Inhibition of ovulation by inhibition of steroidogenesis in immature rats.

Abstract

The following chemicals were employed in examining the relationship of the steroids to ovulation: ethamoxytriphetol (Mer-25) a postulated estrogen antagonist and 2-alpha-cyano-44 17-alpha-trimethylandrost-5-en-17-beta-ol-3-one (cyanoketone) a 3-beta-hydroxysteroid dehydrogenase inhibitor. Although Mer-25 had no effect on ovulation cyanoketone caused complete inhibition of ovulation in immature rats pretreated with pregnant mare serum (PMS) and human chorionic gonadotropin (HCG). Mer-25 prevented the uterine hypertrophy which usually results from the administration of HCG but this inhibition decreased as the dose increased. Sprague-Dawley rats 22 days of age were used. At age 24 days 30 IU of PMS in 1 ml of saline was given im. 40-44 hours later animals were given 30 IU of HCG iv. Experimental animals received either Mer-25 or cyanoketone prior to receiving HCG. The Mer-25 was administered in 2 equal doses but in 3 different amounts at 12 and 6 hours before the HCG. Cyanoketone was given 3.52 mg per 100 gm body weight in a single or 2 divided doses before HCG. It was most effective when given 3 hours before HCG in a single dose. Adrenalectomy done prior to administration of HCG does not prevent ovulation while neither progesterone (500 mcg) nor progesterone and estrogen (500 mcg:1 mcg) overcome the cyanoketone block to ovulation. Ovarian steroidogenesis and ovulation are apparently related.