INVITRO MODULATION OF PORCINE LEYDIG-CELL STEROIDOGENESIS BY PHORBOL-12-MYRISTATE-13-ACETATE AND 1,2-DIOCTANOYLGLYCEROL

Serum-free primary cultures of neonatal (1-day-old) porcine Leydig cells were used to study the effects of phorbol-12-myristate-13-acetate and 1,2-dioctanoylglycerol on testosterone and pregnenolone production. Phorbol-12-myristate-13-acetate alone from 0.001-10 μmol/l stimulated testosterone and pregnenolone production, whereas 1,2-dioctanoylglycerol alone had no effect on steroid production, relative to control. Phorbol-12-myristate-13-acetate and 1,2-dioctanoylglycerol each inhibited pLH-stimulated testosterone and pregnenolone production. To further clarify the influence of these protein kinase C activators on steroidogenesis, cultured Leydig cells were treated with either phorbol-12-myristate-13-acetate or 1,2-dioctanoylglycerol plus forskolin (an adenylate cyclase activator). Both phorbol-12-myristate-13-acetate and 1,2-dioctanoylglycerol inhibited forskolin-stimulated testosterone production. Phorbol-12-myristate-13-acetate had no effect on forskolin-stimulated pregnenolone production and only the highest concentration of 1,2-dioctanoylglycerol (100 μmol/l) inhibited forskolin-stimulated production of pregnenolone. These data demonstrate that porcine Leydig cell steroidogenesis can be modulated by interactions of the protein kinase C and protein kinase A second messenger systems.