Reactive oxygen species produced during vigorous exercise may permeate into
cell nuclei and induce oxidative DNA damage, but the supporting evidence i
s still lacking. By using a 42 km marathon race as a model of massive aerob
ic exercise, we demonstrated a significant degree of unrepaired DNA base ox
idation in peripheral immunocompetent cells, despite a concurrent increase
in the urinary excretion of 8-hydroxy-2'-deoxyguanosine. Single cell gel el
ectrophoresis with the incorporation of lesion-specific endonucleases furth
er revealed that oxidized pyrimidines (endonuclease III-sensitive sites) co
ntributed to most of the postexercise nucleotide oxidation. The oxidative D
NA damage correlated significantly with plasma levels of creatinine kinase
and lipid peroxidation metabolites, and lasted for more than 1 week followi
ng the race. This phenomenon may be one of the mechanisms behind the immune
dysfunctions after exhaustive exercise. (C) 2001 Elsevier Science Inc.