Ovarian secretion of pregnane compounds at first ovulation in rats treated with pregnant mare's serum gonadotropin.

Progesterone, 5 alpha-pregnane-3,20-dione (5 alpha-DHP), 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha-OH), 20 alpha-hydroxy-4-pregnen-3-one (20 alpha-DHP), 20 alpha-hydroxy-5 alpha-pregnan-3-one (20 alpha, 5 alpha), and 5 alpha-pregnane-3 alpha, 20 alpha-diol (DIOL) in ovarian venous plasma at first ovulation in female rats treated on day 30 with 10 IU of pregnant mare's serum gonadotropin (PMSG) were assayed using gas chromatography. Progesterone peaked at late proestrus before ovulation (day 32) and at early diestrus after ovulation (day 34). With the first peak, 5 alpha-DHP and 3 alpha-OH increased. The 20 alpha-DHP level peaked at early diestrus after ovulation (day 34) and remained high thereafter. The 20 alpha, 5 alpha and DIOL peaked at estrus after ovulation (day 33) and then fell slowly. Injection of 2 micrograms of luteinizing hormone (LH) before sample collection increased secretion of 20-keto-pregnane compounds, except when they were at peak levels. The secretion of 20 alpha-hydroxy-pregnane compounds was unaffected by LH at all times tested. These results suggest that rat ovaries without corpora lutea secrete 20-keto-pregnane compounds in response to LH, but that 20 alpha-hydroxy-pregnane compounds are secreted only from ovaries with corpora lutea.