Abstract
On the basis of clinical and pathological examinations, paraquat poisoning was diagnosed in the cases of two dogs that died after vomiting and respiratory insufficiency for several days. Histological examination revealed hemorrhage and edema in the alveoli, diffuse fibrosis of the alveolar walls, and formation of hyaline membranes in the lung. Extensively proliferating bronchiolar epithelial cells and epithelial cells in the alveolar area around the bronchioli were associated with cell-arrangement continuity. Immunohistochemically, the bronchiolar epithelial cells were positive for cytokeratin; and the alveolar epithelial-cell nuclei were positive for 8-OHdG, which is one of the most commonly used markers for evaluating oxidative stress. These findings suggest that, in cases of paraquat poisoning, pulmonary-tissue damage is induced by oxidative damage caused by free radicals and that bronchiolar epithelial cells play an important role in repairing pulmonary tissue when alveolar epithelial cells have been especially affected.-K
