Inhibitory mechanisms of lead on steroidogenesis in MA-10 mouse Leydig tumor cells.

Lead can directly influence Leydig cell steroidogenesis, which results in reduction of testosterone and causes low sperm counts in human beings and animals. This study investigated the effect of 6 h incubation time of lead on steroidogenesis in MA-10 mouse Leydig tumor cells. Lead acetate, ranging from 10(-8) to 10(-5) M, caused profounder inhibitory effects on human chorionic gonadotropin (hCG)- and dibutyryl cAMP (dbcAMP)-stimulated progesterone production for 6 h in MA-10 mouse Leydig tumor cells. Lead acetate significantly inhibited hCG- and dbcAMP-stimulated progesterone production from 20 to 35% in MA-10 cells at 6 h. Lead suppressed the expression of steroidogenesis acute regulatory (StAR) protein from 30 to 55%. Moreover, the activities P450 side-chain cleavage (P450scc) enzyme and 3beta-hydroxysteroid dehydrogenase (3beta-HSD) were reduced by lead from 15 to 25%. Thus, after 6 h exposure to lead caused profounder inhibitory effects on StAR protein expression and steroidogenic enzymes and then progesterone production compared to 2- or 3-h lead treatments in MA-10 mouse Leydig tumor cells.