ALTERATION OF MYOCARDIAL ANTIOXIDANT ENZYME-ACTIVITY AND GLUTATHIONE CONTENT WITH AGING AND EXERCISE TRAINING

Antioxidant enzyme activities and glutathione (GSH) content were inves tigated in the ventricular myocardia of adult (4.5 mo.), mid-age (14.5 mo.), and old (26.5 mo.) male Fischer 344 rats. In addition, the effe ct of 10 wks of exercise training (T) on these antioxidant systems was evaluated at each age. T was performed on a rodent treadmill for 1 hr /day, 5 days/wk at a speed and grade adjusted for the animal's age. Ac tivities of superoxide dismutase (SOD), glutathione peroxidase (GPX), and glutathone disulfide (GSSG) reductase were increased by 39%, 27% a nd 38%, respectively (p < 0.05), in old vs young rats. T has no signif icant effect on antioxidant enzyme activities at any age. Myocardial p rotein concentration of the aged heart was significantly lower compare d to that of the adult or young rats. Total glutathione concentration in the heart was increased in old (12.5 +/- 0.6) vs adult (10.7 +/- 1. 2) and mid-age (9.7 +/- 0.9 nmol/mg protein) rats (p < 0.05), however the GSH/GSSG ratio was not altered by T in any age group. Myocardial m alondialdehyde (MDA) content was increased (p < 0.001) with aging. How ever, MDA content in mid-age and old T rats was decreased by 21 and 25 %, respectively, compared to their untrained counterparts (p < 0.05). It is concluded that aged hearts are susceptible to oxidative stress d espited increased antioxidant capacity and that training may attenuate the age-associated increase in lipid peroxidation in the heart.