EXERCISE TRAINING-INDUCED ALTERATIONS IN SKELETAL-MUSCLE OXIDATIVE AND ANTIOXIDANT ENZYME-ACTIVITY IN SENESCENT RATS

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 (approximately 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 (approximately 60 min, 5 days/wk). Training significantly (p < 0.05) improved VO2max (DELTA-22.8 %) 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 (p < 0.05) 3-hydroxyacyl-CoA dehydrogenase (HADH) activity in the RG when compared to the S group. However, training did not alter (p > 0.05) 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.