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Release of enteropeptidase and other brush-border enzymes from the small intestinal wall in the rat

1972; Elsevier BV; Volume: 289; Issue: 2 Linguagem: Inglês

10.1016/0005-2744(72)90088-5

1878-1454

Christer Nordström,

Coagulation, Bradykinin, Polyphosphates, and Angioedema

1. The release of the enteropeptidase (EC 3.4.4.8; formerly known as enterokinase), sucrase (EC 3.2.1.26), trehalase (EC 3.2.1.28), maltase (EC 3.2.1.20) and alkaline phosphatase (EC 3.1.3.1) activities from the small intestinal wall was studied in vivo in gut segments in the rat for the purpose of clarifying the release mechanism and magnitude of the enterokinase activity in the lumen. First, the release following combined cholecystokinin and secretin stimulation was determined. Then, the release effect of different factors (bile, bile salts, pancreatic juice, pancreatic proteases and different gastrointestinal hormones) was tested in separate experiments. 2. The enterokinase activity was analyzed in presence of activating bile salts, which greatly improved the sensitivity and reliability of the method. Endogenous trypsin was removed from the samples by gel filtration prior to analysis. 3. About 15% of the total enterokinase and alkaline phosphatase activities were found in the lumen after stimulation with cholecystokinin and secretin. The corresponding value for sucrase was only about 7.5%. Other enzymes had intermediate release values. Only minor amounts of these enzymes were present in the lumen at zero time. Both bile salts and trypsin and chymotrypsin were able to release enterokinase, but they also released other brush-border enzymes. 4. The results do not support the concept that enterokinase is secreted or specifically released in vivo. Enterokinase behaved as other brush-border enzymes in all types of release experiments. The rise in luminal enterokinase activity after cholecystokinin and secretin stimulation seems to be partly an effect of a direct action of bile salts and proteases on the intestinal wall. At least part of the action is probably on cell fragments trapped in the surface mucus coating and on cells in a pre-desquamating condition in the tips of the villi. Cholecystokinin and secretin also contribute to the release of enzyme in another way, probably through the strongly increased motility and the fluid secretion.