Repeated exercise regulates glucose transport capacity in skeletal muscle.

The present study was undertaken to test the hypothesis that a muscle's habitual level of contractile activity might act as a long-term regulator of glucose transport capacity. Rats were rendered severely diabetic by injection of streptozotocin, 125 mg kg-1 body wt. Three days after the injection, insulin-stimulated and contraction-induced 3-methylglucose transport in the in vitro epitrochlearis muscle preparation was reduced to 25% and 52% of control capacity, respectively (P less than 0.001). However, when repeated 1-h swimming sessions (twice a day) were introduced during the 3 days of insulin deficiency, the reduction in contraction-induced glucose transport capacity was completely abolished. This indicates that the habitual level of contractile activity of a muscle regulates its capacity for exercise-stimulated glucose transport. Furthermore, one exercise session and a maximal insulin stimulus had an additive effect on 3-methylglucose transport, suggesting that there are two pools of intracellular glucose transporters or two mechanisms for mobilizing the same pool.