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

Abstract

The present studies examined the effects of acidic fibroblast growth factor (aFGF) on 5-ene-3β-hydroxysteroid dehydrogenase-isomerase (3β-HSD) and 5α-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 3β-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 μg/ml insulin or 100 ng/ml insulin-like growth factor-I. Increasing aFGF concentrations (0.1–10 ng/ml) also inhibited hCG-stimulated 5α-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 3β-HSD and 5α-reductase activities and [ 125I]hCG binding to LH receptors, although, generally, higher aFGF concentrations were required to elicit maximal inhibitive effects. However, aFGF differed from the actions of bFGF on 3β-HSD activity and LH receptor levels in that a secondary increase with higher growth factor concentrations was not observed.