Eosinophils cause acute edematous injury in isolated perfused rat lungs

Eosinophils produce oxidants and other toxic substances and thus have the potential to cause acute lung injury. We found that addition of normal human eosinophils and the respiratory burst stimulant phorbol myristate acetate to isolated perfused rat lungs acute edematous injury as reflected in weight gain and morphologic changes. Lung to body weight ratio (x 10(3) was 16.7 +/- 3.3 in the experimental group with stimulated eosinophils added compared with 4.7 +/- 0.38 for the control group. Morphologic examination showed both epithelial and endothelial damage. This injury was ameliorated by the addition of catalase, which neutralizes hydrogen peroxide produced during the respiratory burst. Lung/body weight ratio in the group with stimulated eosinophils plus catalase was 7.8 +/- 1.1, and the specimens were indistinguishable from control specimens by histopathologic examination. Our results indicate that eosinophils are capable of causing acute lung injury. This injury is mediated, at least in part, by toxic oxygen products.