Effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract and liver of the rat

Our plain-English summary of Effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract and liver of the rat, by D.E. Amacher, A. Alarif, S.S. Epstein (Environmental Health Perspectives, 1974).

The study

• Authors: D.E. Amacher, A. Alarif, S.S. Epstein
• Journal: Environmental Health Perspectives
• Published: 1974;9:319-24
• Cited by: 25 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

The effects of chrysotile on DNA synthesis in the gastrointestinal tract of the rat were studied by measuring the uptake of tritium-labeled thymidine; whole stomach, small intestine, colon liver were removed, cleaned, and homogenized and the DNA was isolated and assayed for tritium label.A dose-response study indicated that 2 weeks after a 5 mg/kg dose of chrysotile, DNA synthesis was increased in the small intestine and colon and reduced in the liver; synthesis was reduced in the small intestine 2 weeks after a 500 mg/kg dose. Following a 100 mg/kg dose of chrysotile, a transient increase in DNA synthesis was noted in the stomach and small intestine at 1 and 7 days, respectively, besides increased synthesis in the colon from 28 to 63 days. These data suggest that asbestos penetrates the gastrointestinal mucosa and influences regulation of DNA synthesis in the gastrointestinal tract.

In plain English

In this preliminary rat experiment, the authors tested whether swallowed chrysotile asbestos changes DNA synthesis in the gut and liver. Young adult male rats received one stomach-tube dose of UICC standard chrysotile A. Test groups had five rats; 21 controls got saline only. DNA synthesis was measured by labeled thymidine uptake in whole stomach, small intestine, colon and liver. Two weeks after 5 mg/kg, uptake was higher than in controls in small intestine (p less than 0.05) and colon (p less than 0.01), and lower in liver (p less than 0.02). After 500 mg/kg, small intestine uptake was lower (p less than 0.10). After 100 mg/kg, uptake was higher in stomach on day 1 (p less than 0.01), small intestine on day 7 (p less than 0.10) and colon on days 28 and 63. Liver uptake after 100 mg/kg did not differ significantly from controls at any interval. The authors concluded the data suggest asbestos penetrates the gut lining and influences DNA synthesis there. They noted the affected cell populations were not defined because whole organs were used.

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: Preliminary animal experiment (dose-response and time-response study in rats)
• Who was studied: Young adult male Charles River CD strain rats weighing 300-450 g, in eight test groups of five animals each, plus a combined control group of 21 animals
• Exposure: UICC standard chrysotile A in normal saline, given once by gavage. The dose-response groups received 5, 100 or 500 mg/kg and were killed 2 weeks later. The time-response groups received 100 mg/kg and were examined from 1 day to 9 weeks later. Controls received saline only.
• Main results:
  • Dose-response study, 2 weeks after dosing: thymidine incorporation in the stomach wall did not differ significantly from controls at any dose (p greater than 0.10)
  • Dose-response study, 2 weeks after a 5 mg/kg dose: uptake was greater than in controls in the small intestine (p less than 0.05) and colon (p less than 0.01), and lower in the liver (p less than 0.02)
  • Dose-response study: small intestine uptake was lower than in controls 2 weeks after a 500 mg/kg dose (p less than 0.10). The 100 mg/kg dose in the small intestine, and the 100 and 500 mg/kg doses in liver, stomach and colon, did not differ significantly from controls.
  • Time-response study, 100 mg/kg: stomach uptake was significantly greater than in controls on day 1 (p less than 0.01) but not at 7, 14 or 28 days
  • Time-response study, 100 mg/kg: small intestine uptake was increased 7 days after dosing (p less than 0.10)
  • Time-response study, 100 mg/kg: colon uptake was significantly greater at 28 days (p less than 0.01) and 63 days (p less than 0.02). The 1, 7 and 14 day values were within normal limits.
  • Time-response study, 100 mg/kg: liver DNA synthesis did not differ significantly from controls at any interval
• The authors' conclusion: The authors concluded that the data suggest asbestos penetrates the gastrointestinal mucosa and influences regulation of DNA synthesis in the gastrointestinal tract. They described these as transient early and delayed changes in mitotic activity after chrysotile ingestion.
• Limitations the authors state:
  • Whole organs were used, so the cell populations affected were not identified

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Dose-response relationship.

Related studies

• The dose-dependent effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract, liver, and pancreas of the rat — D.E. Amacher, A. Alarif, et al. (1975)
• Enhancement of benzo[a]pyrene mutagenicity by chrysotile asbestos in rat liver epithelial cells — B. Reiss, C. Tong, et al. (1983)
• Letter: Penetration of asbestos through the digestive tract of rats — R.D. Pontefract, H.M. Cunningham (1973)
• Recovery of ingested asbestos fibers from the gastrointestinal lymph in rats — P. Sebastien, R. Masse, et al. (1980)
• Absence of mutagenic activity of three forms of asbestos in liver epithelial cells — B. Reiss, S. Solomon, et al. (1982)
• On the histopathology of liver and liver tumours in thorium-dioxide patients — J. Visfeldt, H. Poulsen (1972)

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