The effects of ambient levels of O3 on rabbits were studied in terms of combined functional and morphological parameters. First, we measured closing volume and lung volumes in pentobarbitalized adult rabbits by use of the single breath oxygen test and then observed morphological changes in the rabbit's lungs with light microscopy and scanning and transmission electron microscopy. Rabbits were exposed to O3 ranging from 0.46 to 1.09ppm for 12 hours and were examined with regard to both parameters on 6 hours, the 1st, 3rd and 7th day after exposure.
Pathologic changes in rabbits examined 6 hours after O3 exposure were most marked in the area from the terminal bronchioles to the alveolar ducts. Characteristic changes were narrowing of the bronchiolar lumen by infiltrating mononuclear cells and desquamated bronchiolar epithelial cells, “loss of cilia”, surface roughness of cilia and flatness of the Clara cells with ditches. The longer the interval of recovery was, the less prominent the pathologic changes. On the 7th day pathologic changes also returned to near normal morphologically.
Mean CV% value increased significantly in rabbits on 6 hours and 1 day after exposure compared with the control animals which were not exposed to O3, and returned to near normal on the 7th day. In conclusion, there was a close correlation between pathologic alterations in bronchioles and changes of closing volume caused by O3 exposure.
