AJP - Gastrointestinal and Liver Physiology, Vol 268, Issue 5 764-G771, Copyright © 1995 by American Physiological Society
Intestinal anaphylaxis: mediation of the response of colonic longitudinal muscle in rat
M. R. Oliver, D. T. Tan and R. B. Scott
Gastrointestinal Research Group, University of Calgary, Alberta, Canada.
Colonic smooth muscle function may be altered in food protein
hypersensitivity reactions and could contribute to the clinical
manifestation of diarrhea. To characterize such functional changes and
elucidate the mediators and mechanisms involved. Hooded-Lister rats were
sensitized by intraperitoneal injection of egg albumin (10 micrograms), and
controls were sham sensitized with saline. Fourteen days later the
contractility of longitudinally oriented distal colonic segments (mucosa
intact) were studied in standard tissue baths in response to antigen (Ag)
or other agents. After Ag exposure, a contractile response was documented
in animals that were sensitized [specific immunoglobulin E (IgE) antibody
levels > or = 1:64] and was specific for the sensitizing Ag. Mast cell
involvement was suggested by a significant reduction in the number of
granulated mucosal mast cells in sensitized tissues after Ag challenge and
in the magnitude of the Ag-induced contractile response in the presence of
mast cell stabilizers. The antigen-induced response was significantly and
independently inhibited by both cyclooxygenase and lipoxygenase enzyme
inhibitors and by leukotriene D4 and platelet activating factor receptor
antagonists. The Ag-induced response was resistant to histamine and the
5-hydroxytryptamine antagonists, atropine and tetrodotoxin. These results
suggest that the food protein-induced contraction of colonic longitudinal
smooth muscle in the sensitized rat is due to IgE-mediated mast cell
activation with the subsequent production and release of membrane-derived
mediators that, in vitro, act directly on the smooth muscle.
