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

1. Exposure of guinea-pigs to aerosols of platelet activating factor (PAF) (0.01 to 100 micrograms 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 micrograms 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 micrograms 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 micrograms ml-1) was not inhibited by prior treatment with indomethacin, salbutamol or mepyramine.