Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations

Our plain-English summary of Bromo-deoxyuridine (BRDU) uptake in the lungs of rats inhaling amosite asbestos or vitreous fibres at equal airborne fibre concentrations, by K. Donaldson, D.M. Brown, B.G. Miller, et al (Experimental and Toxicologic Pathology, 1995).

The study

• Authors: K. Donaldson, D.M. Brown, B.G. Miller, A.R. Brody
• Journal: Experimental and Toxicologic Pathology
• Published: 1995;47(2-3):207-11
• Cited by: 12 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Rats were exposed, by inhalation, to target airborne fibre concentrations of 1000 f/ml (PCOM fibres by WHO criteria) of a long amosite asbestos sample and a vitreous fibre sample; the target was closely attained for both fibre samples. The size distributions of the two fibre samples was closely similar. Rats were placed in the chambers for 7 hours and then, following a further 16 hours in room air, were injected with bromo-deoxyuridine (BRDU). The presence of BRDU-positive cells in terminal bronchioles/alveolar ducts was assessed in blocks taken from various parts of the left lung, from apex to base. There were significant differences in the proliferative responses between animals but there were also significant differences between the treatments. Lungs from rats exposed to vitreous fibres showed no greater response than the controls, but there was a markedly greater proliferative response in the lungs of rats inhaling long amosite. There was a decreasing gradient of proliferative response from the apex of the lung to the base with all treatments. This could be explained by different degrees of deposition in different areas of the lung. Similar amounts of fibre accumulated in the lungs of rats exposed to the two fibre types and it is unlikely that dissolution could be important over the timescale used here. We conclude that, when amosite asbestos deposits in the lungs of rats it stimulates a proliferative response and that deposition of an equal number of similar-sized vitreous fibres has no effect.

In plain English

This animal experiment exposed Wistar-derived HAN strain rats for 7 hours in whole-body inhalation chambers to either long-fibre amosite asbestos or a glass microfibre (a vitreous fibre, Code 100/475). The target was 1000 fibres per ml by optical microscope counting. Attained concentrations were 912 fibres/ml for the vitreous fibre and 908 for amosite. Single-day electron microscope counts suggested the glass fibre cloud held more fibres. Cell proliferation was measured by counting cells that took up bromo-deoxyuridine (BRDU) in terminal bronchioles opening into alveolar ducts, in 3 control rats, 3 vitreous fibre rats and 4 amosite rats. The average response with the vitreous fibre was very close to that of controls, while amosite's was considerably higher. All amosite-exposed rats responded more than rats in the other two groups. Responses fell from top to base of the lung in all groups. Rats given the same treatment also differed significantly, and the authors advised some caution about the group averages. The authors concluded that deposited amosite stimulated cell proliferation and that an equal number of similar-sized vitreous fibres had no effect.

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 inhalation experiment (short-term, single 7-hour exposure)
• Who was studied: Wistar-derived rats of the HAN strain, 12 weeks old at the start of exposure. BRDU counting was carried out in 3 control rats, 3 vitreous fibre-exposed rats and 4 amosite-exposed rats.
• Exposure: A 7-hour whole-body inhalation exposure to long fibre amosite asbestos or to Johns Manville glass microfibre Code 100/475 (a vitreous fibre). The target was 1000 fibres/ml by phase contrast optical microscopy. Attained concentrations were 912 f/ml for the vitreous fibre and 908 f/ml for long amosite.
• Main results:
  • The mean BRDU responses for controls and for the Code 100/475 vitreous fibre group were very close. The mean for the long fibre amosite group was considerably higher.
  • The difference between fibre types was highly significant. Differences between animals receiving the same treatment were also highly significant.
  • All animals treated with long fibre amosite produced higher responses than animals in either of the other two groups.
  • In all groups, the response decreased from the top (apex) of the lung to the base.
  • Side-by-side samples were taken on a single day. For fibres longer than 5 micrometres, optical microscope counts closely matched the actual fibre number for long amosite but under-estimated Code 100/475 by about 60%. For all fibres longer than 0.4 micrometres, electron microscope counts gave a mean figure of 1748 for long amosite and 3396 for Code 100/475.
• The authors' conclusion: The authors concluded that when amosite asbestos deposits in rat lungs it stimulates a proliferative response, and that deposition of an equal number of similar-sized vitreous fibres has no effect.
• Limitations the authors state:
  • Within each group, one animal produced a lower response than the others. The authors said this suggests some caution in estimating the group means.
  • Responses differed significantly between animals receiving the same treatment.

Topics

The National Library of Medicine indexes this study under subjects our site covers: Amosite.

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

Related studies

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• Pulmonary effects in rats inhaling size-separated chrysotile asbestos fibres or p-aramid fibrils: differences in cellular proliferative responses — D.B. Warheit, M.A. Hartsky, et al. (1996)
• 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)
• Comparison of direct and indirect methods of measuring airborne chrysotile fibre concentration — C. Eypert-Blaison, S. Veissiere, et al. (2010)
• Renal, vascular and cardiac fibrosis in rats exposed to passive smoking and industrial dust fibre amosite — P. Boor, S. Casper, et al. (2009)
• Comparison of cytotoxicity of man-made vitreous fibres — K. Luoto, M. Holopainen, et al. (1997)

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