On the mechanism of insulin action.

Abstract

The generally accepted explanation of the blood sugar lowering the effect of insulin when injected into the mammalian organism, either subcutaneously or intravenously, is that an interaction takes place between the injected hormone and the cells or tissue fluids of the body. The chemical structure of insulin is unknown, and the nature of its chemical reactions within the body has not been determined up to the present time.

Mueller and Corbitt 1 found that in rabbits there was a difference in the blood sugar lowering effect between the intradermal and the subcutaneous administration of insulin. By intradermal injection the blood sugar lowering effect was found to be of longer duration than by subcutaneous injection.

This observation led to further research work upon the effect of the two methods of administration of insulin in human subjects. The results form the basis of the present communication. Diabetics as well as individuals with a normal carbohydrate metabolism were studied. The experiments were done in the morning, with the subject in a fasting condition, or following a breakfast of definite composition, finished at a known time. For the injections the U 40 strength of Insulin Lilly (Iletin) was employed. Two experiments on the same individual, employing like doses of insulin from the same bottle and under the same dietary conditions, but differing in the method of administration of the insulin, constitute a series and are so referred to in the text to follow. A total of 33 such series are here reported.

The blood sugar was determined immediately before the insulin injection, and at one hour, two hours and four hours following the injection. In a sufficient number of cases the same blood sugar curve, but omitting the insulin injection, was determined.