Mitochondrial enzymatic adaptation of skeletal muscle to endurance training

Some mitochondrial enzymatic activities (succinate dehydrogenase, NADH cytochrome reductase, cytochrome oxidase) were studied in the gastrocnemius and soleus muscle of the rat. The modifications of the enzyme activity, induced by endurance training, were found to be functions of 1) daily work load and 2) total training time. The treatment with an effective dose of vasodilating substances (papaverine, nicergoline, dipyridamole, and bamethan) showed that 1) nicergoline, bamethan, and dipyridamole were differently able to shorten the time of appearance of the increase in the enzymatic activities; 2) however, long-term treatments with these drugs did not prove able to modify the plateau level of the enzymatic activity increase, for a given amount of endurance training; 3) the pharmacodynamic effect on enzymatic activities was in no way related to the vasodilating effect of these drugs, since the effect was not observed with papaverine. The transition from a given level of endurance training to a lower one led to a proportional decrease of the mitochondrial enzymatic activities, thus pointing out the relation between amount of training and enzymatic activity. The drugs studied were unable to modify the decrease of enzymatic activity induced by lower work load.