ISOTONIC SMOOTH-MUSCLE RESPONSE IN HUMAN BRONCHI EXPOSED IN-VITRO TO NITROGEN-DIOXIDE

Exposure to nitrogen dioxide (NO2), a common oxidant airborne pollutan t, has been shown to cause reversible effects on lung function and air way responsiveness, in addition to airways inflammation, However, ther e have been conflicting reports concerning NO2-induced airway hyperres ponsiveness, In the present study, we investigated the isotonic smooth muscle response in isolated human bronchi previously exposed in vitro to NO2. Bronchial segments were obtained from 12 patients who had und ergone thoracotomy for lung cancer, Bronchial segments from each patie nt were exposed to air and to 2.5 parts per million (ppm) NO2 for 4 h, The contractile response of bronchial rings to acetylcholine, neuroki nin A (NKA), and substance P was then studied under isotonic condition s, The response to NTK was also studied in rings, with or without epit helium, exposed either to air or 7 ppm NO2. No NO2-induced alteration of the bronchial smooth muscle isotonic response was found under any o f the experimental conditions, We conclude that in vitro exposure to u p to 7 ppm nitrogen dioxide does not cause alterations of the human br onchial smooth muscle shortening capacity.