Original Contribution ENDURANCE EXERCISE RESULTS IN DNA DAMAGE AS DETECTED BY THE COMET ASSAY ANGELA MASTALOUDIS,* ,y TIAN-WEI YU, y ROBERT P. O’DONNELL, z,§ BALZ FREI, y RODERICK H. DASHWOOD, y and MARET G. TRABER* ,y,b,O * Department of Exercise and Sport Science; y Linus Pauling Institute; § Department of Statistics, and b Department of Nutrition and Food Management, Oregon State University, Corvallis, OR 97331, USA; z Hewlett – Packard, Corvallis, OR, USA; and O Department of Internal Medicine, University of California at Davis Medical Center, Davis, CA 95616, USA (Received 23 May 2003; Revised 22 December 2003; Accepted 15 January 2004) Abstract—To determine if 6 weeks of supplementation with antioxidants could alleviate exercise-induced DNA damage, we studied 21 runners during a 50 km ultramarathon. Subjects were randomly assigned to one of two groups: (1) placebos (PL) or (2) antioxidants (AO) (1000 mg vitamin C and 400 IU RRR-a-tocopheryl acetate). The comet assay was used to assess DNA damage in circulating leukocytes at selected time points: pre-, mid-, and 2 h postrace and daily for 6 days postrace. All subjects completed the race: run time 7.1 F 0.1 h, energy expenditure 5008 F 80 kcal for women (n = 10) and 6932 F 206 kcal for men (n = 11). Overall, the percentage DNA damage increased at midrace ( p < .02), but returned to baseline by 2 h postrace, indicating that the exercise bout induced nonpersistent DNA damage. There was a gender  treatment  time interaction ( p < .01). One day postrace, women taking AO had 62% less DNA damage than women taking PL ( p < .0008). In contrast, there were no statistically significant differences between the two treatment groups of men at any time point. Thus, endurance exercise resulted in DNA damage as shown by the comet assay and AO seemed to enhance recovery in women but not in men. D 2004 Elsevier Inc. All rights reserved. Keywords—a-Tocopherol, Ascorbic acid, Oxidative stress, Vitamin E, Vitamin C, Free radicals INTRODUCTION During the resting state the human body produces reactive oxygen species (ROS) continuously, but in healthy individuals these ROS are produced at levels well within the capacity of the body’s antioxidant defense system. However, endurance exercise elicits a 10- to 20-fold increase in whole body oxygen (O 2 ) consumption and O 2 consumption at the level of the skeletal muscle increases 100- to 200-fold. This in- crease in O 2 utilization may result in the production of ROS at rates that exceed the body’s capacity to detoxify them [1]. Potential sources of ROS during exercise include leakage of electrons from the mito- chondrial electron transport chain [2], enhanced purine oxidation, damage to iron-containing proteins, and disruption of Ca 2+ homeostasis [3]. Left unchecked, these ROS may cause protein, lipid, and/or DNA damage. Several studies have demonstrated exercise-induced lipid peroxidation in response to various modes of exercise, including endurance running [4,5]. Recently, there has been growing interest in exercise-induced DNA damage due to its potential involvement in various disease states. There is speculation that oxida- tively damaged DNA is involved in cancer develop- ment and an association between oxidative damage to mitochondrial DNA and age-related degenerative dis- eases has been postulated [6]. Past studies have pri- marily used the 8-hydroxydeoxyguanosine assay [7–9] to assess DNA damage, but this method has been This work was presented in part at the Annual Meeting of the Oxygen Society in San Antonio, Texas, on November 22, 2002, and was published in abstract form (Free Radic. Biol. Med. 33:S334; 2002). Address correspondence to: Angela Mastaloudis, Linus Pauling Institute, 571 Weniger Hall, Oregon State University, Corvallis, OR 97331. Fax: (541) 737-5077; E-mail: mastaloa@onid.orst.edu. Free Radical Biology & Medicine, Vol. 36, No. 8, pp. 966 –975, 2004 Copyright D 2004 Elsevier Inc. Printed in the USA. All rights reserved 0891-5849/$-see front matter doi:10.1016/j.freeradbiomed.2004.01.012 966