EXERCISE TRAINING ALTERS KINETICS OF ANTIOXIDANT ENZYMES IN RAT-TISSUES

Michaelis-Menten constant (K-m) and maximum velocity (V-max) of catala se(CAT), glutathione peroxidase (GSH-Px) and glutathione reductase (GR ) in various tissues of exercise-trained old rats were compared with t he age matched sedentary control. Exercise training increased the maxi mum velocity (V-max) for CAT in the brain (350%), liver (33%), lung (3 4%), muscle (25%) and testes (21%); for GSH-Px (using t-butyl hydroper oxide as a substrate) in the liver (22%), lung (25%), and testes (52%) ; for GSH-Px (using GSH as a cosubstrate) in the brain (64%) and liver (100%), and for GR in testes (50%). This increase in V-max indicates t he potential activation of these enzymes in the specific tissues. Exer cise training differentially altered the affinities of enzyme (K-m) fo r CAT, GSH-Px and GR to their substrates. These studies suggest that e xercise training provided a beneficial role by activation of antioxida nt enzymes in specific tissues of aged rats. Thus, exercise training a ids in coping with oxidative stress in old age.