Basic fibroblast growth factor inhibits delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity in cultured immature Leydig cells.

Basic fibroblast growth factor inhibited basal delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity in cultured Leydig cells from immature rats in a concentration- and time-dependent manner. Maximal inhibition was achieved with 5-10 ng/ml basic fibroblast growth factor following approximately 48 h of exposure. The inhibition of basal delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity was not altered by human chorionic gonadotropin; however, cycloheximide (0.5-2.0 micrograms/ml) partially reversed the effects of basic fibroblast growth factor in a dose-dependent manner. These studies suggest that locally-produced basic fibroblast growth factor may modulate Leydig cell testosterone formation by regulating delta 5-3 beta-hydroxysteroid dehydrogenase-isomerase activity.