The influence of insulin on the liver glycogen and free liver sugar of starving animals.

Abstract

Dudley and Marrian 1 reported diminution in the liver glycogen in one rabbit and in several mice during the convulsive stage of insulin action. Since it was thought that convulsions may produce changes which are not necessarily related to the action of insulin, experiments were performed with animals above the convulsive blood sugar level.

Eight rabbits and fifty mice were used. It was found in rabbits that there is no appreciable change in the glycogen (Pflüger's method) or total carbohydrate content of the liver within the first hour of insulin action, whether the initial glycogen content of the animal was high or low, or whether the fall in blood sugar was slight or great. In the second to sixth hour of insulin action, the glycogen content of the liver may remain constant or may decrease. Thus in three experiments the liver glycogen did not change during the periods of observation of three, four, and six hours respectively, while in three other experiments the glycogen was lowered during the second hour of insulin action. The initial glycogen content in the latter group of experiments was higher than in the former. In the experiments with mice, the fact that they live only two days when deprived of food, was taken into consideration. Consequently starvation times from one to three hours were chosen. The length of time that insulin was allowed to act varied from fifteen minutes to one hour. The livers were analyzed for glycogen by Pflüger's method and the blood sugar of each mouse was determined. An equal number of controls and injected mice was used. The following averages were obtained: 1.47 per cent liver glycogen, 0.131 per cent blood sugar in control mice, 0.91 per cent liver glycogen, 0.066 per cent blood sugar in insulin mice.