Pulmonary lesions produced in A-strain mice by long-term exposure to peroxyacetyl nitrate.

Abstract

Exposure of male mice, strain A, to 15 ppm of peroxyacetyl nitrate for 130 daily six-hour periods over the course of six months caused weight loss and 18 per cent mortality, the latter primarily by predisposition to severe exudative bronchopneumonia of bacterial origin. Uncomplicated lesions produced by peroxyacetyl nitrate consisted essentially of chronic hyperplastic tracheobronchitis, bronchiolitis, and pneumonitis. There were metaplastic epithelial changes, the nature of which varied with the level of respiratory tract involvement. The most noteworthy feature of the bronchial response was the formation of acinar structures within the walls, occasionally with superimposed atypical epithelial changes. Foci of squamous metaplasia were observed in the trachea and mainstem bronchi in approximately 50 per cent of the mice. Peribronchial epithelial hyperplasia was prominent, but adenomas were not produced during the course of the study. Additional components of the response to peroxyacetyl nitrate were bronc...