Benzo\[a\]pyrene uptake into rat liver microsomes: effects of adsorption of benzo\[a\]pyrene to asbestos and non-fibrous mineral particulates

Our plain-English summary of Benzo[a]pyrene uptake into rat liver microsomes: effects of adsorption of benzo[a]pyrene to asbestos and non-fibrous mineral particulates, by J.R. Lakowicz, D.R. Bevan (Chemico-biological Interactions, 1980).

The study

• Authors: J.R. Lakowicz, D.R. Bevan
• Journal: Chemico-biological Interactions
• Published: 1980;29(2):129-38
• Cited by: 22 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

The fluorescence yield of benzo[a]pyrene (BP) increases dramatically upon its transfer from the surface of particulates to rat liver microsomes. Adsorption of BP to Canadian chrysotile, anthophyllite, hematite and silica results in greatly enhanced uptake rates into microsomes when compared to uptake from a microcrystalline dispersion of BP. The fibrous minerals chrysotile and anthophyllite were more effective than silica and hematite in enhancing BP uptake. Simple mixtures of BP microcrystals and particles did not display enhanced transport, indicating that adsorption of BP to the particulate surface is necessary for enhanced microsomal uptake. BP was not released into microsomes from carbon black. We suggest that particulate-enhanced availability of BP may be of significance in the co-carcinogenesis between particulates and polynuclear aromatic hydrocarbons. However, other mechanisms are also possible, and are not excluded by our experiments. The fluorescence methodology, described in this paper provides a novel and convenient means to quantify microsomal uptake of BP and thereby investigate further the mechanisms of cocarcinogenesis.

In plain English

This was a laboratory (in vitro) experiment using fluorescence spectroscopy to measure how benzo[a]pyrene (BP) moves from the surface of mineral particles into rat liver microsomes. Microsomes were prepared from rats injected with Aroclor 1254. BP was adsorbed onto Canadian chrysotile, anthophyllite, silica, hematite or carbon black (0.3 mg BP per gram of particulate), and uptake was followed as an increase in fluorescence at 405 nm; 16.7 mg of particulate carrying 5 micrograms of BP was compared with 5 micrograms of BP as a microcrystalline aqueous dispersion. BP adsorbed to silica fluoresced about 20-fold less intensely than the same amount bound to microsomes. Adsorption of BP to all four mineral particulates greatly increased uptake rates compared with the microcrystalline dispersion, and the fibrous minerals anthophyllite and chrysotile were more effective than silica and hematite. Simple mixtures of BP microcrystals and particles did not accelerate uptake, and under the authors' experimental conditions no release of BP from carbon black to the microsomes was observed. The authors suggested particulate-enhanced availability of BP may matter in co-carcinogenesis, while noting other mechanisms are not excluded.

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: In vitro laboratory experiment: fluorescence spectroscopy of benzo[a]pyrene transfer from mineral particulates to isolated rat liver microsomes
• Who was studied: Rat liver microsomes prepared from Aroclor 1254-induced rats, used with suspensions of mineral particulates; no human or whole-animal subjects
• Exposure: Benzo[a]pyrene adsorbed to Canadian chrysotile, anthophyllite, hematite, silica or carbon black (0.3 mg BP per gram particulate), compared with a microcrystalline aqueous dispersion of BP; 5 micrograms BP with 16.7 mg particulate and 1 ml microsomes (0.6 mg protein)
• Main results:
  • BP adsorbed to silica fluoresced about 20-fold less intensely than an equivalent amount of BP bound to microsomes
  • Adsorption of BP to both asbestos and non-fibrous minerals greatly increased microsomal uptake rates, whereas uptake from an aqueous dispersion of BP microcrystals was very slow
  • Particulates added to preformed BP microcrystals did not accelerate uptake, so adsorption to the particle surface was required
  • The fibrous minerals anthophyllite and chrysotile transported BP into microsomes better than silica and hematite
  • Under the authors' experimental conditions, no release of BP from carbon black to the microsomes was observed
  • Surface areas of the particulates used: anthophyllite 11.8 and Canadian chrysotile 26.8 m2/g; silica 381 m2/g; hematite 8.0 m2/g; carbon black 31.1 m2/g
• The authors' conclusion: The authors concluded that adsorption of BP to particulates can increase its microsomal availability, and suggested this may be of significance in co-carcinogenesis between particulates and polynuclear aromatic hydrocarbons, while stating other mechanisms are possible and not excluded
• Limitations the authors state:
  • The authors stated other mechanisms of co-carcinogenesis are possible and were not excluded by their experiments
  • The authors stated their carbon black results were difficult to explain and that no release was seen under their experimental conditions
  • The authors stated further spectroscopic work was needed to resolve the components of the adsorbed BP emission spectrum
  • The authors emphasized that particle-enhanced transport of carcinogens cannot explain all the varied co-carcinogenesis phenomena

Topics

Medical terms in this study, explained in our Lexicon: Chrysotile, Anthophyllite, Hematite, Carcinogenesis.

Related studies

• Presentation of benzo(a)pyrene to microsomal enzymes by asbestos fibers in the Salmonella/mammalian microsome mutagenicity test — K. Szyba, A. Lange (1983)
• Effects of asbetos, iron oxide, silica, and carbon black on the microsomal availability of benzo[a]pyrene — J.R. Lakowicz, D.R. Bevan (1979)
• Transport of a carcinogen, benzo[a]pyrene, from particulates to lipid bilayers: a model for the fate of particle-adsorbed polynuclear aromatic hydrocarbons which are retained in the lungs — J.R. Lakowicz, D.R. Bevan, et al. (1980)
• Asbestos-mediated membrane uptake of benzo[a]pyrene observed by fluorescence spectroscopy — J.R. Lakowicz, J.L. Hylden (1978)
• Effect of particulates on metabolism and mutagenicity of benzo[a]pyrene — D.R. Bevan, W.E. Manger (1985)
• Effects of asbestos on membrane transport and metabolism of benzo(a)pyrene — C. Kandaswami, P.J. O'Brien (1980)

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