Abstract des Autors

The connection between intensive exercise and the induction of radical-mediated cellular damage is known for a long time. An association between anaerobic exercise and the induction of damage on the DNA level has been shown recently by means of the alkaline comet assay (single cell gel electrophoresis), a sensitive test for the detection of primary DNA damage. The aim of the present study was: (1.) to measure the extent of DNA damage after a triathlon competition and to follow the changes over time, (2.) to investigate, whether the DNA damage detected by the comet assay leads to damage on chromosomal level. To answer this question we used the micronucleus assay, which is well established in human biomonitoring. Venous blood of six triathletes was taken prior to the competition (1,5 km S, 40 km B, 10 km R) and every 24 hrs up to day 5 after the the triathlon, and investigated in the comet and micronucleus assay. A strong increase of damaged DNA was seen in the comet assay in comparison to the pre-exercise level indicated by an elevated number of DNA fragments migrating out of the nucleus during electrophoresis (tail moment, TM). The maximum of DNA damage was observed 3 days after the competition (mean TM 2.37 at day 3 vs. 0.02 before the competition). Even at day 5 after the exercise the TM-values have still been significantly higher than the control values (TM 0.23 vs. 0.02). Despite the distinct effects shown in the comet assay, intensive exercise did not lead to an increased number of micronuclei in the leucocytes of the triathletes (micronucleus frequency before: 0.68%, day 2: 0.73%, day 4: 0.73%). Thus the massive primary DNA damage revealed in the comet assay does not seem to manifest in damage on chromosomal level. The causes and the meaning of the effects observed in the comet assay remain to be clarified. Verf.-Referat