ABSTRACT-The effects of seven lectins with various sugar-specificities on histamine release from rat peritoneal mast cells induced by non-immunologic stimuli were studied. The non-immunologic stimuli used were three basic secretagogues, compound 48/80, bradykinin and PEI6 (polyethylenimine with a molecular weight of 600). In this study, we observed inhibition of the histamine release by Macckia amurensis mitogen and Solanum tuberosum agglutinin (100 tg/ml at 371C for 10 min), which are specific for sialic acid-a2,3 N-acetyl galactosamine (Siaa2,3Ga1NAc) and N-acetyl glucosamine (G1cNAc) oligomers, respectively. The effects of Phytolacca americana mitogen and Sambucus sieboldiana agglutinin were different. Three lectins specific for mucin type oligosaccharides inhibited the histamine release induced by compound 48/80 but not that induced by bradykinin or PEI6. Since bradykinin and PEI6 additively enhanced the histamine release in duced by compound 48/80, they partially shared the same signalling pathways. Glycoproteins with bisecting GIcNAc and Sia residues, as described previously (Jpn. J. Pharmacol. 57, 79-90, 1991), seemed to be one of the action sites for compound 48/80, bradykinin and PEI6. In addition to the direct activation of the per tussis toxin-sensitive G proteins, we propose another mechanism of non-immunologic stimuli via specific glycoproteins on rat peritoneal mast cells. The apparent sugar residues involved were asparagine-linked oligosaccharides with Sia (especially Siaa2,3Gal), G1cNAc oligomers and/or bisecting G1cNAc.

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