[Relation of platelet activating factor induced airway hyperresponsiveness to thromboxane A2 and neutrophil in dogs]

We studied the relation of the airway hyperresponsiveness induced by platelet activating factor (PAF) inhalation to thromboxane (Tx)A2 and neutrophil in ten dogs. Airway responsiveness to inhaled methacholine was determined by Astograph (7 Hz oscillation method), PAF (1000 micrograms/ml) was delivered as an aerosol generated from a Devilbiss 646 nebulizer for ten minutes. After determination of airway responsiveness, we carried out bronchoalveolar lavage and measured the TxB2 levels and the number of neutrophils in bronchoalveolar lavage fluid (BALF). Airway responsiveness developed significantly (p < 0.01), and the levels of TxB2 and the number of neutrophils in BALF were increased (p < 0.01) 3 hr after PAF inhalation. The change in airway responsiveness correlated significantly with the percent change of TxB2 levels (r = 0.746, p < 0.05). However no significant correlation was recognized between the increase in TxB2 levels and the increase in the number of neutrophils, nor between the change in airway responsiveness and the increase in the number of neutrophils. These results suggest that the increase in airway responsiveness induced by PAF inhalation is involved in the hyperproduction of TxA2 but that TxA2 is not released from neutrophils infiltrating into the airway; furthermore neutrophils may not induce airway hyperresponsiveness in dogs.