Effect of dietary supplements containing antioxidants on attenuation of muscle damage in exercising sled dogs

Objective-To determine whether dietary antioxidants would attenuate exercis e-induced increases in plasma creatine kinase (CK) activity in sled dogs. Animals-41 trained adult sled dogs. Procedure-Dogs, randomly assigned to 2 groups, received the same base diet throughout the study. After 8 weeks on that diet, 1 group (21 dogs) receive d a daily supplement containing vitamins E (457 U) and C (706 mg) and beta -carotene (5.1 ms), and a control group (20 dogs) received a supplement con taining minimal amounts of antioxidants. After 3 weeks, both groups perform ed identical endurance exercise on each of 3 days. Blood samples were colle cted before and 3 weeks after addition of supplements and after each day of exercise. Plasma was analyzed for vitamins E and C, retinol, uric acid, tr iglyceride, and cholesterol concentrations, total antioxidant status (TAS), and CK activity. Results-Feeding supplements containing antioxidants caused a significant in crease in vitamin E concentration but did not change retinol or vitamin C c oncentrations or TAS. Exercise caused significantly higher CK activity, but did not cause a significant difference in CK activity between groups. Exer cise was associated with significantly lower vitamin E, retinol, and choles terol concentrations and TAS but significantly higher vitamin C, triglyceri de, and uric acid concentrations in both groups. Conclusions and Clinical Relevance-Use of supplements containing the doses of antioxidants used here failed to attenuate exercise-induced increases in CK activity. Muscle damage in sled dogs, as measured by plasma CK activity , may be caused by a mechanism other than oxidant stress.