The pharmacological effects of disodium cromoglycate (DSCG) were studied in rats during the development of reactions to various allergens or carrageenin. DSCG (10 mg/kg and 100 mg/kg, i.v.) showed pronounced inhibitory effects on type I and type III (passive Arthus) allergic reactions. An immunological degranulation of mast cells and a significant decrease in tissue histamine content were observed in type I allergic reactions but not in type III allergic reactions characterized by an apparent infiltration of neutrophils. An antihistaminic agent, promethazine (1 mg/kg, i.v.) was effective only against type I allergic reactions and totally ineffective against type III allergic reactions. Thus, the results obtained above strongly suggest that DSCG exhibits at least two mechanisms of antiallergic action; one is related to mediator release from mast cells and the other is unrelated to mast cell activation.

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