Deposition pattern of inorganic particles at the alveolar level in the lungs of rats and mice

Our plain-English summary of Deposition pattern of inorganic particles at the alveolar level in the lungs of rats and mice, by A.R. Brody, M.W. Roe (The American Review of Respiratory Disease, 1983).

The study

• Authors: A.R. Brody, M.W. Roe
• Journal: The American Review of Respiratory Disease
• Published: 1983;128(4):724-9
• Cited by: 100 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The early pathogenesis of particle-induced lung disease is likely to be determined in large part by the initial pattern of dust deposition at the alveolar level. We have studied the deposition pattern of 5 aerosolized dusts (chrysotile and crocidolite asbestos, fiber glass, alpha-quartz, and ash from Mt. St. Helens) in the lungs of rats. Mice were exposed to chrysotile asbestos. Quantitative electron microscopy was carried out on tissues fixed by vascular perfusion. Immediately after a brief exposure, significantly (p less than or equal to 0.01) greater numbers of particulates had deposited on alveolar duct bifurcations when compared with the number of particles on duct surfaces adjacent to the bifurcations. Few particles were counted at midpoints between bifurcations, and particles rarely were observed within alveoli. Our data show that regardless of mineral nature, shape, or concentration, inhaled particulates small enough to pass through the conducting airways are deposited primarily at alveolar duct bifurcations. We proposed that the alveolar deposition patterns observed are the result of air-flow characteristics that cause enhanced deposition of particles at alveolar duct bifurcations intersecting the flow. This is similar to deposition patterns that occur at bifurcations of conducting airways.

In plain English

In this animal experiment, the authors exposed groups of 3 to 6 animals in inhalation chambers to one of five dusts. Rats breathed Canadian chrysotile asbestos, UICC crocidolite asbestos, Johns-Manville 100B fiber glass, alpha-quartz, or ash from Mt. St. Helens, and mice breathed chrysotile asbestos. Exposures lasted 1 to 5 hours. Immediately afterward, the lungs were fixed and examined by scanning electron microscopy. Particles were counted on alveolar duct bifurcations (the branch points of the small air ducts) and on nearby duct surfaces. For each dust, the authors reported significantly more particles on bifurcations than on adjacent duct surfaces (p less than 0.01). Few particles were seen at midpoints between bifurcations or inside alveoli, and counts decreased with distance from the terminal bronchioles. Mice showed essentially the same pattern as rats. The authors concluded that, regardless of mineral nature, shape or concentration, particles reaching the alveolar region deposited mainly at duct bifurcations. They proposed air-flow patterns as the cause, but noted that other studies gave no direct confirmation of this. They also said the biological significance was not entirely clear.

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 with quantitative scanning electron microscopy of lung tissue fixed immediately after a brief exposure
• Who was studied: Groups of 3 to 6 animals per dust, laboratory of the National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina. Rats: CD-1 for chrysotile (6 animals), crocidolite (6) and fiber glass (4); Fisher 344 for alpha-quartz (4); Fisher for Mt. St. Helens ash (3). Mice: C57BL/6NxC3H for chrysotile (3). Study dates were not stated.
• Exposure: Aerosolized dusts, by table 1: Canadian chrysotile asbestos for 1 h at 15 mg/m3 (rats); UICC crocidolite asbestos for 1 h at 5 mg/m3; Johns-Manville 100B fiber glass for 1 h at 8 mg/m3; alpha-quartz for 3 h at 110 mg/m3; Mt. St. Helens ash for 1 h at 12 mg/m3; Canadian chrysotile for 5 h at 15 mg/m3 (mice). Concentrations are respirable mass. Animals were examined about 4 minutes after exposure ended.
• Main results:
  • In all rats and mice studied, the percentage of fields of view with no particles was significantly greater on alveolar duct surfaces than on bifurcation surfaces (p less than 0.01).
  • For each of the five dusts in rats, particle counts differed significantly between bifurcations and alveolar ducts (p less than 0.01). Particle concentrations decreased with increasing distance from the terminal bronchioles.
  • In the 1 to 10 particle category, the mean number of particles per field of view (mean and SEM) was higher on bifurcations than on adjacent ducts. At the first bifurcation the figures were: chrysotile 6.0 vs 3.0; crocidolite 4.7 vs 2.8; alpha-quartz 5.4 vs 3.6.
  • Few particles were counted at midpoints between bifurcations, and particles were rarely seen within alveoli.
  • In mice exposed to chrysotile asbestos, the deposition pattern was essentially the same as in rats.
• The authors' conclusion: The authors concluded that, regardless of mineral nature, shape or concentration, inhaled particles small enough to pass through the conducting airways deposited primarily at alveolar duct bifurcations. They proposed that air-flow characteristics cause this pattern.
• Limitations the authors state:
  • The authors noted that the air-flow studies they cited do not directly confirm their proposed explanation.
  • The authors stated that the biological significance of enhanced deposition at alveolar duct bifurcations is not entirely clear.

Topics

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

Related studies

• A striking deposition of mineral particles in the lungs of a farmer: a case report — B. Gylseth, L. Stettler, et al. (1984)
• Sialic acid mediates the initial binding of positively charged inorganic particles to alveolar macrophage membranes — J.E. Gallagher, G. George, et al. (1987)
• Talc deposition and effects after 20 days of repeated inhalation exposure of rats and mice to talc — J.A. Pickrell, M.B. Snipes, et al. (1989)
• Accumulation of mixed mineral dusts in the lungs of rats during chronic inhalation exposure — C.H. McMillan, A.D. Jones, et al. (1989)
• Asbestos dust deposition and retention in rats — J.C. Wagner, J.W. Skidmore (1965)
• Morphologic characterization of alveolar macrophages from subjects with occupational exposure to inorganic particles — T. Takemura, W.N. Rom, et al. (1989)

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