Abstract
A possible role of IgE-constituent carbohydrate in the mediation of histamine release was pharmacologically studied in isolated peritoneal rat mast cells. Among polysaccharides obtained commercially, mannan and dextran induced histamine release, and the ED50 was 4 μg/ml and 52 μg/ml, respectively. At doses higher than 1 mg/ml, Ficoll, hyaluronic acid and heparin induced the release, while agarose did not. The weak histamine releasing polysaccharides did not induce inhibition of the dextran-induced histamine release. Monosaccharides such as N-acetylglucosamine, mannose and N-acetylneuraminic acid induced marked inhibition of the mannan-induced histamine release, although other carbohydrate constituents of IgE fucose and galactose were weak inhibitors. The antagonism of the monosaccharides against polysaccharide-induced histamine release was found to be a competitive type. Also, antigen-induced histamine release from peritoneal mast cells actively immunized with egg albumin appeared to be inhibited competitively by a carbohydrate constituent of IgE N-acetylglucosamine. Hence it appears that IgE-constituent carbohydrate may play an important role in IgE-mediated histamine release.
