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

Our plain-English summary of Functional and biochemical effects on rat lung following instillation of crocidolite and chrysotile asbestos, by S. Hirano, M. Ono, A. Aimoto (Journal of Toxicology and Environmental Health, 1988).

The study

• Authors: S. Hirano, M. Ono, A. Aimoto
• Journal: Journal of Toxicology and Environmental Health
• Published: 1988;24(1):27-39
• Cited by: 9 articles, as counted by NIH iCite
• Read it: PubMed · Publisher
• In J-M's library: Johns-Manville's company medical library held a copy (J-M no. 003637).

Abstract

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.

In plain English

This was an animal experiment from Japan's National Institute for Environmental Studies. Groups of 8 male Fischer 344 rats each received one dose into the windpipe of salt water (the control group), 1.6 mg of UICC crocidolite asbestos, or 1.6 mg of UICC chrysotile asbestos. At 1, 3, 6, 9 and 12 months afterward, the researchers tested breathing and measured lung weight and two lung proteins, collagen and elastin. No rats died. At almost all time points the chrysotile group had significantly more air left in the lungs after a normal breath and greater airflow resistance, and significantly lower outward airflow, than the other groups. Lung weight rose to 113-119% of control in the crocidolite group and 126-140% in the chrysotile group. Collagen and elastin per gram of lung were significantly higher in the chrysotile group. The crocidolite group was close to controls, except at 12 months for collagen and 3 months for elastin. The authors wrote that the findings suggest obstructive small-airway abnormalities with air trapping, more severe with chrysotile. They concluded that chrysotile is more fibrogenic (scar-forming) than crocidolite.

We wrote this plain-English summary from the full article with the help of AI, and a second AI model checked each sentence against the article. It is not the authors' wording; the abstract and the article are their own account.

What the study did and found

• Design: animal experiment (single intratracheal instillation in rats, followed for 12 months)
• Who was studied: Male Fischer 344 rats, 6 weeks old, from Charles River Japan; groups of 8 rats per treatment; studied at the National Institute for Environmental Studies, Tsukuba, Japan; examined at 1, 3, 6, 9 and 12 months after instillation
• Exposure: Single intratracheal instillation of UICC crocidolite (amphibole) or UICC chrysotile (serpentine) asbestos, 1.6 mg per rat in 0.4 ml saline; controls received 0.4 ml saline
• Main results:
  • No rats in any group died during the experimental period.
  • At almost all time points, functional residual capacity and pulmonary flow resistance in the chrysotile group were significantly greater than in the control and crocidolite groups, and peak expiratory flow, forced vital capacity and maximum expiratory flow rates were significantly lower.
  • In both asbestos groups, residual volume increased and expiratory reserve volume decreased.
  • Lung weight increased in both asbestos groups: 113-119% of saline-treated lung weight in the crocidolite group and 126-140% in the chrysotile group.
  • Collagen per unit lung weight in the chrysotile group was significantly greater than in both the control and crocidolite groups. In the crocidolite group it was almost equal to saline-treated lungs except at 12 months.
  • Elastin per unit lung weight increased in the chrysotile group compared with both the control and crocidolite groups. In the crocidolite group it was not very different from saline-treated lungs except at 3 months.
  • Lung DNA concentration was almost the same in the three groups, slightly lower in the chrysotile group. RNA/DNA was slightly elevated in both asbestos groups and higher in the chrysotile group than in the crocidolite group.
• The authors' conclusion: The authors concluded that the results indicate chrysotile is more fibrogenic than crocidolite. They also concluded that a single intratracheal dose of asbestos damaged the bronchoalveolar milieu, that collagen and elastin accumulated as a reparative process within a month, and that obstructive abnormalities with air trapping developed in the peripheral airways.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Chrysotile, Crocidolite.

Medical terms in this study, explained in our Lexicon: Crocidolite, Chrysotile, Collagen, Fibrogenic.

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