Glutathione (GSH) content and antioxidant enzyme activities were investigated in skeletal muscle of young, adult, and old male Fischer 344 rats. Furthermore, the effect of 10 wk of exercise training on these antioxidant 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% decrease of GSH (P < 0.05) in the soleus of young rats and a reduction of the GSH-to-GSSG ratio at all ages. Activity of gamma-glutamyl transpeptidase (GGT), a key enzyme for GSH uptake by muscle, was also significantly decreased with training. GSH, GSSG, and the GSH-to-GSSG ratio were not altered with aging or training in the deep portion of vastus lateralis muscle (DVL). Activities of GSH peroxidase (GPX), GSSG reductase (GR), superoxide dismutase (SOD), catalase (CAT), and GSH sulfur-transferase 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 adult rats and GGT and CAT activities in the old rats. Muscle lipid peroxidation 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 but also a fiber-specific adaptation of GSH system in skeletal muscle. Exercise training, although increasing selective antioxidant enzymes in the young rats, does not offer additional protection against oxidative stress in the senescent muscle.

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The rate of oxidative phosphorylation was investigated in isolated mitochondria from hindlimb muscles of young (4.5 mo) and old (26.5 mo) male Fischer 344 rats with or without endurance training. Further, the susceptibility of the muscle mitochondria to exogenous reactive oxygen species was examined. State 3 and 4 respiration, as well as the respiratory control index (RCI), were significantly lower in muscle mitochondria from aged vs. young rats (P<0.05), using either the site 1 substrates malate-pyruvate (M-P) and 2-oxoglutarate (2-OG), or the site 2 substrate succinate. In both young and old rats, training increased state 4 respiration with M-P, but had no effect on state 3 respiration, resulting in a reduction of RCI. Training also increased state 4 respiration with 2-OG and decreased RCI in young rats. When muscle mitochondria were exposed to superoxide radicals (02.-) and hydrogen peroxide (H202) generated by xanthine oxidase and hypoxanthine, or H202 alone in vitro, state 3 respiration and RCI in both age groups were severely hampered, but those from the old rats were inhibited to a less extent than the young rats. In contrast, state 4 respiration was impaired by 02.-and/or H202 to a greater extent in the old rats. Muscle mitochondria from trained young rats showed a greater resistance to the 02 .-and/or H202-induced state 3 and RCI inhibition than those from untrained young rats. Muscle from aged rats had significantly higher total activities of superoxide dismutase (SOD), catalase, glutathione peroxidase (GPX), and glutathione reductase than that from young rats, however, training increased SOD and GPX activities in young but not old rats. The results of this study suggest that mitochondrial capacity for oxidative phosphorylation is compromised in aging skeletal muscle. Further, the increased mitochondrial resistance to reactive oxygen species demonstrated in aged and young trained muscles may be attributed to enhanced antioxidant enzyme activities.

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A patient is described in which excimer laser percutaneous coronary intervention is performed inside a suboptimally expanded stent due to nondilatable calcified plaque. The use of excimer laser facilitated full expansion of the stent with a balloon.