CHRYSOTILE ASBESTOS INHALATION IN RATS - DEPOSITION PATTERN AND REACTION OF ALVEOLAR EPITHELIUM AND PULMONARY MACROPHAGES

Abstract

The initial deposition and subsequent translocation of chrysotile asbestos were studied in the lungs of rats exposed for 1 h in inhalation chambers. Using scanning and transmission electron microscopy of tissue fixed by vascular perfusion, the majority of fibers that pass through the conducting airways were shown to deposit at the bifurcations of alveolar ducts. The farther an alveolar duct bifurcation was from its terminal bronchiole, the less asbestos was observed. The amount of asbestos present on the alveolar duct surfaces was significantly decreased 5 h after ending the 1 h exposure. Some fibers were taken up by type 1 epithelial cells during the 1st hour of dusting and this process continued through the 8 day period in which the animals were studied. As early as 24 h after exposure there was an accumulation of macrophages at the sites of initial asbestos deposition. This may be a significant cellular response in the early pathogenesis of asbestos.