Phospholipase A2-induced lung edema and its mechanism in isolated perfused guinea pig lung.

Lung injury induced by phospholipase A2 (PLA2, 0.046 IU/ml perfusate) was studied in a continuous weighing system of isolated perfused guinea pig lungs. The results revealed that lung weight increased progressively during the 30-min perfusion of PLA2. No change of pulmonary arterial pressure was observed in the same period. Albumin permeability-surface area product, lung index, lung water content, exudate from pleura, and angiotensin-converting-enzyme activity increased significantly at the end of 30 min PLA2 perfusion. p-Bromophenacyl bromide, a PLA2 inhibitor, may block the above changes nearly completely. The effects of inhibitors of cyclooxygenase (indomethacin, IM), lipoxygenase (diethylcarbamaxine, DE), and platelet-activating factor (SRI 63-441) on PLA2-induced lung injury were also studied. We found: (1) PLA2 may induce high permeability lung edema. The role of endothelial injury in the permeability change remains to be further investigated. (2) DE ameliorated lung injury significantly within 10 min of PLA2 treatment but showed no effect after 15 min. IM ameliorated lung injury during the whole experimental period. SRI 63-441 had no effect. It is suggested that PLA2 may damage lung by inducing products of cyclooxygenase and lipoxygenase besides its direct effect.