Estrogen-Directed Synthesis of Specific Prostaglandins in Uterus

Endogenous uterine prostaglandin levels were monitored in the cycling rat and prostaglandins of the F-type were found to rise at proestrus when estrogen levels have been shown to be maximal. Evidence that this is an estrogen-induced event is furnished by the finding that estradiol-17β caused a similar rise in prostaglandin F levels in uteri of ovariectomized rats, an action blocked by coadministration of progesterone. Examination of in vitro prostaglandin synthetase by uterine microsomal fractions from cycling rats and estrogen-treated ovariectomized rats revealed that the action of estrogen to control prostaglandin synthesis in a directional manner is accomplished, at least in part, by regulation of the prostaglandin synthetase complex, resulting in a patterned alteration in the ratio of prostaglandin F to prostaglandin E. These results demonstrate that prostaglandins are involved in the expression of estrogen action in the rat uterus.