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Academic literature on the topic 'Proximal convoluted tubules'
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Journal articles on the topic "Proximal convoluted tubules"
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Baum, Michel, and Raymond Quigley. "Maturation of rat proximal tubule chloride permeability." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 289, no. 6 (2005): R1659—R1664. http://dx.doi.org/10.1152/ajpregu.00257.2005.
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We have previously shown that neonate rabbit tubules have a lower chloride permeability but comparable mannitol permeability compared with adult proximal tubules. The surprising finding of lower chloride permeability in neonate proximals compared with adults impacts net chloride transport in this segment, which reabsorbs 60% of the filtered chloride in adults. However, this maturational difference in chloride permeability may not be applicable to other species. The present in vitro microperfusion study directly examined the chloride and mannitol permeability using in vitro perfused rat proximal tubules during postnatal maturation. Whereas there was no maturational change in mannitol permeability, chloride permeability was 6.3 ± 1.3 × 10−5 cm/s in neonate rat proximal convoluted tubule and 16.1 ± 2.3 × 10−5 cm/s in adult rat proximal convoluted tubule ( P < 0.01). There was also a maturational increase in chloride permeability in the rat proximal straight tubule (5.1 ± 0.6 × 10−5 cm/s vs. 9.3 ± 0.6 × 10−5 cm/s, P < 0.01). There was no maturational change in bicarbonate-to-chloride permeabilities ( PHCO3/ PCl) in the rat proximal straight tubules (PST) and proximal convoluted tubules (PCT) or in the sodium-to-chloride permeability ( PNa/ PCl) in the proximal straight tubule; however, there was a significant maturational decrease in proximal convoluted tubule PNa/ PCl with postnatal development (1.31 ± 0.12 in neonates vs. 0.75 ± 0.06 in adults, P < 0.001). There was no difference in the transepithelial resistance measured by current injection and cable analysis in the PCT, but there was a maturational decrease in the PST (7.2 ± 0.8 vs. 4.6 ± 0.1 Ω·cm2, P < 0.05). These studies demonstrate there are maturational changes in the rat paracellular pathway that impact net NaCl transport during development.
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Dhanakoti, S. N., M. E. Brosnan, G. R. Herzberg, and J. T. Brosnan. "Cellular and subcellular localization of enzymes of arginine metabolism in rat kidney." Biochemical Journal 282, no. 2 (1992): 369–75. http://dx.doi.org/10.1042/bj2820369.
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Rat kidneys extract citrulline derived from the intestinal metabolism of glutamine and convert it stoichiometrically into arginine. This pathway constitutes the major endogenous source of arginine. We investigated the localization of enzymes of arginine synthesis, argininosuccinate synthase and lyase, and of breakdown, arginase and ornithine aminotransferase, in five regions of rat kidney, in cortical tubule fractions and in subcellular fractions of cortex. Argininosuccinate synthase and lyase were found almost exclusively in cortex. Arginase and ornithine aminotransferase were found in inner cortex and outer medulla. Since cortical tissue primarily consists of proximal convoluted and straight tubules, distal tubules and glomeruli, we prepared cortical tubule fragments by collagenase digestion of cortices and fractionated them on a Percoll gradient. Argininosuccinate synthase and lyase were found to be markedly enriched in proximal convoluted tubules, whereas less than 10% of arginase and ornithine aminotransferase, were recovered in this fraction. Arginine production from citrulline was also enriched in proximal convoluted tubules. Subcellular fractionation of kidney cortex revealed that argininosuccinate synthase and lyase are cytosolic. We therefore conclude that arginine synthesis occurs in the cytoplasm of the cells of the proximal convoluted tubule.
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Dominguez, J. H., K. Camp, L. Maianu, and W. T. Garvey. "Glucose transporters of rat proximal tubule: differential expression and subcellular distribution." American Journal of Physiology-Renal Physiology 262, no. 5 (1992): F807—F812. http://dx.doi.org/10.1152/ajprenal.1992.262.5.f807.
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In the late proximal tubule, glucose reabsorption progressively lowers the concentration of luminal glucose, and concentrative glucose influx increases to ensure complete glucose reabsorption. The change in glucose influx is effected by luminal Na(+)-dependent glucose transporters (Na(+)-GLUT), which exhibit higher Na(+)-to-glucose stoichiometric ratios in the late proximal tubule. In this work, the corresponding changes in the axial distribution of basolateral glucose efflux transporters (GLUTs) were examined. mRNAs encoding high-affinity facilitative basolateral transporter GLUT1, low-affinity GLUT2, and apical Na(+)-GLUT were identified in mixed populations of proximal convoluted and straight tubules. The organization of the cognate proteins was also appraised on Western blots. GLUT1 was present in glomeruli, proximal convoluted, and straight tubules, GLUT2 was only expressed in the proximal convoluted tubule, and Na(+)-GLUT was present in both proximal convoluted and straight segments. GLUT1 and GLUT2 were confined to the basolateral membrane, whereas Na(+)-GLUT was preferentially localized to the brush-border membrane. These data are consistent with the idea that glucose influx in early and late proximal tubule is achieved through Na(+)-GLUT, that GLUT1 and GLUT2 are responsible for glucose efflux in the early proximal tubule, and that in the late proximal tubule, where transcellular glucose flux is lower, only GLUT1 mediates glucose efflux.
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Thekra Atta, Mohammed Nsaif Abbas, Luay Qasim, Ashwaq Talib, and Mohammed Ali. "Morphological description and histological structure of the Hedgehog Kidney (Hemiechinus auritus)." Tikrit Journal of Pure Science 22, no. 9 (2023): 20–25. http://dx.doi.org/10.25130/tjps.v22i9.869.
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This study was aimed to recognize the morphological description and histological structure of the kidney in hedgehog (Hemiechinus auritus). The morphological results showed that the kidney has a small bean shape and reddish brown color. It was situated on both side of the anterior lumbar vertebra in the abdominal cavity behind the peritoneum. The kidney was surrounded by connective tissues capsule. Histological results clarify that the kidney was characterized by two an regions, outer called cortex and inner called medulla. Glomeruli densely distributed in the cortex region with mean diameter of 78 µm, also the cortex contains segments of proximal convoluted tubules and distal convoluted tubules. On the other hand the medulla region consist of both thick and thin segments of Henle’s loop in addition to sections of collecting tubules which forms radial structures which are known as the medullary rays. The histological results also showed that, the renal corpuscle is formed by the glomeruli that is surrounded by Bowman’s capsule, the proximal convoluted tubules, Henle’s loop, the distal convoluted tubules and collecting tubules. The proximal convoluted tubules connected with Bowman’s capsule and lined by simple cuboidal epithelial tissue based on a basement membrane while the free surface was covered with brush border. The results demonstrated that thin segments of the Henley’s loop were started from the end of the proximal convoluted tubule, extend inside of the medulla and lined by simple squamous epithelial tissue. Whilst the thick segments of the Henle’s loop were lined by simple cuboidal epithelial tissue. The current study clarify that, the distal convoluted tubules were lined by simple cuboidal epithelium rested on basement membrane and the free surface covered by small protrusions. Furthermore, the histological examination revealed that the collecting tubules were lined by simple cuboidal epithelium and the free surface of its cells had a cover of a few and short protrusions.
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Ramachandran, C., and M. G. Brunette. "The renal Na+/Ca2+ exchange system is located exclusively in the distal tubule." Biochemical Journal 257, no. 1 (1989): 259–64. http://dx.doi.org/10.1042/bj2570259.
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The movement of Ca2+ across the basolateral plasma membrane was determined in purified preparations of this membrane isolated from rabbit proximal and distal convoluted tubules. The ATP-dependent Ca2+ uptake was present in basolateral membranes from both these tubular segments, but the activity was higher in the distal tubules. A very active Na+/Ca2+ exchange system was also demonstrated in the distal-tubular membranes, but in proximal-tubular membranes this exchange system was not demonstrable. The presence of Na+ outside the vesicles gradually inhibited the ATP-dependent Ca2+ uptake in the distal-tubular-membrane preparations, but remained without effect in those from the proximal tubules. The activity of the Na+/Ca2+ exchange system in the distal-tubular membranes was a function of the imposed Na+ gradient. These results suggest that the major differences in the characteristics of Ca2+ transport in the proximal and in the distal tubules are due to the high activity of a Na+/Ca2+ exchange system in the distal tubule and its virtual absence in the proximal tubule.
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Garvin, J. L., and M. A. Knepper. "Bicarbonate and ammonia transport in isolated perfused rat proximal straight tubules." American Journal of Physiology-Renal Physiology 253, no. 2 (1987): F277—F281. http://dx.doi.org/10.1152/ajprenal.1987.253.2.f277.
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Bicarbonate, ammonia, and fluid transport were studied in isolated perfused proximal straight tubules from rats. The mean rate of fluid absorption (0.77 nl X min-1 X mm-1) and the mean rate of total CO2 absorption (42 pmol X min-1 X mm-1) exceeded corresponding rates measured previously in rabbit proximal straight tubules. The limiting total CO2 concentration when the tubules were perfused at slow flow rates was 5 mM, a value similar to those reported previously for rat proximal convoluted tubules and thick ascending limbs. When rat proximal straight tubules were perfused and bathed with solutions containing 1 mM total ammonia at slow perfusion rates, the measured total ammonia concentration in collected fluid rose to a level predicted by the diffusion trapping model of ammonia secretion in the absence of a luminal disequilibrium pH. We conclude the proximal straight tubule of the rat can absorb bicarbonate at a rate that can account for a large portion of the bicarbonate absorption measured in vivo between the late proximal convoluted tubule and the early distal tubule, the rat proximal straight tubule is capable of transepithelial ammonia secretion, most likely by NH3 diffusion down a concentration gradient generated by luminal acidification, and the rat proximal straight tubule apparently does not generate a luminal disequilibrium pH despite the occurrence of proton secretion, implying the presence of endogenous luminal carbonic anhydrase.
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Abuazza, Ghazala, Amy Becker, Scott S. Williams, et al. "Claudins 6, 9, and 13 are developmentally expressed renal tight junction proteins." American Journal of Physiology-Renal Physiology 291, no. 6 (2006): F1132—F1141. http://dx.doi.org/10.1152/ajprenal.00063.2006.
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The adult proximal tubule is a low-resistance epithelium where there are high rates of both active transcellular and passive paracellular NaCl transport. We have previously demonstrated that the neonatal rabbit and rat proximal tubule have substantively different passive paracellular transport properties than the adult proximal tubule, which results in a maturational change in the paracellular passive flux of ions. Neonatal proximal tubules have a higher PNa/PCl ratio and lower chloride and bicarbonate permeabilities than adult proximal tubules. Claudins are a large family of proteins which are the gate keepers of the paracellular pathway, and claudin isoform expression determines the permeability characteristics of the paracellular pathway. Previous studies have shown that claudins 1, 2, 3, 4, 5, 7, 8, 10, 11, 12, 15, and 16 are expressed in the adult mouse kidney. To determine whether there are developmental claudin isoforms, we compared the claudin isoforms present in the neonatal and adult kidney using RT-PCR to detect mRNA of claudin isoforms. Claudin 6, claudin 9, and claudin 13 were either not expressed or barely detectable in the adult mouse kidney using traditional PCR, but were expressed in the neonatal mouse kidney. Using real-time RT-PCR, we were able to detect a low level of claudin 6 mRNA expression in the adult kidney compared with the neonate, but claudin 9 and claudin 13 were only detected in the neonatal kidney. There was the same maturational decrease in these claudin proteins with Western blot analysis. Immunohistochemistry showed high levels of expression of claudin 6 in neonatal proximal tubules, thick ascending limb, distal convoluted tubules, and collecting ducts in a paracellular distribution but there was no expression of claudin 6 in the adult kidney. Using real-time RT-PCR claudin 6 and 9 mRNA were present in 1-day-old proximal convoluted tubules and were virtually undetectable in proximal convoluted tubules from adults. Claudin 13 was not detectable in neonatal or adult proximal convoluted tubules. In summary, we have identified developmentally expressed claudin isoforms, claudin 6, claudin 9, and claudin 13. These paracellular proteins may play a role in the maturational changes in paracellular permeability.
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Quigley, R., and M. Baum. "Developmental changes in rabbit juxtamedullary proximal convoluted tubule water permeability." American Journal of Physiology-Renal Physiology 271, no. 4 (1996): F871—F876. http://dx.doi.org/10.1152/ajprenal.1996.271.4.f871.
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The mammalian proximal tubule reabsorbs the bulk of the glomerular filtrate in a nearly isosmotic fashion due to the high osmotic water permeability (Pf) of this segment. Although the characteristics of proximal tubule water transport have been studied in the adult proximal tubule, little is known about the neonatal segment. The present study directly measured the Pf and diffusional water permeability (PDW) of neonatal (10 +/- 2 day old) and adult rabbit juxtamedullary proximal convoluted tubules (PCT) using in vitro microperfusion. The Pf of neonatal juxtamedullary PCT was greater than the Pf of adult juxtamedullary PCT. In contrast, the PDW was not different between the two groups. The Pf and PDW values of both neonatal and adult tubules were inhibited to the same degree by p-chloromercuribenzene sulfonate and had identical activation energies. The transepithelial reflection coefficients of NaCl and NaHCO3 were also found to be similar in both the neonatal and adult proximal tubules. Thus neonatal and adult juxtamedullary PCT have many characteristics of water transport that are identical; however, neonatal Pf is three to five times that of the adult value. This difference in Pf with identical PDW values may give an insight into the transepithelial pathway for water movement in the neonatal tubule.
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Scherzer, Pnina, Hanna Wald, Dvora Rubinger, and Mordecai M. Popovtzer. "Indomethacin and sodium retention in the rat: role of inhibition of prostaglandin E2 synthesis." Clinical Science 83, no. 3 (1992): 307–11. http://dx.doi.org/10.1042/cs0830307.
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1. To further explore the Na+-retaining effect of indomethacin along the whole length of the nephron, the Na+-K+-ATPase activity of isolated tubules from indomethacin-pretreated rats was compared with that of tubules isolated from intact rats and exposed directly to prostaglandin E2. 2. Indomethacin increased Na+-K+-ATPase activity in the proximal convoluted tubule (+24%, P<0.001 versus control), proximal straight tubule (+75%, P<0.001 versus control), medullary thick ascending limb (+68%, P<0.001 versus control), cortical thick ascending limb (+7%, not significant) and cortical collecting duct (+18%, P<0.025 versus control). In contrast, in the distal convoluted tubule indomethacin decreased Na+-K+-ATPase activity by −42% (P<0.001 versus control). 3. Indomethacin also strongly increased Na+-K+-ATPase activity in the cortical collecting duct of adrenalectomized rats. 4. In isolated tubules from control rats, prostaglandin E2 reduced Na+-K+-ATPase activity in the proximal convoluted tubule (−33%, P<0.05), proximal straight tubule (−60%, P<0.001), medullary thick ascending limb (−43%, P<0.001), cortical thick ascending limb (−25%, P<0.001) and cortical collecting duct (−45%, P<0.001) and in the distal convoluted tubule, prostaglandin E2 increased Na+-K+-ATPase activity (+32%, P<0.05). 5. That these changes in Na+-K+-ATPase activity in indomethacin-pretreated rats and prostaglandin E2-treated controls are similar in magnitude but occur in opposite directions suggests that the response to indomethacin is mediated by inhibition of prostaglandin E2 synthesis in the nephron. In the cortical collecting duct the effect of indomethacin is aldosterone-independent.
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Jessen, H., та M. I. Sheikh. "Stoichiometric studies of β-alanine transporters in rabbit proximal tubule". Biochemical Journal 277, № 3 (1991): 891–94. http://dx.doi.org/10.1042/bj2770891.
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The coupling ratio for the transport of beta-alanine and Na+, H+ and Cl- in luminal membrane vesicles isolated from proximal convoluted tubules (pars convoluta) and proximal straight tubules (pars recta) of rabbit kidney was examined. Indirect evidence indicates that 1 H+ and approx. 2 Na+, 1 Cl- (Na(+)-dependent, high-affinity) or 1 Na+ (Na(+)-dependent, low-affinity) are co-transported with beta-alanine in the pars convoluta. In pars recta, the two Na(+)-dependent transporters exhibited the same stoichiometric properties respectively as in pars convoluta.
Books on the topic "Proximal convoluted tubules"
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Kibble, Jonathan David. Mechanisms of potassium transport in the proximal convoluted tubule of the anaesthetized rat. University of Manchester, 1994.
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Ellison, David H., and Arohan R. Subramanya. Clinical use of diuretics. Edited by Robert Unwin. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0033.
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Diuretics are widely employed to treat extracellular fluid volume expansion caused by heart failure, cirrhosis of the liver, nephrotic syndrome, and chronic kidney disease. Major classes of diuretic inhibit sodium reabsorption along the proximal tubule, the loop of Henle, the distal convoluted tubule, and the connecting and collecting tubules. Loop diuretics have the highest ceiling of action and often form the cornerstones of diuretic treatment of oedema. Members of this class are short-acting drugs, with different bioavailabilities, the specifics of which contribute importantly to a rational and effective approach to their use. They are not filtered substantially because they are all protein bound. They enter tubules by secretion along the proximal tubule, thereby gaining access to the Na-K-2Cl cotransporter of the thick ascending limb. Their dose–response curves are sigmoidal and altered by several disease processes. Chronic administration can elicit adaptive processes along the nephron that limit their efficacy. Distal convoluted tubule diuretics, such as the thiazides, inhibit NaCl absorption along the distal convoluted tubule. While used predominantly to treat hypertension, they are also useful to treat oedema, especially when combined with loop diuretics. Drugs acting along the connecting tubule and collecting duct either inhibit Na+ channels directly or block mineralocorticoid receptors. These drugs are effective in states of very high aldosterone secretion, and can also be used to reduce the hypokalaemia caused by other classes of diuretics. An evidence-based approach to treating the oedematous patient is described.
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Houillier, Pascal. Magnesium homeostasis. Edited by Robert Unwin. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0027.
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Magnesium is critically important in the process of energy release. Although most magnesium is stored outside the extracellular fluid compartment, the regulated concentration appears in blood. Urinary magnesium excretion can decrease rapidly to low values when magnesium entry rate into the extracellular fluid volume is low, which has several important implications: cell and bone magnesium do not play a major role in the defence of blood magnesium concentration; while a major role is played by the kidney and especially the renal tubule, which adapts to match the urinary magnesium excretion and net entry of magnesium into extracellular fluid. In the kidney, magnesium is reabsorbed in the proximal tubule, the thick ascending limb of the loop of Henle (TALH), and the distal convoluted tubule (DCT). Magnesium absorption is mainly paracellular in the proximal tubule and TALH, whereas it is transcellular in the DCT. The hormone(s) regulating renal magnesium transport and blood magnesium concentration are not fully understood. Renal tubular magnesium transport is altered by a number of hormones, mainly in the TALH and DCT. Parathyroid hormone, calcitonin, arginine vasopressin, ß-adrenergic agonists, and epidermal growth factor, all increase renal tubular magnesium reabsorption; in contrast, prostaglandin E2 decreases magnesium reabsorption. Non-hormonal factors also influence magnesium reabsorption: it is decreased by high blood concentrations of calcium and magnesium, probably via the action of divalent cations on the calcium-sensing receptor; metabolic acidosis decreases, and metabolic alkalosis increases, renal magnesium reabsorption.
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Halperin, Mitchell L., and Kamel S. Kamel. Approach to the patient with metabolic acidosis or alkalosis. Edited by Robert Unwin. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780199592548.003.0035_update_001.
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The pathophysiology, clinical approach, and management of the common causes of metabolic acidosis and alkalosis are discussed. In metabolic acidosis, a quantitative estimate of the extracellular volume (ECFV) is required to determine its content of bicarbonate in a patient with ECFV contraction. Buffering of H+ must occur by the bicarbonate buffer system in muscle to avoid binding to intracellular proteins, this requires low muscle capillary PCO2; acid gain type of metabolic acidosis is detected by the finding of new anions in blood and/or urine. The urine osmolal gap is the best indirect test to assess [NH4+] in urine. In metabolic alkalosis, Cl− depletion alkalosis is misleading. Deficits must be defined as HCl, KCl, and/or NaCl. A quantitative assessment of ECFV helps determine the contribution of individual deficits of Cl− salts. There is no tubular maximum for HCO3− reabsorption. Angiotensin II and the usual pH in proximal convoluted tubule cells, the two major stimuli for NaHCO3 reabsorption, must be removed/ changed for NaHCO3 to be excreted.
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Wagner, Carsten A., and Olivier Devuyst. Renal acid–base homeostasis. Edited by Robert Unwin. Oxford University Press, 2015. http://dx.doi.org/10.1093/med/9780199592548.003.0024.
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The kidney is central to acid–base homeostasis. Major processes are reabsorption of filtered bicarbonate, de novo synthesis of bicarbonate from ammoniagenesis, and net excretion of protons. The latter requires buffers such as ammonium, phosphate, citrate and other bases binding protons (so-called titratable acids). The proximal tubule is the major site of bicarbonate reabsorption and only site of ammoniagenesis. The thick ascending limb and the distal convoluted tubule handle ammonia/ammonium and complete bicarbonate reabsorption. The collecting duct system excretes protons and ammonium, but may switch to net bicarbonate secretion. The kidney displays a great plasticity to adapt acid or bicarbonate excretion. Angiotensin II, aldosterone and endothelin are involved in regulating these processes, and they induce morphological changes along the nephron. Inborn and acquired disorders of renal acid–base handling are caused by mutations in acid–base transport proteins or by dysregulation of adaptive mechanisms.
Book chapters on the topic "Proximal convoluted tubules"
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Rouse, Diane, and Wadi N. Suki. "Calcium Stimulates Sodium-Dependent Phosphate Absorption in Rabbit Proximal Convoluted Tubules Perfused in Vitro." In Phosphate and Mineral Homeostasis. Springer US, 1986. http://dx.doi.org/10.1007/978-1-4684-5206-8_14.
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Larsen, Erik Hviid, and Jens Nørkær Sørensen. "Stationary and Nonstationary Ion and Water Flux Interactions in Kidney Proximal Tubule: Mathematical Analysis of Isosmotic Transport by a Minimalistic Model." In Reviews of Physiology, Biochemistry and Pharmacology. Springer International Publishing, 2019. http://dx.doi.org/10.1007/112_2019_16.
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AbstractOur mathematical model of epithelial transport (Larsen et al. Acta Physiol. 195:171–186, 2009) is extended by equations for currents and conductance of apical SGLT2. With independent variables of the physiological parameter space, the model reproduces intracellular solute concentrations, ion and water fluxes, and electrophysiology of proximal convoluted tubule. The following were shown: Water flux is given by active Na+ flux into lateral spaces, while osmolarity of absorbed fluid depends on osmotic permeability of apical membranes. Following aquaporin “knock-out,” water uptake is not reduced but redirected to the paracellular pathway. Reported decrease in epithelial water uptake in aquaporin-1 knock-out mouse is caused by downregulation of active Na+ absorption. Luminal glucose stimulates Na+ uptake by instantaneous depolarization-induced pump activity (“cross-talk”) and delayed stimulation because of slow rise in intracellular [Na+]. Rate of fluid absorption and flux of active K+ absorption would have to be attuned at epithelial cell level for the [K+] of the absorbate being in the physiological range of interstitial [K+]. Following unilateral osmotic perturbation, time course of water fluxes between intraepithelial compartments provides physical explanation for the transepithelial osmotic permeability being orders of magnitude smaller than cell membranes’ osmotic permeability. Fluid absorption is always hyperosmotic to bath. Deviation from isosmotic absorption is increased in presence of glucose contrasting experimental studies showing isosmotic transport being independent of glucose uptake. For achieving isosmotic transport, the cost of Na+ recirculation is predicted to be but a few percent of the energy consumption of Na+/K+ pumps.
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El-Sabbahy, Marwa, and Karim Fikry. "Anatomy of the Kidney." In Basic Anesthesia Review, edited by Alaa Abd-Elsayed. Oxford University PressNew York, 2024. http://dx.doi.org/10.1093/med/9780197584569.003.0295.
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Abstract Understanding the anatomy of the kidney is critical to understanding its physiology and multiple roles in blood pressure control, fluid and electrolyte balance, as well as other hormonal functions. The kidneys consist of glomeruli and tubules. The glomerulus consists of a network of capillaries that branch from the afferent arteriole. Each tubule consists of proximal tubule, loop of Henle, distal convoluted tubule, collecting tubule, and ends with the papilla. Each part of the tubule has a distinct function. In addition, the kidney is a very vascular organ. The complex vasculature of the kidney is also discussed in this chapter.
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Douglas, Kenneth. "The Kidney." In Bioprinting. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780190943547.003.0011.
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Abstract: This chapter puts forward a series of experiments in which scientists bioprinted one of the critical components of a kidney’s nephron (the filtering unit of the kidney), namely the proximal convoluted tubule where the majority of nutrient absorption back into the bloodstream takes place (and where most drug-induced toxicities of the kidney occur). The same team of researchers bioprinted colocalized (printed very close together) proximal tubules and blood vessels and, with the use of fluorescence microscopy, were able to observe vectorial transport, the process in which valuable nutrients such as serum albumin are selectively reabsorbed into the bloodstream. They also induced a state of hyperglycemia and administered a countermeasure drug, thus demonstrating the ability of their bioprinted kidney tissue to functionally respond as native kidney tissue does to an overdose of glucose and to a drug designed to mitigate this undesirable condition.
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Ruegg, Charles E., and Lazaro J. Mandel. "Isolation and Maintenance of Milligram Quantities of Rabbit Renal Proximal Straight and Convoluted Tubules." In In Vitro Biological Systems. Elsevier, 1993. http://dx.doi.org/10.1016/b978-0-12-461201-3.50038-4.
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Root Allen W. "Genetic Disorders of the Renal Tubule." In Metabolic Diseases. IOS Press, 2017. https://doi.org/10.3233/978-1-61499-718-4-799.
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The embryology, anatomy, and physiology of the multi-functional proximal renal tubule, thick descending tubule, thin, and thick ascending limbs of the loop of Henle, distal convoluted tubule, connecting tubule, and collecting duct are described. The clinical manifestations and biochemical abnormalities of the four forms of renal tubular acidosis (RTA: Type 1 &ndash; Distal tubule, Type 2 &ndash; Proximal tubule, Type 3 &ndash; Mixed, Type 4 &ndash; Hypoaldosteronism) are presented. Forms of pseudohypoaldosteronism are then reviewed. The pathophysiology and genetic variations underlying the Bartter, Gittleman, Liddle, and Fanconi syndromes are presented.
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Emmett, Stevan R., Nicola Hill, and Federico Dajas-Bailador. "Renal medicine." In Clinical Pharmacology for Prescribing. Oxford University Press, 2019. http://dx.doi.org/10.1093/oso/9780199694938.003.0013.
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The kidneys are of fundamental importance in the regulation of fluid and electrolytes, maintaining permissive extracellular fluid composition (salts and water), pH, and volume, while also mediating the removal of waste products. Based on the anatomy of the nephron, three main processes occur in order to deliver this balance: glomerular filtration, tubular secretion, and tubular resorption. Drugs can act at different sites within this system, so that functional equilibrium can be restored in various disease states (e.g. hypertension, heart failure, liver failure, nephrotic syndrome). CKD is a long- term condition that lasts more than 3 months and affects the function of both kidneys. It results from any pathology that reduces renal functional capacity and produces a decrease in GFR to less than 60 mL/ min/ 1.73 m<sup>2</sup>. Prevalence within the UK is high, particularly in the elderly and affects 6– 8% of the population. The most common cause of CKD is idiopathic (unknown, usually with small kidneys), then diabetes mellitus. In both, glomerular damage and mesangial injury (causing metabolic and haemodynamic effects) occur. Mild- moderate essential hypertension does not cause CKD. Knowledge of the functional anatomy of the proximal tubule and loop of Henle is essential in understanding therapeutic targets and treatment of pathologies, as each region and transporter system has a key role. In brief, the journey of solutes from the blood to the production of urine occurs at five main anatomical sites— the glomerulus, the proximal tubule, the loop of Henle, the distal tubule (proximal part and distal part), and the collecting ducts (Figures 5.1 and 5.2). The glomerulus is a network of capillaries (like a ball of string), which merge with the nephron via Bowman’s capsule. It is the first site of filtration and the place where solutes, toxins, and small proteins are removed from the wider circulatory system, after delivery by the renal arteries (via an afferent arteriole). Blood and larger proteins remain in the arteriole and leave via an efferent branch, while the filtrate enters the proximal convoluted tubule. The afferent:efferent system ensures that a constant filtration pressure is maintained irrespective of variations in arterial pressure. The capillary bed is very large, so that permeability and filtration rates are high. A normal glomerular filtration rate (GFR) i.e. 90– 120 mL/ min/ 1.73 m<sup>2</sup>, depends on hydrostatic pressure, the colloid osmotic pressure and hydraulic per¬meability.