A BETA(2)-ADRENERGIC AGONIST INHIBITS DRY AIR-INDUCED INJURY IN CANINE PERIPHERAL AIRWAYS

We examined the effects of a beta(2)-agonist on dry air-induced injury in canine peripheral airways. Dry air-induced bronchoconstriction (AI B) was assessed by measuring peripheral airway resistance in anestheti zed dogs. Salbutamol reduced AIB by similar to 75% compared with contr ol values. Colloidal carbon was used to detect bronchovascular leakage in contralateral sublobar segments that were pretreated with saline o r salbutamol. About 87% of the perimeter of bronchi was damaged after dry air challenge in saline-treated segments. Salbutamol reduced mucos al damage by similar to 30% (P < 0.05). The mucosa of bronchioles was not injured. The average goblet-to-ciliated cell ratio (which reflects mucosal perturbation) in bronchi decreased from 0.38 in control bronc hi to 0.15 in challenged bronchi, and this effect was also evident in bronchioles. Salbutamol did not affect this decrement. Dry air challen ge also caused degranulation of mast cells located below damaged mucos a, dilation of bronchial vessels, and leakage from capillaries and ven ules located below normal ciliated and damaged mucosa of bronchi. Thus , we conclude that salbutamol attenuates epithelial damage and AIB but fails to inhibit mast cell degranulation and vascular hyperpermeabili ty.