Ventilation-induced release of prostaglandinlike material from fetal lungs.

Effects of indomethacin upon ventilation-induced pulmonary vasodilation of fetal goats suggest prostaglandins may be important in perinatal transition of the pulmonary circulation. To further test this hypothesis, left pulmonary arterial and pulmonary venous samples were taken before and after ventilation from anesthetized exteriorized fetal (near-term) goats and sheep utilizing, in different animals, either constant or variable left pulmonary blood flow. Characterization and quantification of prostaglandinlike compounds were accomplished utilizing extraction of acidic lipids, thin-layer chromatography, and tissue cascade bracket bioassay. The primary vascular prostaglandinlike material in both fetal and neonatal animals was PGI2-like (PGI). On passage through the fetal lung, concentrations of prostaglandin I- and E-like compounds decreased considerably. After ventilation and ligation of the umbilical cord, concentrations of both PGE2-like (PGE) and PGI in inferior vena caval blood fell, and there was net production of PGI by the newly ventilated lung. Production of PGI2 by newly ventilated lung could provide an important vasodilator influence that would establish and maintain the low pulmonary vascular resistance that is necessary for successful adaptation to extrauterine life.