Functional stimulation of graft nerves has minor effects on insulin release from transplanted rat pancreatic islets

Introduction. Morphological evidence for reinnervation of pancreatic islet grafts is plentiful. However, to what extent intra-graft nerves influence the endocrine functions of the islet transplant is largely unknown. We therefore aimed to directly stimulate nerves leading to islet grafts with electrodes and measure insulin secretion in response to this. Methods. We implanted syngeneic islets under the renal capsule of rats, and examined them 1 or 7-9 months later. In anesthetized rats blood samples were collected from the renal vein and femoral artery, respectively, during electrode stimulation of the nerves leading to the islet grafts. Results. As expected, nerve stimulation decreased renal blood flow. However, serum insulin concentrations in samples derived from the renal vein or femoral artery changed in concert with one another, both during normoglycemia and acute hyperglycemia. Conclusion. Reinnervation which occurs after islet transplantation under the renal capsule has minor effects on graft endocrine function.