Lung injury produced by pancreatic proteases in dogs.

With an isolated, blood-perfused canine lung-lobe preparation, the potential role of reactive oxygen metabolites and neutrophils in pancreatic protease (alpha-chymotrypsin)-induced acute lung injury was studied. Administration of alpha-chymotrypsin caused a low-pressure pulmonary edema (mean lung lobe weight increased from 71 to 197 gm). Pretreatment with superoxide dismutase alone did not attenuate the injury (58 to 166 gm), but when combined with catalase, the injury was significantly ameliorated (64 to 107 gm). However, depletion of circulating leukocytes did not attenuate the injury (69 to 200 gm). These findings suggest that circulatory proteases can cause lung injury by a mechanism that is mediated, at least in part, by toxic oxygen metabolites that are not of neutrophil origin.