Exercise preconditioning against hydrogen peroxide-induced oxidative damage in proteins of rat myocardium

Both regular physical exercise and low levels of H₂O₂ administration result in increased resistance to oxidative stress. We measured the accumulation of reactive carbonyl derivatives and the activities of proteasome complex and DT-diaphorase in cardiac muscle of trained and untrained rats after chronic i.p. administration of 1 ml t-butyl H₂O₂ (1 mmol/kg for 3 weeks every second day). Twenty-four rats were randomly assigned to a control group administered with saline, control administered with H₂O₂, and exercised administered either saline or H₂O₂. The activity of DT-diaphorase significantly increased in H₂O₂ administered and exercised groups, indicating that an increase in H₂O₂ levels stimulate the activity of this enzyme. The cardiac muscle of H₂O₂ administered nonexercised animals accumulated significantly more carbonyl than control group (P < 0.05). The exercise and H₂O₂ administration resulted in less oxidatively modified protein than found in nonexercised groups (P < 0.05). The peptide- like activity of proteasome complex was induced by the treatment of H₂O₂ and exercise and exercise potentiate the effect of H₂O₂. On the other hand, the chymotrypsin-like and trypsin-like activities were stimulated only by physical training and H₂O₂ administration. The data suggest that chronic administration of H₂O₂ after exercise training decreases the accumulation of carbonyl groups below the steady-state level and induces the activity of proteasome and DT-diaphorase. Hence, the stimulating effect of physical exercise on free radical generation is an important phenomenon of the exercise-induced adaptation process since it increases resistance to oxidative stress. Regular exercise training is a valuable physiological means of preconditioning the myocardium to prolonged oxidative stress. (C) 2000 Academic Press.