Effect of intrabronchially instilled amosite on lavagable lung and pleural cells

Our plain-English summary of Effect of intrabronchially instilled amosite on lavagable lung and pleural cells, by G. Oberdoerster, J. Ferin, N.L. Marcello, et al (Environmental Health Perspectives, 1983).

The study

• Authors: G. Oberdoerster, J. Ferin, N.L. Marcello, S.H. Meinhold
• Journal: Environmental Health Perspectives
• Published: 1983;51:41-7
• Cited by: 26 articles, as counted by NIH iCite
• Read it: PubMed · Publisher · Free full text

Abstract

Rats were instilled intrabronchially with 1 mg UICC amosite suspended in 0.2 mL of filtered saline; control animals received the saline instillation only. Five animals from each group were killed on various days after instillation, up to day 128/129. Total retrieved cell counts and differential cell analysis were performed from lung and pleural lavages. In particular, the appearance of peroxidase-positive macrophages (PPM) as indicators of newly arrived macrophages was investigated. Polymorphonuclear cells (PMN) and PPMs in lung lavages increased in number 24 hr after amosite instillation and remained at increased levels until day 62. Alveolar macrophage numbers were significantly decreased after amosite instillation. There was only a very transient increase of PPMs and PMNs in the saline group. The number of PPMs in pleural lavage fluid was already increased 24 hr after amosite instillation. The pleural PPM increase was sustained throughout the study. No pleural reaction was seen in the saline instilled group. The inflammatory reactions indicated by the composition of the lavaged cells of the lung represent the in vivo toxicity of intrabronchially instilled amosite. The stimulus for recruitment of PMNs and PPMs is different, since no PMN response was detected in the pleural space. It is suggested that the response of the pleural PPMs is caused by the early arrival of fibers at the pleural sites, which results in the recruitment of PPMs to this space by an unknown mechanism.

In plain English

In this animal experiment, the authors placed 1 mg of UICC amosite in saline into the airways of male Long-Evans rats. Control rats received saline only. Five rats from each group were killed on days 1, 3, 8, 27/28, 62/63 and 128/129, and the cells washed out of the lungs and the chest (pleural) cavity were counted. In lung washings of amosite-treated rats, polymorphonuclear cells (a type of white blood cell) made up a significantly larger share than in controls up to day 62/63 (24.32% versus 5.72% on day 1). Peroxidase-positive macrophages, which the authors took as newly arrived macrophages, were significantly increased from day 3. Saline rats showed only a brief rise on day 1. In pleural washings, peroxidase-positive macrophages averaged 0.474 million cells in amosite rats versus 0.160 million in controls, a threefold difference (p less than 0.001), without a rise in polymorphonuclear cells. Fibers were found in lung washings but not in pleural washings. The authors judged the lung response an indicator of amosite toxicity and suggested the pleural response may indicate fibers arriving at the pleura.

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: amosite instilled into rat airways compared with saline-instilled controls, with groups of animals killed at set days and lung and pleural lavage cells counted
• Who was studied: Two groups of 34 male Long-Evans rats each (amosite and saline control). Five per group were killed on days 1, 3, 8, 27/28, 62/63 and 128/129 after instillation; University of Rochester, Rochester, NY
• Exposure: A single intrabronchial instillation of 1 mg UICC amosite suspended in 0.2 mL of 0.9% filtered saline. Controls received 0.2 mL saline only
• Main results:
  • Lung lavage: polymorphonuclear cells were a significantly greater fraction of lung lavage cells in the amosite group up to day 62/63. On day 1 the mean was 24.32 ± 14.16% in amosite rats versus 5.72 ± 4.35% in controls
  • Lung lavage: the fraction of peroxidase-positive macrophages was significantly increased in amosite rats starting at day 3 (6.93 ± 2.80% of alveolar macrophages versus 1.07 ± 0.41% in controls on day 3)
  • Lung lavage: absolute numbers of polymorphonuclear cells and peroxidase-positive macrophages in amosite rats came down to control levels only on day 128/129
  • Saline-instilled control rats showed only a transient increase in polymorphonuclear cell and peroxidase-positive macrophage fractions in lung lavage on day 1
  • Individual alveolar macrophage volume in amosite rats was significantly increased above controls: by 21% on day 8, 20% on day 27/28 and 11% on day 62/63
  • Total lung lavage cell recovery tended to be lower in amosite rats until day 27/28, but this was significant only on day 27/28
  • Pleural lavage: the peroxidase-positive macrophage fraction was significantly increased in amosite rats on days 1 and 3 (day 1: 8.15 ± 2.87% versus 2.29 ± 1.09% in controls), with a trend toward higher percentages afterwards
  • Pleural lavage: from day 1 through day 128/129, the average number of peroxidase-positive macrophages was 0.474 (± 0.240) x 10^6 cells in the amosite group and 0.160 (± 0.092) x 10^6 cells in controls. The authors described this threefold increase as significant at p less than 0.001
  • Unlike the lung lavage, pleural lavage showed no increase in polymorphonuclear cell numbers
  • Total pleural lavage cell numbers rose significantly more in amosite rats beginning at day 62/63 (day 128/129: 1.82 ± 0.36 versus 1.28 ± 0.24 x 10^-7 as printed, in controls)
  • Amosite fibers were found in lung lavage fluid of treated rats on all sacrifice days, decreasing with time. No fibers were detected in pleural lavage samples
• The authors' conclusion: The authors concluded that intrabronchial instillation of 1 mg amosite led to an immediate and lasting increase of polymorphonuclear cells and peroxidase-positive macrophages in the airways, which they judged an indicator of amosite toxicity to the lung. They suggested the early and sustained pleural increase in peroxidase-positive macrophages may indicate the arrival of fibers at pleural sites. They stated that future studies have to show whether this response is involved in pleural plaques or calcification
• Limitations the authors state:
  • Some pleural lavage slides were too weakly stained to identify peroxidase-positive macrophages and had to be excluded
  • Alveolar macrophage volume could not be measured on days 1 and 3 because of the high percentage of polymorphonuclear cells
  • The authors noted that only relatively few instilled fibers are expected to reach the pleura and may be cleared from the pleural space, so failing to find fibers in pleural lavage is not necessarily surprising
  • The authors said the significance of the increase in total pleural lavage cells from day 62/63 remains to be studied, and that the mechanism of pleural macrophage recruitment needs further investigation

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, UICC, Macrophage, Alveolar Macrophage.

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