Functional and biochemical effects on rat lung following instillation of crocidolite and chrysotile asbestos

Groups of rats received a single intratracheal instillation of saline (control), 1.6 mg crocidolite, and 1.6 mg chrysotile. At 1, 3, 6, 9, and 12 mo after instillation, respiratory functional tests were performed and the lungs were biochemically analyzed. Throughout 12 mo, obstructive small-airway abnormalities with air trapping were observed in the asbestos-treated rats. The degree of airway obstruction and air trapping was higher in the chrysotile-treated group than in the crocidolite-treated group. Lung weight increased significantly in both asbestos-treated groups. Collagen and elastin content of unit lung weight significantly increased in the chrysotile-treated group compared with the control and crocidolite-treated group throughout the experimental period up to 12 mo. However, the collagen and elastin content of unit lung weight in the crocidolite-treated group was not as different from the control group. These results indicate that chrysotile is more fibrogenic than crocidolite, as has been suggested in histopathological studies.