The physiological role of intraovarian activin (beta/beta) and inhibin (alpha/beta) dimers in humans in unclear. The identification of follistatin as a beta-subunit-specific high affinity binding protein has added complexities for the interpretation of in vitro studies concerning the functionalities of these ovarian peptides. We, therefore, have attempted to define in vivo compartmental distributions of gene expression and protein localization for inhibin and activin subunits (alpha, beta A, and beta B) concurrent with follistatin in ovarian follicles and corpus lutea obtained from a large number of human ovaries. In situ hybridization and immunohistochemistry were used for detecting the expression of genes encoding inhibin/activin subunits and follistatin and their gene products, the proteins. Granulosa cells of small antral follicles (1-8 mm) were found to express mRNA for alpha-, beta A-, and beta B-subunits as well as follistatin, and the strongest signals were localized in the cumulus granulosa cells. In the thecal cell layer, only alpha-subunit mRNA was detected. Proteins were localized in cellular compartments corresponding to their mRNA, but in addition, proteins for beta A-subunit and follistatin were detected in the thecal cell layers in the absence of gene expression, an observation compatible with a paracrine action. Thus, granulosa cells of the small antral follicle have the potential to form all dimers of inhibin and activin, and their autocrine and paracrine actions may be modulated by follistatin in both granulosa cell and thecal cell layers. With the development of a dominant follicle, remarkable switches in subunit gene expressions occurred; beta B-subunit mRNA was no longer detectable in any cell type, and beta A-subunit expression emerged in the thecal cells along with continued abundant expression of beta A-subunit and follistatin in the granulosa cells. Proteins were found only in granulosa cells corresponding to their mRNAs. In the corpus luteum, the inhibin/activin alpha- and beta A-subunits and follistatin mRNA and proteins were expressed exclusively in the luteinized granulosa cells. Luteinized thecal cells were devoid of detectable mRNA message or proteins. Thus, the inhibin-activin-follistatin system in the corpus luteum appears to function in an autocrine fashion.(ABSTRACT TRUNCATED AT 400 WORDS)

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To discern the potential role of the insulin-like growth factors (IGFs) in polycystic ovary syndrome (PCOS), we examined the expression of the genes encoding the IGFs, IGF receptors (IGFr), insulin receptor (Ir), and IGF-binding proteins (IGFBPs-1-6) as well as the localization of the gene products in specific cellular compartments of normal and PCOS human ovaries. Messenger ribonucleic acid (mRNA) was localized by in situ hybridization with specific 35S-labeled human antisense RNA probes, and protein was detected by immunohistochemistry using specific antisera. Thecal cells, but not granulosa cells (GC), of small antral follicles (3-6 mm) from PCOS ovaries expressed both IGF-I and IGF-II transcripts. Abundant IGF-Ir mRNA was found only in GC, IGF-IIr mRNA was found in both granulosa and thecal cells, and Ir mRNA was detected in all cell types, including granulosa, thecal, and stromal cells. Localization of the gene products revealed no IGF-I immunoreactivity; however, immunostaining for each of the other gene products was colocalized with its corresponding mRNA. The cellular distribution of mRNA and protein in PCOS follicles was indistinguishable from that observed in small antral follicles from normal ovaries. In dominant follicles, however, IGF-I mRNA was no longer detectable, but abundant IGF-II mRNA was expressed exclusively in GC. Although IGF-Ir mRNA was expressed in GC, IGF-IIr mRNA was found in both granulosa and thecal cells. In follicles taken from PCOS ovaries, no IGFBP-1 mRNA was detected, IGFBP-2 mRNA was abundant in both granulosa and thecal cells, moderate IGFBP-3 mRNA was found only in thecal cells, IGFBP-4 and -5 mRNAs were present in all cellular compartments, and IGFBP-6 mRNA was not detected. Localization of the gene products by immunostaining revealed that each protein colocalized with its corresponding mRNA. The cellular distribution of IGFBP mRNA and protein in PCOS follicles was also indistinguishable from that in small antral follicles of normal ovaries, but remarkable differences were found in dominant follicles, where abundant IGFBP-1 mRNA was seen exclusively in GC, IGFBP-2 mRNA in thecal cells, and IGFBP-3 mRNA in both granulosa and thecal cells. Moderate expression of the IGFBP-4 and IGFBP-5 genes was seen in all cell types, including stromal cells, but no IGFBP-6 mRNA was detected. Again, each of the gene products colocalized with its corresponding mRNA. We conclude the following.(ABSTRACT TRUNCATED AT 400 WORDS)

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Insulin resistance is a predominant feature in women with polycystic ovarian syndrome (PCO). The cellular mechanisms for this insulin resistance have not been defined. In this study, major steps in the insulin action cascade, receptor binding, kinase activity, and glucose transport activity were evaluated in isolated adipocytes prepared from PCO subjects (n = 8) without acanthosis nigricans and in a group of age and weight-matched controls [normal cycling (NC) n = 8]. The PCO group was hyperinsulinemic and displayed elevated insulin responses to an iv glucose load. The binding of 125I-insulin to adipocytes was similar in cells from PCO and NC subjects. In PCO, autophosphorylation of the insulin receptor-subunit in the absence of insulin was normal but a significant decrease (30% below control) in maximal insulin stimulated autophosphorylation was observed. However, receptor kinase activity measured against the exogenous substrate poly glu:tyr (4:1) was normal. Cells from PCO subjects transported glucose at the same rate, in both the absence and presence of a maximal insulin concentration, as those from NC subjects. Strikingly, there was a large rightward shift in the insulin dose-response curve for transport stimulation in PCO cells (EC50 = 87 +/- 14 pmol in NC vs. 757 +/- 138 in PCO, P less than 0.0005); 8-fold greater insulin concentrations were required to attain comparable glucose transport rates in cells from PCO against NC. In conclusion, our results suggest that insulin resistance in PCO, as assessed in the adipocyte, is accompanied by normal function of insulin receptors, but involves a novel postreceptor defect in the insulin signal transduction chain between the receptor kinase and glucose transport.