A low dose of ionizing radiation increases luminal release of intestinal peptidases in rats

Purpose: Mucosal inflammation in the small intestine is a potentially hazar dous side effect of abdominal irradiation. In an effort to develop a quanti tative method of evaluating mucosal damage, the luminal release of brush bo rder enzymes in response to ionizing radiation was examined using two inves tigational strategies. Methods: First, a 20 cm segment of the proximal jeju num was perfused in situ and enzymatic activities within the perfusates wer e evaluated. In a second approach, enzymatic activities were directly evalu ated in isolated brush border membranes from the jejunal mucosa. Results: M ost of the peptidase activities measured were increased in the perfusates 1 day after irradiation and had returned to control levels at 4 days. In the brush border membranes, some enzyme activities decreased at 1 day and were , with the exception of leucineamino-peptidase (LAP), similar to control le vels at 4 days. Conclusions: LAP is more strongly affected by radiation tha n the transmembranously bounded enzymes.