EFFECTS OF DIETARY N-6 AND N-3 LIPIDS OIL ANTIOXIDANT DEFENSE SYSTEM IN LIVERS OF EXERCISED RATS

Objective: The present study was designed to investigate the effects o f dietary n-6 and n-3 lipids and exercise on the activities of hepatic antioxidant enzymes and microsomal lipid composition and peroxidation in Fischer-344 male rats. Methods: Weanling male Fischer-344 rats wer e fed ad libitum semipurified diets containing 10% corn oil (CO) or 10 % fish oil (FO) with equal levels of antioxidants. After 2 months on t he diets, weight-matched animals in each diet group were divided into sedentary (S) and exercised (Ex) groups, and the diets were continued. The animals in the exercise group were run on a treadmill 30 to 40 mi nutes to exhaustion 6 days/week for 2 months. At the end of 2 months, the rats were sacrificed and livers were collected; antioxidant enzyme s were determined in the cytosol, fatty acid composition was analyzed in the microsomes, and vitamin E levels were analyzed in the sera Resu lts: The rats in the FO-S group exhibited significantly higher Liver c ytosolic catalase activity, while their superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities were significantly lower c ompared to the CO-S group. The GSH-Px activity was significantly highe r in the FO-Ex group compared to FO-S group. The source of dietary lip ids significantly influenced the fatty acid composition of the total l ipids in the microsomes. Feeding the FO-based diet significantly incre ased 18:0 and n-3 fatty acids incorporation into the microsomes (18:3, 20:5, 22:5, and 22:6) whereas ingestion of CO resulted in a significa nt increase in 14:0, 14.1, 18:1, and n-6 fatty acids (18:2 and 20:4). The serum vitamin E levels were significantly higher in the CO groups, and exercise had no effect on vitamin E levels. Exercise significantl y decreased the generation of thiobarbituric acid reactive substances (TBARS) by liver microsomes. Consumption of FO, which is highly suscep tible to oxidation, did not show any significant changes in membrane l ipid peroxidation. Conclusions: The present study suggests that feedin g FO increases the activity of liver cytosolic catalase in FO-S rats a nd GSH-Px in FO-Ex rats. In addition, exercise significantly decreased the generation of by the liver microsomal Lipids. Serum vitamin E lev els were higher in the CO group and exercise did not alter vitamin E l evels. This suggests that the amount of vitamin E included in the diet s was possibly adequate to cope with the oxidative stress induced duri ng exercise.