The biological reactivity of calcium silicate composites: in vivo studies

Our plain-English summary of The biological reactivity of calcium silicate composites: in vivo studies, by R.J. Richards, T.D. Tetley, J. Hunt (Environmental Research, 1981).

The study

• Authors: R.J. Richards, T.D. Tetley, J. Hunt
• Journal: Environmental Research
• Published: 1981;26(2):243-57
• Cited by: 20 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The biological reactivity of three respirable samples of calcium silicate composites was compared with that of chrysotile and titanium dioxide 1 and 4 weeks after intratracheal instillation of different doses of the minerals into rat lungs. The parameters chosen for investigation were numerical, cytological, and biochemical (RNA, DNA, and hydrolytic enzyme activities) alterations induced in the free cells, biochemical changes in the remaining lavaged lung tissue, and the amount of the lipoprotein-rich fraction (pulmonary surfactant) lavaged from the alveolar surface. Differential, dose-dependent (by mass) effects were produced by the composites which were all more reactive than titanium dioxide initially (1 week) although after clearance (4 weeks) many of the induced alterations produced by two composites were practically reversible. The relationship between the reactivity of the calcium silicates in simple in vitro model systems with their activity in vivo is discussed.

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

In plain English

This was an animal experiment. The authors placed liquid suspensions of three man-made calcium silicate composites, called A, B and C, directly into the windpipes of female rats. Each composite was given at 0.25 to 5.0 mg per animal. The composites were compared with chrysotile asbestos, given at 0.02 to 5.0 mg, and titanium dioxide, given at 0.1 to 5.0 mg. Four rats per group were examined 1 and 4 weeks later. The authors measured the cells washed out of the lungs, the chemistry of the lung tissue, and the amount of pulmonary surfactant, a fatty substance lining the lung surface. A change was called "significant" if it differed from control rats by set percentages, for example 40% for DNA, RNA and enzyme levels. Most effects increased with dose. At 1 week, all three composites caused more changes than titanium dioxide. By 4 weeks, composites A and C showed activity similar to titanium dioxide and less than chrysotile. Composite B's activity remained similar to chrysotile's. The authors concluded that certain calcium silicate composites cause dose-dependent changes in lung tissue, some almost reversible. They stated that the importance of these changes for any later lung disease was not clearly defined.

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: single intratracheal instillation of mineral suspensions into rat lungs, with examination 1 and 4 weeks later
• Who was studied: Female MRC hooded rats aged 4 months, four rats per group, examined 1 and 4 weeks after instillation, in two separate experiments. Animals examined per mineral (Table 1): saline controls 8 in each experiment, chrysotile 56, titanium dioxide 40, composite A 32, composite B 32, composite C 32. The work was done at the Department of Biochemistry, University College, Cardiff, Wales.
• Exposure: Respirable samples of three man-made calcium silicate composites (A, B, C), compared with a specially prepared chrysotile asbestos sample (sedimented in water from UICC material) and titanium dioxide (98% anatase). Each was given as a single 0.5 ml saline suspension. Across all minerals the doses ranged from 0.02 to 5.0 mg per animal. Table 1 gives the doses for each mineral: chrysotile 0.02 to 5.0 mg, titanium dioxide 0.1 to 5.0 mg, and each composite 0.25 to 5.0 mg. Controls received saline only.
• Main results:
  • One week after instillation, all minerals at 5 mg raised the number of free (washed-out) lung cells. Only composite B did so at the lower doses of 0.5 and 1.0 mg.
  • At 1 week, pulmonary surfactant was increased in rats given chrysotile (0.5 to 5 mg), composite A (5 mg), and composites B and C (0.25 to 5 mg).
  • At 4 weeks, surfactant was elevated in rats given chrysotile, titanium dioxide, composite A or composite B, all at the 5 mg dose.
  • The authors' order of biological reactivity at 1 week was titanium dioxide, then composite A, then composite C, with composite B equal to chrysotile.
  • The authors argued that composites A and C produced a greater lung reaction than titanium dioxide at first. After time for clearance, these minerals had equivalent activity and were less reactive than chrysotile.
  • Composite B was more reactive than A or C. Even after time for clearance, its activity in the lung was similar to that of chrysotile by the methods used.
  • A substantial amount of titanium dioxide could still be washed from the lung surface at 4 weeks, unlike the calcium silicate composites.
  • The composites' ability to damage red blood cells in earlier laboratory tests bore very little relationship to their activity in the rat lung.
• The authors' conclusion: The authors concluded that certain forms of calcium silicate composites induce dose-dependent cellular and biochemical changes in lung tissue, which for some minerals are almost reversible after prolonged clearance.
• Limitations the authors state:
  • Instillation is less physiological than inhalation. The mineral is given as a single injection, and clearance may differ from that under constant exposure.
  • Responses varied between individual rats. Individual variation was not considered; results are means from samples pooled from four rats.
  • The importance of the observed changes for any later lung disease, and how the different composites produce different effects, were not clearly understood.
  • Changes in cell appearance caused by titanium dioxide were hard to assess, because cells became packed with particles.

Topics

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

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

Related studies

• Biological reactivity of calcium silicate composites--in vitro studies — J. Hunt, F.D. Pooley, et al. (1981)
• Rat lung reactivity to natural and man-made fibrous silicates following short-term exposure — I. Lemaire, P.G. Dionne, et al. (1989)
• Cytotoxicity of respirable dusts from industrial minerals: comparison of two naturally occurring and two man-made silicates — D. Nadeau, L. Fouquette-Couture, et al. (1987)
• Cytotoxic and genotoxic effects of calcium silicates on human lymphocytes in vitro — M. Aslam, N. Fatima, et al. (1993)
• Wollastonite exposure and lung fibrosis — M.S. Huuskonen, A. Tossavainen, et al. (1983)
• Genotoxicity of dimethylnitrosamine in the presence of chrysotile asbestos UICC B and xonotlite — F. Denizeau, M. Marion, et al. (1985)

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