SO2-induced bronchopathy in the rat: abnormal permeability of the bronchial epithelium in vivo and in vitro after anatomic recovery.

The effects of different SO2 exposures on the uptake and transport of exogenous proteins by the tracheobronchial epithelium were investigated in vivo and in vitro using explanted tissue from rat lungs. By optical and electron microscopy, modifications in ferritin uptake and transport were observed, depending on SO2 exposure and on subsequent structural changes; these changes involved a considerable increase in mucosal permeability, both in vivo and in vitro, affecting the epithelium of the trachea and main bronchi. Such an increase, although reduced, was observed 3 months after SO2 exposure had been discontinued, at a time when the structure appeared normal. These findings suggested that SO2-induced changes in upper respiratory epithelium may be responsible for long-term abnormal permeability and that such changes may contribute to the pathogenesis of chronic bronchopathy.