ABSTRACT
The effect of platelet activating factor (PAF) on bronchial smooth muscleboth in vitro and in vivo in guinea-pigs were observed and its mechanism explored. Theresults showed: 1. Bronchoconstriction can be induced by PAF both by i. v. and via aerosoladministration and was accompanied with a fall of the circulating platelet count. 2. Thecontractile effect of PAF on guinea-pig airway smooth muscle preparations is modest invitro. Yet this effect of PAF can be enhanced by platelet. 3. TXA_2 receptor antagonist(AA-2414) can inhibit bronchoconstriction induced by PAF with platelet significantly.These results suggested that PAF might be a potent endogenous bronchoconstrictor and itseffect was related to platelet. The activated platelets can induce bronchoconstriction byreleasing TXA_2.