INHIBITION BY INDOMETHACIN OF THE ALREADY ACCELERATED SECRETION OF INHIBIN AND ESTRADIOL IN EQUINE CHORIONIC GONADOTROPIN-PRIMED IMMATURE FEMALE RATS

In immature female rats, the secretion of ovarian inhibin and estradio l is greatly accelerated by equine chorionic gonadotropin (eCG) treatm ent. The present study has been carried out to determine whether or no t the levels of the two hormones are inhibited by a single s.c.-inject ion of indomethacin (INDO) 24 h after eCG administration. The levels o f ovarian hormones and gonadotropins were measured by double-antibody radioimmunoassay using I-125-labeled radioligands. The serum levels of inhibin and estradiol were considerably inhibited within 24 and 12h, respectively, after INDO injection. In addition, the serum levels of f ollicle-stimulating hormone (FSH) after INDO injection remained lower than the basal levels before eCG treatment. The luteinizing hormone (L H) levels were significantly reduced within 12 h after INDO treatment. The results demonstrate that the levels of inhibin and estradiol, eve n in the situation where the production of both hormones is already ac celerated by eCG pretreatment, are suppressed by an inhibitor of prost aglandin (PG) synthesis, suggesting that locally produced PGs may play a role in the regulation of the production of both hormones in the ov ary.