BASAL SECRETION AND ANAPHYLACTIC RELEASE OF RAT MAST-CELL PROTEASE-II(RMCP-II) FROM EX-VIVO PERFUSED RAT JEJUNUM - TRANSLOCATION OF RMCP-II INTO THE GUT LUMEN AND ITS RELATION TO MUCOSAL HISTOLOGY

The kinetics of the release of rat mast cell protease-II (RMCP-II) fro m mucosal mast cells in the jejunum of Nippostrongylus brasiliensis pr imed (immune) rats was investigated using ex vivo perfusion of a segme nt of jejunum through the cranial mesenteric artery. The aim of the st udy was to assess the role of the protease in anaphylaxis and in parti cular to ascertain whether it is responsible for the histological chan ges, which include widespread epithelial shedding, seen ire the mucosa in in vivo models of anaphylaxis. Perfusion of the jejunal vasculatur e with a Krebs-Ringer buffer showed that there was basal secretion of RMCP-II by jejunal mast cells in all rats studied. The baseline concen tration of RMCP-II was significantly greater (p<0.05) in immune rats ( >7 ng/ml) exposed to nippostrongylus infection than in control, naive animals (<2 ng/ml). Challenge of immune rats with 100 or 400 worm equi valents of whole worm antigen resulted in an immediate (within 40 seco nds) and significant (p<0.02) increase in the concentration of RMCP-II (to >3 mu g/ml) in the vascular perfusate, which was not seen in naiv e rats or immune rats challenged with an irrelevant antigen. Greater a mounts of RMCP-II were also recovered from the jejunal lumen of immune rats compared with naive rats after challenge of both groups with wor m antigen. Despite the release of microgram quantities of RMCP-II into the gut lumen and vascular perfusate, however, there were no signific ant changes seen in the mucosal histology. These results suggest that RMCP-II alone is not responsible for the loss of gut epithelium seen d uring anaphylaxis in the rat.