Pulmonary and systemic vascular effects of exogenous prostaglandin I2 in fetal lambs.

Effects of PGI2 upon pulmonary vascular resistance and systemic arterial pressure of near term fetuses were evaluated in anesthetized, exteriorized, unventilated fetal lambs by means of an open-chest, pump-perfused lung preparation. These effects were compared to those of PGE1 and PGE2 in the same animals. Intrapulmonary arterial infusions of PGI2 produced dose-dependent decreases in pulmonary vascular resistance and systemic arterial pressure. Effects of PGI2 upon pulmonary vascular resistance are intermediate with respect to those of PGE1 (greater) and PGE2 (less). PGI2 is a potent hypotensive compound when administered to fetal lambs, producing dose-dependent decreases in systemic arterial pressure. When the three prostaglandins are infused into the pulmonary artery, effects on systemic arterial pressure of PGE1 and PGI2 are nearly identical. Effects of PGE2 are considerably less. PGI2 is a potent dilator of fetal lamb vessels and could play a role in circulatory control during perinatal transition.