Glucose delivery: a modulator of glucose uptake in contracting skeletal muscle.

To evaluate glucose delivery and neuromuscular activity as modulators of glucose uptake in skeletal muscle, rat hindlimbs from pentobarbital-anesthetized rats were perfused in the presence of electrically stimulated muscular contractions. Glucose delivery was varied by altering non-cyclic perfusate flow. When flow was increased from 3 to 12 ml/min glucose disappearance increased from 1.1 +/- 0.2 to 4.0 +/- 0.2 mumol/min per 100 g rat (P less than 0.001). When glucose delivery was held constant, glucose disappearance was unaltered during muscular contractions. Insulin enhanced glucose disappearance, and its effect was unaltered during muscular contractions. Muscular contractions increased oxygen disappearance by two- to 3.5-fold and lactate appearance by 4.5- to fivefold (P less than 0.02). It was concluded that glucose delivery and insulin modulate glucose disappearance in isolated perfused rat hindlimbs. Electrical stimulation of muscle enhances lactate appearance and oxygen disappearance but does not alter glucose disappearance when flow is held constant. Because blood flow to muscle increases during exercise in vivo, increased glucose delivery may be a modulator of the augmented muscle glucose consumption observed under these conditions.