Eicosanoids modulate hyperpnea-induced bronchoconstriction in canine peripheral airways.

We examined the role of leukotrienes (LTs) in the development of dry air-induced bronchoconstriction (AIB) in canine peripheral airways. Airway reactivity to exogenous LTs was first tested by using an LTD4 aerosol challenge: peripheral airway resistance increased approximately 130 +/- 51% (n = 4) above baseline when compared with its vehicle control. AIB was then assessed by measuring peripheral airway resistance after, and airway wall temperature during, a dry air challenge (DAC). Treatment with a peptidoleukotriene biosynthesis inhibitor (MK-0591) attenuated AIB by approximately 65% without altering airway wall temperature. The fact that MK-0591 did not alter airway reactivity to aerosolized acetylcholine and completely inhibited Ca2+ ionophore-induced LTB4 generation in canine whole blood attests to the specificity of the drug. Treatment with MK-0591 did not affect the increased number of epithelial cells recovered in bronchoalveolar lavage fluid 5 min after DAC. Concentrations of LTs and other eicosanoids in bronchoalveolar lavage fluid from vehicle-treated DAC airways were increased above baseline values; only LTs were reduced by MK-0591. Before MK-0591, AIB was significantly correlated with the dry air-induced generation of LTC4, LTD4, and LTE4. After treatment with MK-0591, AIB was correlated with thromboxane B2, prostaglandin (PG) F2 alpha, and PGE2. We conclude that hyperpnea with dry air stimulates local production and release of LTs in canine bronchi and, alone with the generation of bronchoconstricting and bronchodilating PGs, plays a central role in the modulation of AIB.