IMPORTANCE OF AIRWAY INFLAMMATION FOR HYPERRESPONSIVENESS INDUCED BY OZONE

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Abstract
Ozone-induced airway hyperresponsiveness may correlate with the development of airway inflammation in dogs. To assess airway responsiveness, increases in pulmonary resistance produced by delivering acetylcholine aerosol to the airways were determined. To assess airway inflammation, the airway mucosa was biopsied and the number of neutrophils present in the epithelium was counted. Airway responsiveness and inflammation were assessed in anesthetized dogs before ozone exposure, and then 1 h and 1 wk after ozone (2.1 ppm, 2 h). Airway responsiveness increased markedly at 1 h after ozone and returned to control levels 1 wk later in each of 6 dogs, but it did not change after ozone in another 4 dogs. Dogs that became hyperresponsive also developed a marked and reversible increase in the number of neutrophils in the epithelium; dogs that did not become hyperresponsive had no change in the number of neutrophils. For the group of dogs, the level of airway responsiveness before and after ozone exposure correlated closely with the number of epithelial neutrophils. Ozone-induced airway hyperresponsiveness may depend on the development of an acute inflammatory response in the airways.