Absorption of protein via the intestinal wall. A quantitative model.

Intact, biological active insulin and pancreatic RNase can be absorbed from the intestinal lumen into the blood circulation. The absorption is dependent on the addition of bile acid (sodium cholate) and proteinase inhibitor. The quantitative absorption of insulin and pancreatic RNase has been demonstrated in an in situ model. The amount of insulin absorbed after 30 min from the ileum to the mesenteric vein was 0.025% of the initial amount. Sodium cholate (10 mg/ml) and 3000 KIU/ml aprotinin enhanced this absorption by 30 times. The amount of pancreatic RNase which was absorbed from the ileum to the blood was 0.002% of the initial amount during 30 min. Sodium cholate (10 mg/ml) and 3000 KIU/ml aprotinin increased the absorption by a factor of 200. No damage occurred to the intestine during the experimental procedures. The sieving characteristics of the intestinal wall were not altered by the presence of sodium cholate and proteinase inhibitor in the intestinal lumen. These results suggest that sodium cholate and proteinase inhibitors can facilitate the absorption of intact, biologically active proteins across the intestinal wall.