[Effects of prostaglandins on pulmonary circulation]

Effects of prostacyclin (PGI2) and thromboxane A2 (TxA2) on pulmonary circulation and pulmonary edema were studied in 24 dogs. The heart and lungs were provided with an autoperfusion circulation. Mean aortic pressure and cardiac output were maintained at 80 mmHg and 40 ml.kg-1.min-1, respectively. The animals were divided evenly into 4 groups: group 1, control; group 2, PGI2-analog loaded; group 3, TxA2-analog loaded; and group 4, TxA2-antagonist loaded. The heart-lung tissues were autoperfused for 4 hours. During the experimental period, respiratory parameters (PaCO2 and PaO2) showed no significant change, but significant elevations of mean pulmonary arterial pressure and mean left atrial pressure were observed in group 3. The radiological pulmonary dilution curve changed significantly during autoperfusion. The half-life and the mean transit time were both prolonged significantly in groups 1, 3 and 4, but unchanged in group 2. Characteristic pathological pulmonary vascular changes, intravascular leukocyte sequestration, capillary dilatation and perivascular edema were observed in groups 1 and 3. Those changes were attenuated in group 4 and prevented in group 2. In conclusions, pulmonary circulation was impaired by TxA2, whereas maintained by PGI2. These findings show that TxA2 and PGI2 may modify blood-vessel interaction, and organ damage may occur in the case of TxA2 and organ may be preserved in the case of PGI2.