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Murata T, Chiba S, Kawaminami M. Changes in the expressions of annexin A1, annexin A5, inhibin/activin subunits, and vitamin D receptor mRNAs in pituitary glands of female rats during the estrous cycle: correlation analyses among these factors. J Vet Med Sci 2022; 84:1065-1073. [PMID: 35705304 PMCID: PMC9412066 DOI: 10.1292/jvms.22-0141] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Pituitary gonadotropin secretion is regulated by several pituitary factors as well as
GnRH and ovarian hormones. To elucidate the regulatory mechanisms of pituitary
gonadotropin secretions, we observed changes in the mRNA levels of pituitary factors,
namely annexin A1 (Anxa1) and Anxa5, inhibin/activin
subunits, follistatin (Fst), and vitamin D receptor
(Vdr), in female rat pituitary glands during the estrous cycle.
Additionally, levels of LHβ subunit (Lhb), FSHβ subunit
(Fshb), and GnRH receptor (Gnrh-r) mRNA were examined.
During proestrus, Anxa1, Anxa5, Vdr, and inhibin α-subunit
(Inha) exhibited the lowest levels, while during estrus, activin
βB-subunit (Actbb), Lhb, and Gnrh-r
were the lowest. Moreover, Fshb exhibited the highest value during
metestrus, whereas Fst did not differ significantly. Correlation analyses
revealed 16 statistically significant gene combinations. In particular, four combinations,
namely Anxa5 and Inha, Anxa5 and Actbb,
Inha and Vdr, and Inha and Actbb, were highly
significant (P<0.0001), while four combinations,
Anxa1 and Anxa5, Anxa1 and Vdr,
Anxa5 and Vdr, and Lhb and
Gnrh-r, were moderately significant (P<0.001). The
remaining eight combinations that exhibited statistical significance were
Anxa1 and Inha, Anxa1 and Actbb,
Vdr and Actbb, Anxa1 and
Fshb, Inha and Lhb, Actbb and
Fshb, Actbb and Lhb, and
Fst and Fshb (P<0.05). These
results highlight strong correlations among Anxa1, Anxa5, Vdr, Inha, and
Actbb, thereby suggesting that an interaction among ANXA1, ANXA5, and
VDR may lead to further communications with inhibin and/or activin in the pituitary
gland.
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Affiliation(s)
- Takuya Murata
- Laboratory of Veterinary Physiology, Faculty of Veterinary Medicine, Okayama University of Science
| | - Shuichi Chiba
- Laboratory of Veterinary Physiology, Faculty of Veterinary Medicine, Okayama University of Science
| | - Mitsumori Kawaminami
- Laboratory of Veterinary Physiology, Faculty of Veterinary Medicine, Okayama University of Science
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Bohaczuk SC, Cassin J, Slaiwa TI, Thackray VG, Mellon PL. Distal Enhancer Potentiates Activin- and GnRH-Induced Transcription of FSHB. Endocrinology 2021; 162:6213400. [PMID: 33824966 PMCID: PMC8157479 DOI: 10.1210/endocr/bqab069] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2021] [Indexed: 11/19/2022]
Abstract
FSH is critical for fertility. Transcription of FSHB, the gene encoding the beta subunit, is rate-limiting in FSH production and is regulated by both GnRH and activin. Activin signals through SMAD transcription factors. Although the mechanisms and importance of activin signaling in mouse Fshb transcription are well-established, activin regulation of human FSHB is less well understood. We previously reported a novel enhancer of FSHB that contains a fertility-associated single nucleotide polymorphism (rs10031006) and requires a region resembling a full (8 base-pair) SMAD binding element (SBE). Here, we investigated the role of the putative SBE within the enhancer in activin and GnRH regulation of FSHB. In mouse gonadotrope-derived LβT2 cells, the upstream enhancer potentiated activin induction of both the human and mouse FSHB proximal promoters and conferred activin responsiveness to a minimal promoter. Activin induction of the enhancer required the SBE and was blocked by the inhibitory SMAD7, confirming involvement of the classical SMAD signaling pathway. GnRH induction of FSHB was also potentiated by the enhancer and dependent on the SBE, consistent with known activin/GnRH synergy regulating FSHB transcription. In DNA pull-down, the enhancer SBE bound SMAD4, and chromatin immunoprecipitation demonstrated SMAD4 enrichment at the enhancer in native chromatin. Combined activin/GnRH treatment elevated levels of the active transcriptional histone marker, histone 3 lysine 27 acetylation, at the enhancer. Overall, this study indicates that the enhancer is directly targeted by activin signaling and identifies a novel, evolutionarily conserved mechanism by which activin and GnRH can regulate FSHB transcription.
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Affiliation(s)
- Stephanie C Bohaczuk
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Jessica Cassin
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Theresa I Slaiwa
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Varykina G Thackray
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
| | - Pamela L Mellon
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California 92093, USA
- Correspondence: Pamela L. Mellon, Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. E-mail:
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3
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Bohaczuk SC, Thackray VG, Shen J, Skowronska-Krawczyk D, Mellon PL. FSHB Transcription is Regulated by a Novel 5' Distal Enhancer With a Fertility-Associated Single Nucleotide Polymorphism. Endocrinology 2021; 162:5917511. [PMID: 33009549 PMCID: PMC7846141 DOI: 10.1210/endocr/bqaa181] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Indexed: 12/17/2022]
Abstract
The pituitary gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone, signal the gonads to regulate male and female fertility. FSH is critical for female fertility as it regulates oocyte maturation, ovulation, and hormone synthesis. Multiple genome-wide association studies (GWAS) link a 130 Kb locus at 11p14.1, which encompasses the FSH beta-subunit (FSHB) gene, with fertility-related traits that include polycystic ovary syndrome, age of natural menopause, and dizygotic twinning. The most statistically significant single nucleotide polymorphism from several GWAS studies (rs11031006) resides within a highly conserved 450 bp region 26 Kb upstream of the human FSHB gene. Given that sequence conservation suggests an important biological function, we hypothesized that the region could regulate FSHB transcription. In luciferase assays, the conserved region enhanced FSHB transcription and gel shifts identified a binding site for Steroidogenic factor 1 (SF1) contributing to its function. Analysis of mouse pituitary single-cell ATAC-seq demonstrated open chromatin at the conserved region exclusive to a gonadotrope cell-type cluster. Additionally, enhancer-associated histone markers were identified by immunoprecipitation of chromatin from mouse whole pituitary and an immortalized mouse gonadotrope-derived LβT2 cell line at the conserved region. Furthermore, we found that the rs11031006 minor allele upregulated FSHB transcription via increased SF1 binding to the enhancer. All together, these results identify a novel upstream regulator of FSHB transcription and indicate that rs11031006 can modulate FSH levels.
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Affiliation(s)
- Stephanie C Bohaczuk
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California
| | - Varykina G Thackray
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California
| | - Jia Shen
- Department of Medicine, School of Medicine, University of California San Diego, La Jolla, California
| | - Dorota Skowronska-Krawczyk
- Shiley Eye Institute, Viterbi Family Department of Ophthalmology, School of Medicine, University of California, San Diego, California
- Department of Physiology and Biophysics, Department of Ophthalmology, Center for Translational Vision Research, School of Medicine, University of California Irvine, Irvine, California
| | - Pamela L Mellon
- Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, La Jolla, California
- Correspondence: Pamela L. Mellon, Department of Obstetrics, Gynecology, and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093, USA. E-mail:
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4
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Das N, Kumar TR. Molecular regulation of follicle-stimulating hormone synthesis, secretion and action. J Mol Endocrinol 2018; 60:R131-R155. [PMID: 29437880 PMCID: PMC5851872 DOI: 10.1530/jme-17-0308] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/29/2018] [Accepted: 02/07/2018] [Indexed: 12/11/2022]
Abstract
Follicle-stimulating hormone (FSH) plays fundamental roles in male and female fertility. FSH is a heterodimeric glycoprotein expressed by gonadotrophs in the anterior pituitary. The hormone-specific FSHβ-subunit is non-covalently associated with the common α-subunit that is also present in the luteinizing hormone (LH), another gonadotrophic hormone secreted by gonadotrophs and thyroid-stimulating hormone (TSH) secreted by thyrotrophs. Several decades of research led to the purification, structural characterization and physiological regulation of FSH in a variety of species including humans. With the advent of molecular tools, availability of immortalized gonadotroph cell lines and genetically modified mouse models, our knowledge on molecular mechanisms of FSH regulation has tremendously expanded. Several key players that regulate FSH synthesis, sorting, secretion and action in gonads and extragonadal tissues have been identified in a physiological setting. Novel post-transcriptional and post-translational regulatory mechanisms have also been identified that provide additional layers of regulation mediating FSH homeostasis. Recombinant human FSH analogs hold promise for a variety of clinical applications, whereas blocking antibodies against FSH may prove efficacious for preventing age-dependent bone loss and adiposity. It is anticipated that several exciting new discoveries uncovering all aspects of FSH biology will soon be forthcoming.
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Affiliation(s)
- Nandana Das
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
| | - T. Rajendra Kumar
- Division of Reproductive Sciences, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Division of Reproductive Endocrinology and Infertility, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Department of Obstetrics and Gynecology, University of Colorado Anschutz Medical Campus, Aurora, Colorado 80045, U.S.A
- Author for Correspondence: T. Rajendra Kumar, PhD, Edgar L. and Patricia M. Makowski Professor, Associate Vice-Chair of Research, Department of Obstetrics & Gynecology, University of Colorado Anschutz Medical Campus, Mail Stop 8613, Research Complex 2, Room # 15-3000B, 12700 E. 19th Avenue, Aurora, CO 80045, USA, Tel: 303-724-8689,
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5
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Coss D. Regulation of reproduction via tight control of gonadotropin hormone levels. Mol Cell Endocrinol 2018; 463:116-130. [PMID: 28342855 PMCID: PMC6457911 DOI: 10.1016/j.mce.2017.03.022] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/30/2016] [Revised: 03/16/2017] [Accepted: 03/21/2017] [Indexed: 01/04/2023]
Abstract
Mammalian reproduction is controlled by the hypothalamic-pituitary-gonadal axis. GnRH from the hypothalamus regulates synthesis and secretion of gonadotropins, LH and FSH, which then control steroidogenesis and gametogenesis. In females, serum LH and FSH levels exhibit rhythmic changes throughout the menstrual or estrous cycle that are correlated with pulse frequency of GnRH. Lack of gonadotropins leads to infertility or amenorrhea. Dysfunctions in the tightly controlled ratio due to levels slightly outside the normal range occur in a larger number of women and are correlated with polycystic ovaries and premature ovarian failure. Since the etiology of these disorders is largely unknown, studies in cell and mouse models may provide novel candidates for investigations in human population. Hence, understanding the mechanisms whereby GnRH regulates gonadotropin hormone levels will provide insight into the physiology and pathophysiology of the reproductive system. This review discusses recent advances in our understanding of GnRH regulation of gonadotropin synthesis.
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Affiliation(s)
- Djurdjica Coss
- Division of Biomedical Sciences, School of Medicine, University of California, Riverside, Riverside, CA 92521, United States.
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6
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Jonak CR, Lainez NM, Boehm U, Coss D. GnRH Receptor Expression and Reproductive Function Depend on JUN in GnRH Receptor‒Expressing Cells. Endocrinology 2018; 159:1496-1510. [PMID: 29409045 PMCID: PMC5839737 DOI: 10.1210/en.2017-00844] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 01/10/2018] [Indexed: 12/19/2022]
Abstract
Gonadotropin-releasing hormone (GnRH) from the hypothalamus regulates synthesis and secretion of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary gonadotropes. LH and FSH are heterodimers composed of a common α-subunit and unique β-subunits, which provide biological specificity and are limiting components of mature hormone synthesis. Gonadotrope cells respond to GnRH via specific expression of the GnRH receptor (Gnrhr). GnRH induces the expression of gonadotropin genes and of the Gnrhr by activation of specific transcription factors. The JUN (c-Jun) transcription factor binds to AP-1 sites in the promoters of target genes and mediates induction of the FSHβ gene and of the Gnrhr in gonadotrope-derived cell lines. To analyze the role of JUN in reproductive function in vivo, we generated a mouse model that lacks JUN specifically in GnRH receptor‒expressing cells (conditional JUN knockout; JUN-cKO). JUN-cKO mice displayed profound reproductive anomalies such as reduced LH levels resulting in lower gonadal steroid levels, longer estrous cycles in females, and diminished sperm numbers in males. Unexpectedly, FSH levels were unchanged in these animals, whereas Gnrhr expression in the pituitary was reduced. Steroidogenic enzyme expression was reduced in the gonads of JUN-cKO mice, likely as a consequence of reduced LH levels. GnRH receptor‒driven Cre activity was detected in the hypothalamus but not in the GnRH neuron. Female, but not male, JUN-cKO mice exhibited reduced GnRH expression. Taken together, our results demonstrate that GnRH receptor‒expression levels depend on JUN and are critical for reproductive function.
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Affiliation(s)
- Carrie R. Jonak
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, California 92521
| | - Nancy M. Lainez
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, California 92521
| | - Ulrich Boehm
- Experimental Pharmacology, Center for Molecular Signaling, Saarland University School of Medicine, 66421 Homburg, Germany
| | - Djurdjica Coss
- Division of Biomedical Sciences, School of Medicine, University of California Riverside, Riverside, California 92521
- Correspondence: Djurdjica Coss, PhD, Division of Biomedical Sciences, School of Medicine, 303 SOM Research Building, University of California, Riverside, Riverside, California 92521. E-mail:
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7
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Wójcik-Gładysz A, Wańkowska M, Gajewska A, Misztal T, Zielińska-Górska M, Szlis M, Polkowska J. Effects of intracerebroventricular infusions of ghrelin on secretion of follicle-stimulating hormone in peripubertal female sheep. Reprod Fertil Dev 2016; 28:2065-2074. [DOI: 10.1071/rd16028] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2016] [Accepted: 04/23/2016] [Indexed: 12/18/2022] Open
Abstract
Reproduction depends on mechanisms responsible for the regulation of energy homeostasis and puberty is a developmental period when reproductive and somatic maturity are achieved. Ghrelin affects the activity of the hypothalamo–pituitary–gonadal axis under conditions of energy insufficiency. An in vivo model based on intracerebroventricular (i.c.v.) infusions was used to determine whether centrally administered acyl ghrelin affects transcriptional and translational activity of FSH in peripubertal lambs and whether ghrelin administration mimics the effects of short-term fasting. Standard-fed lambs received either Ringer–Lock (R-L) solution (120 µL h–1) or ghrelin (120 µL h–1, 100 µg day–1). Animals experiencing a short-term (72 h) fast were treated only with R-L solution. In each experimental group, i.c.v. infusions occurred for 3 consecutive days. Immunohistochemistry, in situ hybridisation and real-time reverse transcription quantitative polymerase chain reaction analyses revealed that short-term fasting, as well as exogenous acyl ghrelin administration to standard-fed peripubertal lambs, augmented FSHβ mRNA expression and immunoreactive FSH accumulation. In addition to the effects of ghrelin on FSH synthesis in standard-fed animals, effects on gonadotrophin release were also observed. Acyl ghrelin increased the pulse amplitude for gonadotrophin release, which resulted in an elevation in mean serum FSH concentrations. In conclusion, the present data suggest that ghrelin participates in an endocrine network that modulates gonadotrophic activity in peripubertal female sheep.
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8
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Skarra DV, Arriola DJ, Benson CA, Thackray VG. Forkhead box O1 is a repressor of basal and GnRH-induced Fshb transcription in gonadotropes. Mol Endocrinol 2013; 27:1825-39. [PMID: 24065703 DOI: 10.1210/me.2013-1185] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Synthesis of the gonadotropin β-subunits is tightly controlled by a complex network of hormonal signaling pathways that may be modulated by metabolic cues. Recently, we reported that insulin regulates FOXO1 phosphorylation and cellular localization in pituitary gonadotropes and that FOXO1 overexpression inhibits Lhb transcription. In the current study, we investigated whether FOXO1 modulates Fshb synthesis. Here, we demonstrate that FOXO1 represses basal and GnRH-induced Fshb transcription in LβT2 cells. In addition, we show that PI3K inhibition, which increases FOXO1 nuclear localization, results in decreased Fshb mRNA levels in murine primary pituitary cells. FOXO1 also decreases transcription from the human FSHB promoter, suggesting that FOXO1 regulation of FSHB transcription may be conserved between rodents and humans. Although the FOXO1 DNA-binding domain is necessary for suppression of Fshb, we do not observe direct binding of FOXO1 to the Fshb promoter, suggesting that FOXO1 exerts its effect through protein-protein interactions with transcription factors required for Fshb synthesis. FOXO1 suppression of basal Fshb transcription may involve PITX1 because PITX1 interacts with FOXO1, FOXO1 repression maps to the proximal Fshb promoter containing a PITX1-binding site, PITX1 induction of Fshb or a PITX1 binding element in CV-1 cells is decreased by FOXO1, and FOXO1 suppresses Pitx1 mRNA and protein levels. GnRH induction of an Fshb promoter containing a deletion at -50/-41 or -30/-21 is not repressed by FOXO1, suggesting that these two regions may be involved in FOXO1 suppression of GnRH-induced Fshb synthesis. In summary, our data demonstrate that FOXO1 can negatively regulate Fshb transcription and suggest that FOXO1 may relay metabolic hormonal signals to modulate gonadotropin production.
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Affiliation(s)
- Danalea V Skarra
- PhD, Department of Reproductive Medicine, University of California, San Diego, 9500 Gilman Drive, MC 0674, La Jolla, CA 92093.
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9
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Reddy GR, Xie C, Lindaman LL, Coss D. GnRH increases c-Fos half-life contributing to higher FSHβ induction. Mol Endocrinol 2012; 27:253-65. [PMID: 23275456 DOI: 10.1210/me.2012-1168] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
GnRH is a potent hypothalamic regulator of gonadotropin hormones, LH and FSH, which are both expressed within the pituitary gonadotrope and are necessary for the stimulation of gametogenesis and steroidogenesis in the gonads. Differential regulation of LH and FSH, which is essential for reproductive fitness, is achieved, in part, through the varying of GnRH pulse frequency. However, the mechanism controlling the increase in FSH during the periods of low GnRH has not been elucidated. Here, we uncover another level of regulation by GnRH that contributes to differential expression of the gonadotropins and may play an important role for the generation of the secondary rise of FSH that stimulates folliculogenesis. GnRH stimulates LHβ and FSHβ subunit transcription via induction of the immediate early genes, Egr1 and c-Fos, respectively. Here, we determined that GnRH induces rapidly both Egr1 and c-Fos, but specifically decreases the rate of c-Fos degradation. In particular, GnRH modulates the rate of c-Fos protein turnover by inducing c-Fos phosphorylation through the ERK1/2 pathway. This extends the half-life of c-Fos, which is normally rapidly degraded. Confirming the role of phosphorylation in promoting increased protein activity, we show that a c-Fos mutant that cannot be phosphorylated by GnRH induces lower expression of the FHSβ promoter than wild-type c-Fos. Our studies expand upon the role of GnRH in the regulation of gonadotropin gene expression by highlighting the role of c-Fos posttranslational modification that may cause higher levels of FSH during the time of low GnRH pulse frequency to stimulate follicular growth.
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Affiliation(s)
- Gaddameedi R Reddy
- Department of Reproductive Medicine, University of California San Diego, La Jolla, California 92093-0674, USA
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10
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Bilezikjian LM, Vale WW. The Local Control of the Pituitary by Activin Signaling and Modulation. OPEN NEUROENDOCRINOLOGY JOURNAL (ONLINE) 2011; 4:90-101. [PMID: 21927629 PMCID: PMC3173763 DOI: 10.2174/1876528901104010090] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The pituitary gland plays a prominent role in the control of many physiological processes. This control is achieved through the actions and interactions of hormones and growth factors that are produced and secreted by the endocrine cell types and the non-endocrine constituents that collectively and functionally define this complex organ. The five endocrine cell types of the anterior lobe of the pituitary, somatotropes, lactotropes, corticotropes, thyrotropes and gonadotropes, are defined by their primary product, growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH) and follicle stimulating hormone (FSH)/luteinizing hormone (LH). They are further distinguishable by the presence of cell surface receptors that display high affinity and selectivity for specific hypothalamic hormones and couple to appropriate downstream signaling pathways involved in the control of cell type specific responses, including the release and/or synthesis of pituitary hormones. Central control of the pituitary via the hypothalamus is further fine-tuned by the positive or negative actions of peripheral feedback signals and of a variety of factors that originate from sources within the pituitary. The focus of this review is the latter category of intrinsic factors that exert local control. Special emphasis is given to the TGF-β family of growth factors, in particular activin effects on the gonadotrope population, because a considerable body of evidence supports their contribution to the local modulation of the embryonic and postnatal pituitary as well as pituitary pathogenesis. A number of other substances, including members of the cytokine and FGF families, VEGF, IGF1, PACAP, Ghrelin, adenosine and nitric oxide have also been shown or implicated to function as autocrine/paracrine factors, though, definitive proof remains lacking in some cases. The ever-growing list of putative autocrine/paracrine factors of the pituitary nevertheless has highlighted the complexity of the local network and its impact on pituitary functions.
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Affiliation(s)
- Louise M Bilezikjian
- Clayton Foundation Laboratories for Peptide Biology, Salk Institute for Biological Studies, La Jolla, California, USA
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11
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Coss D, Mellon PL, Thackray VG. A FoxL in the Smad house: activin regulation of FSH. Trends Endocrinol Metab 2010; 21:562-8. [PMID: 20598900 PMCID: PMC2933269 DOI: 10.1016/j.tem.2010.05.006] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/25/2010] [Revised: 05/26/2010] [Accepted: 05/27/2010] [Indexed: 10/19/2022]
Abstract
Follicle-stimulating hormone (FSH), produced by pituitary gonadotrope cells, is required for maturation of ovarian follicles. The FSHbeta subunit is the limiting factor for production of mature hormone and provides biological specificity. Activin dramatically induces FSHbeta transcription and the secondary rise in FSH, important for follicular development, is dependent on this induction. Thus, regulation of FSHbeta levels by activin is crucial for female reproductive fitness. This review discusses activin signaling pathways, transcription factors and FSHbeta promoter elements required for activin responsiveness. Because FoxL2, a forkhead transcription factor, was recently shown to be instrumental in relaying activin signaling to the FSHbeta promoter, we focus in this paper on its role and the inter-relatedness of several key players in activin responsiveness on the FSHbeta promoter.
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12
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Thackray VG, Mellon PL, Coss D. Hormones in synergy: regulation of the pituitary gonadotropin genes. Mol Cell Endocrinol 2010; 314:192-203. [PMID: 19747958 PMCID: PMC2815122 DOI: 10.1016/j.mce.2009.09.003] [Citation(s) in RCA: 130] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/02/2009] [Revised: 09/02/2009] [Accepted: 09/02/2009] [Indexed: 11/23/2022]
Abstract
The precise interplay of hormonal influences that governs gonadotropin hormone production by the pituitary includes endocrine, paracrine and autocrine actions of hypothalamic gonadotropin-releasing hormone (GnRH), activin and steroids. However, most studies of hormonal regulation of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) in the pituitary gonadotrope have been limited to analyses of the isolated actions of individual hormones. LHbeta and FSHbeta subunits have distinct patterns of expression during the menstrual/estrous cycle as a result of the integration of activin, GnRH, and steroid hormone action. In this review, we focus on studies that delineate the interplay among these hormones in the regulation of LHbeta and FSHbeta gene expression in gonadotrope cells and discuss how signaling cross-talk contributes to differential expression. We also discuss how recent technological advances will help identify additional factors involved in the differential hormonal regulation of LH and FSH.
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Affiliation(s)
| | | | - Djurdjica Coss
- To whom the correspondence should be addressed: Djurdjica Coss, Department of Reproductive Medicine, University of California San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0674, Phone: (858) 534-1762, Fax: (858) 534-1438,
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13
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A mathematical model for the actions of activin, inhibin, and follistatin on pituitary gonadotrophs. Bull Math Biol 2008; 70:2211-28. [PMID: 18690487 DOI: 10.1007/s11538-008-9341-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2008] [Accepted: 07/09/2008] [Indexed: 10/21/2022]
Abstract
The timed secretion of the luteinizing hormone (LH) and follicle stimulating hormone (FSH) from pituitary gonadotrophs during the estrous cycle is crucial for normal reproductive functioning. The release of LH and FSH is stimulated by gonadotropin releasing hormone (GnRH) secreted by hypothalamic GnRH neurons. It is controlled by the frequency of the GnRH signal that varies during the estrous cycle. Curiously, the secretion of LH and FSH is differentially regulated by the frequency of GnRH pulses. LH secretion increases as the frequency increases within a physiological range, and FSH secretion shows a biphasic response, with a peak at a lower frequency. There is considerable experimental evidence that one key factor in these differential responses is the autocrine/paracrine actions of the pituitary polypeptides activin and follistatin. Based on these data, we develop a mathematical model that incorporates the dynamics of these polypeptides. We show that a model that incorporates the actions of activin and follistatin is sufficient to generate the differential responses of LH and FSH secretion to changes in the frequency of GnRH pulses. In addition, it shows that the actions of these polypeptides, along with the ovarian polypeptide inhibin and the estrogen-mediated variations in the frequency of GnRH pulses, are sufficient to account for the time courses of LH and FSH plasma levels during the rat estrous cycle. That is, a single peak of LH on the afternoon of proestrus and a double peak of FSH on proestrus and early estrus. We also use the model to identify which regulation pathways are indispensable for the differential regulation of LH and FSH and their time courses during the estrous cycle. We conclude that the actions of activin, inhibin, and follistatin are consistent with LH/FSH secretion patterns, and likely complement other factors in the production of the characteristic secretion patterns in female rats.
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Blount AL, Vaughan JM, Vale WW, Bilezikjian LM. A Smad-binding Element in Intron 1 Participates in Activin-dependent Regulation of the Follistatin Gene. J Biol Chem 2008; 283:7016-26. [DOI: 10.1074/jbc.m709502200] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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Williamson M, Viau V. Androgen receptor expressing neurons that project to the paraventricular nucleus of the hypothalamus in the male rat. J Comp Neurol 2007; 503:717-40. [PMID: 17570493 DOI: 10.1002/cne.21411] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Androgen receptors are distributed throughout the central nervous system and are contained by a variety of nuclei that are known to project to or regulate the paraventricular nucleus (PVN) of the hypothalamus, the final common pathway by which the brain regulates the hypothalamic-pituitary-adrenal (HPA) response to homeostatic threat. Here we characterized androgen receptor staining within cells identified as projecting to the PVN in male rats bearing iontophoretic or crystalline injections of the retrograde tracer FluoroGold aimed at the caudal two-thirds of the nucleus, where corticotropin-releasing hormone-expressing neurons are amassed. Androgen receptor (AR) and FluoroGold (FG) double labeling was revealed throughout the limbic forebrain, including scattered numbers of cells within the anterior and posterior subdivisions of the bed nuclei of the stria terminalis; the medial zone of the hypothalamus, including large numbers of AR-FG-positive cells within the anteroventral periventricular and medial preoptic cell groups. Strong and consistent colabeling was also revealed throughout the hindbrain, predominantly within the periaqueductal gray and the lateral parabrachial nucleus, and within various medullary cell groups identified as catecholaminergic, predominantly C1 and A1 neurons of the ventral medulla. These connectional data predict that androgens can act on a large assortment of multimodal inputs to the PVN, including those involved with the processing of various types of sensory and limbic information, and provide an anatomical framework for understanding how gonadal status could contribute to individual differences in HPA function.
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Affiliation(s)
- Martin Williamson
- Department of Cellular and Physiological Sciences, University of British Columbia, Vancouver, British Columbia, Canada
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Zheng W, Jimenez-Linan M, Rubin BS, Halvorson LM. Anterior pituitary gene expression with reproductive aging in the female rat. Biol Reprod 2007; 76:1091-102. [PMID: 17344471 DOI: 10.1095/biolreprod.106.057877] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Although reproductive aging in women is classically attributed to loss of ovarian follicles, recent data have suggested that the entire hypothalamic-pituitary-ovarian axis undergoes functional changes with time. The aim of this study was to characterize age-related changes in pituitary gene expression for factors with known importance for gonadotroph function, including 1) steroid hormone receptors (Esr and Pgr), 2) orphan nuclear receptors [Nr5a1 (steroidogenic factor-1) and Nr5a2 (liver receptor homologue-1)], and 3) pituitary-derived polypeptides (activin, inhibin, and follistatin), as well as 4) gonadotropin subunits and 5) GnRH receptors. We chose to utilize a middle-aged rat model for these studies. Young (Y; 3-mo-old) and middle-aged (MA; 9- to 12-mo-old) rats were ovariectomized, primed with estradiol, and injected with progesterone to induce an LH surge. The mRNA levels for the gonadotropin subunits and GnRH receptors were decreased in middle-aged females relative to young animals. Nr5a1 and follistatin mRNA levels were significantly greater in Y versus MA animals following ovariectomy. Furthermore, steroid-induced regulation of these genes was lost in the MA animals. Regulation of the Nr5a2, Inhba, and Inhbb transcripts was also limited to the young animals. In contrast, there were no significant differences in the mRNA levels of Esr or Pgr family members between age groups at any time point. Although this in vivo model normalizes ovarian steroid levels, it does not control for potential differences in GnRH stimulation with aging. Therefore, in a second set of experiments, we used an in vitro perifusion system to compare the effects of pulsatile GnRH in the two age groups. Nr5a1 mRNA expression was greater in Y than MA animals and was significantly decreased by GnRH pulses in both age groups. Follistatin mRNA levels increased significantly with GnRH treatment in Y animals but were not significantly changed in the MA females. Taken together, these data demonstrate gene-specific blunting of pituitary gene expression postovariectomy and during the steroid-induced surge in middle-aged rats. We propose that age-related changes in pituitary physiology may contribute to reproductive senescence.
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MESH Headings
- Aging/genetics
- Animals
- Female
- Follistatin/genetics
- Follistatin/metabolism
- Gene Expression/drug effects
- Gonadotropin-Releasing Hormone/genetics
- Gonadotropin-Releasing Hormone/metabolism
- Gonadotropin-Releasing Hormone/pharmacology
- Gonadotropins, Pituitary/genetics
- Gonadotropins, Pituitary/metabolism
- Inhibins/genetics
- Inhibins/metabolism
- Luteinizing Hormone/blood
- Ovariectomy
- Pituitary Gland, Anterior/metabolism
- Protein Subunits/genetics
- Protein Subunits/metabolism
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Receptors, Cytoplasmic and Nuclear/genetics
- Receptors, Cytoplasmic and Nuclear/metabolism
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Receptors, Progesterone/genetics
- Receptors, Progesterone/metabolism
- Reproduction/genetics
- Steroidogenic Factor 1
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Affiliation(s)
- Weiming Zheng
- Division of Reproductive Endocrinology, Department of Obstetrics and Gynecology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75390-9032, USA
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McGillivray SM, Thackray VG, Coss D, Mellon PL. Activin and glucocorticoids synergistically activate follicle-stimulating hormone beta-subunit gene expression in the immortalized LbetaT2 gonadotrope cell line. Endocrinology 2007; 148:762-73. [PMID: 17082263 PMCID: PMC2932480 DOI: 10.1210/en.2006-0952] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
FSH is produced by the pituitary gonadotrope to regulate gametogenesis. Production of the beta-subunit of FSH is the rate-limiting step in FSH synthesis, and a number of peptide and steroid hormones within the reproductive axis have been found to regulate transcription of the FSH beta-subunit gene. Although both activin and glucocorticoids are notable regulators of FSHbeta by themselves, we find that cotreatment results in a synergistic interaction on the mouse FSHbeta promoter at the level of the gonadotrope using transient transfection of a reporter gene into the LbetaT2 immortalized gonadotrope-derived cell line. This synergistic interaction is specific to FSHbeta, because only additive effects of these two hormones are observed on LH beta-subunit, GnRH receptor, and mouse mammary tumor virus gene expression. Components of both activin and glucocorticoid signaling are found to be necessary for synergy, and there are specific cis elements on the mouse FSHbeta promoter that contribute to the synergistic response as well. We also identify novel activin-responsive regions in the mouse FSHbeta promoter and find that the -120 site can bind Smad2/3 in vitro. In addition, the glucocorticoid receptor and Smad3 are sufficient to confer a striking synergy with glucocorticoids on the mouse FSHbeta promoter. Our studies provide the first evidence of a synergistic interaction between activin and glucocorticoids within the gonadotrope cell and demonstrate that this synergy can occur directly at the level of the mouse FSHbeta promoter.
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Affiliation(s)
- Shauna M McGillivray
- Department of Reproductive Medicine, University of California at San Diego, 9500 Gilman Drive, La Jolla, California 92093-0674, USA
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18
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Gore AJ, Philips DP, Miller WL, Bernard DJ. Differential regulation of follicle stimulating hormone by activin A and TGFB1 in murine gonadotropes. Reprod Biol Endocrinol 2005; 3:73. [PMID: 16384533 PMCID: PMC1351181 DOI: 10.1186/1477-7827-3-73] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/02/2005] [Accepted: 12/29/2005] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Activins stimulate the synthesis of follicle stimulating hormone (FSH) in pituitary gonadotropes, at least in part, by inducing transcription of its beta subunit (Fshb). Evidence from several laboratories studying transformed murine LbetaT2 gonadotropes indicates that activins signal through Smad-dependent and/or Smad-independent pathways, similar to those used by transforming growth factor beta-1 (TGFB1) in other cell types. Therefore, given common intracellular signaling mechanisms of these two ligands, we examined whether TGFBs can also induce transcription of Fshb in LbetaT2 cells as well as in purified primary murine gonadotropes. METHODS Murine Fshb promoter-reporter (-1990/+1 mFshb-luc) activity was measured in LbetaT2 cells treated with activin A or TGFB1, and in cells transfected with either activin or TGFB receptors. The ability of the ligands to stimulate phosphorylation of Smads 2 and 3 in LbetaT2 cells was measured by western blot analysis, and expression of TGFB type I and II receptors was assessed by reverse transcriptase polymerase chain reaction in both LbetaT2 cells and primary gonadotropes purified from male mice of different ages. Finally, regulation of endogenous murine Fshb mRNA levels by activin A and TGFB1 in purified gonadotropes and whole pituitary cultures was measured using quantitative RT-PCR. RESULTS Activin A dose-dependently stimulated -1990/+1 mFshb-luc activity in LbetaT2 cells, but TGFB1 had no effect at doses up to 5 nM. Similarly, activin A, but not TGFB1, stimulated Smad 2 and 3 phosphorylation in these cells. Constitutively active forms of the activin (Acvr1b-T206D) and TGFB (TGFBR1-T204D) type I receptors strongly stimulated -1990/+1 mFshb-luc activity, showing that mechanisms down stream of Tgfbr1 seem to be intact in LbetaT2 cells. RT-PCR analysis of LbetaT2 cells and whole adult murine pituitaries indicated that both expressed Tgfbr1 mRNA, but that Tgfbr2 was not detected in LbetaT2 cells. When cells were transfected with a human TGFBR2 expression construct, TGFB1 acquired the ability to significantly stimulate -1990/+1 mFshb-luc activity. In contrast to LbetaT2 cells, primary murine gonadotropes from young mice (8-10 weeks) contained low, but detectable levels of Tgfbr2 mRNA and these levels increased in older mice (1 yr). A second surprise was the finding that treatment of purified primary gonadotropes with TGFB1 decreased murine Fshb mRNA expression by 95% whereas activin A stimulated expression by 31-fold. CONCLUSION These data indicate that TGFB1-insensitivity in LbetaT2 cells results from a deficiency in Tgfbr2 expression. In primary gonadotropes, however, expression of Tgfbr2 does occur, and its presence permits TGFB1 to inhibit Fshb transcription, whereas activin A stimulates it. These divergent actions of activin A and TGFB1 were unexpected and show that the two ligands may act through distinct pathways to cause opposing biological effects in primary murine gonadotropes.
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Affiliation(s)
- A Jesse Gore
- Department of Molecular and Structural Biochemistry, Box 7622, North Carolina State University, Raleigh, NC 27695-7622, USA
| | - Daniel P Philips
- Center for Biomedical Research, Population Council, 1230 York Ave., New York, NY 10021, USA
| | - William L Miller
- Department of Molecular and Structural Biochemistry, Box 7622, North Carolina State University, Raleigh, NC 27695-7622, USA
| | - Daniel J Bernard
- Center for Biomedical Research, Population Council, 1230 York Ave., New York, NY 10021, USA
- The Rockefeller University, 1230 York Ave., New York, NY 10021, USA
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Moore JP, Burger LL, Dalkin AC, Winters SJ. Pituitary Adenylate Cyclase Activating Polypeptide Messenger RNA in the Paraventricular Nucleus and Anterior Pituitary During the Rat Estrous Cycle1. Biol Reprod 2005; 73:491-9. [PMID: 15917345 DOI: 10.1095/biolreprod.105.041624] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
The neuropeptide pituitary adenylate cyclase activating polypeptide (ADCYAP 1, or PACAP) has been demonstrated to enhance gonadotropin-releasing hormone (GnRH)-induced gonadotropin secretion and regulate gonadotropin subunit gene expression in cultures of anterior pituitary cells. In the present study, we used in situ hybridization and real-time polymerase chain reaction to examine the expression of Pacap mRNA within the paraventricular nucleus (PVN) and anterior pituitary throughout the estrous cycle of the rat. Levels of luteinizing hormone in serum and pituitary gonadotropin subunit mRNAs were evaluated and displayed cyclic fluctuations similar to those reported previously. Pacap mRNA expression in the PVN and pituitary varied significantly during the estrous cycle, with the greatest changes occurring on the day of proestrus. Pacap mRNA levels in the PVN declined significantly on the morning of diestrus. During proestrus, PVN Pacap mRNA levels significantly increased 3 h before the gonadotropin surge and then declined. Pituitary expression of Pacap mRNA also varied on the afternoon of proestrus with a moderate decline at the time of the gonadotropin surge and a significant increase later in the evening. Expression of the mRNA species encoding the 288 amino acid form of follistatin increased significantly following the rise in pituitary Pacap mRNA, at the termination of the secondary surge in follicle-stimulating hormone beta (Fshb) gene expression. These results suggest that PACAP is involved in events before and following the gonadotropin surge, perhaps through increased gonadotroph sensitivity to GnRH and suppression of Fshb subunit expression through increased follistatin, as previously observed in vitro.
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Affiliation(s)
- Joseph P Moore
- Division of Endocrinology and Metabolism, Department of Medicine, University of Louisville, Louisville, Kentucky 40202, USA.
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Fernández-Fernández R, Tena-Sempere M, Navarro VM, Barreiro ML, Castellano JM, Aguilar E, Pinilla L. Effects of ghrelin upon gonadotropin-releasing hormone and gonadotropin secretion in adult female rats: in vivo and in vitro studies. Neuroendocrinology 2005; 82:245-55. [PMID: 16721030 DOI: 10.1159/000092753] [Citation(s) in RCA: 147] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2005] [Accepted: 02/14/2006] [Indexed: 01/10/2023]
Abstract
A reproductive facet of ghrelin, a stomach-derived orexigenic peptide involved in energy homeostasis, has been recently suggested, and predominantly inhibitory effects of ghrelin upon luteinizing hormone (LH) secretion have been demonstrated in rat models. Yet, the modulatory actions of ghrelin on the gonadotropic axis remain scarcely evaluated. We report herein a detailed analysis of the effects of ghrelin upon LH and follicle-stimulating hormone (FSH) secretion in the female rat, using a combination of in vivo and in vitro approaches. Intracerebroventricular administration of ghrelin (3 nmol/rat) evoked a significant inhibition of LH secretion in cyclic female rats throughout the estrous cycle (proestrus afternoon, estrus, metestrus), as well as in ovariectomized females. In good agreement, gonadotropin-releasing hormone (GnRH) secretion by hypothalamic fragments from ovariectomized females was significantly inhibited by ghrelin. In contrast, ghrelin dose-dependently stimulated basal LH and FSH secretion by pituitary tissue in vitro; a phenomenon that was proven dependent on the phase of estrous cycle, as it was neither detected at estrus nor observed after ovariectomy. Conversely, GnRH-stimulated LH secretion in vitro was persistently inhibited by ghrelin regardless of the stage of the cycle, whereas stimulated FSH secretion was only inhibited by ghrelin at estrus. In addition, cyclic fluctuations in mRNA levels of growth hormone secretagogue receptor (GHS-R)1a, i.e. the functional ghrelin receptor, were observed in the pituitary, with low values at estrus and metestrus. GHS-R1a mRNA levels, however, remained unchanged after ovariectomy. In summary, our data illustrate a complex mode of action of ghrelin upon the gonadotropic axis, with predominant inhibitory effects at central (hypothalamic) levels and upon GnRH-induced gonadotropin secretion, but direct stimulatory actions on basal LH and FSH secretion. Overall, our results further document the reproductive role of ghrelin, which might be relevant for the integrated control of energy balance and reproduction.
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Prendergast KA, Burger LL, Aylor KW, Haisenleder DJ, Dalkin AC, Marshall JC. Pituitary Follistatin Gene Expression in Female Rats: Evidence That Inhibin Regulates Transcription1. Biol Reprod 2004; 70:364-70. [PMID: 14561646 DOI: 10.1095/biolreprod.103.021733] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Follistatin (FS), along with the members of the transforming growth factor beta family activin and inhibin, are important regulators of FSH secretion and messenger RNA production. While activin and inhibin appear to function as tonic modulators of FSH (stimulatory and inhibitory, respectively), dynamic changes in FS are noted through the estrous cycle and under varying physiological experimental paradigms. This suggests that FS is a major contributor to the precisely coordinated secretion of FSH that maintains reproductive function. The aim of this study was to investigate changes in FS, in particular the early (<12 h) rise observed after ovariectomy (OVX), and to determine whether these changes were as a consequence of variations in gene transcription rates. FS primary transcript (PT) and mRNA were found to increase 3-fold 12 h post-OVX, indicating increased gene transcription during this time period. Replacement with estradiol and/or blockade of GnRH had only modest effects on FS PT concentration. Inhibin immunoneutralization of intact rats resulted in a 3-fold increase in FS PT 12 h after administration of inhibin alpha antisera. Significant increases in FS mRNA at both 2 and 12 h also suggested that inhibin also may have effects on message stability. After administration of recombinant human inhibin A, there was a prompt decline in both FS PT and mRNA. These results indicate that inhibin is a major regulator of FS, both by transcriptional and nontranscriptional mechanisms.
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Affiliation(s)
- Kathleen A Prendergast
- Department of Internal Medicine, and the Center for Research in Reproduction, University of Virginia, Charlottesville, Virginia 22908, USA.
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22
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Welt C, Sidis Y, Keutmann H, Schneyer A. Activins, inhibins, and follistatins: from endocrinology to signaling. A paradigm for the new millennium. Exp Biol Med (Maywood) 2002; 227:724-52. [PMID: 12324653 DOI: 10.1177/153537020222700905] [Citation(s) in RCA: 237] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
It has been 70 years since the name inhibin was used to describe a gonadal factor that negatively regulated pituitary hormone secretion. The majority of this period was required to achieve purification and definitive characterization of inhibin, an event closely followed by identification and characterization of activin and follistatin (FS). In contrast, the last 15-20 years saw a virtual explosion of information regarding the biochemistry, physiology, and biosynthesis of these proteins, as well as identification of activin receptors, and a unique mechanism for FS action-the nearly irreversible binding and neutralization of activin. Many of these discoveries have been previously summarized; therefore, this review will cover the period from the mid 1990s to present, with particular emphasis on emerging themes and recent advances. As the field has matured, recent efforts have focused more on human studies, so the endocrinology of inhibin, activin, and FS in the human is summarized first. Another area receiving significant recent attention is local actions of activin and its regulation by both FS and inhibin. Because activin and FS are produced in many tissues, we chose to focus on a few particular examples with the most extensive experimental support, the pituitary and the developing follicle, although nonreproductive actions of activin and FS are also discussed. At the cellular level, it now seems that activin acts largely as an autocrine and/or paracrine growth factor, similar to other members of the transforming growh factor beta superfamily. As we discuss in the next section, its actions are regulated extracellularly by both inhibin and FS. In the final section, intracellular mediators and modulators of activin signaling are reviewed in detail. Many of these are shared with other transforming growh factor beta superfamily members as well as unrelated molecules, and in a number of cases, their physiological relevance to activin signal propagation remains to be elucidated. Nevertheless, taken together, recent findings suggest that it may be more appropriate to consider a new paradigm for inhibin, activin, and FS in which activin signaling is regulated extracellularly by both inhibin and FS whereas a number of intracellular proteins act to modulate cellular responses to these activin signals. It is therefore the balance between activin and all of its modulators, rather than the actions of any one component, that determines the final biological outcome. As technology and model systems become more sophisticated in the next few years, it should become possible to test this concept directly to more clearly define the role of activin, inhibin, and FS in reproductive physiology.
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Affiliation(s)
- Corrine Welt
- Reproductive Endocrine Unit and Endocrine Unit, Massachusetts General Hospital, Boston 02114, USA
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Baratta M, West LA, Turzillo AM, Nett TM. Activin modulates differential effects of estradiol on synthesis and secretion of follicle-stimulating hormone in ovine pituitary cells. Biol Reprod 2001; 64:714-9. [PMID: 11159377 DOI: 10.1095/biolreprod64.2.714] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In several physiological paradigms, secretion of FSH and LH are not coordinately regulated. Because these hormones appear to be produced by a single cell type in the anterior pituitary gland, their discordant regulation must be related to differential intracellular responses to various stimuli. Estradiol-17beta (estradiol) has been shown to influence secretion of both FSH and LH and some of its effects are mediated directly on the gonadotrope. Changes in expression of intrapituitary factors such as activin and follistatin may mediate effects of estradiol and account for discordant patterns of FSH and LH. The aims of this study were 1) to determine if estradiol alters expression of genes encoding activin, follistatin, or both in ovine pituitary cells; and 2) to observe the effects of immunoneutralizing activin B in vitro on gonadotropin secretion. Pituitary cells from five ewes in the anestrous season were cultured for 24 h with estradiol (0.01 or 1.0 nM). Estradiol reduced basal secretion of FSH in a dose-dependent manner (P: < 0.001) and simultaneously increased basal secretion of LH (P: < 0.001). Decreased secretion of FSH in estradiol-treated cultures was accompanied by suppressed levels of FSHbeta subunit mRNA (P: < 0.001). Amounts of mRNA for activin beta(B) were reduced in a dose-dependent manner by estradiol (27% +/- 4.9% at 0.01 nM, P: < 0.02; and 46% +/- 3.9% at 1.0 nM, P: < 0.002). In contrast, mRNA for follistatin was not affected by treatment with estradiol. Treatment of pituitary cells with an antibody to activin B reduced secretion of FSH by 50% (P: < 0.01) without influencing secretion of LH. These data lead us to conclude that discordant secretion of gonadotropins can be induced by estradiol acting directly at the pituitary level. The inhibitory effect of estradiol on FSH secretion may be mediated indirectly through decreased pituitary expression of the activin gene.
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Affiliation(s)
- M Baratta
- Institute of Veterinary Physiology, University of Parma, 43100 Parma, Italy
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Bohnsack BL, Szabo M, Kilen SM, Tam DH, Schwartz NB. Follistatin suppresses steroid-enhanced follicle-stimulating hormone release in vitro in rats. Biol Reprod 2000; 62:636-41. [PMID: 10684805 DOI: 10.1095/biolreprod62.3.636] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
Previous in vitro and in vivo studies from our laboratory showed that progesterone (P(4)), corticosterone (B), and testosterone (T) increase intracellular content and release of FSH in the anterior pituitary. Activin (Act) and inhibin (Inh) are structurally related proteins with antagonistic actions, as Act stimulates and Inh inhibits FSH secretion from the anterior pituitary. Together with follistatin (FS), a protein that bioneutralizes Act, they form an autocrine-paracrine loop in the anterior pituitary that tightly regulates FSH secretion. The objective of the present study was to test the hypothesis that P(4), B, and T modulate this autocrine-paracrine loop to favor increased FSH secretion. If Act were to mediate steroid-induced FSH release, FS would be expected to block these effects. To test this interaction, cell cultures were prepared from anterior pituitaries of male and female rats, and treated with Act, B, P(4), or T in the absence or presence of FS. Act, B, P(4), and T increased FSH release; FS suppressed both basal and Act- and steroid-stimulated FSH release to approximately 50% below basal levels. Cell cultures from anterior pituitary of female rats were used to compare the interaction of incremental concentrations of FS on dose-related Act- and P(4)-stimulated FSH release. With increasing concentrations of Act, the FS-induced suppression of FSH release was attenuated and eventually abolished; in contrast, maximally stimulatory concentrations of P(4) did not fully overcome the FS-induced suppression of FSH release. The effects of P(4), B, and Act in the presence and absence of estradiol on steady-state mRNA levels of FSHbeta, Actbeta(B), and FS were determined in primary pituitary cell cultures from metestrous female rats by reverse transcription-polymerase chain reaction. Whereas Act, P(4), B increased FSHbeta mRNA levels, only Act raised the level of FS mRNA, and neither steroid increased Actbeta(B) mRNA. The results support the hypothesis that endogenous Act is a common mediator of the action of P(4), B, and T in the rat primary anterior pituitary cell culture. We conclude that the stimulation of FSH release and intracellular content in the gonadotroph by P(4), B, and T is mediated, in part, by Act and involves modulation of a tightly regulated Act/FS autocrine-paracrine loop.
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Affiliation(s)
- B L Bohnsack
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA
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Szabo M, Kilen SM, Nho SJ, Schwartz NB. Progesterone receptor A and B messenger ribonucleic acid levels in the anterior pituitary of rats are regulated by estrogen. Biol Reprod 2000; 62:95-102. [PMID: 10611072 DOI: 10.1095/biolreprod62.1.95] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In target tissues of most mammalian and avian species, progesterone receptors (PR) are expressed as structurally related, but functionally distinct, isoforms A and B, and they are regulated by estrogen (E) as well as by their cognate ligand, progesterone (P(4)). The objectives of the present work were to identify mRNA expression for the A and B isoforms of PR in the anterior pituitary of the rat, to examine its regulation by gonadal steroids, and to compare this regulation with that in the primary target organ, the uterus. Messenger RNAs for the PR isoforms, determined by two separate reverse transcription-polymerase chain reaction protocols, one that detects PR A and PR B equally and the other specific for PR B, were identified in anterior pituitary of female and male rats. In anterior pituitary of cycling female rats, steady-state mRNA levels for both PR A+B and PR B were highest at 0900 h on proestrus, declined rapidly to nadir values at 0900 h on metestrus (PR A+B) or 0900 h on estrus (PR B), and remained below proestrous values through 2100 h on diestrus. Administration of E to intact proestrous female rats caused significant increases in mRNA for both PR A+B and PR B on estrus and metestrus. Blockade of P(4) action by administration of the antiprogestins RU-486 and ZK-98299 on proestrus had no effect on PR mRNA levels on the morning of estrus. Ovariectomy two and ten days after surgery markedly reduced mRNA levels for both PR A+B and PR B. Whereas treatment of 10-day-ovariectomized rats with E led to marked induction of mRNA for PR A+B and PR B two days later, treatment with P(4) one day after treatment had no effect on basal or E-stimulated PR mRNA. Regulation of PR mRNA expression in the pituitary differed from that in the uterus, in which P(4) treatment of ovariectomized rats antagonized the E-induced rise in mRNA for PR B, and antiprogestins increased mRNA for both isoforms. In addition to induction of PR mRNA in the pituitary of female rats by E in vivo, we also demonstrated induction by E in primary culture of anterior pituitary cells in vitro. We conclude that in the anterior pituitary of female rats, both the A and B isoforms of PR are expressed and regulated by E.
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Affiliation(s)
- M Szabo
- Department of Neurobiology and Physiology, Northwestern University, Evanston, Illinois 60208, USA.
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Inhibin and Activin: Their Roles in Ovarian Tumorigenesis and Their Diagnostic Utility in Surgical Pathology Practice. Appl Immunohistochem Mol Morphol 1999. [DOI: 10.1097/00129039-199903000-00008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Inhibin and Activin: Their Roles in Ovarian Tumorigenesis and Their Diagnostic Utility in Surgical Pathology Practice. ACTA ACUST UNITED AC 1999. [DOI: 10.1097/00022744-199903000-00008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Abstract
Follistatin was first described in 1987 as a follicle-stimulating hormone inhibiting substance present in ovarian follicular fluid. We now know that this effect of follistatin is only one of its many properties in a number of reproductive and nonreproductive systems. A majority of these functions are facilitated through the affinity of follistatin for activin, where activin's effects are neutralized through its binding to follistatin. As such, the interplay between follistatin and activin represents a powerful regulatory mechanism that impinges on a variety of cellular processes within the body. In this review we focus on the biochemical characteristics of follistatin and its interaction with activin and discuss the emerging role of these proteins as potent tissue regulators in the gonad, pituitary gland, pregnancy membranes, vasculature, and liver. Consideration is also given to the larger family of proteins that contain follistatin-like modules, in particular with regard to their functional and structural implications.
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Affiliation(s)
- D J Phillips
- Institute of Reproduction and Development, Monash University, Clayton, Victoria, 3168, Australia.
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Wilson ME, Handa RJ. Activin subunit, follistatin, and activin receptor gene expression in the prepubertal female rat pituitary. Biol Reprod 1998; 59:278-83. [PMID: 9687296 DOI: 10.1095/biolreprod59.2.278] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
In the prepubertal female rat, a transient and selective increase in FSH secretion and mRNA expression by the pituitary gland occurs toward the end of the second postnatal week of life. To begin to investigate the possibility that activin may play a role in up-regulating FSH during this time, we have studied the ontogeny of the expression of the activin ss subunits, follistatin, and activin receptor subtypes in the prepubertal female rat pituitary. The levels of expression of ssA, ssB, and follistatin mRNAs were determined in the pituitary gland on postnatal days (PND) 8, 10, 12, 15, and 21 by semiquantitative reverse transcription-polymerase chain reaction. All values were compared to those of adult females killed on diestrus. mRNA levels of subunit ssA were significantly (p < 0.05) elevated on all postnatal days examined; ssB mRNA levels were elevated above adult levels only on PND 10 (p < 0.05). Follistatin mRNA was high on PND 8 (p < 0.05) and then decreased to adult levels. The level and distribution of activin receptor type II subtype mRNAs were determined by in situ hybridization. Activin receptor type II (Act RII) mRNA expression was diffusely expressed throughout all areas of the pituitary. Activin receptor type IIB (Act RIIB), on the other hand, was highly expressed by a subset of anterior pituitary cells. In situ hybridization for activin receptor subtype mRNAs was combined with immunocytochemistry to detect FSH-containing cells. We determined that in the infantile female pituitary, Act RII mRNA was generally not expressed in FSH-immunoreactive cells, while Act RIIB mRNA was expressed in FSH-immunoreactive cells. Act RII mRNA was lower on PND 10 and 15 when compared to PND 21 (p < 0.05), whereas Act RIIB mRNA expression did not change with age. These data suggest that the essential components of the activin regulatory system are present in the infantile female pituitary gland and thus may be involved in the differential regulation of FSH at this time.
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Affiliation(s)
- M E Wilson
- Program in Molecular Biology and Department of Cell Biology, Neurobiology, and Anatomy, Loyola University, Stritch School of Medicine, Maywood, Illinois 60153, USA
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Childs GV, Unabia G. Cytochemical studies of the effects of activin on gonadotropin-releasing hormone (GnRH) binding by pituitary gonadotropes and growth hormone cells. J Histochem Cytochem 1997; 45:1603-10. [PMID: 9389763 DOI: 10.1177/002215549704501203] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Activin stimulates the synthesis and secretion of follicle-stimulating hormone (FSH). It inhibits the synthesis and release of growth hormone (GH). It acts on gonadotropes by stimulating the synthesis of gonadotropin-releasing hormone (GnRH) receptors. To test activin's effects on GnRH target cells, pituitary cells from diestrous or proestrous rats were exposed to media with and without 60 ng/ml activin for 24 hr and stimulated with biotinylated GnRH (Bio-GnRH). The populations were double-labeled for Bio-GnRH and/or luteinizing hormone-beta (LH-beta), FSH-beta, or GH antigens. In both diestrous and proestrous rats, activin stimulated more LH and FSH cells and increased the percentages of GnRH target cells. In diestrous rats, activin stimulated increases in the average area and density of Bio-GnRH label on target cells. In addition, more FSH, LH, and GH cells bound Bio-GnRH. The increment in binding by gonadotropes was not as great as that normally seen from diestrus to proestrus, suggesting that additional factors (such as estradiol) may be needed. These data suggest that activin plays an important role in the augmentation of Bio-GnRH target cells normally seen before ovulation. Its actions on GH cells may reflect a role in the transitory change from a somatotrope to a somatogonadotrope that is seen from diestrus to proestrus.
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Affiliation(s)
- G V Childs
- Department of Anatomy and Neurosciences, University of Texas Medical Branch, Galveston, Texas 77555-1043, USA
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Abstract
Studies have focused on the roles of the gonadotrope subsets defined by cytochemical and morphological tools. The evidence points to groups of gonadotropes that may be stimulated to mature and secrete to support surge activity. We postulate that these gonadotropes stem from the medium-sized subset. Other gonadotropes may more involved with maintenance functions. Perhaps these come from the larger cell pools. Monohormonal gonadotropes may play unique roles, such as FSH secretion early in estrus. Some may be immature, others may be regulatory and play both paracrine or autocrine roles in the pituitary cell population. We also recognize that one of the limitations of the current-day cytochemical techniques is that it does not define the entire gonadotrope population in any given two-label protocol. Nevertheless, based on past cytochemical studies, assumptions are made about the extent to which the cells express both hormones or behave in a uniform manner. These assumptions have led researchers to focus on one subset of the gonadotrope population. In their attempts to simplify the population to be studied, they may have eliminated important regulatory, secretory, or monohormonal gonadotropes from the pool. The approach is valid, as long as they recognize that they are studying a subset of a complex and dynamic population.
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Affiliation(s)
- G V Childs
- University of Texas Medical Branch, Galveston 77555, USA.
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Abstract
OBJECTIVE To review the available information regarding the polypeptide factors inhibin, activin, and follistatin in reproductive physiology. DESIGN The protein structure, tissue expression, regulation, and effects of these factors are outlined, with an emphasis on the reproductive tissues in both females and males. Although some information is only available in animal model systems, human data has been selected whenever possible. CONCLUSIONS Inhibin and activin are closely related peptides with opposing actions, whereas follistatin is a structurally unrelated peptide that may act indirectly through modulation of inhibin-activin effects. These three peptides are secreted in highest levels by the adult gonads; however, they are also present in a wide variety of reproductive and nonreproductive tissues where they are believed to exert local, tissue-specific effects. Within the reproductive system, these peptides play a role in the regulation of gonadotropin biosynthesis and secretion, ovarian and placental steroidogenesis, and oocyte and spermatogonial maturation.
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Affiliation(s)
- L M Halvorson
- Department of Obstetrics and Gynecology, Tufts University School of Medicine, Boston, Massachusetts 02111, USA
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Schwartz NB. The 1994 Stevenson Award Lecture. Follicle-stimulating hormone and luteinizing hormone: a tale of two gonadotropins. Can J Physiol Pharmacol 1995; 73:675-84. [PMID: 7585337 DOI: 10.1139/y95-087] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Although most gonadotropes synthesize both luteinizing hormone and follicle-stimulating hormone, the transcription, content, and secretion rates of the two gonadotropins can be separated. The signals external to the gonadotropic cells that appear to be important in the differential regulation are gonadotropin-releasing hormone pulse frequency (high pulse frequency favors luteinizing hormone), steroid feedback (works on both but induces a more powerful negative feedback on luteinizing hormone), and gonadal peptide feedback (activin increases follicle-stimulating hormone; inhibin and follistatin decrease it). We know very little about the pathways within the gonadotropes that favor one gonadotropin rather than another. It is expected that the cloning of the genes for both gonadotropins and the use of specific cell lines and transfections will lead to elucidation of these pathways.
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Affiliation(s)
- N B Schwartz
- Department of Neurobiology and Physiology, Northwestern University, Evanston, IL 60208-3520, USA
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