Reversal of the Enhanced Somatostatin Release from the Isolated, Perfused Diabetic Rat Pancreas after the Amelioration of Diabetes by Whole Pancreas Transplantation

Abstract

To investigate the pancreatic endocrine function in streptozotocin-diabetic rats before and after the whole pancreas was transplanted, pancreatic insulin, gluca-gon, and somatostatin content and release were measured. Highly inbred Lewis male rats were divided into the following three groups: normal control rats; streptozo-tocin-induced-diabetic rats; and streptozotocin-diabetic rats transplanted with whole pancreas. Studies in vivo revealed normalization of elevated blood glucose and marked improvement of the impaired arginine-induced plasma insulin release by the transplantation of a healthy pancreas into the diabetic rats. Neither basal nor arginine-induced plasma glucagon levels in the diabetic rats were significantly different from the normal group, but significantly higher plasma glucagon levels were found in the transplanted rats. Studies in vitro using the isolated perfused rat pancreas revealed a significant increase of somatostatin release from the diabetic pancreas, with a marked reduction of insulin release and almost normal glucagon release. In the transplanted rats, on the other hand, arginine-induced somatostatin release from the host pancreas was reduced to normal without a significant change in insulin or glucagon release. In addition, the endocrine function of the graft remained normal in the transplanted rats. Pancreatic somatostatin release, thus, appears to be affected by changes in circulating insulin, since pancreatic transplantation effectively corrects the circulating insulin level.