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 (p<0.05) improved V̇O2 max (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 (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.
Key words
Free radical - glutathione peroxidase - succinate dehydrogenase - exercise - hydroperoxides
