RESPONSE OF MUCOSAL MAST-CELLS TO INTESTINAL ISCHEMIA-REPERFUSION INJURY IN THE RAT

The goals of this study were to investigate the in vivo effects of int estinal ischemia-reperfusion on mucosal mast cells, and to evaluate th e morphological changes induced by standardized arterial occlusion in anesthetized rats. Complete segmental ileal ischemia was maintained fo r 15, 30, or 60 min, and was followed by a 30 min reperfusion period. Intestinal biopsies taken at the end of ischemia and in the 30th min o f reperfusion were evaluated by image analysis, and the rate of releas e of type II rat mast cell protease, a marker of mast cell exocytosis, was determined from the venous effluent of the segment. Electron micr oscopy revealed cytoplasmic vacuolization of the mast cells of the vil li after the 15 min ischemia. Ischemia induced a continuous diminution of the mucosal thickness and a significant fall in the number of mast cells in the villi; with immunoperoxidase staining with a monoclonal antibody that recognizes the ADI mast cell surface antigen, the decrea se was 57, 49, and 66% in the 15, 30, and 60 min ischemia groups, resp ectively. In these groups, the mucosal type II mast cell protease conc entration increased to 2.4-, 2.5-, and 3.6-fold, respectively, and a s ignificant increase in plasma protease levels was observed on reperfus ion. These results lead us to conclude that mucosal mast cells are ver y sensitive to intestinal ischemia, with the majority of mast cells in the ileal villi already involved in the response to ischemia after a short period of arterial occlusion.