抄録
The qualitative and quantitative determinations on the intestinal absorption of insulin in rabbits have been performed immunologically and biologically, and following results were obtained;
1. In experiments with the isolated perfused intestine in which artificial plasma was circulated through its vascular system, a considerable amount of insulin disappeared from the intestinal lumen (10.8-30.9% of the added insulin) and was recovered from the venous effluent (5.9-15.9%) during the two hour perfusion. In these experiments, the amount of insulin absorbed was directly correlated to the dose of insulin added. By the acrylamide-gel electrophoresis of the venous effluent, there was clearly demonstrated a component with the relative mobility similar to crystalline insulin.
2. Administration of insulin into the stomach and duodenum at a dose of 100 U/kg did not cause a significant increase in plasma insulin levels. When insulin at doses over 40 U/kg was infused to the upper jejunum via an indwelling catheter, there was a significant increase in plasma insulin levels, followed by a significant fall in blood glucose. A considerable increase in plasma insulin was observed following administration of insulin at doses over 20 U/kg to the Thiry-Vella loop of the jejunum, in which no pancreatic secretion entered. With a dose of 100 U/kg, the mean plasma insulin rose promptly to the peak of 241 μU/ml followed by a severe hypoglycemia.
3. The fraction of insulin absorbed from the intestine in vivo was estimated by measuring the increase in plasma insulin in the portal vein and the portal vein blood flow. The amount of insulin absorbed was found to be small, corresponding to the amount less than 2% from the jejunum and less than 4% from the ileum during the time of three hours.
From these results, it is concluded that insulin can be absorbed from the intestine of mammals in a biologically and immunologically active form, but the fraction of insulin absorbed is relatively small. The relatively small absorption of insulin might be attributable either to inactivation of a portion by intestinal proteolytic enzymes or to inherent physical difficulties to diffusion imposed by protein character.
