The possible role of protein kinase C and phospholipids in the regulation of steroid production in rat Leydig cells

Abstract

We have studied the possible involvement of the activation of calcium-dependent phospholipid-activated protein kinase (PK-C) in the stimulatory action of LHRH on Leydig cells, using 4β-phorbol-12-myristate-13-acetate (PMA) and phospholipase C (PL-C). LHRH agonist (LHRH-A) and PL-C had a large synergistic effect on LH-stimulated steroid production, whereas PMA inhibited the effect of LH. However, PMA always caused an increase in steroid production stimulated by various doses of dibutyryl cAMP. LH and PMA stimulated the phosphorylation of 17 and 33 kDa proteins, whereas LHRH-A and PL-C had no effect. Of all effectors used, LH had the most pronounced effect on the synthesis of 14, 27 and 30 kDa proteins. The present results suggest that the mechanisms of action of LHRH-A and PL-C on steroid production in Leydig cells may be similar and different from PMA, and may involve stimulation of a specific type of PK-C or hydrolysis of a specific pool of phospholipids.