The effect of platelet activating factor on pulmonary beta-adrenoceptors.
An intravenous infusion of platelet activating factor (Paf) in the guinea-pig elicits an increase in bronchial responsiveness to the spasmogens, histamine and bombesin. 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. Isoprenaline induced a comparable dose-related relaxation in vitro of tracheal smooth muscle isolated from Paf- and vehicle-treated animals. No change in beta-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. The reduced bronchodilator responsiveness to isoprenaline in Paf-treated animals is not related to changes in pulmonary beta-adrenoceptor function. These results suggest that non-spasmogenic elements may contribute to airways obstruction induced in hyper-responsive animals.
D000818:Animals; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000494:pharmacology; D008168:Lung / Q000187:drug effects*; D008297:Male; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D010972:Platelet Activating Factor; D011943:Receptors, Adrenergic, beta / Q000032:analysis / Q000187:drug effects*; D014132:Trachea / Q000187:drug effects
D010972:Platelet Activating Factor; D011943:Receptors, Adrenergic, beta; D006632:Histamine; D020120:Iodocyanopindolol; D010869:Pindolol; D007545:Isoproterenol