Ovarian Secretion of Progesterone and 20α-Hydroxypregn-4-en-3-one During Pseudopregnancy and Pregnancy in Rats

Abstract

The present study has investigated the concentrations of ovarian vein blood progesterone and 20[alpha]-hydroxypregn-4-en-3-one during various days of pseudopregnancy and pregnancy in the rat. The measurement of small concentrations of these steroids was made possible through the use of thin layer chromatographic and spectro-photometric techniques. Blood collections were taken on the following days of pregnancy: 2, 3, 4, 5, 7, 9, 11, 13, 15, 18, 20 and the first postpartum estrus. In addition, days 2, 3, 4, 5, 7, 9, and the first estrus following pseudopregnancy were studied. While high concentrations of ovarian progesterone were secreted from the onset of pregnancy, and reached maximum concentrations on day 13, during the first 3 days of pseudopregnancy the hydroxylated steroid was secreted in higher concentrations than progesterone. At day 4 and thereafter, the concentrations of progesterone during pseudopregnancy paralleled the pregnancy values. From day 18 of pregnancy both progestins decreased sharply, with the hydroxylated steroid being secreted in higher concentrations than progesterone. Blood obtained from rats the first estrus following parturition or pseudopregnancy contained extremely high concentrations of the 20[alpha]-hydroxypregn-4-en-3-one.