Effect of insulin on potassium efflux from rat muscle in the presence and absence of glucose

¹ Department of Medicine, The Johns Hopkins University and Hospital, Baltimore, Maryland

Potassium efflux from rat extensor digitorum longus muscle was measured by counting the decrease in K⁴² in muscle bathed in K⁴²-free solution. The rate constant for K efflux was 0.27 hr.^–1 at 37°C and 0.16 hr.^–1 at 26°C. Insulin decreased the rate constant for K efflux to 0.22 hr.^–1 at 37°C and to 0.09 hr.^–1 at 26°C. The effect of insulin on efflux was quantitatively the same when glucose was removed from the bathing solution. From measurement of net change in intracellular K and from measurement of changes in the driving potential for K it is concluded that insulin probably also decreases K influx, but to a lesser degree. However, when half the chloride is removed from the bathing solution, efflux and influx are decreased equally. The data can be interpreted by the hypothesis that insulin increases the positive fixed charge within the muscle membrane.

Note:
With the Technical Assistance of Ellen Rogus and William J. Sullivan

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