Exercise Training-Induced Alterations in Skeletal Muscle Oxidative and Antioxidant Enzyme Activity in Senescent Rats

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Abstract
Limited data exist concerning exercise training-induced alterations in skeletal muscle oxidative and antioxidant enzyme activity in senescent animals. Therefore, the purpose of this study was twofold: 1) to examine the exercise training-induced changes in oxidative and antioxidant enzyme activity in skeletal muscle of old rats; and 2) to critically analyze the relationship between oxidative and antioxidant enzyme activities in skeletal muscle in both trained and untrained senescent rats. Female Fischer-344 rats (∼ 24-mo-old) were divided into 1) exercised trained (ET; n = 10) and 2) sedentary (S; n = 6) groups. The ET rats performed a 10-week training program of treadmill exercise (∼ 60 min, 5 days/wk). Training significantly (p2max (Δ22.8%) in the ET rats above their age-matched controls. Further, the ET group had significantly elevated (p<0.05) activities of succinate dehydrogenase (SDH) in the soleus and red gastrocnemius (RG) muscles as well as greater (p0.05) HADH activity within the white gastrocnemius (WG) or soleus muscles. Activity of the antioxidant enzyme, glutathione peroxidase (GPX) was higher (p<0.05) in the soleus and RG in ET rats when compared to the S rats; in contrast, training did not alter (p<0.05) GPX activity in the WG. Finally, the correlation coefficients between SDH and GPX activities (combined ET and S groups) for the RG, WG, and soleus muscles were r = .73, .17 and .36, respectively. We conclude that endurance training in senescent rats elevates both SDH and GPX activities in hindlimb muscles containing a high percentage of type I or type IIa fibers; however, endurance training does not result in increases in oxidative and antioxidant enzyme activities in all hindlimb muscles in aged rats.

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