Effect of Exercise on the Turnover of Cytochrome c in Skeletal Muscle

The concentration of cytochrome c has previously been shown to increase 2-fold in leg muscles of rats subjected to a program of prolonged exercise. In the present study it was found that the radioactivity of cytochrome c labeled with δ-amino[14C]levulinate decreased significantly more slowly in quadriceps muscles of rats subjected to a program of running than in muscles of sedentary animals. The t½ of muscle cytochrome c was 32 days in the sedentary animals and 48 days in the runners. The synthesis rate of cytochrome c was calculated to be approximately 0.630 nmole per muscle per day in the sedentary and 0.771 nmole per muscle per day in the exercised animals. Thus, a decrease in the rate of degradation plays the major role in accounting for the adaptive increase in the concentration of cytochrome c that occurs in muscle in response to exercise.