Pathways and quantification of insoluble particles in the lung compartments of the rat

Our plain-English summary of Pathways and quantification of insoluble particles in the lung compartments of the rat, by I. Trosić, M. Matausić-Pisl, N. Hors (International Journal of Hygiene and Environmental Health, 2000).

The study

• Authors: I. Trosić, M. Matausić-Pisl, N. Hors
• Journal: International Journal of Hygiene and Environmental Health
• Published: 2000;203(1):39-43
• Cited by: 7 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The aim of this investigation was focused on mechanisms involved in toxicokinetics of particles and fibers within the rat lung. Biologically inert polystyrene particles or an asbestos--particle comixture were followed in their pathways of deposition and retention in the lung, particularly in the alveolar space and their accumulation in the lymph node tissue of exposed rats. One group of Wistar rats was intratracheally instilled with 0.4 ml phosphate buffered saline containing 2.4 x 10(8) inert polystyrene microspheres, a second group of animals was instilled with comixture containing 1.25 mg/ml of crocidolit asbestos fibers and previously prepared microspheres. Bronchoalveolar lavage of each lung was performed on post-instillation days 1, 7, 30, 80 and 150. Particles associated with alveolar phagocytes were counted using light microscopy. The lung and lymph node tissues were chemically dissolved and tissue aliquots passed through Nucleopor membrane filters. The number of particles in the tissue aliquot samples was determined using fluorescence microscopy. The results show that the fate of particulates in the respiratory system is highly dependent on the physical properties of the instilled material. Clearance patterns for particles and fibers are markedly different. Long-term consequences are the translocation and retention of fibrous material in the interstitum, involving the major route of clearance through the lymphatics.

In plain English

In this animal experiment, the authors placed material directly into the windpipes of Wistar rats. One group of 30 received inert polystyrene microspheres. A second group of 30 received the microspheres mixed with crocidolite asbestos fibers. On days 1, 7, 30, 80 and 150, the lungs were washed out and lung and lymph node tissue was dissolved for particle counting. In the microsphere-only group, the lungs' scavenger cells (alveolar macrophages) held the most particles at day 7, a median of about 8.3 million, with significant falls after that. In the asbestos-mixture group, the number of particles held by these cells was significantly lower throughout and peaked on day 80. That group's lung tissue held nearly 20 million particles at 24 hours, dropped by day 7, then rose slowly to the end. Its lymph node counts rose significantly only on day 150. The authors concluded that the fate of particles depends on the material's physical properties, and that particles and fibers clear differently. In their view, fibrous material was retained in lung tissue, where clearance is slow and, if it occurs, would be mainly through the lymphatics.

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: intratracheal instillation in rats, followed by bronchoalveolar lavage and chemical digestion of lung and lymph node tissue at set times after instillation
• Who was studied: Two groups of Wistar rats, 30 per group (G1 and G2), aged 12-14 weeks and weighing 325-355 g. The authors worked at the Institute for Medical Research and Occupational Health, Zagreb, Croatia. Animals were examined on days 1, 7, 30, 80 and 150 after instillation, with about 5 or 6 rats per time point and measure.
• Exposure: G1 received 0.4 ml phosphate buffered saline containing 2.4 x 10 to the 8th inert polystyrene microspheres (2.13 micrometres in diameter). G2 received 0.4 ml of a comixture containing 1.25 mg/ml of ultrasonically disintegrated crocidolite asbestos fibers plus the microspheres.
• Main results:
  • In G1 (microspheres only), particles in lavaged alveolar macrophages peaked at a median of 8.3 x 10 to the 6th on day 7 after instillation.
  • In G1, macrophage particle burdens decreased significantly (p less than 0.05) at each following sacrifice day until the end of the experiment.
  • In G2 (crocidolite-microsphere comixture), macrophage particle burdens (the number of microspheres associated with the lavaged phagocytes) were significantly lower than in G1 throughout the experiment and peaked on day 80.
  • In G2, the macrophage burden fell to 3.9 x 10 to the 5th engulfed particles on day 150. The article's table, which lists 39.0 x 10 to the 4th, confirms this value.
  • In G1, the particle burden in lung tissue grew until day 30 and then dropped significantly on days 80 and 150.
  • In G2, lung tissue held a significantly higher number of particles 24 hours after instillation than G1, nearly 2.0 x 10 to the 7th per lung (the table lists 1975.0 x 10 to the 4th). This fell substantially by day 7.
  • In G2, after day 7 the lung tissue burden increased slowly until the end of the experiment.
  • In G1, particles in the regional lymph nodes peaked on day 7 and then decreased through days 30, 80 and 150.
  • In G2, the lymph node particle burden increased significantly (p less than 0.05) only on day 150, to a median of 4.1 x 10 to the 5th particles (the table lists 41.0 x 10 to the 4th).
• The authors' conclusion: The authors concluded that the fate of particulates in the respiratory system is highly dependent on the physical properties of the instilled material, and that clearance patterns for particles and fibers are markedly different. In their discussion they wrote that fibers in the interstitium may stay for long periods, that clearance from there is slow, and that, should it occur, the major routes of clearance would be through the lymphatics. They also suggested that asbestos may delay the phagocytic activity of lung macrophages, and that the comixture penetrates lung tissue more rapidly than inert particles.

Topics

Medical terms in this study, explained in our Lexicon: Deposition, Bronchoalveolar Lavage (BAL), Translocation.

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