Enteropancreatic circulation of digestive enzyme as a conservation mechanism

Abstract

THE permeability of the intestine to pancreatic digestive enzymes has been known for some years^1–7. Recently it was demonstrated⁸ that chymotrypsinogen and amylase are transported across the pancreatic acinar cell as well. Taken together these observations suggest that some of the digestive enzymes which are secreted into the intestinal lumen are circulated by way of the bloodstream and acinar cell back into the intestine. This prediction was borne out experimentally. ³H-chymotrypsinogen instilled into the intestinal lumen reappeared in pancreatic secretion within minutes⁸. The question remained, however, whether this “enteropancreatic circulation” was a trace process either of a trivial nature or serving a regulatory function; or, whether —analogous to the enterohepatic circulation of bile salts—it was a process in which substantial amounts of digestive enzyme could be circulated and thereby conserved. The experiments reported here are consistent with this latter view and suggest the circulation of approximately 60% of a mixture of digestive enzymes instilled into the duodenum (82–92% at steady state).