Activin-Induced Inhibin α-Subunit Production by Rat Granulosa Cells Requires Endogenous Insulin-Like Growth Factor-I1

Inhibin-α subunit (Inh-α) gene expression is important for granulosa cell (GC) differentiation and prevention of ovarian tumorigenesis. Studies on Inh-α regulation have implicated activin and insulin-like growth factor-I (IGF-I) in the mechanisms of expression. Here we present evidence that endogenously produced IGF-I plays an obligatory role in activin-induced Inh-α production. Primary cultures of rat GC were incubated with increasing...