Immature female rats treated with superovulatory doses of pregnant mare serum gonadotropin (PMSG) were used to study the effects of the antiandrogen hydroxyflutamide on steroid production, particularly the biologically active androgens, in two experiments. In the first experiment, animals were given either 5 mg hydroxyflutamide or vehicle alone at 30 and 36 h following 40 IU PMSG. Compared with the vehicle group, hydroxyflutamide treatment significantly reduced the percentage of degenerate oocytes recovered from oviducts (p < 0.05). Serum levels of testosterone and androstenedione, and their aromatized product 17β-estradiol, significantly decreased (p < 0.05) in the hydroxyflutamide-treated group; however, nonaromatizable androgen, 5α-dihydrotestosterone, was not affected. In the second experiment, ovaries obtained 48 h after stimulation with 4 or 40 IU PMSG were incubated with and without hydroxyflutamide (10−5 M) and (or) testosterone (10−7 M) to study [4-14C]pregnenolone metabolism to major steroids. In 40 IU stimulated ovaries, hydroxyflutamide significantly decreased the metabolism of pregnenolone to progesterone (p < 0.01) and androstenedione (p < 0.01), while the production of 17β-estradiol increased significantly (p < 0.05); however, pregnenolone conversions to testosterone and 5α-dihydrotestosterone were not affected. Testosterone completely reversed the hydroxyflutamide-induced alteration of pregnenolone metabolism. In contrast, there was no difference in the pregnenolone conversion patterns between untreated and hydroxyflutamide or hydroxyflutamide plus testosterone groups in 4 IU stimulated ovaries. Present results confirm our previous finding that hydroxyflutamide decreases the percentage of abnormal oocytes recovered from superovulating rats and indicates that this hydroxyflutamide effect may be partly mediated by altered ovarian steroidogenesis following inhibition of androgen binding in the ovary.Key words: superovulation, pregnant mare serum gonadotropin, antiandrogen, hydroxyflutamide, androgen.
ANTERIOR PITUITARY OVULATING CAPACITY IN THE PMSG-PRIMED IMMATURE FEMALE RAT