Sequence of bronchoalveolar lavage and histopathologic findings in rat lungs early in inhalation asbestos exposure

Our plain-English summary of Sequence of bronchoalveolar lavage and histopathologic findings in rat lungs early in inhalation asbestos exposure, by C.M. Smith, S. Batcher, A. Catanzaro, et al (Journal of Toxicology and Environmental Health, 1987).

The study

• Authors: C.M. Smith, S. Batcher, A. Catanzaro, J.L. Abraham, R. Phalen
• Journal: Journal of Toxicology and Environmental Health
• Published: 1987;20(1-2):147-61
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To assess the early cellular inflammatory response of the lungs, 7 rats per group were exposed nose-only to 13 mg/m3 of chrysotile asbestos, 7 h/day for 2, 4, or 6 wk. Lung histopathology and bronchoalveolar lavage (BAL) were analyzed. In exposed animals, dose-related bronchiolitis and fibrosis were found that were not seen in control rats (p less than 0.001). In exposed rats, total BAL cells were increased six-to sevenfold over matched controls, and more cells were retrieved with longer exposure (p less than 0.001). In the BAL, counts of macrophages, lymphocytes, and polymorphonuclear cells (PMNs) were each elevated in the exposed rats (each p less than 0.001). PMNs seen histologically and in the BAL may be related to the time period examined. PMNs and lymphocytes observed throughout this 6-wk study support the idea that these cells may have an important role in the early events of asbestos lung injury.

In plain English

This was an animal experiment. The authors exposed male Fischer-344 rats to chrysotile asbestos by nose-only inhalation at a mean concentration of 13 mg/m3, 7 hours a day, 5 days a week, for 2, 4 or 6 weeks. At each time point, 7 exposed rats and 7 matched control rats that had breathed filtered air were examined. The authors washed out the right lung (bronchoalveolar lavage) to count cells, and graded lung tissue for bronchiolitis and fibrosis. Exposed rats yielded more lavage cells than controls at every time point, and counts rose with longer exposure. At 6 weeks the mean total count was 22.9 in exposed rats versus 3.3 in controls, in the table's units of cells times 10 to the fifth power. Macrophages, lymphocytes and polymorphonuclear cells (PMNs) were all increased. PMN numbers were raised by 2 weeks but did not rise further. Control rats showed no fibrosis or bronchiolitis. In exposed rats, median fibrosis grades were 0.5, 1.0 and 1.5, and median bronchiolitis grades were 1.0, 1.5 and 2.0, at 2, 4 and 6 weeks. The authors concluded that these findings suggest all three cell types play a role in the early events of asbestosis.

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 inhalation experiment with exposed and matched control rats examined at 2, 4 and 6 weeks
• Who was studied: 48 male Fischer-344 rats, 2 to 3 months old. 6 were used for infection screening and 42 were studied: 21 exposed and 21 controls, with 7 of each examined at 2, 4 and 6 weeks. Exposures were done at the University of California, Irvine, Air Pollution Health Effects Laboratory.
• Exposure: Chrysotile asbestos (Plastibest-20, Johns-Manville Jeffrey Mine, Quebec), given nose-only at a mean concentration of 13 mg/m3, 7 hours a day, 5 days a week, for up to 6 weeks. The measured mean over the study was 12.9 plus or minus 7.5 mg/m3. Controls breathed HEPA-filtered air.
• Main results:
  • Mean total lavage cells from the right lung, given in the table in units of cells times 10 to the fifth power, were 8.7, 11.6 and 22.9 in exposed rats at 2, 4 and 6 weeks, versus 1.5, 1.7 and 3.3 in controls. The increase over controls at each time point, and the rise with longer exposure, were each reported with p less than 0.001.
  • In exposed rats, macrophages made up a smaller percentage of lavage cells (73%, 68% and 76% at 2, 4 and 6 weeks, versus 95%, 94% and 95% in controls). PMNs and lymphocytes made up higher percentages (PMNs 19%, 18% and 10% versus 1%, 1% and 0%).
  • Absolute numbers of lymphocytes, macrophages and PMNs were each increased in exposed rats (each p less than 0.001). Macrophages and lymphocytes increased with longer exposure. PMNs were raised by 2 weeks but did not increase further.
  • Control rats had no fibrosis or bronchiolitis (grade 0) at any time point.
  • Exposed rats at 2 weeks had median bronchiolitis grade 1.0 and median fibrosis grade 0.5. At 4 weeks the medians were fibrosis 1.0 and bronchiolitis 1.5. At 6 weeks they were fibrosis 1.5 and bronchiolitis 2.0. Scores increased with longer exposure (p less than 0.001).
  • Exposed rats at 6 weeks had a median fibrosis grade of 1.5 and a median bronchiolitis grade of 2.0.
  • In lung tissue sections, PMNs appeared in large numbers only in the rats exposed for 2 weeks.
• The authors' conclusion: The authors concluded that the increased numbers of macrophages, PMNs and lymphocytes suggest that all these cells play a role in the early events of asbestosis.
• Limitations the authors state:
  • The authors stated that the study could not determine what mechanism caused the effects seen.

Mines named here

Asbestos mines this study is about. Each mine's page says who ran it, when it worked, and what it produced.

• Jeffrey mine, Asbestos, Quebec

All asbestos mines

Topics

Medical terms in this study, explained in our Lexicon: Bronchoalveolar Lavage (BAL), Asbestos Exposure, Chrysotile, Histopathology, Fibrosis, Macrophage.

Related studies

• Brief inhalation of asbestos compromises superoxide production in cells from bronchoalveolar lavage — J.M. Petruska, J. Marsh, et al. (1990)
• Comparative proliferative and histopathologic changes in rat lungs after inhalation of chrysotile or crocidolite asbestos — K.A. BéruBé, T.R. Quinlan, et al. (1996)
• Biochemical components of bronchoalveolar lavage in early experimental asbestosis of the sheep: phospholipase A2 activity, prostaglandin E2 and proteins — P. Sirois, G. Drapeau, et al. (1983)
• Enhanced lipid peroxidation in lung lavage of rats after inhalation of asbestos — J.M. Petruska, K.O. Leslie, et al. (1991)
• The effects of chrysotile and crocidolite asbestos on the lower respiratory tract: analysis of bronchoalveolar lavage constituents — E. Kagan, Y. Oghiso, et al. (1983)
• Additional histopathologic examination of the lungs from a 3-month inhalation toxicity study with multiwall carbon nanotubes in rats — S. Treumann, L. Ma-Hock, et al. (2013)

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