Objective To study the changes of total SOD activity and expression in major organs and observe the effects of antioxidant N-acetylcysteine (NAC) on antioxidant status in diabetic rats. Methods Normal rats (group C, n=8) or streptozotocin (STZ)-induced diabetic rats (group D, n=8) were treated with NAC 1.5 g/kg/d (Group D+N, n=8) or equal volume of normal saline once daily by gastric gavage for 4 weeks. Blood samples were collected and the 15-F2t-isoprostane, total antioxidant concentration and SOD activity were assayed. The heart, lung, liver and kidney tissues were collected for assay of the total SOD activity using a kit and the protein expression of SOD isoforms, including Cu/Zn-SOD and Mn-SOD, was determined by western blot.Results The levels of 15-F2t-isoprostane and total antioxidant concentration in plasma, total SOD activity in the heart, protein expression of Cu/Zn-SOD in the heart and lung, and Mn-SOD expression in the liver were significantly increased (PPConclusions The levels of total SOD activity and protein expression of Cu/Zn-SOD and Mn-SOD in diabetic rats are tissue specific, and antioxidant NAC can attenuate the target organ damages to a certain degree by restoring the antioxidant levels in diabetic rats.