Inhibition of hormonal-induced cAMP and steroid production by inhibitors of pregnenolone metabolism in adrenal and Leydig cells.

ABSTRACT

The effects of inhibitors of pregnenolone metabolism, WIN-24540 and spironolactone, on adrenocorticotropic hormone (ACTH)- and human chorionic gonadotropin (hCG)-induced cAMP and steroid production by bovine (BAC) and ovine (OAC) adrenal cells and pig Leydig cells (PLC) were investigated. The inhibitors reduced cAMP production by adrenal and Leydig cells by about 75% and 60%, respectively (P less than 0.001). Further, the inhibitors also reduced the cholera toxin- and forskolin-induced cAMP production by pig Leydig cells. In the presence of the inhibitors, corticosterone and testosterone production by BAC and PLC, respectively, following hormonal stimulation was reduced by more than 90%. However, pregnenolone production by BAC and PLC under these conditions represented only 12% and 42% of the corticosterone and testosterone production, respectively, in the absence of inhibitors. Moreover, the inhibitors also reduced the steroidogenic response of PLC to 8-Br-cAMP and the conversion of 22(R)-hydroxycholesterol to pregnenolone by BAC and PLC. The reduced production of pregnenolone in the presence of inhibitors was in part due to the weak inhibition of 17 alpha-hydroxylase by spironolactone. However, when OAC cells were incubated in the presence of WIN-24540 and SU-10603, a potent 17 alpha-hydroxylase inhibitor, the amount of pregnenolone produced in response to ACTH or 22(R)-hydroxycholesterol was only 10% and 19%, respectively, of the steroids (corticosterone plus cortisol) secreted in the absence of inhibitors. The results show that the inhibitors of pregnenolone metabolism reduced, in both adrenal and Leydig cells, the response of adenylate cyclase to several effectors and the activity of the cholesterol side-chain cleavage.(ABSTRACT TRUNCATED AT 250 WORDS)