[Acute lung injury and chemical mediators].

The essential abnormality in acute lung injury is an increase in pulmonary permeability. The mechanisms involved are complex, and may include direct effects on endothelial cells; the actions of neutrophils, macrophages, and lymphocytes; and chemical mediators generated by these cells. Neutrophils are known to be important in acute lung injury, and the mediators they produce, especially protease and oxidants, may be responsible for endothelial cell injury. We studied the roles of neutrophil elastase and oxygen radicals in acute lung injury by Escherichia coli endotoxin in sheep with lung lymph fistulae. The results of these and other studies indicate that these substances are related to the increase in pulmonary permeability during the late phase of injury.