In vivo exposure to ozone causes increased in vitro responses of small airways

We examined the effects of in vivo exposure to 3 ppm ozone on in vitro reactivity of large and small airways from dogs. No effects in large airways were detected. However, small airways exposed to O₃ had larger responses to receptor-mediated stimuli and similar responses to KCl plus phorbol ester. These results suggest that small airways are more vulnerable to O₃ inhalation than are large airways and that receptor-mediated pathways reflect that sensitivity. Another possible explanation is that O₃ exposure prevents the epithelium from playing its normal dampening role in responses to contractile agonists.