Sheep Pituitary Research Articles

Comparative Transcriptomics Identify Key Pituitary Circular RNAs That Participate in Sheep (Ovis aries) Reproduction.

CircRNAs have been found to play key roles in many biological processes and have diverse biological functions. There have been studies on circRNAs in sheep pituitary, and some important circRNAs have been found. But there are still few studies on circRNAs in sheep pituitary with different fecundity. In this study, we obtained the circRNAs expression profiles in the pituitary of FecB ++ genotype Small Tail Han sheep with different fecundity and estrous phases. A total of 34,878 circRNAs were identified in 12 pituitary samples, 300 differentially expressed circRNAs (DE circRNAs) (down: 104; up: 196) were identified in polytocous sheep in the follicular phase (PF) and monotocous sheep in the follicular phase (MF) (PF vs. MF), and 347 DE circRNAs (down: 162; up: 185) were identified in polytocous sheep in the luteal phase (PL) and monotocous sheep in the luteal phase (ML) (PL vs. ML). Cortisol synthesis and secretion pathway (follicular phase) and estrogen signaling pathway (luteal phase) were obtained by functional enrichment analysis of circRNAs source genes. Competing endogenous RNA (ceRNA) network analysis of key DE circRNAs revealed that oar-circ-0022776 (source gene ITPR2, follicular phase) targeted oar-miR-432, oar-circ-0009003 (source gene ITPR1, luteal phase) and oar-circ-0003113 (source gene PLCB1, luteal phase) targeted oar-miR-370-3p. We also explored the coding ability of DE circRNAs. In conclusion, our study shows that changes in the pituitary circRNAs may be related to the response of the pituitary to steroid hormones and regulate the reproductive process of sheep by affecting the pituitary function. Results of this study provide some new information for understanding the functions of circRNAs and the fecundity of FecB ++ genotype sheep.

Identification and characterization of unique and common lncRNAs and mRNAs in the pituitary, ovary, and uterus of Hu sheep with different prolificacy

LncRNAs are regarded as regulators in various animal reproductive physiological processes. However, the regulation of lncRNAs in the reproductive organ development of Hu sheep with different prolificacy remains unknown. Herein, numerous tissue-unique and -common differentially expressed lncRNAs (DELs) and differentially expressed genes (DEGs), and fecundity-unique DELs and DEGs were identified among different comparison groups at horizontal and vertical levels. Moreover, the tissue-unique and -common, and fecundity-unique female reproduction-associated DEGs and DELs were screened, and the interaction networks were constructed. Furthermore, MSTRG.43442.1 was mainly present in the cytoplasm of tested cells. The key genes ADAMTS1 and DCN were mainly localized in the granulosa cells, pituitary cells and/or endometrial epithelial cells of ovary, pituitary and/or uterus. Overall, this study identified large numbers of unique and common DELs and DEGs in the female reproductive organs of Hu sheep with different prolificacy and provided new insights into understanding the regulation of Hu sheep fecundity.

Genome-Wide Analysis and Function Prediction of Long Noncoding RNAs in Sheep Pituitary Gland Associated with Sexual Maturation

Long noncoding RNA (lncRNA) plays a crucial role in the hypothalamic-pituitary-testis (HPT) axis associated with sheep reproduction. The pituitary plays a connecting role in the HPT axis. However, little is known of their expression pattern and potential roles in the pituitary gland. To explore the potential lncRNAs that regulate the male sheep pituitary development and sexual maturation, we constructed immature and mature sheep pituitary cDNA libraries (three-month-old, TM, and nine-month-old, NM, respectively, n = 3) for lncRNA and mRNA high-throughput sequencing. Firstly, the expression of lncRNA and mRNA were comparatively analyzed. 2417 known lncRNAs and 1256 new lncRNAs were identified. Then, 193 differentially expressed (DE) lncRNAs and 1407 DE mRNAs were found in the pituitary between the two groups. Moreover, mRNA-lncRNA interaction network was constructed according to the target gene prediction of lncRNA and functional enrichment analysis. Five candidate lncRNAs and their targeted genes HSD17B12, DCBLD2, PDPK1, GPX3 and DLL1 that enriched in growth and reproduction related pathways were further filtered. Lastly, the interaction of candidate lncRNA TCONS_00066406 and its targeted gene HSD17B12 were validated in in vitro of sheep pituitary cells. Our study provided a systematic presentation of lncRNAs and mRNAs in male sheep pituitary, which revealed the potential role of lncRNA in male reproduction.

Analysis of pituitary transcriptomics indicates that lncRNAs are involved in the regulation of sheep estrus.

Seasonal estrus is a key factor limiting animal fertility, and understanding the molecular mechanisms that regulate animal estrus is important for improving animal fertility. The pituitary gland, which is the most important endocrine gland in mammals, plays an important role in regulating the physiological processes such as growth, development, and reproduction of animals. Here, we used RNA-seq technology to study the expression profile of lncRNAs in the anterior pituitary of sheep during estrus and anestrus. In this study, we identified a total of 995 lncRNAs, of which 335 lncRNAs were differentially expressed in two states (including 38 up-regulated and 297 down-regulated lncRNAs). RT-qPCR verified the expression levels of several lncRNAs. Target predictive analysis revealed that these lncRNAs can act in cis or trans and regulate the expression of genes involved in the regulation of sheep estrus. Target gene enrichment analysis of differentially expressed lncRNAs indicates that these lncRNAs can regulate sheep estrus by regulating hormone metabolism and energy metabolism. Through our research, we provide the expression profile of lncRNAs in the pituitary of sheep, which provides a valuable resource for further understanding of the genetic regulation of seasonal estrus in sheep from the perspective of lncRNAs.

Comprehensive Expression Profiling Analysis of Pituitary Indicates that circRNA Participates in the Regulation of Sheep Estrus

The pituitary gland is the most important endocrine organ that mainly regulates animal estrus by controlling the hormones synthesis. There is a significant difference between the estrus state and anestrus state of sheep pituitary system. Here, we studied the circular RNA (circRNA) expression profiles of the anterior pituitary of estrus and anestrus sheep using RNA-seq technology. Through this study, we identified a total of 12,468 circRNAs and 9231 differentially expressed circRNAs in the estrus and anestrus pituitary system of sheep. We analyzed some differentially expressed circRNAs by reverse transcription quantitative-PCR (RT-qPCR), and some circRNAs were demonstrated using RNase-R+ resistance experiments. CircRNAs involving the regulation of estrus-related terms and pathways are enriched by using gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis. In addition, we also predicted partial microRNA-circRNA interaction network for circRNAs that regulate sheep estrus. Overall, this study explored a potential substantial role played by circRNAs involved in pituitary regulation on sheep estrus and proposed new questions for further study.

In the ovine pituitary, CXCR4 is localized in gonadotropes and somatotropes and increases with elevated serum progesterone

The pituitary is the central endocrine regulator of reproduction and in addition to various hormones regulating its actions, other molecules, such as chemokines, influence pituitary physiology as well. Despite reports over 2 decades ago that chemokines regulate the pituitary, much of the basic biology discerning chemokine action in the pituitary is unclear. A small number of chemokines and their receptors have been localized to the pituitary, yet chemokine ligand 12 (CXCL12) and its receptor, CXCR4, have received the most attention as both are increased in human pituitary adenomas. This chemokine duo was also reported in normal human and rat pituitary, suggestive of a functional role and that this chemokine axis might function in pituitaries from other mammalian species. To date, reports of CXCL12 and CXCR4 in pituitary from livestock are lacking, and research on pituitary during pregnancy in any mammalian species is limited. Moreover, progesterone regulates CXCR4 expression in a tissue-dependent manner, but whether differing concentrations of progesterone reaching the pituitary modulate CXCL12 or CXCR4 is not known. To address these gaps, our first objective was to determine if CXCL12 and CXCR4 expression and protein abundance differ in sheep pituitary during early gestation (days 20, 25, and 30 of gestation) compared to nonpregnant ewes. The second objective was to determine if CXCL12 or CXCR4 production was altered in the ovine pituitary when circulating progesterone concentrations are elevated. The expression of CXCL12 messenger RNA decreased on day 20 of gestation compared to nonpregnant ewes; CXCL12 protein was similar across all days tested. In nonpregnant and pregnant ewes, CXCR4 was localized to somatotropes and gonadotropes on all days tested. Abundance of CXCR4 increased in the pituitary tissue of pregnant ewes with elevated circulating progesterone compared with pregnant ewes with normal circulating progesterone concentrations (control). The present study details CXCL12 and CXCR4 in normal ovine pituitary and reveals that gonadotropes and somatotropes may be regulated by CXCL12/CXCR4, underscoring this signaling axis as a potential new class of modulator in endocrine functions.

106 Effect of β-hydroxybutyrate on gene expression in the hypothalamus and pituitary of sheep

106 Effect of β-hydroxybutyrate on gene expression in the hypothalamus and pituitary of sheep

Ultrastructural changes in lactotrophs and folliculo-stellate cells in the ovine pituitary during the annual reproductive cycle.

In seasonal mammals living in temperate zones, photoperiod regulates prolactin secretion, such that prolactin plasma concentrations peak during the summer months and are lowest during the winter. In sheep, a short-day breeder, circulating prolactin has important modulatory effects on the reproductive system via inhibitory actions on pituitary gonadotrophs and hypothalamic gonadotrophin-releasing hormone release. The exact cellular mechanisms that account for the chronic hypersecretion of prolactin during the summer is not known, although evidence supports an intrapituitary mechanism regulated by melatonin. Folliculo-stellate (FS) cells are non-endocrine cells that play a crucial role in paracrine communication within the pituitary and produce factors controlling prolactin and gonadotrophin release. The present study examined the morphology of the FS and lactotroph cell populations and their distribution in the sheep pituitary during the annual reproductive cycle. Ovine pituitary glands were collected in the winter (breeding season; BS) and summer (nonbreeding season; NBS) and were prepared for quantitative electron microscopy to assess the effects of season on FS and lactotroph cell density, morphology and distribution, as well as on junctional contacts between cells. It was found that lactotrophs in the NBS are larger in size and contain more numerous PRL granules than lactotrophs in the BS. FS cells were also larger in the NBS compared to BS and showed altered morphology such that, in the BS, long cell processes surrounded clusters of adjacent secretory cells. Although no significant change in the number of junctions was observed between lactotrophs and FS cells, or lactotrophs and gonadotrophs, there was a significant increase in the number of adherens junctions between lactotrophs and between FS cells. These findings demonstrate seasonal plasticity in the morphology of lactotrophs and FS cells that reflect changes in PRL secretion.

MRNA expression of prolactin receptor in sheep pituitary and its effect on maternal behavior.

Prolactin receptor (PRLR) is the specific receptor for prolactin. Brain-specific control of PRLR gene expression is correlated with the induction of maternal behavior. The aim of this study was to investigate the dynamic changes in the PRLR mRNA level in the sheep pituitary gland and its effect on ewe maternal behavior. The mRNA expression of PRLR during non-pregnancy stage was maintained at low but detectable levels, as was the case during mid-gestation. After that, expression began increasing and reached a maximum during the early postpartum followed by a gradual decline during the mid-postpartum and late postpartum stages. A trend of higher PRLR mRNA expression was observed during the postpartum stage relative to the non-pregnancy and pregnancy stages. Expression of PRLR mRNA was significantly higher in the normal maternal behavior group than that in the abnormal maternal behavior group. There may be a correlation between PRLR mRNA expression and ewe maternal behavior, especially in early postpartum.

Identification of Eya3 and TAC1 as Long-Day Signals in the Sheep Pituitary

Seasonally breeding mammals such as sheep use photoperiod, encoded by the nocturnal secretion of the pineal hormone melatonin, as a critical cue to drive hormone rhythms and synchronize reproduction to the most optimal time of year. Melatonin acts directly on the pars tuberalis (PT) of the pituitary, regulating expression of thyrotropin, which then relays messages back to the hypothalamus to control reproductive circuits. In addition, a second local intrapituitary circuit controls seasonal prolactin (PRL) release via one or more currently uncharacterized low-molecular-weight peptides, termed "tuberalins," of PT origin. Studies in birds have identified the transcription factor Eya3 as the first molecular response activated by long photoperiod (LP). Using arrays and in situ hybridization studies, we demonstrate here that Eya3 is the strongest LP-activated gene in sheep, revealing a common photoperiodic molecular response in birds and mammals. We also demonstrate TAC1 (encoding the tachykinins substance P and neurokinin A) to be strongly activated by LP within the sheep PT. We show that these PRL secretagogues act on primary pituitary cells and thus are candidates for the elusive PT-expressed tuberalin seasonal hormone regulator.

Cerebral Hypoperfusion Increases Estrogen Receptor Abundance in the Ovine Fetal Brain and Pituitary

Background/Aims: Estrogen is an important component of fetal neuroendocrine function in late-gestation fetal sheep; however, little is known about the regulation of estrogen receptor abundance in the brain and pituitary of fetuses. The present study was performed to test the hypotheses that estrogen receptor abundance in the fetal brain and pituitary are influenced by circulating estradiol concentrations and that they are acutely regulated after cerebral hypoperfusion. Methods: We studied 16 time-dated fetal sheep (124–128 days gestation) that were chronically catheterized and instrumented at least 5 days before study. Four groups (n = 4 each) were studied in which fetuses received estradiol (0.25 mg/day, producing physiological increases in fetal plasma estradiol concentrations) or placebo implants, and in which fetuses received a 10-min period of brachiocephalic occlusion (BCO) or sham-BCO. One hour after BCO or sham-BCO, fetuses were euthanized and tissues rapidly removed for analysis of estrogen receptors (ER)-α and -β at the mRNA and protein levels. Results: Both BCO and estradiol treatment were effective in changing ER expression, although the effects were region-specific. BCO dramatically increased ER-α in the pituitary and both ER-α and ER-β in the brainstem, while decreasing ER-α expression in the hypothalamus. Estradiol treatment decreased ER-α expression in the hypothalamus, whereas it increased ER-α expression in the brainstem, cerebral cortex and hippocampus. Conclusions: We conclude that the expression of ER-α and ER-β in the brain and pituitary of fetal sheep are influenced by circulating estrogen concentrations and acutely regulated in response to cerebral hypoperfusion.

Subpopulations of Corticotrophs in the Sheep Pituitary during Late Gestation: Effects of Development and Placental Restriction

The prepartum surge in fetal plasma cortisol is essential for the normal timing of parturition in sheep and may result from an increase in the ratio of ACTH to proopiomelanocortin (POMC) in the fetal circulation. In fetuses subjected to experimental induction of placental restriction, the prepartum surge in fetal cortisol is exaggerated, whereas pituitary POMC mRNA levels are decreased, and in vitro, unstimulated ACTH secretion is elevated in corticotrophs nonresponsive to CRH. We therefore investigated the changes in the relative proportions of cells expressing POMC, ACTH, and the CRH type 1 receptor (CRHR(1)) shortly before birth and during chronic placental insufficiency. Placental restriction (PR) was induced by removal of the majority of placental attachment sites in five ewes before mating. Pituitaries were collected from control and PR fetal sheep at 140 d (control, n = 4; PR, n = 4) and 144 d (control, n = 6; PR, n = 4). Pituitary sections were labeled with specific antisera raised against POMC, ACTH, and CRHR(1). Three major subpopulations of corticotrophs were identified that expressed POMC + ACTH + CRHR(1), ACTH + CRHR(1), or POMC only. The proportion of pituitary corticotrophs expressing POMC + ACTH + CRHR(1) decreased (P < 0.05) between 140 (control, 60 +/- 1%; PR, 66 +/- 4%) and 144 (control, 45 +/- 2%; PR, 56 +/- 6%) d. A significantly higher (P < 0.05) proportion of corticotrophs expressed POMC + ACTH + CRHR(1) in the pituitary of the PR group compared with controls. This study is the first to demonstrate subpopulations of corticotrophs in the fetal sheep pituitary that differentially express POMC, ACTH, and CRHR(1) and the separate effects of gestational age and placental restriction on these subpopulations of corticotrophs.

BMP-4 inhibits follicle-stimulating hormone secretion in ewe pituitary

Activins and inhibins, members of the transforming growth factor-beta family are able to stimulate and inhibit, respectively, FSH synthesis and release. Other members of this superfamily, the bone morphogenetic proteins (BMPs), may also affect FSH synthesis in the mouse. The aim of this work was to determine whether BMPs are expressed in the ovine pituitary and whether they play a role in the regulation of FSH release. The mRNAs encoding BMP-2, BMP-4, BMP-7 and the oocyte-derived growth factor, growth differentiation factor (GDF)-9 were detected in the pituitaries of cyclic ewes by reverse-transcriptase PCR, as well as the mRNAs encoding the BMP type I receptors, BMPR-IA (activin-receptor-like kinase (ALK)-3) and BMPR-IB (ALK-6), and type II receptors (BMPR-II). Immunolabeling of pituitary sections revealed the presence of BMPR-IA (ALK-3) and BMPR-II in gonadotrope cells. To investigate the potential effects of BMPs on FSH secretion, ewe pituitary cell cultures were treated with BMP-4 (10(-11) M to 10(-9) M) for 48 h. Interestingly, FSH release was decreased in a dose-dependent manner. At 10(-9) M BMP-4 both FSH concentration and FSHbeta mRNA expression were reduced by 40% of control values. In contrast, there was no inhibitory effect on either LH or LHbeta mRNA expression. A similar result was found with BMP-6. BMP-4 triggered the phosphorylation of Smad1, suggesting that the effect of BMP-4 on FSH secretion is due to the activation of the BMPs signaling pathway. Furthermore, BMP-4 blocked the stimulatory effect of activin on both FSH release and FSHbeta mRNA and amplified the suppression of FSH release and FSHbeta mRNA levels induced by 17beta-estradiol. These results indicate that a functional BMP system operates within the sheep pituitary, at least in vitro, to decrease FSH release and to modulate the effect of activin.

Differential expression and seasonal modulation of VGF peptides in sheep pituitary

The inducible gene vgf and its peptide products are relevant to the neuroendocrine regulation of homeostasis and reproduction in rodents. We show here that in the anterior pituitary of female sheep the somatotrope, gonadotrope, and lactotrope/thyrotrope cell populations each expressed vgf mRNA, but displayed a distinct profile of VGF immunoreactive peptides. ProVGF C-terminus and VGF(443-588) immunoreactivities were found in lactotropes and thyrotropes, often in a subcellular location restricted to the Golgi area and suggestive of rapid peptide (or proVGF) release upon biosynthesis, while high molecular weight bands consistent with proVGF were shown in pituitary extracts. Distinct seasonal changes were revealed, proVGF C-terminus immunoreactive cells being largely identified as lactotropes during the summer (83.7 +/- 2.1% (mean +/-s.e.m.) versus 27.0 +/- 1.9% during the winter), as opposed to thyrotropes during the winter (73.0 +/- 1.9% versus 16.3 +/- 2.1% during the summer). Conversely, antisera to peptides adjacent to the 'Arg-Pro-Arg' cleavage site, and to the VGF(553-555) N-terminus of the proVGF-derived peptide V, selectively labeled gonadotropes, indicating processing to small peptides not retaining the proVGF C-terminus in such cells. Finally, a peptide related to the VGF(4-240) region was immunostained in somatotropes, shown in a Western blot as a band of relative molecular mass of approximately 16,000. In conclusion, a complex, endocrine cell-type-specific processing of proVGF was revealed. Further to the known inducibility of vgf mRNA upon a range of stimuli, discreet, selective modulations of VGF-peptide profile/s are suggested, possibly involved in specific neuro/endocrine or modulatory mechanisms.

Effects of prolactin on the luteinizing hormone response to gonadotropin- releasing hormone in primary pituitary cell cultures during the ovine annual reproductive cycle.

In the sheep pituitary, the localization of prolactin (PRL) receptors in gonadotrophs and the existence of gonadotroph-lactotroph associations have provided morphological evidence for possible direct effects of PRL on gonadotropin secretion. Here, we investigated whether PRL can readily modify the LH response to GnRH throughout the ovine annual reproductive cycle. Cell populations were obtained from sheep pituitaries during the breeding season (BS) and the nonbreeding season (NBS), plated to monolayer cultures for 7 days, and assigned to receive one of the following treatments: 1) nil (control), 2) acute (90- min) bromocriptine (ABr), 3) chronic (7-day) bromocriptine (CBr), 4) ABr and PRL, 5) CBr and PRL, 6) PRL alone, or 7) thyrotropin-releasing hormone. Cells were treated as described above, with the aim of decreasing or increasing the concentrations of PRL in the culture, and simultaneously treated with GnRH for 90 min. The LH concentrations in the medium were then determined by RIA. GnRH stimulated LH in a dose-dependent manner during both stages of the annual reproductive cycle. During the NBS, single treatments did not significantly affect the LH response to GnRH. However, when PRL was combined with bromocriptine, either acutely or chronically, GnRH failed to stimulate LH release at all doses tested (P < 0.01). In contrast, during the BS, the LH response to GnRH was not affected by any of the experimental treatments. These results reveal no apparent effects of PRL alone, but an interaction between PRL and dopamine in the regulation of LH secretion within the pituitary gland, and a seasonal modulation of this mechanism.

Ontogeny of corticotropin-releasing hormone binding in anterior pituitaries of fetal sheep.

Previous studies have shown that anterior pituitary expression of corticotropin-releasing hormone type 1 receptor (CRH-R1) decreases during late gestation. This study sought to determine whether this reduction is from a decrease in the number of cells expressing CRH receptors or a decrease in the number of CRH receptors per cell. Fetuses were studied at 100 days' gestational age (100 dGA), 120 dGA, or 140 dGA. Dispersed anterior pituitary cells were incubated with or without fluorescein-conjugated CRH (FL-CRH). FL-CRH binding was assessed by flow cytometry. The number of CRH receptors per cell decreased at 120 dGA and 140 dGA. However, because of an increase in the percentage of cells expressing CRH receptors at 120 dGA, the total receptor index was similar at 100 dGA and 120 dGA. The receptor index tended to decrease at 140 dGA. FL-CRH binding was decreased at 140 dGA due to a decrease in the percentage of cells binding CRH and the number of CRH receptors per cell. This could contribute to the decrease in CRH-stimulated adrenocorticotropin release during late gestation in fetal sheep.

Ontogeny of Corticotropin-Releasing Hormone Binding in Anterior Pituitaries of Fetal Sheep

Ontogeny of Corticotropin-Releasing Hormone Binding in Anterior Pituitaries of Fetal Sheep

Clusterin is expressed in the anterior and intermediate lobes, but not in the posterior pituitary of sheep.

We have examined the expression of the ovine clusterin gene in the sheep pituitary gland, with the aim of determining its site of synthesis in this tissue. Northern blotting analysis of extracted polyadenylated RNA, using a (32)P-labelled rat clusterin cDNA probe, detected the greatest amounts of clusterin mRNA in the anterior part of dissected pituitary glands. In situ hybridisation studies showed clusterin mRNA in anterior and intermediate pituitary cells, with lower amounts in vascular endothelium and posterior pituicytes. Clusterin protein, detected by immunohistochemistry, was observed in some single secretory cells, within the capillary lumen and in cells around capillaries in the anterior and intermediate lobes, but no immunoreactivity was observed in posterior pituitary tissue. The pattern of clusterin expression in anterior and intermediate pituitary cells suggests possible roles for the protein in secretory cell turnover and/or hormone secretion or lipid uptake. Clusterin does not appear to be involved in ovine posterior pituitary hormone neurosecretion.

Corticotropin-releasing factor receptor expression in the pituitary of fetal sheep after lesion of the hypothalamic paraventricular nucleus.

Both the capacity of CRF to release ACTH and the number of binding sites for CRF in the anterior pituitary decline during the final weeks of gestation in fetal sheep. The present study examined regulation of pituitary CRF receptor expression by the hypothalamic paraventricular nucleus (PVN) during late gestation in fetal sheep. Bilateral radiofrequency lesions of the PVN (PVN-Lx; n = 4) or sham lesions (SHAM; n = 5) were performed in fetal sheep at 118-122 days of gestational age (dGA). Pituitary glands from PVN-Lx and SHAM fetuses were collected at 139-142 dGA (term, approximately 148 dGA). Dual-label in situ hybridization was performed using a digoxigenin-labeled ovine POMC complementary RNA, together with a 35S-labeled ovine CRF type I (CRF1) receptor complementary RNA, to localize and quantify CRF1 receptor mRNA in POMC-hybridizing cells. Binding of [125I]-ovine CRF was also examined in the fetal pituitary of both PVN-Lx and SHAM fetuses using in situ autoradiography. The hybridization signal for the CRF1 receptor mRNA was primarily restricted to POMC-expressing cells in the anterior pituitary of both PVN-Lx and SHAM fetuses; no hybridization signal for the CRF1 receptor was observed in the neurointermediate lobe (NIL) in either group. The hybridization signal for CRF1 receptor mRNA in anterior pituitary corticotropes of PVN-Lx fetuses was significantly lower in both the inferior and superior regions of the anterior pituitary, compared with SHAM fetuses (P < 0.05). In the inferior region of the anterior pituitary, the percentage of POMC-hybridizing cells containing CRF1 receptor hybridization signal was significantly greater in PVN-Lx (90+/-7%; mean +/- SEM), compared with SHAM (67+/-6%; P < 0.05) fetuses. No differences in the percentage of POMC cells containing CRF1 receptor hybridization signal were observed in the superior region of the anterior pituitary between PVN-Lx (89+/-8%) and SHAM (87+/-9%). Binding of [125I]-ovine CRF (oCRF) was significantly greater in anterior pituitaries of PVN-Lx (140+/-19 mean arbitrary densitometry U +/- SEM), compared with SHAM (73+/-23; P < 0.05) fetuses. For both PVN-Lx and SHAM fetuses, there were no differences within group in [125I]-oCRF binding between the inferior and superior regions of the anterior pituitary. A weak, but significant (P < 0.05), autoradiographic signal for [125I]-oCRF binding was observed in the NIL of both SHAM and PVN-Lx fetal sheep. The level of [125I]-oCRF binding was significantly lower in the NIL, compared with anterior pituitary, for both SHAM (P < 0.01) and PVN-Lx fetuses. There were no differences in [125I]-oCRF binding in the NIL between SHAM and PVN-Lx fetal sheep. Our findings support a role for the PVN in regulating anterior pituitary CRF1 receptor expression in the late-gestation sheep fetus.

Corticotropin-Releasing Factor Receptor Expression in the Pituitary of Fetal Sheep after Lesion of the Hypothalamic Paraventricular Nucleus

Corticotropin-Releasing Factor Receptor Expression in the Pituitary of Fetal Sheep after Lesion of the Hypothalamic Paraventricular Nucleus