Vasoconstrictive effects of prostaglandins in sheep placental circulations

Changes in the uterine and umbilical circulations after intra-aortic injection of prostaglandin E2 (PGE2) or protaglandin F2alpha (PGF2alpha) to either the fetus or the mother have been examined in 13 ewes at late gestation. PGF2alpha vien to either the fetus or the mother is vasoconstrictive in both uterine and umbilical circulations. PGE2 given to the fetus results in a dissociated response with vasodilation of the uterine circulation and vasoconstriction of the umbilical circulation. PGE2 given to the mother causes a uterine contraction that precludes specific hemodynamic analysis. Therefore, exposure of either maternal or fetal ovine circulation to exogenous prostaglandins in associated with acute changes in both placental circulations. Similar responses to pertubations in endogenous prostaglandin levels may exist in pregnant sheep.