Regulation of glucose uptake by muscle. 2. The effects of insulin, anaerobiosis and cell poisons on the penetration of isolated rat diaphragm by sugars.

The utilization of glucose by muscle is thought to be limited by the rate at which glucose enters the muscle cell and insulin is believed to stimulate glucose uptake by speeding its entry (Levine & Goldstein, 1955; Park, Bornstein & Post, 1955; Park & Johnson, 1955). We have shown that the uptake of glucose by isolated rat diaphragm incubated in a bicarbonate-buffered medium is increased by anoxia and by substances which inhibit oxidative phosphorylation, as well as by insulin (Randle & Smith, 1957, 1958). These observations led us to suggest that the entry of sugars such as glucose into the muscle cell is restrained under basal conditions by a process dependent upon a supply of energy-rich phosphate. We have now attempted to obtain more direct evidence in support of this suggestion by studying the effects of insulin, anaerobiosis and substances which inhibit oxidative phosphorylation on the accumulation of glucose and xylose in isolated diaphragm. We will express the amount of glucose or xylose accumulating in diaphragm as a space, the glucose or xylose space being that fraction of the volume of the tissue which appears to contain fluid of the same specific gravity and glucose or xylose content as the incubation medium. Interpretation of these results in terms of the distribution of sugar between extracellular and intracellular water in-