Inhibitory effects of tannins on superoxide-induced histamine release from rat peritoneal mast cells

Previously, we demonstrated that potassium superoxide (KO2) elicited degranulation and histamine release from rat peritoneal mast cells by biological reactions. In the present study, we investigated the effects of 20 tannins and 10 antiallergic drugs on KO2- and compound 48/80 (48/80)-induced histamine release from rat peritoneal mast cells. Rat peritoneal mast cells were preincubated with various concentrations of tannins or antiallergic drugs at 37° for 15 min, and KO2 (10 mM) or 48/80 (0.5 μg/ml) were added. The reactions were continued for 20 min and terminated by chilling the test tubes in an ice bath. The amount of histamine in the supernatant and the residual histamine content were determined fluorometrically. The pretreatment with tannins (1-100 μ M), which have many hexahydroxydiphenoyl (HHDP) groups and galloyl groups, prevented KO2-induced histamine release, significantly. Higher molecular weight tannins prevented 48/80-induced histamine release, significantly. The pretreatment with azelastine, astemizole, ketotifen and epinastine prevented KO2-induced histamine release, dose-dependently. On the other hand, DSCG, repirinast, ibudilast and tazanolast had no effect. These findings indicate that the radical-scavenging activities may participate in the inhibitory effects of tannins, and antiallergic drugs may inhibit histamine release due to membrane-stabilizing action. The inhalation of tannins in the airway may prevent airway hypersensitivity.