Sulfur dioxide-induced chronic bronchitis in beagle dogs.

This study was done to produce a model of chronic bronchitis. Twelve beagle dogs were exposed to 500 ppm sulfur dioxide (SO2) for 2 h/d, 5 d/wk for 21 wk and 4 dogs were sham-exposed to filtered ambient air for the same period. Exposure effects were evaluated by periodically examining the dogs using chest radiographs, pulmonary function, tracheal mucous clearance; and the cellular and soluble components of bronchopulmonary lavage fluids. Dogs were serially sacrificed after 13 and 21 wk of exposure and after 6 and 14 wk of recovery. Clinical signs produced in the SO2-exposed dogs included mucoid nasal discharge, productive cough, moist rales on auscultation, tonsilitis, and conjunctivitis. Chest radiographs revealed mild peribronchiolar thickening. Histopathology, tracheal mucous clearance measurements, and lavage cytology were consistent with a diagnosis of chronic bronchitis. It is concluded that repeated exposure to 500 ppm SO2 for 21 wk produced chronic bronchitis in the beagle dog. Complete recovery occurred within 5 wk following cessation of SO2 exposure.