AGING AND EXERCISE TRAINING IN SKELETAL-MUSCLE - RESPONSES OF GLUTATHIONE AND ANTIOXIDANT ENZYME-SYSTEMS

Glutathione (GSH) content and antioxidant enzyme activities were inves tigated in skeletal muscle of young, adult, and old male Fischer 344 r ats. Furthermore, the effect of 10 wk of exercise training on these an tioxidant systems was evaluated at all ages. In the soleus muscle, GSH concentration increased markedly with age, with no significant change in glutathione disulfide (GSSG) content. Training caused a 30% decrea se of GSH (P < 0.05) in the soleus of young rats and a reduction of th e GSH-to-GSSG ratio at all ages. Activity of gamma-glutamyl transpepti dase (GGT), a key enzyme for GSH uptake by muscle, was also significan tly decreased with training. GSH, GSSG, and the GSH-to-GSSG ratio were not altered with aging or training in the deep portion of vastus late ralis muscle (DVL). Activities of GSH peroxidase (GPX), GSSG reductase (GR), superoxide dismutase (SOD), catalase (CAT), and GSH sulfur-tran sferase were increased significantly with aging in both soleus and DVL . In DVL, training increased GPX and SOD activities in the young rats, whereas in soleus, training decreased GR and CAT activities in the ad ult rats and GGT and CAT activities in the old rats. Muscle lipid pero xidation was significantly increased with aging in both DVL and soleus but was not affected by training. These data indicate that aging may cause not only an overall elevation of antioxidant enzyme activities b ut also a fiber-specific adaptation of GSH system in skeletal muscle. Exercise training, although increasing selective antioxidant enzymes i n the young rats, does not offer additional protection against oxidati ve stress in the senescent muscle.