METHYLENE-BLUE PREVENTS PULMONARY INJURY AFTER INTESTINAL ISCHEMIA-REPERFUSION

Objective: To investigate the effect of methylene blue, an inhibitor o f oxygen radicals, on lung injury caused by reperfusion of ischemic ti ssue. Methods: Intestinal ischemia-reperfusion injury was induced in r ats by clamping the superior mesenteric artery for 1 hour. Thereafter, the experimental group was administered 1% methylene blue intraperito neally and the control group received saline. After 4 hours, pulmonary histopathologic features were assessed, and lung wet-weight to dry-we ight ratios and tissue xanthine oxidase were determined. Results: The control group suffered from severe pulmonary parenchymal damage, compa red with slight damage in the experimental group. The number of seques tered neutrophils was significantly higher in the control group (319 /- 60 polymorphonuclear cells per 10 high-power fields) than in the me thylene blue-treated group (91 +/- 8 polymorphonuclear cells per 10 hi gh-power fields; p < 0.001). The wet-weight to dry-weight ratio was si gnificantly increased in the saline-treated rats compared with the met hylene blue-treated group (6.19 +/- 0.28 vs. 5.07 +/- 0.21; p < 0.001) . Xanthine oxidase activity was similar in both groups. Conclusion: Me thylene blue attenuated lung injury after intestinal ischemia-reperfus ion. Inhibition of oxygen free radicals may be the protective mechanis m.