate for the bile acid transporter, were used as substrates. ATP-dependent and saturable uptake of TCA, DNP-SG, LTC4, E-glu, E2–17G, and GPFXG was observed in all human CMV preparations examined, suggesting that these compounds are excreted in the bile via a primary active transport system in humans. Primary active transport of the other substrates was also seen in some of CMV preparations but was negligible in the others. The ATP-dependent uptake of all the compounds exhibited a large inter-CMV variation, and there was a significant correlation between the uptake of glutathione conjugates (DNP-SG, LTC4, and BSP-SG) and glucuronides (E-glu, E2–17G, and GPFXG). However, there was no significant correlation between TCA and the other organic anions, implying that the transporters for TCA and for organic anions are different also in humans. When the average value for the ATP-dependent uptake by each preparation of human CMVs was compared with that of rat CMVs, the uptake of glutathione conjugates and nonconjugated anions (pravastatin, BQ-123, and methotrexate) in humans was ∼3- to 76-fold lower than that in rats, whereas the uptake of glucuronides was similar in the two species. Thus there is a species difference in the primary active transport of organic anions across the bile canalicular membrane that is less marked for glucuronides.

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Togawa, Natsuko, Takaaki Miyaji, Sho Izawa, Hiroshi Omote, and Yoshinori Moriyama. "A Na+-phosphate cotransporter homologue (SLC17A4 protein) is an intestinal organic anion exporter." American Journal of Physiology-Cell Physiology 302, no. 11 (June 1, 2012): C1652—C1660. http://dx.doi.org/10.1152/ajpcell.00015.2012.

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The SLC17 anion transporter family comprises nine members that transport various organic anions in membrane potential (Δψ)- and Cl−-dependent manners. Although the transport substrates and physiological relevance of the majority of the members have already been determined, little is known about SLC17A4 proteins known to be Na+-phosphate cotransporter homologue (NPT homologue). In the present study, we investigated the expression and transport properties of human SLC17A4 protein. Using specific antibodies, we found that a human NPT homologue is specifically expressed and present in the intestinal brush border membrane. Proteoliposomes containing the purified protein took up radiolabeled p-aminohippuric acid (PAH) in a Cl−-dependent manner at the expense of an electrochemical gradient of protons, especially Δψ, across the membrane. The Δψ- and Cl−-dependent PAH uptake was inhibited by diisothiocyanostilbene-2,2′-disulfonic acid and Evans blue, common inhibitors of SLC17 family members. cis-Inhibition studies revealed that various anionic compounds, such as hydrophilic nonsteroidal anti-inflammatory drugs, pravastatin, and urate inhibited the PAH uptake. Proteoliposomes took up radiolabeled urate, with the uptake having properties similar to those of PAH uptake. These results strongly suggested that the human NPT homologue acts as a polyspecific organic anion exporter in the intestines. Since SLC17A1 protein (NPT1) and SLC17A3 protein (NPT4) are responsible for renal urate extrusion, our results reveal the possible involvement of a NPT homologue in urate extrusion from the intestinal duct.

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30

Lepsy, Christopher S., Robert J. Guttendorf, Alan R. Kugler, and David E. Smith. "Effects of Organic Anion, Organic Cation, and Dipeptide Transport Inhibitors on Cefdinir in the Isolated Perfused Rat Kidney." Antimicrobial Agents and Chemotherapy 47, no. 2 (February 2003): 689–96. http://dx.doi.org/10.1128/aac.47.2.689-696.2003.

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ABSTRACT Cefdinir (Omnicef; Abbott Laboratories) is a cephalosporin antibiotic primarily eliminated by the kidney. Nonlinear renal elimination of cefdinir has been previously reported. Cefdinir renal transport mechanisms were studied in the erythrocyte-free isolated perfused rat kidney. Studies were performed with drug-free perfusate and perfusate containing cefdinir alone to establish the baseline physiology and investigate cefdinir renal elimination characteristics. To investigate cefdinir renal transport mechanisms, inhibition studies were conducted by coperfusing cefdinir with inhibitors of the renal organic anion (probenecid), organic cation (tetraethylammonium), or dipeptide (glycylsarcosine) transport system. Cefdinir concentrations in biological samples were determined using reversed-phase high-performance liquid chromatography. Differences between treatments and controls were evaluated using analysis of variance and Dunnett's test. The excretion ratio (ER; the renal clearance corrected for the fraction unbound and glomerular filtration rate) for cefdinir was 5.94, a value indicating net renal tubular secretion. Anionic, cationic, and dipeptide transport inhibitors all significantly affected the cefdinir ER. With probenecid, the ER was reduced to 0.59, clearly demonstrating a significant reabsorptive component to cefdinir renal disposition. This finding was confirmed by glycylsarcosine studies, in which the ER was elevated to 7.95, indicating that reabsorption was mediated, at least in part, by the dipeptide transporter system. The effects of the organic cation tetraethylammonium, in which the ER was elevated to 7.53, were likely secondary in nature. The anionic secretory pathway was found to be the predominant mechanism for cefdinir renal excretion.

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31

Watanabe, Masayoshi, Hiroyuki Tokuda, and Shunsuke Muto. "Anionic effect on ion transport properties in network polyether electrolytes." Electrochimica Acta 46, no. 10-11 (March 2001): 1487–91. http://dx.doi.org/10.1016/s0013-4686(00)00743-x.

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32

Novak, Donald, Mark Beveridge, and Jill Verlander-Reed. "Rat Erythrocytes Express the Anionic Amino Acid Transport Protein EAAC1." Blood Cells, Molecules, and Diseases 29, no. 3 (November 2002): 261–66. http://dx.doi.org/10.1006/bcmd.2002.0566.

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33

Périé, M., J. Périé, M. Chemla, and J. J. Camp. "Equilibrium and transport properties of boron species in anionic membranes." Journal of Electroanalytical Chemistry 365, no. 1-2 (February 1994): 107–18. http://dx.doi.org/10.1016/0022-0728(93)02982-n.

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34

Petzinger, E., W. Follmann, M. Blumrich, R. Schermuly, S. Schulz, J. Hahnen, and P. W. Feit. "Interaction of bumetanide derivatives with hepatocellular bile acid uptake." American Journal of Physiology-Gastrointestinal and Liver Physiology 265, no. 5 (November 1, 1993): G942—G954. http://dx.doi.org/10.1152/ajpgi.1993.265.5.g942.

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The loop diuretic bumetanide is an organic monocarboxylic organic anion assumed to be transported into hepatocytes by a transport system for bile acids. The structural requirements of 22 bumetanide analogues were analyzed for an interaction with bile acid uptake into isolated rat hepatocytes. Whereas bumetanide inhibited the hepatocellular uptake of [14C]cholate to the same degree as its own uptake, derivatization altered affinity and specificity and yielded compounds that selectively inhibited either cholate or taurocholate uptake or uptake of both. No correlation was found between the diuretic potency of bumetanide derivatives, reflecting the affinity to the Na(+)-K(+)-Cl- cotransporter, and their affinity to hepatic bile salt transport. Computer-aided model building combined with the calculation of potential energy maps showed a strictly amphipathic charge separation in bumetanide analogues as in bile acids. Ranking bumetanide compounds by their mean inhibitory concentration values, inhibition constants, and their type of competition, we conclude that at least three binding domains in the proteins are essential for recognition by bile acid transporters, namely two hydrophobic and an anionic side, and that for the anionic binding region a carbonyl atom in the ligands as an electron donor group is sufficient for ligand interaction.

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35

Fouldrin, Karine, Anis Limami, and Thierry Lamaze. "Calcium (45Ca) Mobility in Chicory Root (Cichorium intybus L.) as Affected by the Anionic Composition of the Nutrient Solution during Forcing." Journal of the American Society for Horticultural Science 118, no. 5 (September 1993): 587–92. http://dx.doi.org/10.21273/jashs.118.5.587.

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During forcing, the witloof chicory taproot produces an etiolated bud, the chicon. The axis of this organ often is brown as a consequence of a disorder associated with a localized Ca deficiency. The effect of the main anions (NO3-, Cl-, SO42) in the nutrient solution on Ca (45Ca) absorption and translocation in the chicon was investigated. Although the amount of Ca that accumulated in the chicon was not affected by nutrient solution composition, Ca (45Ca) mobility was modified. The amount of radioactivity in the chicon increased slightly when the main anion in the solution was sulfate and decreased markedly when the main anion was chloride, compared to nitrate. Calculations of the specific radioactivity of Ca reaching the chicon and in root tissue suggest that, when slowed down, Ca transport consists of a homogeneous flow in all root tissues, whereas, in other cases, Ca moves along a preferential pathway, such as the xylem vessels. Modifying the anionic composition of the nutrient solution to avoid a localized Ca deficiency is discussed.

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36

Hansen, Lory, Andrew Taylor, and Luigi G. Marzilli. "Synthesis of the Sulphonate and Phosphonate Derivatives of Mercaptoacetyltriglycine. X-Ray Crystal Structure of Na2[ReO(Mercaptoacetylglycylglycylaminomethanesulphonate)]·3H2O." Metal-Based Drugs 1, no. 1 (January 1, 1994): 31–39. http://dx.doi.org/10.1155/mbd.1994.31.

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Mercaptoacetyltriglycine forms complexes with R186/188e and T99mc radionuclides that are useful in nuclear medicine because they are substrates of the renal anion transport system. However, the renal clearance of [MO(MAG3)]2- (MAG3 = penta-anionic form of mercaptoacetyltriglycine, M = Re, Tc) complexes are less than ideal. Organic sulphonates are also transported by the renal anion transport system and phosphonates are similar to sulphonates in size and shape. In an effort to develop new ligands that form Re and Tc complexes and have improved renal clearances compared to [MO(MAG3)]2- complexes, the sulphonate and phosphonate derivatives of mercaptoacetyltriglycine were synthesized. The dianion [ReO(MAG2-AMS)]2- (MAG2-AMS = penta-anionic form of mercaptoacetylglycylglycylaminomethanesulphonic acid) was prepared for characterization by exchange reaction of ReOCl3(Me2S)(OPPh3) and isolated as the disodium salt. The structure of Na2[ReO(MAG2-AMS)]·3H2O (6) was determined by X-ray diffraction. The coordination geometry is pseudo square pyramidal, with the nitrogen and sulfur donor atoms forming a square base and the oxo ligand at the apex. The deprotonated sulphonate group has a syn conformation with respect to the oxo ligand. The renal clearances of [T99mcO(MAG2-AMS)]2- and [T99mcO(MAG2-AMP)]3- were similar in rats and suggest that the difference in total charge between the SO3- and PO32- groups is not important to renal clearance. However, their renal clearances were 40-50% less than that of [T99mcO(MAG3)]2- suggesting that the size and shape of the large tetrahedral SO3- and PO32- groups of [T99mcO(MAG2-AMS)]2- and [T99mcO(MAG2-AMP)]3- inhibit recognition by the renal transport system compared to the small planar CO2- group of [T99mcO(MAG3)]2-.

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37

Spencer, Cierra, Barbara A. Bensing, Nagendra N. Mishra, and Paul M. Sullam. "Membrane trafficking of the bacterial adhesin GspB and the accessory Sec transport machinery." Journal of Biological Chemistry 294, no. 5 (December 4, 2018): 1502–15. http://dx.doi.org/10.1074/jbc.ra118.005657.

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The serine-rich repeat (SRR) glycoproteins of Gram-positive bacteria are large, cell wall–anchored adhesins that mediate binding to many host cells and proteins and are associated with bacterial virulence. SRR glycoproteins are exported to the cell surface by the accessory Sec (aSec) system comprising SecA2, SecY2, and 3–5 additional proteins (Asp1 to Asp5) that are required for substrate export. These adhesins typically have a 90-amino acid-long signal peptide containing an elongated N-region and a hydrophobic core. Previous studies of GspB (the SRR adhesin ofStreptococcus gordonii) have shown that a glycine-rich motif in its hydrophobic core is essential for selective, aSec-mediated transport. However, the role of this extended N-region in transport is poorly understood. Here, using protein–lipid co-flotation assays and site-directed mutagenesis, we report that the N-region of the GspB signal peptide interacts with anionic lipids through electrostatic forces and that this interaction is necessary for GspB preprotein trafficking to lipid membranes. Moreover, we observed that protein–lipid binding is required for engagement of GspB with SecA2 and for aSec-mediated transport. We further found that SecA2 and Asp1 to Asp3 also localize selectively to liposomes that contain anionic lipids. These findings suggest that the GspB signal peptide electrostatically binds anionic lipids at the cell membrane, where it encounters SecA2. After SecA2 engagement with the signal peptide, Asp1 to Asp3 promote SecA2 engagement with the mature domain, which activates GspB translocation.

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Peddagopu, Nishant, Patrizia Rossi, Carmela Bonaccorso, Ausrine Bartasyte, Paola Paoli, and Graziella Malandrino. "Facile synthesis of novel lithium β-diketonate glyme adducts: the effect of molecular engineering on the thermal properties." Dalton Transactions 49, no. 4 (2020): 1002–6. http://dx.doi.org/10.1039/c9dt04732h.

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Coordination of monoglyme and diglyme to Li ion, in addition to the anionic hexafluoro-acetylacetone, gives rise, respectively, to a polymeric network and dimeric units with challenging mass transport properties.

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39

Nieto-Malagón, Guillermo, Cristina Cuautli, and Joel Ireta. "Interlaminar Anionic Transport in Layered Double Hydroxides: Estimation of Diffusion Coefficients." Journal of Physical Chemistry C 122, no. 1 (December 28, 2017): 171–76. http://dx.doi.org/10.1021/acs.jpcc.7b10384.

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40

Rudnick, G., K. L. Kirk, H. Fishkes, and S. Schuldiner. "Zwitterionic and Anionic Forms of a Serotonin Analog as Transport Substrates." Journal of Biological Chemistry 264, no. 25 (September 1989): 14865–68. http://dx.doi.org/10.1016/s0021-9258(18)63781-0.

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41

Thalhammer, Therese, and Jürg Graf. "Hepatobiliary transport of the anionic organomercury compound (mersalyl) is carrier mediated." Biochemical Pharmacology 38, no. 19 (October 1989): 3223–31. http://dx.doi.org/10.1016/0006-2952(89)90618-7.

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42

Aljayyoussi, Ghaith, Will Ford, Neil McKeown, and Mark Gumbleton. "Differential transport of anionic PAMAM dendrimers across in vitro biological barriers." Drug Discovery Today 15, no. 23-24 (December 2010): 1114. http://dx.doi.org/10.1016/j.drudis.2010.09.440.

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43

Felipe, Antonio, Octavi Viñas, and Xavier Remesar. "Cationic and anionic amino acid transport studies in rat red blood cells." Bioscience Reports 10, no. 6 (December 1, 1990): 527–35. http://dx.doi.org/10.1007/bf01116613.

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The transport of L-proline, L-lysine and L-glutamate in rat red blood cells has been studied. L-proline and L-lysine uptake were Na+-independent. When the concentration dependence was studied both showed a non-saturable uptake assimilable to a difussion-like process, with high Kd values (0.718 and 0.191 min−1 for L-proline and L-lysine respectively). Rat red blood cells showed high impermeability to L-glutamate. No sodium dependence was observed and the Kd value was low (0.067 min−1). Our results show firstly, that rat red blood cells do not have amino acid transport systems for anionic and cationic amino acids and secondly that erythrocytes show no sodium-dependent L-proline transport, and that these cells are very permeable to this amino acid.

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44

Aboudzadeh, M. Ali, Alexander S. Shaplov, Guiomar Hernandez, Petr S. Vlasov, Elena I. Lozinskaya, Cristina Pozo-Gonzalo, Maria Forsyth, Yakov S. Vygodskii, and David Mecerreyes. "Supramolecular ionic networks with superior thermal and transport properties based on novel delocalized di-anionic compounds." Journal of Materials Chemistry A 3, no. 5 (2015): 2338–43. http://dx.doi.org/10.1039/c4ta05792a.

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45

Perret, Florent, Yannick Tauran, Kinga Suwinska, Beomjoon Kim, Cyrielle Chassain-Nely, Maxime Boulet, and Anthony W. Coleman. "Molecular Recognition and Transport of Active Pharmaceutical Ingredients on Anionic Calix[4]arene-Capped Silver Nanoparticles." Journal of Chemistry 2013 (2013): 1–9. http://dx.doi.org/10.1155/2013/191828.

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A series of six anionic calix[4]arenes, having sulphonate, carboxylate, or phosphonate functions at either the para-aromatic position or the phenolic face were used to cap silver nanoparticles. Their molecular recognition properties were studied with regard to three active pharmaceutical ingredients, chlorhexidine, chloramphenicol, and. gentamycin sulfate. Of these APIs chlorhexidine is known to form cocrystals with the anionic calix[4]arenes, gentamicin sulfate is an aminoglycosidic antibiotic, and chloramphenicol is a neutral antibiotic. As expected the former two APIs show clear complexation behavior as demonstrated by shifts in the visible spectra whereas the last shows no modification in the wavelength of the plasmon resonance of the silver nanoparticles.

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46

Kanai, N., R. Lu, Y. Bao, A. W. Wolkoff, M. Vore, and V. L. Schuster. "Estradiol 17 beta-D-glucuronide is a high-affinity substrate for oatp organic anion transporter." American Journal of Physiology-Renal Physiology 270, no. 2 (February 1, 1996): F326—F331. http://dx.doi.org/10.1152/ajprenal.1996.270.2.f326.

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Although substantial evidence indicates that estradiol-17 beta (E2) is conjugated to the glucuronide in the kidney and then excreted by a direct tubular secretory route and that the liver transports E2 glucuronides via carrier-mediated mechanisms, the transporters involved in these processes have not been identified. The so-called "organic anion-transporting polypeptide" (i.e., oatp) has a number of known substrates, including bromosulfophthalein (BSP) and taurocholic acid (TCA) (E. Jacquemin, B. Hagenbuch, B. Stieger, A. W. Wolkoff, and P. J. Meier. Proc. Natl. Acad. Sci. USA 91: 133-137, 1994). In a companion study, we determined that steroid hormones represent a class of hormones that interact strongly with oatp when the latter is transiently expressed in vitro. Here, we studied more extensively steroids and steroid anion conjugates as candidate oatp substrates. In HeLa cell monolayers transfected with a full-length oatp cDNA, [3H]estradiol 17 beta-D-glucuronide ([3H]E2-17G) was transported with a signal-to-noise ratio of 15:1 over that of monolayers transfected with a control plasmid. The affinity of oatp for [3H]E2-17G was significantly higher than that for TCA (K(m) of 3 microM vs. 27 microM, respectively). In contrast to E2-17G, unconjugated estradiol (E2) was not significantly transported by oatp. Several unconjugated steroids and anionic steroid conjugates were tested for their ability to compete with tracer E2-17G for oatp-mediated transport. Conjugation at the 17 or 3 position with the anion of a strong acid (sulfate) resulted in a greater degree of inhibition of tracer E2-17G transport than did conjugation at the 17 or 3 position with an uncharged group (acetate), suggesting that the strength of the negative charge at these positions is an important determinant of the affinity of a given steroid conjugate for oatp. We conclude that the preferred substrates for oatp are steroids with a strong 17- or 3-position anionic group. Since steroid sulfotransferases and glucuronosyltransferases are expressed in the proximal tubule, as is oatp, the transporter may serve as an apical exit pathway for steroids following their conjugation within the tubule cell.

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47

Grubbs, R. D., C. A. Wetherill, K. Kutschke, and M. E. Maguire. "Magnesium transport in murine S49 lymphoma cells: pharmacology and divalent cation selectivity." American Journal of Physiology-Cell Physiology 248, no. 1 (January 1, 1985): C51—C57. http://dx.doi.org/10.1152/ajpcell.1985.248.1.c51.

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The murine S49 lymphoma cell transports Mg2+ by a system distinct from systems responsible for Ca2+ influx (J. Physiol. London 337: 351-371, 1983). We have now determined the ability of various cations, anions, and drugs to modulate Mg2+ influx. Neither sulfate, nitrate, phosphate, nor bicarbonate altered Mg2+ influx. Among cations only T1+, Ba2+, Zn2+, Mn2+, Sc3+, and La3+ potently inhibited Mg2+ influx without causing obvious cell toxicity. Seventeen other cations were ineffective at maximal nontoxic concentrations. T1+ inhibition (Ki = 300 micron) is noncompetitive and apparently derives from its ability to dissipate membrane potential. The noncompetitive nature of and the rather poor inhibition constants for Ca2+ (Ki approximately equal to 5 mM) and Mn2+ (Ki = 200 micron) indicate that neither cation is an effective physiological antagonist of Mg2+ influx. Only Ba2+ exhibited competitive inhibition of Mg2+ influx (Ki = 1 mM). Cisplatin and Ca2+ channel antagonists also did not inhibit Mg2+ influx. These data further differentiate Mg2+ transport systems from those for Ca2+. In addition, the selectivity series for group IIa cation inhibition of influx (Mg2+ greater than Ba2+ much greater than Ca2+ greater than or equal to Sr2+) has not been observed previously in biological systems and is indicative of a very high anionic field strength at the Mg2+ recognition site.

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48

van Aubel, Rémon A. M. H., Pascal H. E. Smeets, Janny G. P. Peters, René J. M. Bindels, and Frans G. M. Russel. "The MRP4/ABCC4 Gene Encodes a Novel Apical Organic Anion Transporter in Human Kidney Proximal Tubules: Putative Efflux Pump for Urinary cAMP and cGMP." Journal of the American Society of Nephrology 13, no. 3 (March 2002): 595–603. http://dx.doi.org/10.1681/asn.v133595.

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ABSTRACT. The cyclic nucleotides cAMP and cGMP play key roles in cellular signaling and the extracellular regulation of fluid balance. In the kidney, cAMP is excreted across the apical proximal tubular membrane into urine, where it reduces phosphate reabsorption through a dipyridamole-sensitive mechanism that is not fully understood. It has long been known that this cAMP efflux pathway is dependent on ATP and is inhibited by probenecid. However, its identity and whether cGMP shares the same transporter have not been established. Here the expression, localization, and functional properties of human multidrug resistance protein 4 (MRP4) are reported. MRP4 is localized to the proximal tubule apical membrane of human kidney, and membrane vesicles from Sf9 cells expressing human MRP4 exhibit ATP-dependent transport of [3H]cAMP and [3H]cGMP. Both probenecid and dipyridamole are potent MRP4 inhibitors. ATP-dependent [3H]methotrexate and [3H]estradiol-17β-d-glucuronide transport by MRP4 and interactions with the anionic conjugates S-(2,4-dinitrophenyl)-glutathione, N-acetyl-(2,4-dinitrophenyl)-cysteine, α-naphthyl-β-d-glucuronide, and p-nitrophenyl-β-d-glucuronide are also demonstrated. In kidneys of rats deficient in the apical anionic conjugate efflux pump Mrp2, Mrp4 expression is maintained at the same level. It is concluded that MRP4 is a novel apical organic anion transporter and the putative efflux pump for cAMP and cGMP in human kidney proximal tubules.

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49

McAvoy, D. C., C. E. White, B. L. Moore, and R. A. Rapaport. "Chemical fate and transport in a domestic septic system: Sorption and transport of anionic and cationic surfactants." Environmental Toxicology and Chemistry 13, no. 2 (February 1994): 213–21. http://dx.doi.org/10.1002/etc.5620130205.

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50

Hoeltzli, S. D., L. K. Kelley, A. J. Moe, and C. H. Smith. "Anionic amino acid transport systems in isolated basal plasma membrane of human placenta." American Journal of Physiology-Cell Physiology 259, no. 1 (July 1, 1990): C47—C55. http://dx.doi.org/10.1152/ajpcell.1990.259.1.c47.

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The placenta absorbs anionic amino acids from the maternal and fetal circulations but does not significantly transfer these amino acids from mother to fetus. Uptake of L-aspartate and L-glutamate by basal (fetal-facing) plasma membrane vesicles from placental syncytiotrophoblast was stimulated by an inward sodium and an outward potassium gradient. Measurable saturable uptake was entirely sodium dependent and electrogenic. Studies of concentration dependence resolved a high-affinity (microM) system that has characteristics of the X-AG system found in other tissues including the placental microvillous plasma membrane. Uptake of 0.2 microM L-glutamate was inhibited by 2 mM L-glutamate, L-aspartate, D-aspartate, L-cysteate, and L-cysteinesulfinic acid and was uninhibited by 2 mM D-glutamate, L-glutamine, L-alanine, L-serine, L-asparagine, and taurine or by 1 mM methylaminoisobutyric acid. The X-AG system in the two membranes of the placental syncytiotrophoblast may mediate the concentrative uptake of anionic amino acids from the maternal and fetal circulations into the placenta.

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Journal articles on the topic 'Anionic transport'

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