Dissertations / Theses on the topic 'Prostaglandin-f2-alpha'

Prostaglandin F2 alpha (PGF₂α) regulates physiological responses including lowering of intraocular pressure, luteolysis, and parturition. FP prostanoid receptors are GPCRs mediating the actions of PGF₂α. mRNA splice variants exist for the ovine FP receptor gene and are designated FP(A) and FP(B). Thus far, receptor heterogeneity for the human FP receptor gene has yet to be established. This dissertation identifies human FP receptor isoforms and their pharmacological significance. Utilizing PCR, a putative human FP(B) (hFP(B)) ortholog from placenta and CX-1 (colon adenocarcinoma) cDNA was identified. These clones produced similar cDNA sequence both containing inverted repeat sequences. However, the mechanism by which the hFP(B) is produced appears different from alternative mRNA splicing and remains unexplained. Pharmacological characterization of the hFP(B) ortholog is ongoing and its significance remains unknown. Additionally, we report the cloning of a FP receptor mRNA splice variant from human heart and placenta cDNA, named human FP sevenless (hFP(S)). The cDNA encoding hFP(S) has a 71 base pair insert that produces a frame shift resulting in a truncated receptor lacking transmembrane-7 and a carboxyl tail. This sequence is identified as a distinct exon localized on the human FP receptor gene. hFP(S) mRNA are expressed in human skeletal muscle, heart and placenta. Immunohistochemical staining showed positive immunoreactivity in vascular endothelium, trophoblast, and decidual cells from placenta. hFP(S) represents the first confirmed alternative splice variant of the human FP prostanoid receptor gene, however, its function is unknown. Pharmacological characterization of hFP(S) demonstrated no significant PGF₂α binding or PGF₂α-mediated inositol phosphate hydrolysis. FLIPR high throughput screening membrane potential assays yielded four potential agonists for hFPS activation that were not observed in (-)293-EBNA cells; oxytocin, PGB₂, AGNA9B9, and AGNA10B10. These potential agonists require further investigation for hFP(S) selectivity and until such data is determined, hFP(S) should continue to be considered an orphan receptor. In conclusion, these studies demonstrate one FP receptor splice variant of the six transmembrane (6TM) nature exists in humans. In addition, preliminary evidence suggests the existence of a hFP(B) receptor ortholog potentially generated from a mechanism other than traditional mRNA splicing and could contribute to the development of colon carcinogenesis.

Thesis (Ph. D.)--West Virginia University, 2009.
Title from document title page. Document formatted into pages; contains xvi, 218 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references (p. 92-114).

Two-hundred-seventy-two sows were utilized in two trials to evaluate the effects of prostaglandin and pregnant mare serum on reducing weaning to estrus interval, increasing the degree of estrus synchrony and improving fertility at estrus resulting in improved pregnancy rates and subsequent litter performance. Sows were randomly allotted to treatments. In trial 1, sows were assigned to one of three treatments: T1 (n=18; l0mg of PGF2α /hd 24-48 hrs. after parturition), T2 (n=20; lOmg of PGF 2 α /hd at weaning) and controls (n=20). No differences (P>.05) were observed for survival rate and 21D litter wt. among treated and the control sows (83.71 vs. 81.57%; 103.89 vs. 108.36, respectively). As well, WEI, farrowing rate, and subsequent NBA did not differ between treat 1, treat 2, and controls (4.73 vs. 4.81 vs 4.75; 83.33 vs 80 vs 80%; 11.13 vs. 11.06 vs. 10.25, respectively). Trial 2 was performed with two experiments. The first experiment was performed in July 1996. Sows were assigned to one of two treatments: 1) controls ( n=52); 2) Administration of 60mg pregnant mare serum (n=39; injected at weaning). Farrowing rate was higher (P<0001) for PMSG treated sows than controls (100 vs. 63.46%, respectively). PMSG showed no significant (P>.05 effect upon improving number born alive among treated and control sows (11.13 vs. 10.57, respectively); however, there was a trend toward increased litter size among the treated sows. Experiment 2 occurred in February and March 1997. Sows were allotted to one of three treatments: 1) controls (n=42); 2) 60mg pregnant mare serum (n=42; administered at weaning); 60mg pregnant mare serum gamma radiated (n=39; administered at weaning). Data showed no significant difference among PMSG, GR-PMSG and controls for 5d estrus rate and 30d pregnancy rate (83.33 vs. 89.74 vs. 80.95%; 92.86 vs. 97.44 vs. 88.10%, respectively). Evidence from trial 1 showed that the use of prostaglandin did not enhance reproductive performance in swine. In addition, PMSG had little effect on improving fertility at post-treatment estrus and increasing number born alive. Although not statistically significant, trends toward larger litter sizes as well as improved 5d estrus rates and 30d pregnancy rates were evident in the treated sows. However, treatment with PMSG appeared to be effective in improving farrowing rates in the warmer months, perhaps masking the anestrus conditions typically detected during the summer.

Human anaphylatoxin C3a increases glycogenolysis in perfused rat liver. This action is inhibited by prostanoid synthesis inhibitors and prostanoid antagonists. Because prostanoids but not anaphylatoxin C3a can increase glycogenolysis in hepatocytes, it has been proposed that prostanoid formation in nonparenchymal cells represents an important step in the C3a-dependent increase in hepatic glycogenolysis. This study shows that (a) human anaphylatoxin C3a (0.1 to 10 mug/ml) dose-dependently increased prostaglandin D2, thromboxane B, and prostaglandin F2alpha formation in rat liver macrophages (Kupffer cells); (b) the C3a-mediated increase in prostanoid formation was maximal after 2 min and showed tachyphylaxis; and (c) the C3a-elicited prostanoid formation could be inhibited specifically by preincubation of C3a with carboxypeptidase B to remove the essential C-terminal arginine or by preincubation of C3a with Fab fragments of a neutralizing monoclonal antibody. These data support the hypothesis that the C3a-dependent activation of hepatic glycogenolysis is mediated by way of a C3a-induced prostanoid production in Kupffer cells.

A inibição da secreção pulsátil de prostaglandina F2alfa (PGF2α) uterina (atividade antiluteolítica) pela ação do interferon-tau (IFN-τ) trofoblástico, mantêm a secreção de progesterona pelo corpo lúteo, fundamental ao estabelecimento da gestação nas fêmeas bovinas. Supõe-se que essa atividade antiluteolítica esteja presente no microambiente uterino bovino, portanto objetivou-se estudá-la. Dada à inexistência de ensaios que meçam especificamente a atividade antiluteolítica propôs-se elaborar um ensaio biológico para tal. Observou-se que células BEND tratadas com forbol 12,13 dibutirato (PdBu) por 6 horas em cultivo sintetizam PGF2α e tal síntese é inibida na presença de interferon-tau recombinante bovino (rbIFN-τ). Em outro estudo definiu-se que 25 ng/mL de PdBu promove estímulo consistente à síntese de PGF2α. A partir da análise de regressão do percentual de inibição à síntese de PGF2α estimulada por PdBu, em função da concentração de interferon-tau recombinante (rbIFN-τ), calculou-se a concentração de rbIFN-τ que inibiu em 50% a síntese máxima de PGF2α (observada na presença apenas de PdBu). Definiu-se a atividade antiluteolítica como o recíproco da concentração proteica requerida para atingir esse percentual de inibição (50%), e que a solução com uma unidade antiluteolítica é aquela que com um micrograma exerça tal efeito. Caracterizou-se a utilização dessa isoforma como padrão do ensaio antiluteolítico e calculou-se a atividade antiluteolítica do mesmo, 9,61 x 10² UA/µg de proteína. Em estudo seguinte observou-se a modulação da síntese de PGF2α estimulada por PdBu, em função da concentração proteica de um pool de lavados uterinos ou meios condicionados por conceptos obtidos no décimo sétimo dia de gestação. Notou-se que para cada fluido testado há um intervalo de concentrações onde observa-se aumento linear na atividade antiluteolítica em função do acréscimo proteico. A partir da análise por regressão linear desse evento calculou-se a atividade antiluteolítica de cada amostra. Para o pool de lavados uterinos calculou-se 1,63 x 10-¹ UA/ µg de proteína, e para o pool de meios condicionados por conceptos 1,66 x 10² UA/µg de proteína. Estes estudos permitiram desenvolver uma metodologia para observar a atividade antiluteolítica em humores biológicos. Aplicando o ensaio antiluteolítico estudou-se a atividade antiluteolítica presente em lavados uterinos obtidos durante o período crítico de fêmeas bovinas prenhes ou cíclicas ( respectivamente, 56,2 e 33,9 UA/µg de proteina), notou-se que a atividade antiluteolítica foi maior no microambiente uterino de fêmeas gestantes. Tal resultado associado à potente atividade antiluteolítica observada para os meios condicionados por conceptos indicam a participação do IFN-τ secretado pelo concepto na modulação da síntese de PGF2α. Entretanto, observou-se atividade antiluteolítica nos lavados uterinos obtidos de fêmeas cíclicas, o que indica que a síntese de PGF2α estimulada por PdBu pode ser modulada por outras proteínas, além do IFN-τ. Sugere-se que a atividade antiluteolítica, observada através do ensaio biológico proposto, é resultante da atuação de fatores estimulatórios e inibitórios presentes nos humores biológicos. Conclui-se que a atividade antiluteolítica pode ser mensurada pelo ensaio biológico proposto, no entanto outros estudos devem ser conduzidos para correlacionar essa atividade com a atuação do IFN-τ.
The inhibition of pulsatile secretion of PGF2α mediated by interferon-tau (IFN) is fundamental on the maternal recognition of pregnancy, maintaining the progesterone secretion by corpus luteum. Therefore the measurement of interferon activity in the uterine microenvironment was studied. Due to a lack of assays those measure specific antiluteolytic capacities we suggest develop a biological assay for it. In this research we observed that BEND cells treated with PdBu synthesize PGF2α, wich is inhibited by the presence of recombinant bovine interferon-tau (rbIFN-τ). Following we defined 25ng/mL as PdBu (phorbol 12,13 dibutirate) stimulus at the PGF2α synthesis to be applied in this biological assay. Studies about the modulation of PdBu-stimulated PGF2α synthesis by the rbIFN-τ validate the use of this isoform as a reference, defining a standard-curve and allowing estimating the antiluteolytic activity of 9.61 x 10² antiluteolytic units per microgram (UA/µg) of protein. Further, we observed the modulation of PdBu-stimulated PGF2α synthesis exerted by a pool of uterine flushings or conceptus conditioned medium, and for each tested fluid, there is a range of concentrations where is observed an increasing rate on the inhibition of PGF2α synthesis. A restrict analysis on this concentrations range shows a linear behavior and allow calculate the antiluteolytic activity of each sample1.63 x 10-¹ UA/ µg of protein from a pool of uterine flushings, and 1.66 x 10² UA/µg from conceptus conditioned medium. These studies validated a method to observe the antiluteolytic activity from biological fluids. Using the antiluteolytic assay, we studied the antiluteolytic activity present in uterine flushings obtained during the critic period by pregnant or cyclic bovine females cíclicas (respectively 56,2 e 33,9 UA/µg of protein). We observed higher antiluteolytic activity from pregnant uterine microenvironment than in cyclic uterine microenvironment. This result linked with the high antiluteolytic activity observed to conceptus conditioned medium, suggest the participation of IFN-τ secreted by the conceptus in the PGF2α synthesis modulation. However, we observed the antiluteolytic activity in uterine flushing obtained by cyclic cows, suggesting that the PGF2α synthesis could be modulated by another proteins. We believe that the antiluteolytic activity, observed by the antiluteolytic assay, ensue the action of inhibitors or stimulators factors in the biological fluids. We conclude that the antiluteolytic assay could be measured by the proposed biological assay, nevertheless another studies must be done in order to correlate this activity with the interferon action.

Objectives were to 1) evaluate the use of the CO-Synch + CIDR (COS-C) protocol for synchronization of ovulation and timed AI (TAI) in Bos indicus-influenced cattle, 2) compare cumulative pregnancy rates after COS-C synchronization and TAI to those in a traditional management (TM) scheme, and 3) evaluate specific ovarian, hormonal, and estrual events associated with COS-C. The COS-C regimen included insertion of a controlled internal drug release device (CIDR) containing progesterone and injection of GnRH (GnRH-1) on day 0, removal of the CIDR and injection of prostaglandin F2a (PGF on d 7, and injection of GnRH (GnRH-2) and TAI 48 h later. In experiment 1 (Exp. 1), 335 females were stratified by BCS, parity and d postpartum before random assignment to COS-C or TM. An additional 96 females in which TM controls were not available for comparison also received COS-C. Conception rates to TAI averaged 39% (n = 266). Cumulative pregnancy rates were greater (P < 0.05) after 30 and 60 d of the breeding season in COS-C than in TM (n = 170 and 165 females respectively). In experiment 2 (Exp. 2), 100 postpartum (F1) females were stratified as in Exp. 1 within four replicates (25 each) and assigned randomly to receive either COSC or COS (no CIDR) treatment. No differences were observed between treatments and all data were pooled. Percentages of cows ovulating after GnRH-1, developing a synchronized follicular wave, exhibiting luteal regression to PGF, and ovulating to GnRH-2 were 40, 60, 93, and 72%, respectively. In experiment 3 (Exp. 3), primiparous (F1) heifers (n = 32) and pluriparous cows (n = 18) received the Select Synch + CIDR synchronization regimen (no GnRH-2 or TAI). Mean intervals from CIDR removal to estrus and ovulation, and from estrus to ovulation were 70 ± 2.9, 99 ± 2.8, and 29 ± 2.2 h, respectively. Relatively low TAI conception rates (< 50%) were attributed to failure of 40% of cattle to develop a synchronized follicular wave after GnRH-1 and to inappropriate timing of TAI/GnRH-2. It may be possible to improve TAI conception rates by delaying TAI/GnRH-2 to between 66 and 72 h, and by developing methods to increase the number of ovulations after GnRH-1.

A baixa ingestão de colostro compromete a sobrevivência e o desempenho dos leitões. O objetivo do estudo foi avaliar a produção de colostro de matrizes submetidas à indução ao parto aos 114 dias de idade gestacional e sua influência na taxa de sobrevivência na maternidade e desempenho dos leitões. A produção de colostro foi estimada em 96 matrizes de ordem de parto 3 a 7, divididas em dois grupos: Controle (n=48) composto por fêmeas com parto espontâneo e Induzido (n=48) composto por fêmeas induzidas ao parto aos 114 dias de gestação com análogo da PGF2α. Todos os leitões foram pesados ao nascer e 24 horas depois para estimar a produção de colostro através do ganho de peso individual. Amostras de sangue foram coletadas dos leitões no primeiro dia após o nascimento. Foram coletadas amostras de colostro e sangue de cada fêmea no momento do parto e 24 horas depois. Para avaliar o desempenho dos leitões durante a lactação foram acompanhadas 28 leitegadas de cada grupo contendo 12 leitões cada durante 20 dias após o nascimento. Durante o período lactacional todas as leitegadas foram pesadas nos dia 07, 14 e 20 após o nascimento. A duração da gestação do grupo Controle foi em torno de 12 horas mais longa do que no grupo Induzido (P=0,06). A indução ao parto não afetou (P>0,10) a duração do parto, o número total de leitões nascidos, o número de leitões nascidos vivos, o percentual de natimortos, o peso médio dos leitões, o peso médio da leitegada ao nascimento e a produção de colostro em relação ao grupo controle. Não houve diferença entre os grupos (P>0,05) no percentual de fêmeas com intervenção obstétrica. As concentrações de IgG no soro das fêmeas, dos leitões e do colostro foram similares (P>0,10) entre os dois grupos. Para acompanhar o desempenho dos leitões durante a lactação foram uniformizadas leitegadas com peso inicial e consumo de colostro semelhante (P>0,10) em fêmeas adotivas com semelhante produção de colostro (P>0,10). Não foram observadas diferenças (P>0,10) no peso médio dos leitões e das leitegadas nos dias 07, 14 e 20, bem como não houve diferença (P>0,10) na sobrevivência dos animais no mesmo período. A indução ao parto aos 114 dias de gestação não prejudica a produção de colostro e não altera a quantidade de imunoglobulinas G tanto no colostro quanto no soro dos leitões. O desempenho na fase de lactação de leitegadas de fêmeas induzidas ao parto foi semelhante ao de leitegadas de fêmeas com parto espontâneo.
Low colostrum intake influences piglet survival and performance. The aim of this study was to evaluate colostrum production by sows submitted to farrowing induction and its influence on pre-weaning survival rate and piglet performance. A total of 96 sows of parities three to seven were assigned into two groups: Control (n = 48) composed of sows with spontaneous labor and Induced (n = 48) composed of sows induced on day 114 with PGF2α analogue. Colostrum production was estimated by piglet individual weight gain in the first day of life, which was measured by weighing piglets at birth and 24 hours later. Blood samples were collected from piglets on the first day after birth. Colostrum and blood samples were collected from each sow at farrowing and 24 hours later. To evaluate piglet performance during lactation 28 litters from each group containing 12 piglets each were followed for 20 days after birth. During lactation period, all piglets were weighed on days 07, 14 and 20 after birth. Gestation length of control group was about 12 hours longer than induced group (P = 0.06). Farrowing duration, total born, born alive, stillborn rate, average piglet weight, average litter weight at birth and colostrum production were not significantly affected (P > 0.10) by induction of farrowing compared to control group. There was no difference (P > 0.05) in the percentage of sows with obstetric intervention between groups. IgG concentration in sow and piglet serum and colostrum were similar (P > 0.10) between groups. To monitor piglet performance during lactation litters with similar initial weight and colostrum intake (P > 0.10) were cross-fostered in sows with similar colostrum production (P > 0.10). No differences (P > 0.10) were observed in the average piglet and litter weight on days 07, 14 and 20, and on survival rate in the same period. Induction of labor at 114 days of gestation doesn’t affect colostrum production nor influence colostrum and piglet serum immunoglobulin G level. Litter performance during lactation was similar in sows with induced parturition and spontaneous labor.

Un accroissement de la motricité utérine est induit par 2 inhibiteurs de l'enképhalinase: l'Acétorphan et le Thiorphan chez la rate au 21ème jour de la gestation. Elévation des prostaglandines F2 alpha et E2 et décroissance du Bêta -Oestradiol

In ruminants, prostaglandin F2 alpha (PGF2α) is released from the endometrium in a pulsatile pattern at the time of luteolysis. The luteolytic PGF2α pulses are transported from the uterus to the corpus luteum (CL) through the utero-ovarian plexus (UOP) to cause luteolysis. At the time of establishment of pregnancy, interferon tau (IFNT) secreted by the conceptus suppresses the pulsatile release of PGF2α and thereby rescues the CL and maintains its secretion of progesterone. However, basal concentrations of PGF2α are higher in pregnant ewes than in cyclic ewes. The pulsatile release of PGF2α likely requires selective carrier-mediated transport and cannot be supported by a simple diffusion mechanism. The molecular and functional aspects of carrier mediated transport of PGF2α from the uterus to the ovary through the utero- ovarian plexus (UOP) at the time of luteolysis and recognition/establishment of pregnancy are largely unknown ruminants. Results indicate that intrauterine inhibition of (PGT) prevents the pulsatile release of PGF2α independently of spatial expressions of estrogen receptor (ESR-1) and oxytocin receptor (OXTR) proteins by the endometrium at the time of luteolysis in sheep. PGT protein is expressed in the UOP during the estrous cycle and pharmacological inhibition of PGT prevents transport of luteolytic PGF2α pulse through the UOP in sheep. IFNT activates novel JAK-SRC-EGFR-RAS-RAF-ERK1/2-EGR-1 signaling modules in endometrial luminal epithelial (LE) cells and regulates PGT- mediated release of PGF2α through these novel cell-signaling pathways. IFNT stimulates ERK1/2 pathways in endometrial LE cells and inhibition of ERK1/2 inhibits IFNT action and restores spatial expression of OXTR and ESR-1 proteins in endometrial LE cells and restores endometrial luteolytic pulses of PGF2α in sheep. Collectively, the results of the present study provide the first evidence to indicate that transport of endometrial luteolytic PGF2α pulses from the uterus to the ovary through the UOP is controlled by a PGT-mediated mechanism in sheep, new mechanistic insight into molecular mechanisms regulating cellular and compartmental transport of PGF2α at the time of luteolysis, and new mechanistic understanding of IFNT action and release of PGF2α from the endometrial LE cells and thus opens a new arena of research in IFNT signaling and PGT function.

Corpus luteum is a transient endocrine structure formed from the ruptured ovarian follicle. Its main function is to secrete P4, a pro-gestational hormone, essential for establishment and maintenance of pregnancy in mammals. The modulators of CL structure and function are classified as trophic and lytic factors. The luteotrophic factors include pituitary hormones, growth factors, intra luteal factors and cytokines, while luteolytic factors include PGF2α and oxytocin. The interplay between luteotrophic and luteolytic factors regulates luteal steroidogenesis. The precise timing of expression of various enzymes/proteins required for synthesis and metabolism of P4 constitutes an important process in the overall regulation of CL function. The three hormones LH/CG, E2 and PRL are regarded as luteotrophic factors crucial for control of CL function in mammals. Depending on species, either individually or all three hormones in the form of luteotrophic complex have been shown to participate in the regulation of CL function. In addition to the well-established endocrine role of E2, its secretion is the hallmark of the ovulating follicle, has an important role in the intraovarian growth, differentiation and survival of cells. Chapter I provides a comprehensive review of literature on CL structure and function with emphasis on factors that influence its growth, development, function and demise in bovines and rodents. In Chapter II, studies have been carried out to examine 20α-HSD expression and its activity in the CL of buffalo cow. During induced and spontaneous luteolysis, rapid fall in circulating P4 is one of the early signs of initiation of luteolytic process in several species. In rodents, it is well recognized that during luteolysis, P4 is catabolized into inactive metabolite, 20α-OHP by the reaction of 20α-HSD enzyme during luteolysis. Experiments were carried out to determine 20α-HSD expression and activity throughout the luteal phase and during induced luteolysis in the buffalo cow. Circulating P4 concentration declined rapidly in response to PGF2α treatment, but HPLC analysis of serum samples did not reveal changes in circulating 20α-OHP levels in buffalo cows. In contrast, pseudo pregnant rats receiving PGF2α treatment showed higher 20α-OHP levels at 24 h post treatment. qPCR expression of 20α-HSD in CL during different stages of luteal phase and PGF2α-treated buffalo cows was carried out and higher expression of 20α-HSD was observed at 3 and 18 h post treatment, but its activity was not altered post PGF2α treatment at other time points examined. The expression of the transcription factor Nurr77 which is involved in increased expression of 20α-HSD increased several fold 3 h post PGF2α treatment similar to the observation in PGF2α-treated pseudo pregnant rats. The results suggested that the synthesis rather than catabolism of P4 appears to be primarily affected by PGF2α treatment in buffalo cows in contrast to increased metabolism of P4 as seen in rodents. In bovines, to date no luteotropic actions for E2 has been demonstrated and whether E2 has direct effect on CL function has also not been reported. Expression of CYP19A1 gene that encodes aromatase enzyme although gets down regulated post ovulation but its expression recovers in the CL and also E2 biosynthesis has been reported in the bovine CL. Recently it was observed that CYP19A1 expression was consistently down regulated following administration of luteolytic dose of PGF2α. Experiments were conducted to examine the expression of ERα and ERβ in the CL throughout the buffalo estrous cycle as well as examined the luteal E2 levels post PGF2α treatment. The results indicated that ER expression was detectable during different stages of CL and that circulating and luteal E2 levels declined post PGF2α treatment. It was hypothesized that decrease in luteal E2 levels leads to down regulation of ER signaling and changes in expression of E2 responsive genes in the CL. To test the hypothesis, 89 genes which were regarded as E2 responsive genes were selected and the previously published global gene expression data of the buffalo CL was mined for E2 responsive genes. It was observed that 57 of 89 genes regarded as E2 responsive genes were found to be differentially expressed. Since non pregnant buffalo CL is not regarded as major site of E2 production, to validate the authenticity of differentially E2 expressed genes post PGF2α, CL of another species, the macaque, which is known to secrete abundant E2 was included for the analysis. Incidentally, the global gene expression data for the PGF2 α treated macaques (in which CYP19A1 gene expression also gets down regulated) has previously been reported from the laboratory. Here again, it was observed that nearly 79 of 89 genes were identified to be differentially expressed. To further determine the consequences of decreased ER signaling, molecules associated with survival and apoptosis were examined. The results indicated decreased expression (both mRNA and protein levels) of Akt, Bax and Bcl-2 genes. The results suggested an important role for E2 on CL function in the buffalo cow. In Chapter III, several experiments were conducted in another model system, pregnant rat, in which aromatase expression and therefore E2 production is high in the CL. Experiments were conducted to examine the effects of E2 inhibition and E2 replacement on the expression of genes. For this purpose, pregnant rats were treated with a specific aromatase inhibitor on day 12-15 of pregnancy. Together with AI, exogenous E2 was administered to another group of pregnant rats. The CL collected from different groups of rats on day 16 of pregnancy was subjected to microarray analysis. The analysis post validation of microarray data has shown that clusters of genes could be segregated into various pathways involving luteal steroidogenesis, immune system, various growth factors and apoptotic processes, all directed towards the regulation of CL function. The involvement of E2 in luteal cell proliferation and lipid deposition well corroborated with protein levels for cyclin D1 and ki67 and the results of oil red O staining, respectively. There have been reports implicating PI3K/Akt signaling in cyclin D1 accumulation, but mechanism of action does not appear to involve transcriptional activation of cyclin D1. The results of the present study indicate a decrease in cyclin D1 protein levels due to inhibition of PI3K/Akt signaling by AI treatment which is prevented upon administration of E2 during AI treatment. The findings provide a comprehensive overview for the mechanisms associated with the cell survival, progression, etc. The bioinformatics approach provided complete landscape of functional changes affected by the upstream regulators of genes associated with survival and apoptosis. Also, the findings further strengthen the hypothesis of involvement of E2 in the regulation of CL function by way of activation of Akt, the primary mediator of PI3K signaling in the regulation of cellular component that affect cell survival. In the present study, IGFBP5 which was up regulated during luteal inhibition of E2 with AI treatment was selected for further studies. Although IGFBP5 is known to be associated with follicular atresia in the rat ovary, there is limited data for the involvement of IGFBP5 in either a growth stimulatory or inhibitory action on ovarian cells. Based on present findings, a causal link between reduced ERα transcriptional activities resulting in inhibition of Akt/PKB in the presence of IGFBP5 expression could be proposed. Further, the cellular hypertrophy mediated by E2 has been speculated due to increased proliferation of vascular endothelial cells, blood supply and thus nutrients. E2, together with PRL and placental lactogens, regulates steroidogenesis and cell hypertrophy in the rat CL of pregnancy. In CL, the prominent IGFBP5 mRNA expression in different types of luteal cells has not been reported. The mRNA expression for IGFBP5 across the two types of luteal cells showed higher expression in SLC. Hence, in the present study, it has been speculated that prevention of conversion of SLC to LLC due to lack of E2 biosynthesis in presence of AI might be acting as a source for the increased IGFBP5 levels during mid pregnancy in rat CL and brings about changes associated with lack of E2. Various receptor studies on rat CL have demonstrated the lack of progesterone receptor (PR) mRNA expression in the rat CL negating its involvement as an autocrine/paracrine regulator of CL function through an intracellular receptor, but the involvement of non-PR involvement in mediating such mechanism further strengthens the role of ERs. The luteotrophic complex formation in pregnant rat principally by PRL and E2 has been discussed at length in Chapter III. PRL appears to maintain luteal ER content in the CL during rat pregnancy which further determines the luteotrophic and luteolytic actions of E2. Further, study on expression of E2 responsive genes would help in identifying E2 regulating molecules to get a clear picture on the role of E2 in understanding regulation of the CL function. The interaction of E2 with growth factor signaling including the IGF pathway has been well established in different species and this interaction is tightly linked to ERα expression, an observation interpreted as physiological coupling of growth factor and stress signaling pathways. Attempts were made towards understanding cross talk between the E2 signaling and the IGF1 signaling in few experiments carried out in Chapter IV. Based on the results, it can be proposed that a causal link exists between reduced ERα transcriptional activity and inhibition of Akt/PKB in the presence of IGFBP5. The present study has shown the activity of IGF on ERα activity mediated partly via PI3K/Akt pathway. Hence, the finding further speculates that inhibitory effect of IGFBP5 on E2 induced ERα function was due to sequestration of IGF1, possibly present in serum or produced within the cells. Another striking observation was the down regulation of glucocorticoid receptor (GR) gene, NR3C1, in the data of earlier studies [Priyanka, 2009, GEO accession number GSE8371 and Kunal, 2014, GEO accession number GSE27961] and the present study has been compared and discussed in this thesis. Glucocorticoids provide key signals for differentiation of fetal and placental tissues. Therefore, regulation of glucocorticoid access to the placenta and fetus is recognized as an important determinant of prognosis outcome and subsequent development of the postnatal phenotype. Differential regulation of these genes in CL post E2 deprivation and replacement further emphasize the regulation of CL via various biological, cellular and molecular functions. Interestingly, besides transcriptional regulation of IGF axis components, E2 activated ERα also rapidly influence the activity of IGF axis related to signaling proteins in a non-genomic manner, especially by the PI3K/Akt pathway. PI3K/Akt pathway analysis has been carried out in E2 inhibition and replacement experiments. To further confirm the observations of E2 and growth factor interaction, experiments have been set up with exogenous GH for increasing circulating levels of IGF in the system. The findings suggest that the non-genomic signaling pathway activated by the phosphorylation of ERα induced by E2 gets inhibited in the presence of AI result in increased expression of IGFBP5. The reduction in circulating IGF1 in pregnant rats may be associated with the effect on IGFBP, important for determining biological action of IGF1. The changes observed in the present study emphasize the exclusive effects of the IGFBP5 on the CL function brought about perturbations in luteal E2 content. The experiments described in the present thesis aim at understanding the mechanism responsible for decreased serum and luteal P4 post PGF2α treatment in buffalo cows, i.e. whether PGF2α acts on biosynthetic or catabolic process of P4. In the present study, experiments were designed to elucidate the role of E2 in regulation of CL function, since down regulation of CYP19A1 gene mRNA was one of the early events observed in buffalo cows post PGF2α treatment. This line of research work was extended to rodents, a species that secretes high levels of E2 during pregnancy. Genome wide transcriptional changes data revealed differential expression of several E2 responsive genes following E2 inhibition and replacement treatments. The results revealed importance of ER-mediated PI3K/Akt signaling essential for regulation of many transcriptional regulatory molecules in the CL and an interesting involvement of IGFBP5 as a link between E2 and IGF signaling. These findings further provide an insight into the role of IGFBP5 in E2-mediated actions in rat CL during pregnancy. In conclusion, the present findings suggest inhibitory effect of IGFBP5 on E2-induced ERα function and hence, its selection as a target molecule for regulation of CL function and for many beneficial processes involved in anti-carcinogenic properties can be thought of.