Histopathological changes in the lungs of rats instilled with Korean chrysotile

Our plain-English summary of Histopathological changes in the lungs of rats instilled with Korean chrysotile, by J.H. Han, Y.H. Chung, C.H. Lim (Environmental Analysis, Health and Toxicology, 2021).

The study

• Authors: J.H. Han, Y.H. Chung, C.H. Lim
• Journal: Environmental Analysis, Health and Toxicology
• Published: 2021;36(3):e2021014-0
• Read it: PubMed · Publisher · Free full text

Abstract

To evaluate the pulmonary toxicity of Korean chrysotile (KC), 1 or 2 mg of KC (low- and high-concentration groups, respectively) was instilled in the lungs of Sprague-Dawley rats by a single intratracheal instillation. The lungs were examined using a light microscope at several time points (5 days, 5 weeks, and 10 weeks). Up to 10 weeks after KC instillation, differences were observed in the pathological reactions and ultimately in lung recovery between the two groups. At 5 days after KC instillation, lung weight increased and severe bronchiolitis obliterans developed in proportion to the KC concentration administered. From 5 to 10 weeks after KC administration, the lung weight of the low-concentration group increased and bronchiolitis obliterans worsened. In the high-concentration group, the lung weight and the severity of bronchiolitis obliterans at 10 weeks after administration of KC declined compared to those at 5 weeks. In conclusion, the effects of KC on lung tissue were initially found to be more influenced by the amount of fiber, but over time, the effects were influenced by the residual fibrous material in the lung tissue and its biodurability.

In plain English

This was an animal experiment. Researchers in Korea took chrysotile asbestos from deposits in Chungcheongnamdo, where most of Korea's asbestos is produced, and placed it once directly into the windpipes of male Sprague-Dawley rats. The low-concentration group received 1 mg, the high-concentration group received 2 mg, and a control group received saline only. Five rats per group were examined at 5 days, 5 weeks and 10 weeks. In both chrysotile groups, lung weights were significantly higher than in controls at every time point. Rats given chrysotile developed bronchiolitis obliterans, in which the article described inflammation and fibrosis around the small airways. Control rats did not. At 5 days, all five low-concentration rats were graded + and all five high-concentration rats were graded +++, the highest grade used. In the low-concentration group the condition worsened, and all five rats were graded ++ at 10 weeks. In the high-concentration group, lung weight fell between 5 and 10 weeks, and the authors described the condition as easing. The authors concluded that fiber amount mattered most at first, but later effects depended on fibers remaining in the lung and their biodurability.

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: a single intratracheal instillation of Korean chrysotile in rats, with lungs weighed and examined under a light microscope at three time points
• Who was studied: Seven-week-old specific-pathogen-free male Sprague-Dawley rats from a Korean supplier. There were low-concentration, high-concentration and control groups, each split into 5-day, 5-week and 10-week sub-groups of 5 rats (15 rats per group).
• Exposure: Korean chrysotile collected from asbestos deposits in Chungcheongnamdo, Korea. A single dose of 1 mg (low-concentration group) or 2 mg (high-concentration group) in 0.3 ml saline was instilled into the trachea. Controls received saline only.
• Main results:
  • Lung weights in both the 1 mg and 2 mg chrysotile groups were significantly increased compared with controls at 5 days, 5 weeks and 10 weeks.
  • Over time, lung weight in the low-concentration group kept rising. In the high-concentration group it rose from 5 days to 5 weeks and then fell at 10 weeks.
  • At 5 days, bronchiolitis obliterans was graded + (labelled slight) in the low-concentration group and +++ (labelled moderate) in the high-concentration group. Table 4 shows 5 of 5 rats in each group at those grades and 0 of 5 controls affected at any time point.
  • In the low-concentration group, 1 rat was graded ++ and 4 rats were graded + at 5 weeks. At 10 weeks all rats were graded ++. The authors described this as worsening over time.
  • In the high-concentration group at 5 weeks, 3 of 5 rats were graded +++ and 2 of 5 were graded +. At 10 weeks, Table 4 shows 2 of 5 graded +++ and 3 of 5 graded +. The authors described this as alleviation over time.
  • Body weight was significantly lower than in controls for the low-concentration group at 5 and 10 weeks. For the high-concentration group it was significantly lower at 5 days and 5 weeks, but not significantly different at 10 weeks.
• The authors' conclusion: The authors concluded that the effect of chrysotile on lung tissue was at first influenced by the amount of fiber, but over time by the fibrous material remaining in the lung and its biodurability. They also stated that lung tissue had not recovered by 10 weeks.

Topics

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

Related studies

• Changes in numbers and dimensions of chrysotile asbestos fibers in lungs of rats following short-term exposure — V.L. Roggli, A.R. Brody (1984)
• Chrysotile-induced asbestosis: changes in the free cell population, pulmonary surfactant and whole lung tissue of rats — T.D. Tetley, P.M. Hext, et al. (1976)
• Changes in pulmonary surfactant and phosphatidylcholine metabolism in rats exposed to chrysotile asbestos dust — T.D. Tetley, R.J. Richards, et al. (1977)
• Hyperplastic and Neoplastic Changes in the Lungs of Rats Treated Concurrently with Chrysotile Asbestos and N-Nitrosoheptamethyleneimine — P.T. Harrison, J.A. Hoskins, et al. (2000)
• Acute biological effects of intratracheally instilled titanium dioxide whiskers compared with nonfibrous titanium dioxide and amosite in rats — Y. Ishihara, H. Kyono, et al. (1999)
• Increased production of plasminogen activator inhibitor in vitro by pleural leukocytes from rats intratracheally instilled with crocidolite asbestos — X.Y. Li, G.M. Brown, et al. (1991)

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