ENDOTOXIN-INDUCED HYDROGEN-PEROXIDE PRODUCTION IN INTACT PULMONARY CIRCULATION OF RAT

Although the importance of free oxygen radical has been reported in ac ute lung injury, the direct evidence in vivo model was tacking. We rep ort a new method, which for the first time allows direct detection of hydrogen peroxide in the intact rat pulmonary microcirculation, We use d the computer image-analyzing system and 2', 7'-dichlorofluorescin di acetate for the marker of hydrogen peroxide production in vivo. A rat sepsis model was produced by continuous infusion of endotoxin for 30, 60, and 120 min. Hydrogen peroxide production in the pulmonary microci rculation of the sepsis rat was higher than in the control rat at each time point (p < 0.01) and increased time-dependently (p < 0.01). Cata lase (5,000 U/kg) almost completely inhibited the hydrogen peroxide pr oduction in the sepsis rat (p < 0.01). In high-power view, hydrogen pe roxide was detected in granulocytes that adhered to the capillaries an d endothelial cells that were adjoining adherent granulocytes. These o bservations suggest that hydrogen peroxide in the endothelium was diff used from granulocytes. In this study, we demonstrated direct evidence of hydrogen peroxide production from adherent granulocytes in intact rat lung treated with endotoxin. We conclude that endotoxin causes the granulocyte adhesion and oxidative stress to the endothelium due to a dherent granulocytes within 30 min in the pulmonary microcirculation.