The intestinal absorption of insulin has been studied in a preparation of isolated rabbit intestine in which artificial plasma is circulated through normal vascular channels. After insulin in doses of 100, 200, and 440 U. was introduced into the intestinal lumen, its appearancein the venous effluent was measured immunologically during perfusion for two hours.
Insulin gradually appeared in the venous effluent and reached a peak fifty to ninety minutes after the perfusion was started. The proportion of insulin absorbed was 6.2 to 9.2 per cent with a dose of 100 U., 5.9 to 15.6 per cent with 200 U., and 8.9 to 15.9 per cent with 440 U. The amount of insulin added significantly correlated with the total amount of insulin absorbed from the intestine. The biologic activity in the fraction absorbed was equivalent to that obtained immunologically. In the venous effluent, insulin component was also identified by the relative mobility similar to crystalline insulin on acrylamide gel electrophoresis.
Although the intestinal absorption in this system does not duplicate physiologic absorption, these results indicate that a considerable portion of insulin can be absorbed from the intestine in a physiologically active form.