Effects of acidic fibroblast growth factor on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase and 5 alpha-reductase activities and [125I]human chorionic gonadotrophin binding in cultured immature Leydig cells.

The present studies examined the effects of acidic fibroblast growth factor (aFGF) on 5-ene-3 beta-hydroxysteroid dehydrogenase-isomerase (3 beta-HSD) and 5 alpha-reductase activities and [125I]human chorionic gonadotrophin ([125I]hCG) binding in cultured immature rat Leydig cells. Increasing concentrations of aFGF (0.1-20 ng/ml) progressively decreased basal 3 beta-HSD activity from 0.474 +/- 0.0335 to 0.093 +/- 0.0004 nmol progesterone/30 min/10(5) cells. This inhibition by aFGF (10 ng/ml) was partially reversed by 1 micrograms/ml insulin or 100 ng/ml insulin-like growth factor-I. Increasing aFGF concentrations (0.1-10 ng/ml) also inhibited hCG-stimulated 5 alpha-reductase activity in a dose-dependent manner, but had only a modest effect on basal enzyme activity. Increasing aFGF (0.1-200 ng/ml) also progressively inhibited [125I]hCG binding in cultured immature Leydig cells. These studies demonstrate a similarity in the inhibitive effects of aFGF with bFGF effects on 3 beta-HSD and 5 alpha-reductase activities and [125I]hCG binding to LH receptors, although, generally, higher aFGF concentrations were required to elicit maximal inhibitive effects. However, a FGF differed from the actions of bFGF on 3 beta-HSD activity and LH receptor levels in that a secondary increase with higher growth factor concentrations was not observed.