Dry air- and hypertonic aerosol-induced bronchoconstriction and cellular responses in the canine lung periphery

Dry air and hypertonic saline both create an osmotic stress to the airways, whilst dry air alone induces transient cooling of the airway mucosa. It is unclear whether these two stimuli lead to bronchoconstriction via the same mechanisms. We compared airflow- and hypertonic aerosol-induced bronchoconstriction (AIB and HIB, respectively) in the canine lung periphery, using a wedged bronchoscope to measure collateral system resistance (Rcs). Bronchoalveolar lavage (BAL) was used to examine changes in cells and mediators during AIB and HIB. We found that: 1) peripheral airways are not refractory to either dry air or hypertonic aerosols, and do not exhibit cross-refractoriness to these stimuli; 2) differences in strength of stimulus can alter the magnitude but not the time course of HIB; 3) within an individual, AIB and HIB are significantly correlated; 4) epithelial cells recovered in BAL fluid (BALF) are significantly elevated after AIB, and are similarly increased after HIB; 5) when compared to control, mediators recovered in BALF are significantly elevated after AIB but not HIB; 6) HIB is not altered by cyclo-oxygenase inhibition; and 7) lavage with hypertonic fluid does not affect the number of epithelial cells recovered, although the concentrations of some mediators are increased. We speculate that differences in cell and mediator profiles reflect differences in the time course of AIB and HIB that result from the modulation of temperature sensitive pathways that occurs during dry air, but not during hypertonic aerosol challenge.