Mice with subcutaneous, isogeneic transplants of duct-ligated pancreas from either two or five donors displayed impaired glucose tolerance to gastric or intravenous glucose, or to an overnight fast followed by a 15-min meal of mouse food. Compared with peripheral insulin responses in normal controls, those of transplant recipients were less after gastric or intravenous glucqse, but no different after the meal. Despite normalization of peak insulin levels in the peripheral circulation of isografted mice, glucose clearance was still impaired and this probably resulted, in part, from a relative insufficiency of insulin in the portal circulation. Results of glucose tolerance tests, after transplant recipients consumed a relatively small amount of food, suggested that near-normal glucose homeostasis may be present for these mice under normal feeding conditions.
In mice that received incremental doses of streptozotocin, impaired glucose tolerance to a meal was observed if pancreatic insulin content fell below 26% of normal. We failed to show a similar relationship between glucose tolerance and pancreatic insulin content in transplant recipients since all showed impaired glucose tolerance. Despite the initial transplantation of different amounts of islet tissue, at termination insulin content (transplant plus endogenous pancreas) was essentially the same for all recipients, totaling 19–22% of that found in a normal mouse pancreas.