Effect of insulin on carbohydrate metabolism and on potassium in the forearm of man.

We have described a technique for quantifying skeletal muscle metabolism in man in. situ by measing blood flow through the forearm and appropriate arteriovenous differences in concentration of selected metabolites ( 1 ). The technique lends itself to analysis of local effects of hormones and other possibly potent agents. The agent can be injected into the brachial artery at constant rate with the solution of Evans blue dye used to measure blood flow. The quantity of the agent injected can be sufficiently large to exert a measurable effect in the forearm but sufficiently small so that, upon approximately 100-fold dilution when forearm venous effluent mixes with blood in the heart and great vessels, there is no measurable systemic effect. There are, therefore, no detectable systemic counter-regulatory processes set in motion by the agent to complicate the primary response of the forearm to the agent itself. It is the purpose of this report to describe the effects on forearm muscle metabolism of insulin administered in this fashion. We sought information concerning the following two problems. 1) Only a minor fraction of oxygen consumed by forearm muscle at rest can be accounted for by dissimilation of glucose abstracted from arterial blood (1). Is this because resting muscle is so poorly permeable to glucose? If glucose uptake is increased, say by exhibition of insulin, is oxidation of glucose enhanced necessarily? 2) Do the temporal and molar relations between glucose uptake and potassium uptake by muscle in response to insulin suggest that insulin-induced