Fibroblast growth factor inhibits 5 alpha-reductase activity in cultured immature Leydig cells

The present studies examined the effects of basic fibroblast growth factor (bFGF) on 5 alpha-reductase activity of cultured Leydig cells from immature rats. Basic FGF inhibited both hCG- and 8-bromo-cyclic AMP-stimulated 5 alpha-reductase activity in a dose-dependent manner; however, it had little or no effect on basal enzyme activity. Inhibition was achieved with as little as 0.1 ng/ml bFGF, and maximal inhibition was observed with 10 ng/ml bFGF. These studies suggest that locally produced bFGF may play a role in modulating the age-dependent decline in 5 alpha-reductase activity in Leydig cells.