Hypoglycaemia induces decreased islet blood perfusion mediated by the central nervous system in normal and Type 2 diabetic GK rats

Aims/hypothesis. The aim of this study was to evaluate the effects of induced hypoglycaemia on pancreatic-islet blood flow in normal rats and in the GK rat, an animal model of Type 2 diabetes which normally has an increased islet blood perfusion. Methods. A 50% reduction in blood glucose concentrations was achieved by intravenous administration of a rapidly acting insulin (15 IU/kg body weight). Blood flows were measured by a non-radioactive microsphere technique. Results. A pronounced decrease in islet blood flow was observed in all animals, but preferentially in the Type 2 diabetic GK rats. When a similar dose of insulin was given to whole-pancreas transplanted rats only islet blood flow in the native pancreas was decreased, whereas that of the transplanted, i.e. denervated, pancreas was unchanged. Administration of 2-deoxy-D-glucose, which induces intracellular glucopenia especially in neurons, also decreased islet blood flow despite a systemic hyperglycaemia. Conclusion/interpretation. Hypoglycaemia leads to a preferential decrease in pancreatic-islet blood perfusion. The effect is probably mediated by the central nervous system, since 2-deoxy D-glucose-induced neuronal glucopenia caused a similar decrease in blood flow. The effects of islet blood flow are not likely to be mediated by nervous stimulation of the adrenal glands, with an associated release of catecholamines, because the transplanted pancreas was not affected by hypoglycaemia. The decreased islet blood perfusion could possibly diminish the output of insulin from the islets, thereby preventing a further decrease in blood glucose concentrations.