Regulation of glucose uptake by muscle. 1. The effects of insulin, anaerobiosis and cell poisons on the uptake of glucose and release of potassium by isolated rat diaphragm

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Abstract
Anaerobiosis stimulates the uptake of glucose by isolated rat diaphragm incubated in a medium buffered with bicarbonate. This effect is not observed in media buffered with phosphate or tris (of initial pH 7.4). The lack of response to anaerobiosis in the latter media appears to be related to the marked fall in pH which occurs during incubation. Under aerobic conditions uptake of glucose by diaphragm in bicarbonate medium is increased by 2,4-dinitrophenol (50 [mu]M or 0.25 mM), sodium arsenite (mM), sodium arsenate (10 mM), sodium cyanide (mM) and sodium salicylate (5 mM). Sodium azide (mM or 10 mM) and sodium p-hydroxybenzoate (5 mM) do not augment glucose uptake. In a medium buffered with phosphate, 2,4-dinitrophenol (0.25 mM), sodium salicylate (5 mM) and sodium cyanide (mM) fail to stimulate glucose uptake. In bicarbonate medium the uptake of glucose by diaphragm in the presence of 2,4-dinitrophenol, sodium arsenite or sodium salicylate is increased still further by the addition of insulin (0.1 unit/ml), though the uptake of glucose achieved under these conditions is less than that with insulin alone. The levels of uptake with insulin under either aerobic or anaerobic conditions were of the same order. In the presence of both insulin and cyanide the uptake of glucose is greater than when either is present by itself. There is a small loss of potassium from diaphragm incubated under aerobic conditions either in bicarbonate or in phosphate medium. The loss of potassium in either medium is very much greater under anaerobic conditions or in the presence of 2,4-dinitrophenol, sodium arsenite, sodium arsenate, sodium cyanide, sodium salicylate or sodium azide at the above concentrations. Insulin effected a slight reduction in the loss of potassium under aerobic conditions. There was no obvious quantitative relation between the loss of potassium from the muscle and the change in glucose uptake. The significant of these results in relation to the mode of uptake of glucose by diaphragm, to the Pasteur effect in diaphragm and to the mechanism of action of insulin on diaphragm is discussed.