Effects of ascorbic acid on in vitro steroidogenesis in guinea pigs.

Guinea pig ovarian whole tissue homogenates were incubated with [14C]-labelled cholesterol, pregnenolone, and progesterone. Testicular homogenates were incubated with [14C]-progesterone. All incubations were carried out in the presence of 0, 0.5, 1.0, or 2.0 mM ascorbic acid. The conversion of cholesterol to pregnenolone was significantly decreased in testosterone and progesterone production. The addition of 0.5 mM ascorbic acid increased the conversion of pregnenolone to delta 4 steroids and decreased its conversion to delta 5 steroids, relative to the other ascorbic acid treatments. The conversion of progesterone to 17 A-hydroxyprogesterone was significantly decreased in the presence of 1.5 mM ascorbic acid over the O mM treatment. The data supports a general inhibitory effect of high ascorbic acid on the steroid hydroxylations, and a possible regulatory role of ascorbic acid on the conversion of pregnenolone to delta 4 and delta 5 steroids.