ENHANCED MUSCLE GLUCOSE-METABOLISM AFTER EXERCISE - MODULATION BY LOCAL FACTORS

Studies in the rat suggest that after voluntary exercise there are 2 phases of glycogen repletion in skeletal muscle (preceding study). In phase I glucose utilization and glycogen synthesis are enhanced both in the presence and absence of insulin, whereas in phase II only the increase in the presence of insulin is found. To determine whether these alterations and in particular those mediated by insulin are due to local or systemic factors, 1 hindlimb of an anesthetized rat was electrically stimulated and both hindlimbs were perfused immediately thereafter. Glucose and glycogen metabolism in the stimulated leg closely mimicked that observed previously after voluntary exercise on a treadmill. With no insulin added to the perfusate, glucose incorporation into glycogen was markedly enhanced in muscles that were glycogen depleted as were the uptake of 2-deoxyglucose and 3-O-methylglucose. Likewise, the stimulation of these processes by insulin was enhanced and continued to be so 2 h later when the muscles of the stimulated leg had substantially repleted their glycogen stores. Increases in insulin-mediated glucose utilization and glycogen synthesis in muscle after exercise evidently are modulated by local contraction-induced factors.