Effect on ovulation of 20 alpha-hydroxy-4-pregnen-3-one and its 5 alpha-reduced metabolites in immature rats treated with pregnant mare serum gonadotrophin.
The ability of 20 alpha-hydroxy-4-pregnen-3-one (20 alpha-dihydroprogesterone, 20 alpha-DHP) and its 5 alpha-reduced metabolites, 20 alpha-hydroxy-5 alpha-pregnan-3-one and 5 alpha-pregnane-3 alpha,20 alpha-diol, to facilitate ovulation was examined in immature female rats which had been treated on day 22 of age with a non-ovulatory dose (12 i.u.) of pregnant mare serum gonadotrophin. An increased incidence of ovulation occurred in rats treated on the morning of day 24 with 20 alpha-DHP. However, a dose of 20 alpha-DHP three to four times that of progesterone was required to induce ovulation in all animals. In contrast, neither 20 alpha-hydroxy-5 alpha-pregnan-3-one (at doses ranging from 0.5 to 5.0 mg) nor 5 alpha-pregnane-3 alpha,20 alpha-diol (tested at 3.0 or 4.0 mg) facilitated ovulation. Therefore both 20 alpha-DHP and progesterone, the two major progestins of the rat oestrous cycle, have the ability to facilitate ovulation. It is concluded that the ability of 20 alpha-DHP to facilitate ovulation does not appear to be by way of conversion to its 5 alpha-reduced metabolites.
D004092:20-alpha-Dihydroprogesterone / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D006064:Gonadotropins, Equine / Q000494:pharmacology*; D010060:Ovulation / Q000187:drug effects*; D011276:Pregnanediol / Q000494:pharmacology; D011280:Pregnanolone / Q000494:pharmacology / Q000031:analogs & derivatives; D011374:Progesterone / Q000031:analogs & derivatives*; D051381:Rats; D012741:Sexual Maturation
D006064:Gonadotropins, Equine; D004092:20-alpha-Dihydroprogesterone; C016836:allopregnane-3,20-diol; D011374:Progesterone; C028952:allopregnan-20 alpha-ol-3-one; D011280:Pregnanolone; D011276:Pregnanediol