Changes in serum concentration and ovarian content of 5 alpha-androstane-3 alpha,17 beta-diol in the female rat approaching first ovulation.

Concentrations of 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) in serum were estimated in rats bled once during a 10-day period preceding first ovulation; ovarian contents of 3 alpha-diol were estimated over the same period. Serum values of 3 alpha-diol, measured at 1100 h, showed a significant decrease towards first ovulation; there was good correlation (r = 0.78; n = 10) between mean serum and ovarian concentrations. In 33-day-old rats no significant difference was found in serum concentrations measured at either 1100 or at 1500 h. However at first proestrus, significantly elevated serum and ovarian concentrations of 3 alpha-diol were found between 1400 and 2100 h as compared to those at 1100 h. A similar pattern was seen on the afternoon of second proestrus. On the days following first ovulation, serum and ovarian concentrations of 3 alpha-diol were comparable to those during the days preceding this ovulation. The prepubertal decrease in 3 alpha-diol production is discussed in relation to concomitant changes in secretion of estradiol and luteinizing hormone. It is concluded that, in view of the preovulatory resynthesis of considerable amounts of 3 alpha-diol, it is inappropriate to view loss of biosynthetic capacity for 3 alpha-diol as a key event in the onset of puberty.