Scanning electron microscopy of the lungs of vitamin E-deficient rats exposed to a low concentration of ozone.

The acute effects of a low concentration of ozone on the surface morphologic features of the conducting airways and alveoli were studied by scannging electron microscopy. Rats were exposed to approximately 0.3 ppm of ozone for 3 hours daily for as many as 16 consecutive days. Animals were killed at intervals of time, and their lungs were processed. Throughout the airways, cilia were seen to be swollen, showing hemispheric extrusions and considerable surface roughness. Groups of severely injured cilia had a tendency to adhere to each other. Small, round bodies were frequently noted, mainly in the large airways and the proximal bronchioles, in some areas thickly covering the airway epithelial surface. In addition, the luminal surfaces of the epithelium of the regions were often covered with a pseudomembrane. The surfaces of protruding nonciliated cells (Clara cells) showed many small swellings and discrete, round bodies. These changes were most marked in the terminal airways. The surfaces of alveolar ducts and alveolar walls showed scattered areas of cytoplasmic swelling and attachment of round bodies throughout the parenchyma. The findings described were more prominent in vitamin E-deficient rats than in rats fed a diet supplemented with vitamin E, suggesting an antioxidant effect of the vitamin.