Effect of diabetes on the rat hepatic glucose-6-phosphatase system in endoplasmic reticulum subfractions

Diabetes-induced alterations in the activities of the components of the glucose-6-phosphatase system (i.e., the enzyme, the glucose-6-P translocase (T(1)), and the phosphate translocase (T(2)) were examined in smooth and rough subfractions of hepatic endoplasmic reticulum from streptozotocin-injected rats. A significant effect of diabetes on the maximal velocity of glucose-6-P hydrolysis by the enzyme was present in both endoplasmic reticulum subfractions (3.1-fold increase in rough endoplasmic reticulum; 3.8-fold increase in smooth endoplasmic reticulum). Based on latency values, diabetes did not result in a proportional increase in capacity of T(1) or T(2). In contrast to the control condition, the relationship between transport capacity and hydrolytic capacity was not significantly different in the two subfractions from diabetic animals. Elucidation of the effects of diabetes on the components of the glucose-6-phosphatase system associated with smooth and rough endoplasmic reticulum membranes enhances our understanding of the hepatic contribution to diabetic hyperglycemia.