Effects of particulate matter on rates of membrane uptake of polynuclear aromatic hydrocarbons

Our plain-English summary of Effects of particulate matter on rates of membrane uptake of polynuclear aromatic hydrocarbons, by D.R. Bevan, S.C. Riemer, J.R. Lakowicz (Journal of Toxicology and Environmental Health, 1981).

The study

• Authors: D.R. Bevan, S.C. Riemer, J.R. Lakowicz
• Journal: Journal of Toxicology and Environmental Health
• Published: 1981;8(1-2):241-50
• Cited by: 13 articles, as counted by NIH iCite
• Read it: PubMed · Publisher

Abstract

Investigations of the mechanism of particle-enhanced uptake of benzo [a] pyrene into model membranes and microsomes have been extended by studying the effects of particulates on the rates of uptake of four additional polynuclear aromatic hydrocarbons (PAH) into model membranes. Adsorption of dibenzo [a, h] anthracene, benzo [g,h,i] perylene, and 3-methylcholanthrene to the surface of particles resulted in enhanced rates of membrane uptake of these PAH. Adsorption to the fibrous asbestos minerals (chrysotile and anthophyllite) produced the greatest enhancement in membrane uptake rates compared to uptake from microcrystalline dispersions of the PAH. Adsorption of these PAH to nonfibrous minerals resulted in uptake rates intermediate between those of the asbestos-adsorbed and microcrystalline states. In contrast, adsorption of dibenzo-[c,g] carbazole to particles did not result in enhanced uptake. In this case, the rates of uptake in the absence and presence of particles were all extremely high, presumably as a result of the high water solubility of this PAH. The methods described in this paper permit characterization of particles-PAH mixtures in terms of the rate of PAH uptake into membranes.

In plain English

This was a laboratory experiment, not a study of people. The authors coated particles, including the asbestos minerals chrysotile and anthophyllite, titanium dioxide and other particles, with one of four cancer-causing chemicals from the polynuclear aromatic hydrocarbon (PAH) family, at 0.3 mg of chemical per 1 g of particle. Using fluorescence, they measured how fast each chemical moved into artificial fat membranes (vesicles made of a synthetic lipid) at 37°C. They compared this with the chemical alone as tiny crystals. For dibenzo[a,h]anthracene, benzo[g,h,i]perylene and 3-methylcholanthrene, uptake from crystals was 20-30% complete in 30 minutes, and uptake from titanium dioxide was similar. Uptake from chrysotile and anthophyllite was more than 80% complete in 30 minutes. Other particles gave rates in between. For dibenzo[c,g]carbazole, which dissolves in water far more readily, uptake was extremely rapid with or without particles. The authors concluded that attaching poorly soluble PAH to particles should raise cells' exposure to them. They cautioned that results from model membranes cannot be applied directly to living bodies.

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: Laboratory (in vitro) experiment measuring by fluorescence the rate at which PAH chemicals moved from particles or from microcrystals into model lipid membranes
• Who was studied: No people or animals. The test system was model membranes: 10 mg of vesicles made of synthetic dipalmitoyl-L-alpha-phosphatidylcholine (DPPC) in buffer at 37°C; each experiment was averaged from at least two runs
• Exposure: Four PAH (dibenzo[a,h]anthracene, benzo[g,h,i]perylene, 3-methylcholanthrene, dibenzo[c,g]carbazole) adsorbed onto particles at 0.3 mg PAH per 1 g particle. The particles included the fibrous asbestos minerals chrysotile and anthophyllite, titanium dioxide and other particles. These were compared with microcrystalline suspensions of the PAH alone.
• Main results:
  • For dibenzo[a,h]anthracene, benzo[g,h,i]perylene and 3-methylcholanthrene as microcrystals, membrane uptake was 20-30% complete in 30 min
  • Uptake of these three PAH from titanium dioxide-adsorbed particles was similar to uptake from microcrystals, within experimental error
  • When these three PAH were adsorbed to the asbestos particles (anthophyllite and chrysotile), uptake was more than 80% complete in 30 min, the greatest enhancement
  • Uptake of these three PAH from the other particles was intermediate between the asbestos-adsorbed and microcrystalline states
  • Dibenzo[c,g]carbazole, the most water-soluble of the four, was taken up extremely rapidly from microcrystals and from particles alike, so particles did not enhance its uptake
• The authors' conclusion: The authors concluded that their method gives a way to quantify PAH delivery rates. They stated that adsorbing highly insoluble carcinogenic PAH to particles should produce higher cellular exposures to the PAH and increased tumor yields. They proposed that dissolving in water is the rate-limiting step for uptake.
• Limitations the authors state:
  • The experiments used synthetic model bilayer membranes, so the authors stated the results cannot be extrapolated directly to the in vivo situation
  • The authors stated that their results are hard to relate to the asbestos-smoking synergism in humans, and that other explanations are also reasonable

Topics

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

Related studies

• 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)
• Mass transfer rates of polycyclic aromatic hydrocarbons between micron-size particles and their environment--theoretical estimates — P. Gerde, P. Scholander (1989)
• Elemental modifications and polycyclic aromatic hydrocarbon metabolism in human fibroblasts — R.W. Hart, F.B. Daniel, et al. (1980)
• Asbestos-mediated membrane uptake of benzo[a]pyrene observed by fluorescence spectroscopy — J.R. Lakowicz, J.L. Hylden (1978)
• Asbestos affects the in vitro uptake and detoxification of aromatic compounds — R.C. Brown, G.T. Fleming, et al. (1983)
• Benzo[a]pyrene uptake into rat liver microsomes: effects of adsorption of benzo[a]pyrene to asbestos and non-fibrous mineral particulates — J.R. Lakowicz, D.R. Bevan (1980)

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