Gonadotropic Control of Secretion of Dimeric Inhibins and Activin A by Human Granulosa–Luteal Cells In Vitro

Oxford Brookes University, Oxford, England, United Kingdom
Journal of Assisted Reproduction and Genetics (Impact Factor: 1.72). 12/1997; 14(10):566-74. DOI: 10.1023/A:1022524516824
Source: PubMed


It is well established that human granulosa cells and luteal cells express inhibin/activin subunit protein and secrete immunoreactive inhibin. The gonadotropic control of secretion of different molecular forms of inhibin and activin A by granulosa-luteal cells (G-LCs) was investigated using recently developed specific enzyme immunoassays (EIAs).
Granulosa-luteal cells obtained at IVF egg pickup were cultured in a serum-free medium at 37 degrees C in a water-saturated incubator with 5% CO2 for up to 5 days. Experiments with varying concentrations of human FSH, hLH, and hCG were carried out.
FSH raised the secretion of inhibin A and pro-alpha C-containing inhibins after 24 and 48 hr in culture. Inhibin B was raised after 24 hr and activin A was raised after 48 hr of FSH treatment. LH treatment for 24 hr stimulated inhibin A, inhibin B, pro-alpha C, and activin A. hCG stimulated G-LC secretion of inhibin A after 48 hr and pro-alpha C after 24 hr. Paradoxically, inhibin B secretion was inhibited by 1 and 10 ng/ml hCG after 48 hr. Activin A was stimulated by hCG after 24 and 48 hr of incubation. G-LC secretion of estradiol and progesterone was also stimulated significantly by LH and hCG.
Secretion of dimeric inhibins and activin A is controlled differentially by gonadotropins.

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Available from: William L Ledger, Jul 03, 2014
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    • "The effect of hCG in luteinised granulosa cells is to continue to remove activin action and this occurs at three levels: the synthesis of inhibin A, the increase in its receptor and the synthesis of the activin-binding protein follistatin. In corpora lutea and luteal cells in vitro (Illingworth et al. 1996, Muttukrishna et al. 1997) and in cultured luteinised granulosa cells (Myers et al. 2007a), hCG increases inhibin A expression. We have shown that hCG upregulated the a subunit and that activin A itself can inhibit this response. "
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    ABSTRACT: The transition of the dominant follicle into the corpus luteum is of fundamental reproductive importance. Luteinisation involves disparate changes in the gene expression of follicular granulosa cells that differentiate into the granulosa-lutein cells of the corpus luteum after the gonadotrophin surge. We have shown that activin and human chorionic gonadotropin (hCG) have opposing effects during luteolysis. Therefore, we hypothesised that activin A was an inhibitor of luteinisation that was blocked during the pre-ovulatory gonadotrophin surge. Ovarian tissue and cells were collected from women with regular cycles having hysterectomy and women undergoing oocyte retrieval for assisted conception. Genes that changes during luteinisation were investigated in primary cultures of luteinised granulosa cells exposed to activin A and hCG in vitro. hCG promotes a luteinised granulosa cell phenotype, while activin A promotes a more follicular phenotype in luteinised cells by upregulating granulosa cells markers such as FSHR, HSD11B2 and downregulating LHCGR. In addition, activin A blocked hCG upregulation of STAR, HSD3B1 and HSD11B1 and downregulation of oestrogen receptor alpha. Activin A antagonised hCG effects in a dose-dependent manner and could block the hCG-stimulated molecular inhibitors of activin action (inhibin alpha-subunit, follistatin and TGFBR3). These studies show that hCG and activin A have opposing effects on luteinised granulosa cells and some effects of activin are seen only in the presence of hCG. While hCG can inhibit activin action in granulosa cells to facilitate luteinisation, activin A can promote an unluteinised phenotype in luteinised granulosa cells. This confirms the importance of adequate activin withdrawal during luteinisation in women.
    Full-text · Article · Sep 2008 · Journal of Endocrinology
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    • "Increased inhibin B secretion can be explained by the activin A-induced B-subunit gene expression reported previously (Erämaa et al. 1995). Activin A is produced by human granulosa-luteal cells (Muttukrishna et al. 1997) enabling it to have a physiological autocrine/paracrine role in the regulation of ovarian inhibin production. In our experiments activin A did not increase inhibin A secretion, which is in contrast to rat granulosa cell data (Lanuza et al. 1999), but fits well with the human mRNA data showing no induction of -or A-subunit gene expression during activin treatment (Erämaa et al. 1995). "
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    ABSTRACT: Inhibins are gonadal glycoproteins with endocrine effects on pituitary FSH secretion and para/autocrine effects on ovarian and testicular function. The purpose of this study was to investigate the endocrine and para/autocrine regulation of inhibin A and inhibin B secretion in human ovarian granulosa-luteal cells. The cells were obtained from women undergoing in vitro fertilization, and the primary cultures were treated with FSH, LH, human chorionic gonadotropin (hCG), activin A, 8-bromo cyclic AMP (8-BrcAMP), staurosporine (a protein kinase C inhibitor) and an antagonist of IGF action (type-1 IGF receptor antibody alpha IR3). The secretion of inhibins was measured by ELISA assays capable of reliably distinguishing between inhibin A and B. FSH, LH, hCG and 8-BrcAMP increased inhibin A secretion on average up to 180% (P<0.01), 192% (P<0.05), 210% (P<0.01) and 243% (P<0.01) respectively of the control level, while their stimulatory effect on inhibin B secretion was less pronounced (up to 167%, P<0.01; 139%, P<0.05; 127%, P>0.05; 133%, P>0.05 of the controls respectively). alpha IR3 decreased inhibin A and B secretion down to 70% (P<0.01) and 50% (P<0.01) respectively of the control. Staurosporine decreased inhibin B secretion down to 49% (P<0.01) of the control; its effect on inhibin A secretion was not significant. Activin A increased inhibin B secretion up to fourfold of the control (P<0.05) while its effect on inhibin A secretion was insignificant. We conclude that gonadotropins via the protein kinase A signal transduction pathway are the main positive regulators of inhibin A and B secretion in human granulosa-luteal cells. The protein kinase C signal transduction pathway seems to be important especially for inhibin B secretion. Locally produced IGFs are probably important inducers of the production of both forms of inhibin in human ovaries while activins seem to upregulate inhibin B secretion.
    Preview · Article · Dec 2000 · Journal of Endocrinology
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    • "Gonadotropin-and protein kinase C-dependent regulation of the expression of inhibin and A subunit genes has previously been described in ovarian granulosa cells at mRNA level (Erämaa et al. 1994, Tuuri et al. 1996) but information about the inhibin peptide secretion by these cells is scant (Muttukrishna et al. 1997). The aim of the present work was to shed more light on the endocrine (FSH, luteinizing hormone (LH), human chorionic gonadotropin (hCG)) and local (activins, insulin-like growth factor (IGF) system) regulation of inhibin A and B secretion in human ovaries by using cultured granulosaluteal cells with highly sensitive and specific inhibin assays. "

    Preview · Article · Nov 2000 · Journal of Endocrinology
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