Insulin and glucagon secretion in streptozotocin-diabetic rats: influences of islets transplanted to the renal subcapsular space.

Two days after diabetes induction by streptozotocin 70 mg/kg i.v. in rats, 1,000 freshly hand-picked islets were transplanted to the renal subcapsular space. The insulin and glucagon secretory capacities were evaluated during the first 10 days after transplantation by the use of arginine infusion and glucose injection. Already at day 3 after transplantation, the basal hyperglycemia and hyperglucagonemia were markedly reduced. However, no plasma insulin response to arginine or glucose was observed in the transplanted rats, whereas the glucagon response to arginine exaggerated that both in the diabetic and in the healthy controls. At day 10 after transplantation, the plasma insulin response to arginine was significantly improved to that at day 3, but it was still lower than in controls. In contrast, the glucose-induced increase in plasma insulin levels was now normalized. Also the glucagon response to arginine was similar in the transplanted animals as in the healthy controls. In conclusion, (a) streptozotocin-diabetic rats transplanted with 1,000 freshly hand-picked islets to the renal subcapsular space had near-normal plasma insulin and glucagon responses to arginine and glucose already at 10 days after transplantation, (b) the insulin response to glucose seemed normalized prior to that of arginine, and (c) the basal hyperglucagonemia was normalized already at day 3 after transplantation, i.e., it was restored earlier than was the insulin response to arginine or glucose.