Reinnervation of allografted pancreatic islets in the rat liver

Rat pancreatic islets were allografted in the liver and were studied morphologically in order to evaluate possible reinnervation. Islets isolated from rat pancreas were allotransplanted in the liver of streptozocin-induced diabetic rats via the portal vein. Electron microscopy revealed nerve endings with synaptic vesicles in the transplanted islets 100 days after transplantation, whereas axons in the islets appeared to degenerate several hours after isolation and prior to transplantation. These findings suggest that the nerve endings observed in the transplanted islets regenerate from nerves that innervate the recipient's liver. The tissue specimens were also investigated immunohistochemically using antityrosine hydroxylase antibody, and histochemically by the modified Karnovsky and Roots' method for visualizing acetylcholinesterase. Some nerve endings in the transplanted islets reacted positively to antityrosine hydroxylase antibody. Acetylcholinesterase was visualized in other nerves. These results indicate that norepinephrine- and acetylcholinesterase-containing nerves may reinnervate the transplanted islets.