Toxic effect on the rat small intestine of chronic administration of asbestos in drinking water

Our plain-English summary of Toxic effect on the rat small intestine of chronic administration of asbestos in drinking water, by T.J. Delahunty, D. Hollander (Toxicology Letters, 1987).

The study

• Authors: T.J. Delahunty, D. Hollander
• Journal: Toxicology Letters
• Published: 1987;39(2-3):205-9
• Cited by: 5 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Sprague-Dawley rats were given a 0.5 g/l Chrysotile asbestos solution in their drinking water (approximately 7 mg/day ingested) for 1.5 years and compared to control rats of the same age. During this time there were no differences in weight or appearance of the asbestos-treated rats in comparison to controls maintained under the same conditions. However, when in vivo intestinal permeability studies were performed using a gavage/urinary collection technique, some significant changes were noted. The recovery of lactulose in the urine of asbestos-treated rats was 0.66 +/- 0.07%, significantly less than that of the controls (1.01 +/- 0.08, P less than 0.005). The recovery of mannitol was similarly decreased (2.2 +/- 0.28 vs. 3.0 +/- 0.17, P less than 0.02), but that of rhamnose was unchanged. Creatinine clearance studies indicated that there was no impairment of kidney function in the asbestos-treated group and polarized light microscopy did not reveal any asbestos fibers in sections of the small bowel. The results suggest that the chronic exposure of rats to asbestos fibers in the drinking water results in a decreased ability of the intestine to absorb some non-metabolizable sugars.

In plain English

In this animal experiment, male Sprague-Dawley rats drank water containing chrysotile asbestos at 0.5 g/l (about 7 mg a day) for 1.5 years. They were compared with untreated rats of the same age; the results table appears to list 3 control rats and 4 treated rats. To measure how permeable the intestine was, the authors gave the rats three test sugars by stomach tube and measured how much appeared in the urine over 6 hours. Treated rats did not differ from controls in weight or appearance. Urinary lactulose recovery was 0.66 ± 0.07% in treated rats (0.66 ± 0.06% in the results table) versus 1.01 ± 0.08% in controls (p less than 0.005). Mannitol recovery was 2.20 ± 0.28% versus 3.00 ± 0.17% (p less than 0.02). Rhamnose recovery did not differ significantly. Kidney function was similar in both groups, and no asbestos fibers were seen in small-bowel sections. The authors concluded that the results suggest chronic exposure to asbestos in drinking water decreases the rat intestine's ability to absorb some non-metabolizable sugars. The study did not examine cancer.

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 (long-term feeding study in rats, treated versus control)
• Who was studied: Male Sprague-Dawley rats (initial weight 150-200 g), studied at the University of California, Irvine. Asbestos-treated rats were compared with untreated controls of the same age. The OCR-garbled Table I appears to give 3 control rats and 4 treated rats. Each animal was tested 3 times, and these repeat tests are not additional animals.
• Exposure: Chrysotile asbestos (from the Bureau of Mines) suspended in agar water at 0.5 g/l and given as drinking water, about 7 mg/day ingested, for 1.5 years
• Main results:
  • Urinary recovery of lactulose was 0.66 ± 0.07% in asbestos-treated rats versus 1.01 ± 0.08% in controls (P less than 0.005), as stated in the article's summary. Table I gives 0.66 ± 0.06 for treated rats and a 35% decrease.
  • Urinary recovery of mannitol was 2.20 ± 0.28% in asbestos-treated rats versus 3.00 ± 0.17% in controls (P less than 0.02), a 27% reduction
  • Rhamnose recovery was unchanged: 5.10 ± 0.70% in treated rats versus 5.83 ± 0.16% in controls, not statistically significant
  • Creatinine clearance was 94 ± 12 in asbestos-treated rats and 95 ± 11 in controls, indicating no impairment of kidney function in the treated group
  • Polarized light microscopy found no asbestos fibers in sections of the small bowel
  • No differences in weight or appearance were seen. After 1.5 years, mean weight was 353 g in asbestos-treated rats and 368 g in controls.
• The authors' conclusion: The authors concluded that the results suggest chronic exposure of rats to asbestos fibers in drinking water results in a decreased ability of the intestine to absorb some non-metabolizable sugars. They suggested that the usual route by which lactulose and mannitol pass was partially blocked by the fibers.
• Limitations the authors state:
  • The authors state that they do not know how lactulose crosses the intestinal barrier. Their explanation that fibers block the tight junctions is speculation, which they say electron microscopy will explore.

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Polarized Light Microscopy (PLM).

Related studies

• A preliminary study of biochemical changes in the rat small intestine following long-term ingestion of chrysotile asbestos — R. Jacobs, K.S. Dodgson, et al. (1977)
• Distribution of 6-6(n)-3[H]sucrose and its radiolabeled degradation products from isolated, perfused rat small intestine loops following prolonged ingestion of chrysotile asbestos — R. Jacobs, R.J. Richards (1980)
• The mesotheliomas of the small intestine — M. Paul, G. Panabokke, et al. (1965)
• Primary Peritoneal Mesothelioma Resulting in Small Bowel Obstruction: A Case Report and Review of Literature — S.C. Frontario, A. Loveitt, et al. (2015)
• Mucin-positive epithelial mesothelioma of the peritoneum: small bowel involvement — J.H. Kim, K.Y. Kwon, et al. (2011)
• Cancer incidence and asbestos in drinking water, Town of Woodstock, New York, 1980-1998 — M.L. Browne, D. Varadarajulu, et al. (2005)

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