ROLE OF OXYGEN-DERIVED FREE-RADICALS IN INDOMETHACIN-INDUCED GASTRIC INJURY

The role of oxygen-derived free radicals in the pathogenesis of acute gastric ulceration induced by indomethacin (Indo) was investigated in rats. Gastric damage was assessed by blood-to-lumen leakage of Cr-51-EDTA, as well as by measuring the extent of macroscopically visible hemorrhagic lesions. The stomach was perfused with isotonic saline for 30 min, followed by Indo (10 mg/ml for 30 min) and HCl (100 mM for 60 min). Rats were given a continuous intravenous infusion of the antioxidant enzymes superoxide dismutase (SOD) or catalase or the iron-chelating agent deferoxamine. Additional rats received an intravenous infusion of the vehicle (control group) or were pretreated with prostaglandin E2 (100-mu-g/kg ip) or allopurinol (50 mg/kg po). Exposure of the stomach to Indo caused a fourfold increase in Cr-51-EDTA leakage compared with that observed in rats receiving only the vehicle for Indo. Subsequent exposure of the stomach to HCl resulted in a further twofold increase in Cr-51-EDTA leakage. Treatment with SOD, catalase, or deferoxamine significantly (P < 0.05) reduced Cr-51-EDTA leakage during the intragastric perfusion with Indo and during the subsequent exposure to HCl. Pretreatment with PGE2 reduced Cr-51-EDTA leakage during perfusion with HCl only. Pretreatment with allopurinol did not significantly affect Cr-51-EDTA leakage at any time during the experiment. In addition to reducing the leakage of Cr-51-EDTA into the gastric lumen, SOD, catalase, and PGE2 significantly reduced the extent of macroscopically visible mucosal damage (P < 0.05). These results support the hypothesis that oxygen-derived free radicals, probably derived from neutrophils, contribute to the pathogenesis of Indo-induced ulceration.