Ovarian hormones inhibit the release of prostacyclin-like material from isolated rat uterus.

The influence of sex steroids on the production of prostacyclin (PGI2) like material by the isolated rat uterus incubated in a buffer medium was explored by monitoring its ability to inhibit ADP-induced platelet aggregation. Chopped uterine strips from rats in natural estrus can generate an unstable substance that inhibits platelet aggregation and suggest to be prostacyclin. This capacity was significantly enhanced in preparations from spayed animals. The injection of 17-beta estradiol; progesterone or both diminished the production of the prostacyclin-like material by the uterus from ovariectomized rats. The already existing notion that ovarian steroids are able to regulate the synthesis of stable prostaglandins is discussed together with the present results suggesting in addition a depressive effect of sex hormones on the uterine PGI2 synthetase system.