The action of insulin in normal young rabbits

Abstract

THE early publications by the discoverers of insulin gave evidence that under the influence of insulin the glycogen content of the liver increased. Later, however, contradictory results were obtained. Dudley and Further they found that a dose of insulin big enough to produce convulsions depletes the liver and muscles of glycogen. Collazo, Hiindel and Rubino [1924], however, investigating the glycogen of liver and muscles in normal guinea-pigs 4 hours after the injection of 7 units of insulin, found a marked increase in both situations. Their animals were starved for 18 hours and received 3 g. of glucose by stomach tube before the injection of the insulin. The degree of rise in glycogen in these experiments both in liver and muscle was about 50 to 70 % above the controls. Cori [1925] found that starving rabbits showed no appreciable change in their liver-glycogen in the first hour of insulin action and that this was true whether the initial glycogen content was high or low and whether the fall in blood-sugar was large or small. In the second hour after insulin the liver-glycogen was found to remain constant or decrease. Similar reslts were obtained with mice, the average liver-glycogen of 16 injected animals being 39 % lower than the average of 16 controls. On the other hand completely phloridzinised and starving cats, dogs and rabbits were found to deposit liver-glycogen under the influence of insulin. Cori [1924] found an increased glycogen formation as a result of insulin action. Grevenstuk and Laqueut [1925], however, questioned this result. Frank and Hartmann [1926] criticised the findings of Grevenstuk and Laqueur, and Frank,-Nothmann and Hartmann [1925] claim to have found an increase in liver-glycogen in fasting rabbits using small doses of insulin. Barbour et al. [1927], using a large number of standard rats, examined the changes in blood-sugar and. muscleand liver-glycogen induced by insulin. The e1fect :produced depended on the dose of insulin. Thus, with 1 or 2 units per kg. body weight-the liver-glycogen; fell during the first 14 hours and rose slightly after 2 hours: with 3 units per- kg. there occurred a steadily progressive fall in the liver-glycogen. The muscle- glycogen of starving animals fell in all cases' after insulin. In fed animals, 6-2