EFFECT OF EXERCISE ON ALPHA-GLYCEROPHOSPHATE DEHYDROGENASE ACTIVITY IN SKELETAL MUSCLE

The level of activity of cytochrome oxidase, expressed per gram of fresh muscle, doubled in the gastrocnemius muscles of rats subjected to a strenuous program of treadmill running. The concentration of cytochrome c also increased twofold. In contrast, the levels of activity of mitochondrial and of eytoplasmic α-glycerophosphate dehydrogenase per gram of muscle were unaffected by the exercise. The protein content of the mitochondrial fraction from gastrocnemius muscles was increased approximately 60% in the exercising group. As a result, when cytochrome oxidase activity was expressed per milligram of mitochondrial protein, the difference between the exercising and sedentary groups was no longer significant. On the other hand, when mitochondrial α-glycerophosphate dehydrogenase activity was expressed per milligram of mitochondrial protein the value for the exercising group was significantly lower than that for the sedentary controls. These findings provide evidence that the adaptive response to prolonged exercise involves a change in the composition of the cristae of skeletal muscle mitochondria, rather than a simple uniform increase in size or number. © 1969.