Functional participation in endocrine system : activin-follistsatin interaction

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The localization ob betaA subunit of inhibin/activin in rat testis was studied by means of immunohistochemistry using antibody raised against synthetic polypeptides. The intense reaction with and-betaA antibody was shown in the cytoplasm but not in the nucleus and the plasma membrane of late pachytene spermatocytes. The reaction was also found in the cytoplasm of spermatids, although the immunostaining pattern was different between the two cells ; the granule-like one in spermatocytes and diffused one in spermatids, respectively. Furthermore, the plasma membrane became positive in spermatids, suggesting that betaA subunit may be produced in spermatocytes phase and secreted from spermatids phase. These results suggest that inhibin or activin may have a significant role in spermatogenesis.Cyclic changes in follistatin localization and the role of primary gonadotropin surges in regulating follistatin expression were studied in rat ovary. Immunoreactive follistatin was detected in the gran … More ulosa cells of secondary to mature follicles by immunohistochemistry using polyclonal antibodies raised against synthetic peptides of human follistatin. Granule-like reactions with Anti-follistatin (123-134) in the granulosa cells of mature follicles drastically decreased their intensity on the evening of proestrus. The blockade of primary gonadotropin surges by injection of pentobarbitone (40 mg/kg) at 1330h on proestrus, resulted in sustaining the follistatin granules in mature follicles at 2300h on proestrus. The sustainment of follistatin was broken down by injection of exogenous LH (20 mug) or FSH (10 mug) to pentobarbitone-treated animals at 1530h on proestrus. These results indicate that expression of follistatin in preovulatory follicles is suppressed by primary gonadotropin surge on proestrus. These drastic changes in follistatin in the preovulatory follicles suggest that follistatin plays a significant role in some physiological phenomena such as cumulus expansion and germinal vesicle break down prior to ovulation.We first detected the mRNA expression of follistatin and three subunits of inhibin/activin in rat pancreatic islets by RT-PCR.Immunohistochemistry using anti-follistatin serum revealed that follistatin was localized only in insulin producing B cells. Although the betaA subunit was detectable in the islets, the immunostainable cell type were completely different with two betaA antisera, i.e.anti-betaA (1-10)-Tyr stained B cells, while anti-betaA (87-99) stained glucagon producing A cells. This inconsistent immunoreactivity was probably related to follistatin binding to subunits of inhibin/activin. This study indicates that follistatin and inhibin/activin in the islet serve as paracrine or autocrine modulators in the endocrine pancreas. Less