MICRODETERMINATION OF PROGESTINS IN RAT OVARIES: PROGESTERONE AND 20α-HYDROXY-PREGN-4-EN-3-ONE CONTENT DURING PROOESTRUS, OESTRUS AND PSEUDOPREGNANCY

Abstract

A method is described for the determination of progesterone (P) and 20[alpha]-hydroxy-pregn-4-en-3-one (20[alpha]OHP) in rat ovaries by combined paper- and vapour-phase chro-matography. In pseudopregnant rats during the 4th to 7th day of leuco -cytic vaginal smear, the progesterone content of a pair of ovaries about a mean of 1 [mu]g, and the ratio P/20[alpha]OHP ranged from 2.2 to 3.0. The ovarian progesterone content was minimal (0.15 [mu]g/pair) on the morning of proestrus, rose significantly on the afternoon of proestrus (0.4 ng) and declined again before the morning of estrus. Throughout dioestrus, proestrus and estrus the ovarian content of 20[alpha]OHP exceeded that of progesterone (P/20[alpha]OHP = 0.27-0.51). This inversion of the p/20[alpha]OHP ratio reflects the increase in ovarian 20[alpha] -hydroxy-steroid dehydrogenase activity known to occur during follicular proliferation. Cyclic changes observed in the content of progestins in the ovaries, including the preovulatory rise, parallel those previously described in ovarian venous blood.