Interrelation of actions of glucose, insulin, and glucagon on induction of adenosine triphosphate: D-hexose phosphotransferase in rat liver.

Insulin does not modify the low levels of liver adenosine triphosphate : hexose phosphotransferase attained in rats fed a carbohydrate-free diet, nor does insulin accelerate the induction of phosphotransferase by glucose, indicating that endogenous hormone is sufficient. Glucagon prevents the induction of ATP: hexose phosphotransferase, and this effect is not counteracted by an excess of insulin. A small dose of glucagon that has only a slight effect on phosphotransferase induction causes a definite glycogenolysis in the liver. Furthermore, certain observations on the levels of liver glycogen in animals receiving insulin indicate that secretion of glucagon secondary to insulin hypoglycemia does not interfere seriously with enzyme induction. A hypothesis is presented in an attempt to understand the interplay of different factors affecting ATP: hexose phosphotransferase activity in liver. Glucose and glucagon are considered as inducer and repressor, respectively. Insulin might be a permissive agent, probably acting at the inner membranes of liver cells.