Effects of repeated bouts of long-duration endurance exercise on muscle and urinary levels of 8-hydroxy-2ʹ-deoxyguanosine in moderately trained cyclists

Abstract

The purpose of this study was to determine the effects of repeated bouts of long-duration endurance exercise on both muscle and urinary levels of oxidative DNA damage in moderately trained individuals. Seven moderately trained male cyclists participated in this study. All participants repeated two sessions consisting of a 5-h cycling period (equivalent to approximately 52%O₂peak) followed by a 15-h rest, then a 40-km time trial. During the sessions, participants were instructed to take water ad libitum and to consume a standard sports drink consisting of 0.12 g·kg⁻¹ body weight·hr⁻¹ of carbohydrates. For each session, 24 h urine output was collected on the day before the 5-h exercise, and also between the 5-h exercise and 40-km time trial, in addition to between days 1–5 post-exercise. Subsequently, muscle and urinary levels of 8-hydroxy-2ʹ- deoxyguanosine (8-OHdG) were determined using high performance liquid chromatography with electrochemical detection. No significant alterations were observed between two sessions at the muscle or urinary levels of 8-OHdG. These results suggest that repeated bouts of exercise with a 7-day washout period may not lead to an accumulation of DNA damage products after a second 5-h stationary cycling bout.

Keywords:

• exercise intensity
• ultra-endurance exercise
• oxidative stress
• DNA oxidation
• apoptosis

Acknowledgements

The authors are indebted to Dr. Dustin Slivka, Messrs. John Cuddy and Walt Hailes, and Mrs. Stephanie Harger for their technical assistance in the present study. A part of the data was presented at the 14th annual meeting of Free Radical Biology and Medicine in Washington, D. C., USA., 2007.

Additional information

Funding

This work was supported partly by the United States Air Force Research Laboratories [grant number FA8650-06-1-679 to B. C. R.]; National Institute on Aging [grant number 1R15AG023604-01 to F. C. P.]; National Institutes of Health [grant number P20RR015583-07], [grant number P20RRP20RR017670-04 to F. C. P.].