Acute pulmonary toxicity of beryllium sulfate inhalation in rats and mice: Cell kinetics and histopathology

Abstract

The acute response in the lung of mice and rats exposed to an aerosol of BeSO 4 was characterized by cell kinetics and histopathology. Animals were exposed for 1 hour in a nose-only chamber to a 13 μg/liter chamber concentration of BeSO 4 or to H 2SO 4 as control aerosol, and killed thereafter over a period of 21 days. Lung cell kinetics were evaluated as the labeling index (LI), defined as the percentage of cells labeled with tritiated thymidine. The labeled cells were also differentiated as to type. In rats, the LI showed a peak response on Day 8 following exposure, while the LI of mice showed a maximum response at Day 5. In rats, the proliferative response involved type II alveolar epithelial cells, interstitial and capillary endothelial cells. Histopathology showed type II alveolar cell hyperplasia and vacuolization of their cytoplasm, a thickened interstitium with infiltrates of interstitial macrophages and segmental leukocytes; a prominent feature was alveolar macrophages with ragged membranes. Three weeks after exposure, the interstitial response was largely resolved. In mice, the proliferative response was mainly found in the alveolar macrophage population and the interstitial and endothelial cells. Histopathological changes were similar to those found in rats, although less severe.