Inhibin and activin in human fetal membranes: evidence for a local effect on prostaglandin release

Trophoblast and fetal membranes (amnion and chorion) are the tissues forming the anatomical/functional interface between the mother and the fetus. The aim of the present study was to evaluate the presence and a possible effect of inhibin and activin in human amnion and chorion. The expression of inhibin/activin alpha, beta A, and beta B subunit messenger RNA (mRNA) and the localization of immunoreactive material were evaluated in amnion and chorion collected at term pregnancy by a Northern blot analysis and by immunohistochemistry. Amnion cells expressed the mRNA of the three inhibin/activin subunits, with the beta B message the most abundantly expressed. The epithelial layer of the amnion showed an intense fluorescent staining of beta B inhibin/activin subunit, and positive signals were also observed for the alpha and beta A subunits. Inhibin/activin alpha and beta A subunit mRNAs were found highly expressed in chorion. The cytotrophoblast of the chorion showed a positive staining for the three inhibin/activin subunit antisera. The addition of activin A increased the release of prostaglandin E2 from human amnion-derived cultured cells. The effect was dose and time dependent. Inhibin A did not induce significant changes of prostaglandin E2 release from amnion cells. The present results show that amnion and chorion produce inhibin and activin subunits and that activin stimulates the release of prostaglandin E2 from cultured amnion cells, suggesting a possible role of inhibin and activin in fetal membranes.