Human recombinant activin-A inhibits proliferation of human fetal adrenal cells in vitro.

Activins and inhibins are dimeric peptides which are structurally and functionally related to transforming growth factor-beta (TGF-beta). The mRNA for the activin and inhibin subunits is expressed in the adrenal gland. Because members of the TGF-beta superfamily have effects on mitogenesis, we examined the effect of recombinant human activin-A (rh-activin-A) on proliferation of midgestation human fetal adrenal cells in vitro. Dose-dependent growth inhibition by rh-activin-A was obtained, with an ED50 of 1 ng/ml. Rh-activin-A inhibited basal and epidermal growth factor (EGF)-stimulated fetal zone cell proliferation, but did not alter basic fibroblast growth factor (bFGF)-stimulated growth. TGF-beta combined with rh-activin-A demonstrated additive inhibition of fetal adrenal growth. These findings suggest a potential autocrine or paracrine role for activin-A in modulating the growth and/or subsequent involution of the human fetal adrenal gland.