EFFECTS OF EXOGENOUS TESTOSTERONE ON OVARIAN WEIGHT, FOLLICULAR MORPHOLOGY AND INTRAOVARIAN PROGESTERONE CONCENTRATION IN ESTROGEN-PRIMED HYPOPHYSECTOMIZED IMMATURE FEMALE RATS

Experiments were designed to examine the effects of exogenous testosterone on preantral follicles in the ovaries of estrogen-primed, hypophysectomized immature, female rats (HIFR). Parameters examined included ovarian weight, follicular morphology and intraovarian progesterone concentrations. Results show dose- and time-related decrements in ovarian weight and stimulation of follicular atresia during 4 days of treatment with testosterone at doses between 1 μg and 1 mg/day. The relationship between ovarian weight and logarithmic increments in the daily dose of testosterone was shown to be completely linear (correlation coefficient = 0.999, P<0.001). A similar relationship prevailed between ovarian weight and duration of testosterone treatment (1 mg/day) (correlation coefficient = 0.998, P<0.005). Ovarian weight reduction was directly related to concomitant stimulation of follicular atresia and was apparent within 24-48 h of initiating treatment with testosterone (1 mg). The effects of androgen on estrogen-primed ovaries were quantitatively and qualitatively reproduced by withdrawal of estrogen (in the absence of androgen) suggesting an antiestrogenic action of testosterone. Follicular atresia induced by testosterone or by withdrawal of estrogen was associated with a striking degree of thecal hypertrophy and evidence for the contribution of the atretic follicles to the ovarian interstitial tissue was adduced. Since intraovarian concentrations of progesterone were not altered by treatment with exogenous testosterone, it is concluded that the atretic action of androgen represents its primary action on estrogen-stimulated preantral follicles in the absence of gonadotropic support.