Eosinophil accumulation in pulmonary airways of guinea‐pigs induced by exposure to an aerosol of platelet‐activating factor: effect of anti‐asthma drugs

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Abstract
1 Exposure of guinea-pigs to aerosols of platelet activating factor (PAF) (0.01 to 100 μg ml−1) induced a dose-dependent increased incidence of eosinophils in bronchoalveolar lavage fluid (BAL) at 48 h. Total leucocyte numbers and the percentages of lymphocytes and neutrophils were unchanged in BAL fluid. 2 Increased numbers of eosinophils were detected in BAL 1 h after exposure to PAF but eosinophilia was not maximal until 48 h. One week after exposure to PAF, the percentage of eosinophils in BAL was within the normal range. 3 Depletion of circulating platelets or neutrophils by intravenous injection of specific antisera did not modify accumulation of eosinophils in the airway lumen following inhalation of PAF (10 μg ml−1). 4 PAF-induced pulmonary airway eosinophil accumulation was inhibited by treatment with SDZ 64–412, a selective PAF-antagonist, whether the compound was administered before, or 30 min after, inhalation of PAF. 5 Pulmonary airway eosinophil accumulation due to inhaled PAF (10 μg ml−1) was inhibited by prior treatment with aminophylline, cromoglycate, ketotifen, dexamethasone and AH 21–132. 6 Pulmonary airway eosinophil accumulation due to inhaled PAF (10 μg ml−1) was not inhibited by prior treatment with indomethacin, salbutamol or mepyramine.