ACTION OF INSULIN ON THE EXTRAHEPATIC TISSUES* BY ARNE N. WICK, DOUGLAS R. DRURY, RICHARD W. BANCROFT, AiVD

There is still much that is controversial concerning the action of insulin on glucose metabolism. There is general agreement that in the intact animal, with the blood sugar maintained at a normal or supernormal level, large doses of insulin will promote the storage of glucose. Workers in the field, however, do not agree as to whether storage will only take place if the liver is functioning or whether this is a process that can be handled by the extrahepatic tissues. Thus Bouckaert and de Duve in a recent review state (l), “It is clear that doses of insulin higher than the physiologically secreted amounts of this hormone act almost exclusively on the liver, where they promote glucose-retention in a remarkable way, the ratio hepatic action/peripheral action being 25.” Another action ascribed to insulin is that of increasing the immediate oxidation of glucose. That this is still controversial may be judged from the following quotation from the monograph of Soskin and Levine ((2) p. 181). “One of the most firmly intrenched notions about insulin in the metabolic literature is that it increases the dissimilation of carbohydrate. This is without basis in fact, for, as pointed out in chapter XIV, no overall measure of dissimilation in the living organism is yet available.” By dissimilation these authors mean the complete oxidation of a substrate to carbon dioxide and water ((2) p. 148). The chief argument used to support the claim that insulin increases the “complete oxidation”i of glucose has been that there is an increase in the respiratory quotient after administration of this hormone. A rise in the respiratory quotient could occur as a result of an increased conversion of glucose to fat in some special organ or tissue, while the rest of the tissues maintained a constant type of metabolism. The conversion of glucose to fat is ordinarily thought to take place