BACKGROUND:We investigated the effects of three weeks of renutrition with a normal protein diet on oxidant/antioxidant status in malnourished rats using biochemistry and histology.METHODS:Eighteen young Wistar rats were divided into three groups:control group was fed on a normal protein diet;malnourished group was fed on low protein diet and renourished group was fed on low protein diet followed by a normal protein diet.Serum albumin was evaluated.Malondialdehyde,protein carbonyl,superoxide dismutase and catalase levels were determined in the intestine,muscle and liver.Intestinal and hepatic damage were assessed by histological examination.RESULTS:Protein malnutrition resulted in a significant decrease of body weight,albumin level,villus length,intraepithelial lymphocytes counts (IELC) and superoxide dismutase level (liver and muscle).However,catalase activity increased significantly in muscle and gut but there was no difference in liver.In all organs,malondialdehyde and protein carbonyl content of malnourished group showed a significant increase.Interestingly,a normal protein diet for three weeks resulted in a retu to normal levels of superoxide dismutase,albumin,malondialdehyde and protein carbonyl in all organs.Catalase activity decreased in the muscle and gut and exhibited no significant difference in the liver.The renutrition diet enhanced also the recovery of intestinal epithelium by increasing villus length.Hepatic damage of rats fed normal protein diet was markedly reduced (macrovesicular steatosis decreased by 45％).CONCLUSION:The normal protein diet could improve the oxidant/antioxidant imbalance and organ damage induced by protein malnutrition.