The effect of platelet activating factor on pulmonary β‐adrenoceptors

Abstract

1 An intravenous infusion of platelet activating factor (Paf) in the guinea-pig elicits an increase in bronchial responsiveness to the spasmogens, histamine and bombesin. 2 Airways obstruction induced by bombesin in Paf-treated animals is poorly reversed by isoprenaline compared to comparable airways obstruction induced by bombesin in vehicle-treated animals. 3 Isoprenaline induced a comparable dose-related relaxation in vitro of tracheal smooth muscle isolated from Paf- and vehicle-treated animals. 4 No change in β-adrenoceptor numbers or binding affinity was observed in lungs removed from Paf-treated animals in comparison with those from vehicle-treated animals, or after direct incubation with Paf in vitro. 5 The reduced bronchodilator responsiveness to isoprenaline in Paf-treated animals is not related to changes in pulmonary β-adrenoceptor function. These results suggest that non-spasmogenic elements may contribute to airways obstruction induced in hyper-responsive animals.