Uterine production of prostaglandins F 2α and 6-keto-F 1α by ovariectomized pregnant rats receiving antiprogesterone steroid or in which progesterone has been withdrawn

Abstract

Ovariectomized early pregnant rats given continuous steroid replacement therapy have been treated with antiprogesterone steroid, ZK98299 or RU38486. At 24 h following treatment, uterine explants in culture were found to produce significantly greater amounts of PGF 2α, but not of 6-keto-PGF 1α, when compared to controls. ZK98299 and RU38486 gave almost identical levels of uterine PG production. The 6-keto- PGF 1α PGF 2α production ratio for uteri of treated rats was decreased by 45% relative to controls. Similar changes in uterine PGF 2α production and 6-keto- PGF 1α PGF 2α ratio have been shown for ovariectomized early pregnant rats in which progesterone has been withdrawn when compared to control animals. It has been suggested that inhibiting or withdrawing progesterone in rat uteri exposed to estradiol and progesterone may lead to a stimulation of endoperoxide F-reductase and/or E 2 9-ketoreductase activities. The presence of luminal fluid in the uteri was observed for animals treated with antiprogesterone steroid or in which progesterone had been withdrawn. This was associated with a decrease in % dry weight for the uteri of these animals.