Mediation of food protein-induced jejunal smooth muscle contraction in sensitized rats.

Alterations in myoelectric and motor activity are important features of food protein-induced intestinal anaphylaxis. To determine the mediator(s) involved, rats were sensitized by injection of egg albumin (10 micrograms ip), and controls were sham sensitized with saline. Fourteen days later the contractility of longitudinally oriented jejunal segments (mucosa intact) was examined in standard tissue baths in response to antigen (Ag) or other agents. Although control and sensitized tissues similarly contracted to stretch, bethanechol, histamine, or 5-hydroxytryptamine (5-HT), Ag contracted only sensitized segments. Contractile response 1) was specific to the sensitizing Ag, as bovine serum albumin did not induce contraction, and 2) could be passively transferred with serum containing specific IgE antibody. Mast cell degranulation after Ag challenge was suggested by a significant loss of granulated mast cells in sensitized compared with control rats challenged with Ag. Concanavalin A, which degranulates mucosal and connective tissue-type mast cells, and compound 48/80, which degranulates only connective tissue-type mast cells, produced a contractile response. Ag-induced contraction was significantly inhibited by the mucosal and connective tissue-type mast cell stabilizer doxantrazole (P less than 0.001) and the connective tissue mast cell stabilizer disodium cromoglycate (P less than 0.05). Diphenhydramine and cimetidine together blocked histamine-induced contraction but failed to affect Ag-induced contraction in sensitized tissues.(ABSTRACT TRUNCATED AT 250 WORDS)