Effect of Very Small Concentrations of Insulin on Forearm Metabolism. Persistence of Its Action on Potassium and Free Fatty Acids without Its Effect on Glucose*

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Abstract
Insulin was infused into the brachial artery of normal men at a rate of either 1, 10 or 100 [mu]U/minute/kg body weight. The smallest dose was without measurable effect on forearm metabolism. The largest dose produced uptake of glucose and K by forearm and blockade of free fatty acid (FFA) release from adipose tissue. The intermediate dose, which raised brachial arterial insulin concentration by an average of 38 [mu]U per ml markedly increased K uptake by both forearm muscle and adipose tissue and sharply reduced FFA release from adipose tissue. Glucose uptake by forearm (muscle and adipose tissue) was not altered. It is concluded that insulin''s actions on K uptake and on FFA release do not require that insulin translocate glucose.