Melatonin Reduces Lipid Peroxidation and Tissue Edema in Cerulein-Induced Acute Pancreatitis in Rats

Since oxygen free radicals and lipidperoxidation have been implicated in the pathogenesis ofan early stage of acute pancreatitis, we examinedwhether melatonin, a recently discovered free-radicalscavenger, could attenuate pancreatic injury inSprague-Dawley rats with cerulein-induced pancreatitis.Acute pancreatitis was induced by four intraperitonealinjections of cerulein (50 g/kg body wt) given at1-hr intervals. Thirty minutes after the lastcerulein injection, the rats were killed and the degreeof pancreatic edema, the level of lipid peroxidation inthe pancreas, and serum amylase activity were increased significantly. Pretreatment with melatonin (10or 50 mg/kg body wt) 30 min before each ceruleininjection resulted in a significant reduction inpancreatic edema and the levels of lipid peroxidation.Serum amylase activity, however, was notsignificantly influenced by either dose of melatonin.Moreover, we found that cerulein administration wasassociated with stomach edema as well as high levels oflipid peroxidation in the stomach and smallintestine, which were also reduced by melatonin.Melatonin's protective effects in cerulein-treated ratspresumably relate to its radical scavenging ability andto other antioxidative processes induced bymelatonin.