Functional aspects of mouse islets transplanted to the kidney

To test whether the transplantation of pancreatic islets affects their basic functions, collagenase-isolated mouse islets were inserted under the left renal capsule of recipient animals. After various periods of time, grafts were removed from the kidney and examined for insulin content and secretory dynamics in a perifusion system. During syngeneic (C57BL/6, BALB/c) or subsyngeneic (NMRI) intrastrain transplantation, the graft insulin content fell drastically during the first week and stayed low for at least 6 weeks; first-phase secretion in general appeared suppressed. Immunosuppression by cyclosporin A had little effect on (sub)syngeneic grafts but markedly improved the performance of allotransplants. Daily injections of the calcium antagonist, verapamil, enhanced the insulin secretory responses of isolated grafts, whether (sub)syngeneic or allogeneic. In syngeneic and subsyngeneic grafts, the potentiating effect of acetylcholine on glucose-induced insulin release was markedly diminished, whereas that of caffeine was not. Transplanted islets also exhibited a subnormal responsiveness to the inhibiting action of noradrenaline. It is concluded that chronic denervation and transplantation of pancreatic islets may cause fundamental changes in the beta-cell responses to physiological regulators of insulin release.