EFFECTS OF 19-HYDROXYLATED ANDROGENS ON SEXUAL DIFFERENTIATION IN THE NEONATAL FEMALE RAT

Administration of testosterone to newborn female rats suppresses cyclic gonadotrophin secre-tion and sexual receptivity in adulthood (Barraclough, 1961). This effect probably depends upon the conversion of testosterone to oestrogen in the brain (Reddy, Naftolin & Ryan, 1974; Doughty, Booth, McDonald & Parrott, 1975). Hydroxylation of the androgen molecule at carbon-19 is the initial step in aromatization (Gual, Morato, Hayano, Gut & Dorfman, 1962), and injecting 19-hydroxytestosterone (17\g=b\-hydroxy-4-androsten-19-ol-3-one;19HT) into neonatal female rats prevents cyclic ovulation in adulthood (McDonald & Doughty, 1974). On the other hand, 5\g=a\-reduction of testosterone blocks conversion to oestrogen as the product, dihydrotestosterone (17\g=b\-hydroxy-5\g=a\-androstan-3-one;DHT), cannot be aromatized. Since DHT does not affect sexual differentiation of the brain (McDonald & Doughty, 1974), the non-aromatizable 5\g=a\-reduced form of 19HT (17\g=b\-hydroxy-5\g=a\-androstan-19-ol-3-one;5\g=a\-19HT) should similarly be ineffective. This study compares the defeminization induced in female rats treated neonatally with testosterone, 19HT or 5\g=a\-19HT. Female litter-mates from Sprague-Dawley (M.R.C.) mothers were assigned to one of four groups, and received daily s.c. injections in 01 ml corn oil from the day of birth (day 1) t