Effects of intensive endurance exercise on DNA damage in leucocytes

Objective. It has been shown that highly intensive anaerobic exercise induces DNA damage in leucocytes (LEU). The present study was designed to investigate whether intensive endurance exercise is capable of inducing comparable effects. Experimental design. A prospective study. Participants. Twelve men (aged 27.3±4.1 years) who undertook a regular training of different extent (running volume 45±25 km. week^-1) volunteered in the study. Interventions. The subjects competed in a half marathon (HM) of 21.1 km, 93.0±10.4 min. Measurements. Blood was taken at rest, 1 and 24 hrs after HM for determination of creatine kinase, neutrophil (PMN), lymphocyte and monocyte counts. DNA damage in LEU at rest and 24 hrs after HM was quantified using the single cell gel-electrophoresis (SCG) assay. Results. PMN increased from 2.81±0.69 to 13.13±2.91 1hrs after HM (p<0.01) and returned to 3.26±0.47 10⁹ cells-I^-1 by 24 hr recovery. DNA migration (image length, IL) reflecting the extent of DNA damage was elevated significantly in 10 of 12 subjects one day after HM. IL rose from 32.7±2.2 to 40.7±3.9 μm (p<0.01). Correlation analysis revealed a relationship between DNA migration 24 hrs after HM and PMN count 1 hr post-exercise (r=0.67, p<0.05). Conclusions. The results confirm the hypothesis that DNA damage in LEU occurs after intensive endurance exercise. We suppose our observation of exercise- induced DNA damage in LEU is affected by reactive oxygen species which are released from PMN. It is quite unclear whether DNA damage in LEU is causal involved in exercise-induced modifications of the immune system.