Melatonin reduces lipid peroxidation and tissue edema in cerulein-induced acute pancreatitis in rats

Since oxygen free radicals and lipid peroxidation have been implicated in t he pathogenesis of an early stage of acute pancreatitis, we examined whethe r melatonin, a recently discovered free-radical scavenger, could attenuate pancreatic injury in Sprague-Dawley rats with cerulein-induced pancreatitis . Acute pancreatitis was induced by four intraperitoneal injections of ceru lein (50 mu g/kg body wt) given at l-hr intervals. Thirty minutes after the last cerulein injection, the rats were killed and the degree of pancreatic edema, the level of lipid peroxidation in the pancreas, and serum amylase activity were increased significantly. Pretreatment with melatonin (10 or 5 0 mg/kg body wt) 30 min before each cerulein injection resulted in a signif icant reduction in pancreatic edema and the levels of lipid peroxidation. S erum amylase activity, however, was not significantly influenced by either dose of melatonin. Moreover, we found that cerulein administration was asso ciated with stomach edema as well as high levels of lipid peroxidation in t he stomach and small intestine, which were also reduced by melatonin. Melat onin's protective effects in cerulein-treated rats presumably relate to its radical scavenging ability and to other antioxidative processes induced by melatonin.