Inhibition of testosterone biosynthesis by ethanol: relation to the pregnenolone‐to‐testosterone pathway

The concentrations of metabolites in the pregnenolone → testosterone pathway were determined in freezestopped testes in control rats and during ethanol intoxication (2 h after injection of 1.5 body wt). Ethanol lowered the mean testicular concentrations of testosterone (by 63–74%), androstenedione (49–81%), 17-hydroxyprogesterone (60–76%), progesterone (29–67%) and pregnenolone (12–25%). 4-Methylpyrazole had no effect on the ethanol-induced changes. The present results reveal no inhibition at the 17-hydroxyprogesterone → androstenedione → testosterone steps, but do not exclude inhibition before the step yielding pregnenolone and at the pregnenolone → progesterone → 17-hydroxyprogesterone steps.