Effect of KW-4679, a novel antiallergic drug, on platelet-activating factor (PAF)-induced bronchoconstriction, airway hyperresponsiveness and pulmonary cell accumulation in guinea pigs

We assessed the effects of KW-4679 on bronchoconstriction, airway hyperresponsiveness and infiltration of inflammatory cells into the bronchoalveolar lavage (BAL) fluid induced by plateletactivating factor (PAF) in guinea pigs. (1) KW-4679 (1, 10 mg/kg, p.o.) significantly inhibited PAF-induced bronchoconstriction in anesthetized, ventilated guinea pigs. Ketotifen (1, 10 mg/kg, p.o.) also significantly inhibited that reaction. (2) Intravenous administration of PAF (600 ng/kg /hr) to ventilated anesthetized guinea pigs induced bronchial hyperresponsiveness to histamine or substance P. PAF-induced bronchial hyperresponsiveness was significantly attenuated by pretreatment with KW-4679 (3 mg/kg, i.v.). (3) Exposure of guinea pigs to an aerosol of PAF induced an increase in the numbers of total leukocytes, eosinophils, neutrophils and lymphocytes in BAL fluid at 24hr. KW-4679 (10 mg/kg, p.o.) reduced the increase in eosinophils in BAL fluid. Ketotifen (10 mg/kg, p.o.) partially reduced the increase in eosinophils in BAL fluid. (4) KW-4679 did not inhibit PAF-induced rabbit platelet aggregation. These observations indiate that KW-4679 attenuates the PAF-induced pulmonary reactions in guinea pigs and that these actions may be beneficial for the treatment of allergic bronchial asthma.