Fate of trypsin and chymotrypsin in the human small intestine

The present consensus regarding the fate of the pancreatic proteases trypsin and chymotrypsin in the human intestinal tract rests largely upon experiments by Borgstrom, Dahlqvist, Lundh, and Sjovall (1957), who measured their activity in juice obtained by intubation of the small intestine. The results indicated a progressive fall in activity from the pylorus towards the ileocaezal valve. Support for their conclusion that enzyme degrad-ation takes place in the small intestine has come from Pelot and Grossman (1962), who demon-strated rapid inactivation of pancreatic enzymes in the rat. Studies in this laboratory have shown binding of trypsin and chymotrypsin to human intestinal cells (Goldberg, Campbell, and Roy, 1968a), and have demonstrated that the spectrophotometric assay of Lundh (1957), as used by Borgstrom et al (1957), was incapable of estimating bound enzymes. An alternative possibility was that the enzymes became bound to the surface of cells during transit through the intestine and to components of intestinal debris. Measurement of the daily output of trypsin in subjects on ileal drainage (Roy, Campbell, and Goldberg, 1967) gave data which, when compared with the trypsin concentration of human pancreatic juice (Haverback, Dyce, Bundy, and Edmondson, 1960), suggested that most of the enzyme reached the terminal ileum intact. It therefore seemed desirable to examine the fate of pancreatic enzymes in the human small intestine, considering all the factors that can interact with the enzymes from the point of their release into the duodenum. Such a study is the subject of the present report. MATERIALS AND METHODS The following materials were employed:-ILEAL FLUID This was obtained from patients with an established ileostomy as previously described (Roy et al