Glycolytic enzymes in different types of skeletal muscle: adaptation to exercise.

BALDWN, K. M., W. W. WINDER, R. L. TERJUNG, AND J. 0. HOLLOSZY. Glycoi’ytic enzymes in di$erent types of skeletal muscle: adaptation to exercise. Am. J. Physiol. 225(4): 962-966. 1973.-The level of activity of hexokinase increased 1700/;, in red skeletal muscle (red portion of quadriceps), 50y0 in intermediate (soleus), and 30% in white skeletal muscle (white portion of quadriceps) in rats subjected to a program of treadmill running. The only other change found in the levels of the glycolytic enzymes in white muscle was a 15 y0 decrease in lactate dehydrogenase activity. In red muscle a small but consistent decrease (approximately 20(%) occurred in the levels of activity of glycogen phosphorylase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, pyruvate kinase, lactate dehydrogenase, and cytoplasmic aglycerolphosphate dehydrogenase in response to the exercise program. In contrast to the decrease in the levels of these enzymes in red muscle, the exercise induced a 50% increase in cytoplasmic a-glycerolphosphate dehydrogenase activity, and 18-35 y. increases in the levels of phosphorylase, phosphofructokinase, glyceraldehyde-3-phosphate dehydrogenase, and pyruvate kinase in intermediate muscle. As a result of the adaptions induced by exercise, the red and intermediate types of skeletal muscle become more like heart muscle in their enzyme patterns.