Mechanism of free radical production in exhaustive exercise in humans and rats; Role of xanthine oxidase and protection by allopurinol

Exhaustive exercise generates free radicals, However, the source of this ox idative damage remains controversial. The aim of this paper was to study fu rther the mechanism of exercise-induced production of free radicals, Testin g the hypothesis that xanthine oxidase contributes to the production of fre e radicals during exercise, me found not only that exercise caused an incre ase in blood xanthine oxidase activity in rats but also that inhibiting xan thine oxidase with allopurinol prevented exercise-induced oxidation of glut athione in both rats and in humans. Furthermore, inhibiting xanthine oxidas e prevented the increases in the plasma activity of cytosolic enzymes (lact ate dehydrogenase, aspartate aminotransferase, and creatine kinase) seen af ter exhaustive exercise. Our results provide evidence that xanthine oxidase is responsible for the free radical production and tissue damage during ex haustive exercise, These findings also suggest that mitochondria play a min or role as a source of free radicals during exhaustive physical exercise.