Cigarette smoke exposure causes constriction of rat lung explant airways

Cigarette smoke is known to cause acute increases in airway resistance, but the mechanisms behind this effect are unknown. Lung explants were utilized to examine the constrictive effects of acute ci garette smoke exposure on bronchioles from rats in vitro that had or had no t been previously exposed to cigarette smoke in vivo. It was found that smoke induced a small but consistent degree of contractio n of the airways in vitro, which could be reduced by an endothelin receptor antagonist in the animals which had had no previous smoke exposure in vivo , and reduced by the oxidant scavengers superoxide dismutase or catalase in the animals with previous smoke exposure. In conclusion, cigarette smoke induces acute small airways constriction thr ough both endothelin release and direct oxidant effects; which mechanisms a re operative depends on the prior smoking status.