THE EFFECT OF INSULIN ON PHOSPHORUS TURNOVER IN MUSCLE

Abstract

The effect of insulin on phosphate turnover in striated muscle has been studied in cats by means of radioactive phosphorus (P32). In both fasting and post-absorptive animals given glucose, insulin increased the turnover rates of phospho-creatine and the 2 labile phosphate groups of adenosine tri-phosphate, in resting muscle. It also increased the turnover rate of glucose-6-phosphate in resting muscles of post-absorptive animals. The increase in turnover of P which normally takes place in the post-absorptive state, in recovery from prolonged activity, did not occur when insulin was administered. Insulin did not modify the extent of formation of glucose-6-phosphate on the muscle cell membrane in resting muscles of either fasting or post-absorptive animals. Insulin increased the formation of glucose-6-phosphate on the cell membrane during recovery from muscular activity, in fasted, but not in post-absorptive animals. Insulin did not counteract the effect of glucose in reducing P turnover in the post-absorptive state. The evidence indicates that insulin accelerates the rate of glucose oxidation within the muscle cell, but that other factors are of greater importance in determining the rate of passage of glucose across the cell membrane.