Passive cigarette smoke exposure induces airway hyperreactivity to histamine but not to acetylcholine in guinea-pigs

Abstract

We have investigated the changes in airway reactivity induced in guinea-pigs by passive cigarette smoke exposure. In particular, we studied the development of airway hyperresponsiveness both in vivo and in vitro after passive exposure of the animals to cigarette smoke in a plexiglass box. Passive smoke exposure significantly (p<0.01) increased histamine induced bronchoconstriction. The dose-ratio calculated between histamine doseresponse curves constructed in control and smoke exposed animals was 2.13 (95% confidence limits: 146–309). Acetylcholine induced bronchoconstriction was not potentiated after the same smoke exposure, indicating some specificity of the mediators involved in the airway hyperresponsiveness triggered by passive smoke exposure. The airway hyperreactivity induced by smoke exposure was associated with a specific increase in histamine contraction induced in vitro in lung parenchymal strips but not in tracheae or pulmonary arteries. Maximal histamine contraction in parenchymal strips taken from smoke exposed animals was significantly (p<0.01) enhanced by approximately 110% when compared to control. There was a significant (p<0.01) increase in the number of macrophages and eosinophils in the bronchoalveolar lavage fluid of animals passively exposed to cigarette smoke, but no mucus hypersecretion was evident. Our data demonstrate the occurrence of airway hyperrreactivity induced by passive cigarette smoke exposure, which involves increased smooth muscle reactivity and cell recruitment.