Effects of platelet-activating factor on rat airways.
Effects of platelet-activating factor (PAF) on the rat airways were investigated. Male Wistar rats were anesthetized, and PAF was inhaled into the lungs through a tracheal cannula for 5 min using an ultrasonic nebulizer. The bronchomotor response was measured with a modified Konzett-Rössler method in rats immobilized with decamethonium bromide. The inhalation of PAF caused a marked bronchoconstriction, dose-dependently, in a concentration range of 0.0001 to 0.01%. The bronchoconstrictor potency of PAF was about ten times higher than that of ACh. On the other hand, histamine inhalation gave only a slight bronchoconstriction even at the high concentration of 0.1%. The bronchomotor response to PAF was accompanied by a marked, sustained decrease in systemic blood pressure, in a dose-dependent manner. Repeated inhalations of PAF (0.001%) at an interval of 60 min resulted in a pronounced tachyphylaxis in the bronchoconstrictor response, but not in the hypotensive response. Combined inhalations of PAF with ACh or histamine did not produce a potentiation by PAF of the bronchoconstrictor responses to ACh and histamine. These findings show that PAF is a strong bronchoconstrictor agent in rats and that there is no interaction between PAF and other mediators in the acute bronchoconstrictor response.
Misawa
M
M
Department of Applied Pharmacology, School of Pharmacy, Hoshi University, Tokyo, Japan.
Takata
T
T
D000109:Acetylcholine / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D001980:Bronchi / Q000187:drug effects*; D004347:Drug Interactions; D006632:Histamine / Q000494:pharmacology; D008297:Male; D010972:Platelet Activating Factor / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains
D010972:Platelet Activating Factor; D006632:Histamine; D000109:Acetylcholine