Influence of cortisol on prostaglandin synthesis by fetal membranes, placenta, and uterus of pregnant rabbits

Abstract

Two experiments were designed to assess the effects of cortisol on prostaglandin formation in amniotic fluid and the prostaglandin-forming cyclooxygenase in 4 gestational tissues of rabbits. Cortisol treatment (12 mg/kg body wt/h) was initiated on Day 21 of pregnancy and continued for a 24-h period. Each experiment included 5 treated and 5 vehicle-injected controls, killed at 48 (Experiment 1) or 62 h (Experiment 2) after initial injection. In both experiments, amniotic fluid was collected; cortisol, prostaglandin F (PGF), and prostaglandin E2 (PGE2) were quantified by radioimmunoassay. Microsomes prepared from amnion, yolk sac splanchnopleure, uterus, and placenta were analyzed for prostaglandin-forming cyclooxygenase activity. In Experiment 2, blood drawn at 12-h intervals was quantified for PGF, PGE2, and progesterone. In cortisol-treated rabbits, plasma progesterone decreased (p less than 0.01) from 7.2 +/- 0.8 ng/ml on Day 21 (pre-treatment) to 1.6 +/- 0.2 ng/ml on Day 23, 48 h after the initiation of cortisol treatment. By 62 h, PGF, PGE2, and cortisol concentrations were all significantly higher (p less than 0.05) in the amniotic fluid of treated animals. However, prostaglandin-forming cyclooxygenase activity had not increased in most fetal or maternal tissues at either 48 or 62 h. Therefore, even though increased prostaglandin production may be responsible for the cortisol-induced abortion, increased cyclooxygenase activity in the fetal membranes, placenta, or uterus probably is not the primary stimulus for the increased prostaglandin synthesis