Inhibition of Ovulation by Inhibition of Steroidogenesis in Immature Rats 1

Summary Immature female rats treated with PMS on day 24 and HCG on day 26 ovulate and have ova in the oviduct on day 27. Treatment with ethamoxytriphetol (Mer-25) prior to the administration of HCG has no effect on ovulation but treatment with the 3β-hydroxysteroid dehydrogenase inhibitor 2α - cyano − 4,4,17α - trimethylandrost − 5 − en −17β-ol-3-one (cyanoketone), also given before HCG, effectively inhibits ovulation. Adrenalectomy performed prior to administration of HCG does not prevent ovulation while neither progesterone (500 μg) nor progesterone: estrogen, 500 μg:1 μg overcome the cyanoketone block to ovulation. Ovarian steroidogenesis and ovulation are apparently related.