Ultrastructure of the lung in the rat following exposure to crocidolite asbestos and quartz

Abstract

Lung tissue from rats that had inhaled U.I.C.C. crocidolite asbestos or quartz particles showed thickening of the interstitial tissue and the presence of collagen fibres. Aggregates of macrophages in the alveolar spaces were a dominant feature of all the sections examined from asbestos exposed rats. According to the ultrastructural studies described here, all the macrophages were mature cells, indicating that the ingested crocidolite asbestos was non-toxic. Lung sections of rats exposed to quartz particles were significantly different. Single cells were found in the alveolar spaces and many macrophages showed a characteristic pattern of vacuole formation. Other cells contained intracellular membranous lamellated bodies, similar to those found in Type II pneumocytes. Cells containing lamellated bodies were also found in the interstitial tissue. These findings suggest that the two mineral dusts have quite different biological effects on the macrophage and that the development of pulmonary fibrosis may, to some extent, be caused by a different mechanism in each instance.

Asbestos‐induced changes in rat lung parenchyma

“…Type II cell hyperplasia following asbestos inhalation has been reported previously (Davis, 1963;Miller et al, 1978); however, these studies did not involve the short exposure periods used in this experiment and only gave subjective opinions of the changes in type II cell numbers. This is the first report of a rapid increase in cell numbers following dust exposure and thus suggests an initial direct action of the dust on type II cells rather than a response mediated by factors produced by other cell types.…”

Alterations in Macrophage Functions by Environmental Chemicals

“…After ingestion of asbestos, macrophages developed large flattened pseudopodia, an increase in cytoplasmic blebbing, asbestos bodies and more extensive cytoplasmic processes (60,93). The cytoplasm was filled with numerous lysosomes, free and aggregated ribosomes, mitochondria, and strands of rough endoplasmic reticulum (94). After ingestion of quartz, macrophages showed pronounced intracytoplasmic vacuolation deterioration of the plasma membrane and assumed wild, bizarre shapes (95).…”

Pathogenesis of Mesothelial Reactions to Asbestos Fibers

“…This hypothesis is based on the results of previous investiga tions showing different morphological and functional re sponses of alveolar, pleural, and peritoneal macrophages to different mineral particles. Miller and Kagan [10,II] and Miller et al [12] observed different ultrastructural characteristics of rat alveolar and peritoneal macrophages following exposure to silica particles or crocidolite asbes tos fibers. Macrophages isolated from animals exposed to silica were vacuolated, did not spread in culture, and showed morphologic evidence of membrane damage [II], In contrast, macrophages isolated from animals after exposure to crocidolite asbestos showed morphologic evi dence of activation [ 10,12], Other investigators observed that a single intraperitoneal injection of 2.5 mg of croci dolite or chrysotile asbestos fibers in mice increased mac rophage spreading and decreased phagocytosis, but did not increase their ability to kill tumor cells [ 13].…”