Endothelin-1 Increases the Pulmonary Microvascular Pressure and Causes Pulmonary Edema in Salt Solution but not Blood-Perfused Rat Lungs

Endothelin-1 (ET-1) is a potent vasoactive peptide that has been reported to cause lung edema. This study tested if the edemagenic effect of ET-1 is due to preferential venoconstriction and, if so, whether the site of resistance is similar with salt solution (PSS) and more physiologic blood perfusate. ET-1 caused concentration-dependent contraction of pulmonary arterial and venous rings, with an EC50 of 1.3 nM in artery and 0.6 nM in vein (p less than 0.05). In PSS-perfused lungs, 5 nM ET-1 caused a 7.0 +/- 0.8 torr pressor response that was associated with a 5.0 +/- 0.3 torr increase in microvascular pressure and a 530 +/- 20 mg increase in lung weight within 10 min. In contrast, KCl-treated lungs had an equivalent pressor response (7.4 +/- 1.1 torr), yet the microvascular pressure increased by only 2.5 +/- 0.4 torr (p less than 0.05 from ET-1) and the lung weight was unchanged. Meclofenamate did not prevent the effect of ET-1 on microvascular pressure or lung weight. In blood-perfused lungs, ET-1 caused a 7.3 +/- 0.1 torr pressor response but only a 2.0 +/- 0.5 torr increase in microvascular pressure and no increase in lung weight. ET-1 had no effect on permeability either of cultured endothelial cell monolayers or in the pulmonary microvasculature in vivo. We conclude that the edemagenic effect of ET-1 in PSS-perfused lungs is mediated through venoconstriction and an increase in microvascular pressure.(ABSTRACT TRUNCATED AT 250 WORDS)