Induction of enterokinase in the rat small intestine following hypersecretion of trypsinogen by chronic trypsin inhibitor feeding.

The interrelationship between trypsin/trypsinogen and enterokinase (EK) was studied in rats following induction of trypsinogen hypersecretion by various agents. Both soybean trypsin inhibitor and para-aminobenzamidine increased intraluminal tryptic activities to a level about twice that found in the control rats. This resulted in an increase in the mucosal and the intraluminal contents of EK in the rat small intestine. On the other hand, in cholecystokinin-treated rats, although there was an increase of intraluminal trypsin, the increase was about 80% less than in the inhibitor-fed rats. Under this condition, there was no effect on the mucosal or the intraluminal EK. These results suggested that substantial increase in intraluminal trypsin/trypsinogen levels (two-fold over control) will increase the mucosal and the intraluminal concentrations of EK in the rat small intestine. Our observation extends previous reports that a decreased level of trypsin/trypsinogen, such as in pancreatic insufficiency, leads to a decrease in mucosal EK. These observations, when taken together, strongly support the modulating role of intraluminal trypsin/trypsinogen levels in controlling the EK concentrations in the small intestine.