An investigation of the penetration of ingested asbestos into the normal and abnormal intestinal mucosa of the rat

Our plain-English summary of An investigation of the penetration of ingested asbestos into the normal and abnormal intestinal mucosa of the rat, by M.E. Meek, P. Grasso (Food and Chemical Toxicology, 1983).

The study

• Authors: M.E. Meek, P. Grasso
• Journal: Food and Chemical Toxicology
• Published: 1983;21(2):193-200
• Cited by: 3 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

To characterize the tissue response associated with the presence of asbestos fibres in the gastro-intestinal wall, duodenal tissues of Wistar rats were examined by light microscopy following injection of a suspension containing amosite fibres into the wall of the duodenum. Intestinal tissues were also examined by light microscopy following oral administration of amosite for 5 days to healthy animals and for up to 7 days to animals with induced gastro-intestinal ulcers. Injection of amosite into the wall of the gastro-intestinal tract resulted in granulomatous lesions characterized by large numbers of macrophages containing crystals with the polarizing characteristics of amosite fibres. Examination by polarizing light microscopy following ingestion of asbestos revealed no such lesions or other histopathological abnormalities in the gut wall of the healthy animals and no intracellular fibres were observed in the animals with ulcers. Light microscopy, therefore, yielded no pathological evidence of widespread transmigration of asbestos from the gastro-intestinal tract of rats, even under conditions of mucosal loss. Further studies involving analysis by electron microscopy are under way.

In plain English

This was an animal experiment in adult female Wistar rats. It asked whether swallowed amosite asbestos gets into the intestinal wall, judged by light microscopy. First, the authors injected an amosite suspension or salt water into the duodenal wall of two rats each. One rat in each group died overnight. In the surviving amosite-injected rat, the injection sites showed granulomas: dense masses of macrophages holding crystals that looked like amosite under polarized light. The saline rat showed smaller reactions of a different kind. Second, five healthy rats were given amosite by tube daily for 5 days, and three controls got corn oil. No macrophage response or other changes were seen in the gut walls of the amosite-fed rats. Third, six rats got amosite and six got corn oil, and ulcers were induced with indomethacin. Ulcers appeared in all of them. Masses of fibres lay in debris inside the gut, but no fibres were seen inside macrophages. The authors concluded that the rat gut wall may be an effective barrier. They called the ulcer results preliminary, because fibres too small for light microscopy could be missed.

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 (three short-term experiments in rats, with tissues examined by light and polarizing light microscopy)
• Who was studied: Adult female inbred Wistar albino rats from the University of Surrey Animal Breeding Unit, UK. Injection experiment: 2 amosite-injected and 2 saline-injected rats. Oral experiment in healthy rats: 5 test and 3 control rats. Oral experiment in rats with induced ulcers: 6 test and 6 control rats.
• Exposure: UICC reference amosite. Injection experiment: five 0.1 ml injections of an amosite suspension in physiological saline into the duodenal wall during surgery. Healthy rats: 100 mg amosite per rat in corn oil by tube into the oesophagus, daily for 5 days. Rats with ulcers: 100 mg amosite daily for 2 days, then indomethacin 10 mg/kg on day 3 to induce ulcers, then 25 mg amosite daily until killed. Controls received saline or corn oil.
• Main results:
  • Injection experiment: in the one surviving amosite-injected rat, the injection sites showed granulomas made up mainly of macrophages. These macrophages contained crystals with the polarizing characteristics of amosite.
  • Injection experiment: the one surviving saline-injected rat showed smaller, more localized reactions at the injection sites, with relatively scanty macrophages.
  • Healthy rats given amosite by mouth (5 test animals): light microscopy of about 25 sections per animal showed no macrophage response or other pathological changes in the gut wall of the asbestos-fed animals.
  • Indomethacin experiment: at autopsy, ulcers were seen in all treated and control animals.
  • Rats with ulcers given amosite (6 test animals): masses of fibres were present in debris inside the gut, but no fibres were seen inside macrophages in the ulcers.
  • Occasional fibres lying clearly outside cells were seen in tissues of several test and control animals. The authors presumed these were contamination.
• The authors' conclusion: The authors concluded that light microscopy gave no pathological evidence of widespread movement of asbestos out of the rat gut, even where the gut lining was lost. They concluded that the rat gut wall may present an effective barrier to asbestos fibres.
• Limitations the authors state:
  • Finding no tissue response does not entirely rule out limited passage of small fibres, and the method may not be adequate to exclude this with confidence.
  • The ulcer results are preliminary. Electron microscopy might reveal fibres smaller than the light microscope can resolve.
  • Fibres might have been extracted during processing of the tissue sections, which needs further study.

Topics

Medical terms in this study, explained in our Lexicon: Amosite, Macrophage.

Related studies

• Intestinal transport of some macromolecules in food — M.L. Weiner (1988)
• Early response of gastric mucosa to ingested asbestos dust and the dissolution of nickel — S.H. Zaidi, G.S. Gupta, et al. (1976)
• Review of published studies on gut penetration by ingested asbestos fibers — P.M. Cook (1983)
• Transmigration of ingested asbestos — M.E. Meek (1983)
• Unusual intestinal talcosis — P.A. Anani, C. Ribaux, et al. (1987)
• Cardiorespiratory responses to incremental exercise in patients with asbestos-related pleural thickening and normal or slightly abnormal lung function — A. Miller, A. Bhuptani, et al. (1993)

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