Airway Levels of Mast Cell—derived Mediators in Exercise-induced Asthma

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Abstract
In order to assess the role of mast cell-derived mediators in the pathogenesis of exercise-induced asthma (EIA), we completed pre- and postexercise bronchoalveolar lavage (BAL) in seven atopic subjects with EIA. The study subjects were defined as having EIA if they exhibited a greater than 15% decrease in FEV1 after completing 6 min of treadmill exercise. There were no significant differences between mean preexercise and mean postexercise mast cell-derived BAL histamine (186 .+-. 67 versus 148 .+-. 36 pg/ml), tryptase (4.5 .+-. 2.0 versus 2.8 .+-. 2.0 ng/ml), prostaglandin D2 (26 .+-. 11 versus 32 .+-. 25 pg/ml), or leukotriene C4 (< 100 versus < 100 pg/ml). In addition, mast cells present in BAL fluid after exercise contained similar amounts of cellular histamine compared with BAL mast cells obtained before exercise (preexercise BAL cellular histamine, 26.6 .+-. 12.3 ng/106 BAL cells; postexercise BAL cellular histamine, 22.7 .+-. 9.1 ng/106 BAL cells), indicating that depletion of preformed mast cell mediators are unlikely to account for the refractory period in EIA. This study suggests that the cellular pathogenesis of EIA (mast cell-independent) differs from current theories of the pathogenesis of extrinsic allergen-induced asthma (mast cell-dependent).