Exercise-induced asthma is not associated with mast cell activation or airway inflammation

Exercise-induced asthma (EIA) may affect up to 90% of patients with asthma. Hyperpnea associated with exercise leads to increased airway water and heat loss, which contributes to the development of EIA. Measurement of circulating mediators has suggested that mast cells may participate in the development of EIA via release of histamine and neutrophil chemotactic factor. To evaluate further the contribution of pulmonary mast cell-mediator release in the pathogenesis of EIA and to determine whether EIA is associated with enhancement of airway inflammation, we studied 11 subjects with mild stable asthma (FEV1, 93% +/- 3% predicted; mean +/- SEM) with significant EIA (after exercise fall in FEV1, 41% +/- 5%). Bronchoalveolar lavage (BAL) was performed immediately (less than 1 hour) after exercise challenge (EC) and repeated 24 hours later (exercise studies). On another occasion, paired BALs were done 24 hours apart (control studies). A minimum of 2 weeks separated the exercise and control pairs. No changes were observed in BAL cell counts, differentials, or reactive oxygen species metabolism after EC. Neither BAL histamine nor BAL tryptase levels increased, either shortly (less than 1 hour) or 24 hours after EC. We conclude that EC in subjects with asthma is not associated with cellular influx to airspace and that mechanisms other than histamine release by pulmonary mast cells may be responsible for EIA.