Platelet derived growth factor inhibits 5 alpha-reductase and delta 5-3 beta-hydroxysteroid dehydrogenase activities in cultured immature Leydig cells.

Platelet derived growth factor inhibited both hCG- and 8-Br-cAMP-stimulated 5 alpha-reductase activity in cultured immature Leydig cells in a dose-dependent manner, while not significantly inhibiting basal enzyme activity. Platelet derived growth factor also inhibited basal delta 5-3 beta-hydroxysteroid dehydrogenase activity and hCG-stimulated testosterone formation. Maximal inhibitions were achieved with 10 ng/ml of platelet derived growth factor. These studies suggest that platelet derived growth factor should be included among the variety of locally produced regulatory factors which modulate Leydig cell function.