Effects of glucose on phosphorylase and glycogen synthase in hepatocytes from diabetic rats

The effects of glucose on phosphorylase and glycogen synthase were investigated in hepatocytes isolated from acutely (40 h) and chronically (90 h) alloxan-diabetic rats. The glucose-induced inactivation of phosphorylase proceeded normally in all conditions. The ensuing activation of glycogen synthase was slightly blunted in acute diabetes, but became virtually absent in 72 h diabetes of similar severity. In hepatocytes from rats with various degrees of chronic diabetes, the maximal activation of glycogen synthase (at 60 mM-glucose) was inversely correlated with the plasma glucose concentration.