Recovery from ozone-induced injury in the lungs of the Syrian golden hamster

Abstract

In order to examine the morphological and cytokinetic changes in the hamster pulmonary epithelium after a high dose of ozone, Syrian golden hamsters were exposed to 15 ppm of ozone for 6 hr and killed 2 hr to 96 days later. Two hours before death, each animal was injected intraperitoneally with tritiated thymidine. Autoradiographs were prepared from 1-μm glycol methacrylate sections of lung tissue. Ozone produced immediate epithelial desquamation in all airways, leaving a single layer of either squamous cells or nonciliated cells which began to proliferate within 1 day of the exposure. The overall morphology of the airway epithelium returned to normal within 7 days. Damage in the alveolar region was localized to alveoli near the terminal bronchioles and consisted of desquamation of Type I epithelial cells and endothelial cells and the presence of inflammation. Hyperplastic regions of cuboidal, squamous, and ciliated cells formed at the bronchiolar-alveolar junction within 2 days of exposure. The greatest increase in proliferation was seen in airway epithelial cells which reached a maximal labeling index of 50%. We conclude that the hamster pulmonary epithelium has a great proliferative capacity to repair damage due to a high concentration of ozone. Foci of hyperplasia in both airway and alveolar epithelium appear during this repair process.