Abstract
Cell proliferation was examined in the lung parenchyma, the ciliated airway epithelium and the lymph nodes of Fischer-344 rats following a 6-h exposure to fly ash obtained from the baghouse of an experimental fluidized bed combustor. The fly ash concentration was 142 mg/m 3 with a mass median aerodynamic diameter (MMAD) of approximately 3.0 μm and a geometric standard deviation ( σ g ) of approximately 2.6. Lung deposition of fly ash was measured in the right lung to be 90 ± 20 and 80 ± 30 mg for male and female rats, respectively, resulting in a calculated value for male rats of (140 ± 30 μg/animal) and for female rats of (130 ± 50 μg/animal). Autoradiographic methods were used to detect cells that incorporated [ 3H] thymidine. About a 10-fold increase in labeling of the lung epithelial type II cells was observed following the 6-fly ash exposure. There was also an increase in [ 3H] thymidine incorporation into DNA of alveolar macrophages. Labeling activity of macrophages within the lung was increased for up to 4 dyas following fly ash exposure; however, the size of the macrophage population was not altered. Following exposure, a higher labeling index was also observed in the epithelial cells of the airways. Labeling in the trachea reached a peak at 4 days after exposure while in the bronchi and in small airways (inside diameter of less than 0.35 mm) the highest level of labeling was observed at 1 day after exposure. Labeling in airway epithelial cells was increased 2–4 times above that of sham-exposed animals. Lung-associated lymph nodes accumulated particulate material and had variable amounts of [ 3H] thymidine incorporation. These results demonstrate that acute inhalation exposure to fly ash initiated cell division or DNA synthesis in several cell populations of lung parenchyma and airways.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have