UNILATERAL OVARIECTOMY, FLUTAMIDE TREATMENT AND HCG REVERSE THE ANOVULATORY ACTION OF ANTIPROGESTERONE RU486 IN RAT

Administration of antiprogesterone RU486 (4 mg/day) from estrus throug h proestrus to cyclic rats blocked ovulation. Moreover, RU486 increase d basal serum concentrations of LH, PRL, testosterone and estradiol, w hile it decreased basal serum concentration of FSH. Both unilateral ov ariectomy and antiandrogen flutamide treatment, as well as an ovulator y injection of HCG in the proestrus afternoon partially reversed, the ovulatory blockade of RU486. These results indicate that both the decr eased FSH concentration and the increased testosterone concentration, as well as the reduced ovulatory LH release are responsible for the an ovulatory effects of RU486.