Nonneoplastic effects of vinyl chloride in mouse lung

Abstract

In a previous study, a high incidence of pulmonary tumors (alveologenic neoplasia in mouse lung exposed to vinyl chloride at heavy dose (2500 and 6000 ppm) for long durations (5 and 6 months) was reported ( Y. Suzuki, 1978, Environ. Res. 16, 285–301 ). In the present study, nonneoplastic effects in mouse lung were investigated by light and electron microscopy. As major light microscopic alterations, proliferation and hypertrophy of the terminal bronchiolar cells, consisting of ciliated and Clara cells, hypersecretion of the epithelial mucin in the goblet cells of both the bronchial and the proximal bronchiolar epithelium, hyperplasia of alveolar epithelium, mobilization of alveolar macrophages, and occasional presence of peribronchial or bronchiolar chronic inflammation, were observed. Electron microscopically, Clara cells of the terminal bronchiolar epithelium showed proliferation of the rough and smooth surfaced endoplasmic reticulum and appearance of large and abnormally shaped mitochondria. Similar alterations were found in the ciliated cells. Submicroscopic changes of pulmonary alveoli were represented by focal thickening of the basement membrane, multiple foci of hyperplastic type II cell (the precondition of the alveologenic tumor), active discharge of osmiophilic lamellar bodies from the type II cell and phagocytosis of the bodies by macrophages, appearance of cholesterol crystalloids in the macrophages, degeneration of alveolar septal cells and occasional appearance of a large nucleus with swelling of the capillary endothelium.