Recovery of ingested asbestos fibers from the gastrointestinal lymph in rats

Our plain-English summary of Recovery of ingested asbestos fibers from the gastrointestinal lymph in rats, by P. Sebastien, R. Masse, J. Bignon (Environmental Research, 1980).

The study

• Authors: P. Sebastien, R. Masse, J. Bignon
• Journal: Environmental Research
• Published: 1980;22(1):201-16
• Cited by: 36 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Using the transmission electron microscope, asbestos fibers have been assessed in lymph fluid collected from the thoracic lymph duct in five groups of rats previously exposed to asbestos fibers (by ingestion). Ten rats were gavaged a single dose weighing approximately 20 mg. Five were given pure UICC chrysotile A while another group of five had pure UICC crocidolite. All the rats of the chrysotile group were positive animals with recovery rate values ranging from 6.9 × 10^-7 to 3 × 10^-5 (90% of the fibers being recovered during the first 16 hr following the gavage). The crocidolite group had only three positive animals and lower recovery rate values of 5.7 × 10^-8 to 5.6 × 10^-7. A third group was fed a synthetic diet containing 1%, by weight, chrysotile with a majority of short fibers (90% below 4 µm). Of the 15 rats comprising this group, 13 were positive with maximum daily recovery rates ranging from 2.1 × 10^-7 to 2.1 × 10^-6. A group of eight rats fed the same kind of diet but containing a higher proportion of long fibers, showed only four positive animals, however, they had higher daily recovery rates ranging from 1.9 × 10^-5 to 2.1 × 10^-4. No fibers were encountered in the samples of the two control rats. This study demonstrates the passage of chrysotile and crocidolite fibers across the gastrointestinal wall, with the passage rate being higher for long fibers than short ones.

PubMed has no abstract for this study. This is the authors' abstract, copied from the article.

In plain English

In this animal experiment, the authors used a transmission electron microscope to look for asbestos fibers in gut lymph fluid from male Sprague-Dawley rats. Ten rats received one capsule of asbestos (12.5 to 37.8 mg) pushed down the esophagus: five got UICC chrysotile A and five got UICC crocidolite. Twenty-three rats ate a synthetic diet containing 1% chrysotile by weight for 3 hours to 12 days. Of these, 15 got a diet made with short-range fibers (grade S) and 8 a diet made with intermediate-range fibers (grade I). Two control rats ate a conventional diet. Fibers were found in the lymph of 5 of 5 chrysotile rats, 3 of 5 crocidolite rats, 13 of 15 grade S rats and 4 of 8 grade I rats. Neither control rat's sample contained fibers. Recovery rates were lower for crocidolite than for chrysotile, and lower for grade S than for grade I. Longer fibers were over-represented in lymph compared with the material given. The authors concluded that chrysotile and crocidolite fibers pass through the gut wall, and noted that their figures may underestimate this passage.

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 with two parts: a single dose given by gavage (capsule placed in the esophagus) and feeding of an asbestos-containing diet, with lymph fluid collected by catheter and examined by transmission electron microscopy
• Who was studied: Male SPF Sprague-Dawley rats weighing 250-300 g: 10 given a single gavage dose (5 chrysotile, 5 crocidolite), 23 fed a chrysotile diet (15 grade S, 8 grade I), and 2 controls fed a conventional diet
• Exposure: Gavage: a single capsule of pure UICC chrysotile A or UICC crocidolite, 12.5 to 37.8 mg. Feeding: a synthetic diet containing 1% chrysotile by weight, either grade S (short-range fibers) or grade I (intermediate-range fibers), for 3 hours to 12 days. The authors reported a slightly greater proportion of long fibers (above 5 micrometres) in the grade I diet, though short fibers outnumbered long ones in both diets.
• Main results:
  • Gavaged rats: fibers were found in the lymph of 5 of 5 rats given UICC chrysotile A and 3 of 5 rats given UICC crocidolite
  • Maximum recovery rates (fibers recovered in lymph relative to fibers given) were lower in the crocidolite gavage rats than in the chrysotile A gavage rats
  • In the chrysotile A gavage rats, 90% of the recovered fibers had been recovered from the lymph within the first 16 hours after ingestion
  • In gavaged rats, fibers appeared as early as 2 hours after gavage, and some lymph samples that had been negative for many hours were positive again up to 64 hours after gavage
  • Fed rats: fibers were found in the lymph of 13 of 15 rats fed the grade S diet and 4 of 8 rats fed the grade I diet
  • Daily maximum recovery rates were lower in the grade S diet rats than in the grade I diet rats
  • Comparing recovery rates with duration of exposure in the fed rats showed no long-term retention in the lymphatic compartment
  • The lymph samples from the two control rats contained no fibers
  • Of the 25 rats with fibers in their lymph, 20 had only short fibers (median length always below 3 micrometres, maximum below 6 micrometres). The other 5 had both short and long fibers (median above 3 micrometres, maximum above 20 micrometres).
  • One chrysotile fiber 89.6 micrometres long and 0.178 micrometres thick was found in lymph. Some lymph samples from the feeding experiment contained fibers longer than the longest fibers measured in the diet.
  • When the length distribution of lymph fibers was compared with that of the ingested fibers, the highest lymph-to-ingested ratios were in length categories above 8 micrometres
  • The magnesium-to-silicon ratio of chrysotile fibers recovered from lymph did not differ significantly from that of fibers in the material given, which the authors took to suggest that magnesium had not been leached out of the chrysotile
• The authors' conclusion: The authors concluded that chrysotile and crocidolite fibers pass through the gastrointestinal wall into the gastrointestinal lymph, with a higher passage rate for long fibers than short ones. They also wrote that, if long fibers are the most carcinogenic, this preferential passage of long fibers should be taken into account when setting rules on fibers in food grade material.
• Limitations the authors state:
  • The results may underestimate the amount of fiber crossing the gut wall, because some fibers may have crossed by a route other than the lymph
  • Because passage rates varied greatly from rat to rat, the authors found it difficult to predict dose-response relationships for possible cancer effects in distant organs
  • For the crocidolite gavage group, lymph sampling was not divided into enough time periods to calculate how fiber recovery changed over time

Topics

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

Related studies

• Effects of ingested chrysotile on DNA synthesis in the gastrointestinal tract and liver of the rat — D.E. Amacher, A. Alarif, et al. (1974)
• 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)
• Quantitative assessment of chrysotile fibrils in the bloodstream of rats which have ingested the mineral under different dietary conditions — M. Weinzweig, R.J. Richards (1983)
• Ingested mineral fibers. Do they penetrate tissue or cause cancer? — P. Gross, R.A. Harley, et al. (1974)
• On the mechanism of cogenotoxic action between ingested amphibole asbestos fibres and benzo[a]pyrene: I. Urinary and serum mutagenicity studies with rats — C. Varga, G. Horváth, et al. (1998)
• Accumulation of ingested asbestos fibers in rat tissues over time — K. Patel-Mandlik, J. Millette (1983)

Browse more research in Environmental Research, or return to medical research.