Antiallergic action of 6-ethyl-3-(1h-tetrazol-5-yl) chromone (aa-344) on immediate hypersensitivity reaction in rats

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Abstract
A newly synthesized compound, 6-ethyl-3-(1H-tetrazol-5-yl)chromone (AA-344) given i.v. or orally inhibited considerably the 72 h passive cutaneous anaphylaxis (72 h PCA) induced by Ig[immunoglobulin]E in rats. The antiallergic action of AA-344 was neither due to the antihistamine or antiserotonin effect nor was it mediated via adrenergic mechanisms. The results obtained in a double sensitization with 2 IgE antibodies suggested that AA-344 may not impair antigen-antibody combination but probably prevents the release of chemical mediators including histamine. This assumption was supported by observation that AA-344 inhibited a reduction in the skin histamine content caused by the 72 h PCA, without effect on the compound 48/80[p-methoxyphenethyl methylamine formaldehyde product]-induced histamine reduction. AA-344 also partially inhibited the IgGa-mediated 3 h PCA in rats. The inhibitory action of AA-344 on the immediate hypersensitivity reactions is apparently due to prevention of the release of chemical mediators from the mast cells, by acting on some process in sequential events leading to the mediator release following antigen-antibody combination.