Effect of experimental alterations in serum levels of 5 alpha-androstane-3 beta,17 beta-diol on the timing of puberty in the female rat.

It has been suggested that in the rat, 5 alpha-androstane-3 alpha,17 beta-diol (3 alpha-diol) is physiologically involved in restraining the onset of female puberty. To test this hypothesis several experiments were performed. In normal rats, serum levels of 3 alpha-diol decline slightly during the initial phases of puberty and then sharply several hours before the afternoon preovulatory LH surge on the day of first proestrus. Inhibition of 5 alpha-reductase activity with a highly specific inhibitor, 17 beta-N,N-diethylcarbamoyl-4-methyl-4-aza-5 alpha-androstane-3-one (4-MA) strikingly depressed both ovarian content and serum levels of 3 alpha-diol, but failed to advance vaginal opening or first ovulation. Administration of different doses of 3 alpha-diol to juvenile rats via Silastic capsules produced a dose-related increase in serum 3 alpha-diol levels. Titers attained ranged from values similar to those of untreated juvenile rats to levels more than 10-fold higher. None of the concentrations, however, inhibited the LH surge and ovulation induced by pregnant mare serum gonadotropin (PMSG). When a similar treatment was administered to normally maturing rats, only the high dose of 3 alpha-diol delayed the age of vaginal opening and of first ovulation. Serum 3 alpha-diol levels attained with this dose were markedly higher than those of untreated juvenile rats (1,086 +/- 267 vs. 124 +/- 14 pg/ml, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)