Differential Effect of Denervation on Free‐Radical Scavenging Enzymes in Slow and Fast Muscle of Rat

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Abstract
To determine the effect of denervation on the free-radical scavenging systems in relation to the mitochondrial oxidative metabolism in the slow-twitch soleus and fast-twitch extensor digitomm longus (EDL) muscles, the sciatic nerve of the rat was crushed in the mid-thigh region and the muscle tissue levels of five enzymes were studied 2 and 5 weeks following crush. Recently developed radioimmunoassays were utilized for the selective measurement of cuprozinc (cytosolic) and man-gano (mitochondrial) superoxide dismutases. Total tissue content of cuprozinc superoxide dismutase showed a mild decrease after denervation in slow but not in fast muscle. Manganosuperoxide dismutase and fumarase decreased markedly at 2 weeks and returned toward control levels by 5 weeks, the changes appearing to be greater in slow than in fast muscle. At 2 weeks, cytochrome c oxidase decreased significantly in slow, but not in fast muscle. GSH-peroxidase at baseline was 10-fold higher in slow than in fast muscle, markedly decreased at 2 weeks in slow muscle, and returned toward control levels at 5 weeks, whereas the total enzyme activity in fast muscle did not change through 5 weeks. These data represent the first systematic report of free radical scavenging systems in slow and fast muscles in response to denervation. Selective modification of cuprozinc and manganosuper-oxide dismutases and differential regulation of GSH-peroxidase was demonstrated in slow and fast muscle.