Biochemical Changes in Guinea Pig Lungs Due to Amosite Asbestos

Our plain-English summary of Biochemical Changes in Guinea Pig Lungs Due to Amosite Asbestos, by V. Misra, Q. Rahman, P.N. Viswanathan (1978).

The study

• Authors: V. Misra, Q. Rahman, P.N. Viswanathan
• Published: Environmental Research 16:55-61(1978). Received March 11, 1977
• Type of article: Journal article
• Our copy: from Johns-Manville's own medical library. The article is still under copyright, so we describe it here rather than post it.

In plain English

This animal experiment, from the Industrial Toxicology Research Centre in Lucknow, India, tracked chemical changes in guinea pig lungs after amosite asbestos was injected into the windpipe. Thirty-five adult guinea pigs each received 50 mg of amosite dust. At 40, 80, 120 and 160 days, six animals from each group were examined, and results were compared with controls. Lung protein did not change significantly. Collagen rose clearly only at 120 and 160 days. Compared with controls, glucosamine was 24% higher at 160 days, and glucuronic acid was 14% higher at 120 and 160 days. Sialic acid rose early, fell, then reached 2.75 times the control value. Lung carbonic anhydrase, an enzyme, rose early, though the authors cautioned against emphasizing early findings. At 120 days it showed a 27% decrease. At 160 days, compared with controls, serum bicarbonate was 53% lower and chloride 200% higher. In test-tube experiments, amosite, anthophyllite, chrysotile, mica, kaolin and talc all reduced this enzyme's activity in lung tissue, chrysotile most. The authors concluded that lung cell membranes are among the targets of asbestos toxicity, and that dissolved silicic acid could possibly be responsible for the enzyme inhibition.

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 injection of amosite in guinea pigs, with measurements at four time points), plus in vitro tests of several silicate dusts on lung tissue homogenates
• Who was studied: Thirty-five adult guinea pigs from the ITRC animal colony, Industrial Toxicology Research Centre, Lucknow, India. Six animals from each group were sacrificed at each interval (40, 80, 120 and 160 days), and the values were compared with control values. The in vitro tests used lung homogenates pooled from two normal guinea pigs.
• Exposure: A single intratracheal injection of 50 mg of amosite dust in 1.5 ml of normal saline. In the in vitro tests, 50 mg each of amosite, anthophyllite, chrysotile, mica, kaolin and talc was added to lung homogenate.
• Main results:
  • Lung protein content in amosite-treated guinea pigs showed no statistically significant change at any stage.
  • Lung collagen increased only marginally up to 80 days, then increased at 120 and 160 days.
  • At 160 days, lung glucosamine content showed a 24% increase.
  • Lung glucuronic acid increased in the later stages, with values at 120 and 160 days 14% higher than controls.
  • Lung sialic acid was higher at 40 days, near control values at 80 days and lower at 120 days. At the later stage it rose to 2.75-fold the control value.
  • Lung carbonic anhydrase activity in the amosite-treated animals rose at 40 and 80 days, then showed a 27% decrease at 120 days. At 120 days, serum bicarbonate decreased 10% and chloride increased, reported as significant (P less than 0.01).
  • At 160 days after injection, serum bicarbonate decreased by 53% (P less than 0.01) and serum chloride increased by 200% (P less than 0.001). Table 2 shows these values alongside control values. Carbonic anhydrase was also decreased.
  • In vitro, all six dusts inhibited carbonic anhydrase activity in lung homogenates. In the sucrose homogenate, activity was 4.04 for the control and 2.00 with amosite. Inhibition was greatest with chrysotile, then anthophyllite, then amosite.
  • Chrysotile and anthophyllite released more silicic acid. Kaolin, talc and mica had the lowest solubilities and inhibited the enzyme less.
• The authors' conclusion: The authors concluded that the changes in sialic acid, hexosamine and glucuronic acid, together with those in carbonic anhydrase, support the view that membrane structures of lung cells are among the targets of asbestos toxicity. They also concluded that lung carbonic anhydrase is a target that may be involved in respiratory impairment, and that silicic acid could possibly be responsible for the enzyme inhibition in vivo.
• Limitations the authors state:
  • The authors cautioned that little emphasis can be placed on the early-stage changes, because of macrophage proliferation and changes in cellularity.
  • The authors stated they could not yet decide whether sialic acid turnover was increased or sialic acid was released from membranes.
  • In vitro, there was no quantitative correlation between silicic acid formation and enzyme inhibition, only a qualitative relation.

Topics

Medical terms in this study, explained in our Lexicon: Amosite, Collagen, Anthophyllite, Chrysotile, Mica, Talc.

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