Hepatic Glycogen Metabolism and Insulin Receptor Status After Long-term Peripheral Insulin Delivery in the Islet-Transplanted Diabetic Rat

Severely diabetic (0.15 g/kg streptozocin) rats were transplanted with fetal pancreatic islets (1) under the renal capsule to model peripheral insulin delivery, or (2) into the splenic pulp to model portal delivery. In both groups of transplanted rats, weight gain and blood glucose concentrations were normal. Peripheral insulin delivery abolished the physiologic portal-peripheral insulin concentration gradient but was not associated with peripheral hyperinsulinemia. Incorporation of ³H₂O into liver glycogen and the increase in hepatic glycogen concentration after a meal were normal in animals receiving insulin peripherally for 10 wk. Activation of liver glycogen synthase in response to the meal was also normal. Hepatic insulin receptor status in animals with peripheral insulin delivery was identical to that of normal control and splenic pulp islet-transplanted rats. The findings indicate that portal insulin delivery is not a prerequisite for normal hepatic glycogen metabolism in the rat, and that receptor upregulation and increased hepatic extraction of insulin are unlikely to explain the normal hepatic metabolism with peripheral insulin delivery.