EFFECT OF 20α-HYDROXYY-4-PREGNEN-3-ONE ON LUTEINIZING HORMONE SECRETION IN THE FEMALE RABBIT

Abstract

Experiments were performed in the rabbit to determine whether 20.alpha.-hydroxy-4-pregnen-3-one (20-OHP) can maintain luteinizing hormone (LH) secretion after injections of LH-releasing hormone (LH-RH). Female rabbits were castrated at least 2 wk prior to investigation. On the day before LH-RH injection they were cannulated and given i.m. estradiol benzoate (OeB), 100 .mu.g/kg i.m., LH-RH, 500 ng/kg via the cannula and i.m. 20-OHP, 100 .mu.g/kg and 2.5 mg/kg. Blood was withdrawn at intervals for up to 5.5 h after LH-RH injection. LH secretion dropped to pre-stimulation levels within 3 h after LH-RH alone or in combination with 20-OHP. Administration of LH-RH to estrogen primed intact females also gave a peak of LH which returned to pre-stimulation levels within 3 h. Mating seemed to maintain LH levels for a greater period of time.