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Free radicals and environmental toxins.

Abstract

Some chemicals that contaminate our environment exert their toxic effects by virtue of their ability to form free radicals. In the absence of sufficient quenching reactions, these reactive radicals can attack biomolecules, resulting in their oxidative degradation. Biological membranes which contain polyunsaturated fatty acids are most susceptible to oxidative degradation (lipid peroxidation), although oxidation of DNA may have more severe biological consequences. Free radicals species can be generated by at least two mechanisms in vivo. The first, of which carbon tetrachloride (CCl4) is the classic example, is the biotransformation of the chemical to a free radical species. Metabolism of CCl4 to the trichloromethyl radical by the hepatic mixed-function oxidase system results in the initiation of lipid peroxidation, protein-lipid cross linkages, and trichloromethyl adducts with DNA, protein, and lipid. The second mechanism for forming free radicals involves their reduction to less stable free radical intermediates which are oxidized by molecular oxygen to give superoxide (O2-.). In the presence of transition metals, such as iron, O2-. can be converted to other oxygen radical species, such as the hydroxyl radical (.OH), an extremely powerful oxidant capable of cleaving DNA, oxidizing protein, and initiating lipid peroxidation. Under many conditions, lipid peroxidation appears not to be initiated by .OH, but rather by an iron-oxygen complex. Regardless of the identity of the initiating species, transition metals are required for most of the deleterious reactions of oxygen. Superoxide and certain organic radicals have been found to release iron from ferritin.

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  • Publisher Full Text
  • Authors

    ,

    Source

    Annals of emergency medicine 15:9 1986 Sep pg 1075-83

    MeSH

    Air Pollutants
    Carbon Tetrachloride
    Chemical Phenomena
    Chemistry
    Free Radicals
    Humans
    Iron
    Lipid Peroxides
    Mixed Function Oxygenases
    Oxidation-Reduction

    Pub Type(s)

    Journal Article
    Review

    Language

    eng

    PubMed ID

    3526996

    Citation

    Thomas, C E., and S D. Aust. "Free Radicals and Environmental Toxins." Annals of Emergency Medicine, vol. 15, no. 9, 1986, pp. 1075-83.
    Thomas CE, Aust SD. Free radicals and environmental toxins. Ann Emerg Med. 1986;15(9):1075-83.
    Thomas, C. E., & Aust, S. D. (1986). Free radicals and environmental toxins. Annals of Emergency Medicine, 15(9), pp. 1075-83.
    Thomas CE, Aust SD. Free Radicals and Environmental Toxins. Ann Emerg Med. 1986;15(9):1075-83. PubMed PMID: 3526996.
    * Article titles in AMA citation format should be in sentence-case
    TY - JOUR T1 - Free radicals and environmental toxins. AU - Thomas,C E, AU - Aust,S D, PY - 1986/9/1/pubmed PY - 1986/9/1/medline PY - 1986/9/1/entrez SP - 1075 EP - 83 JF - Annals of emergency medicine JO - Ann Emerg Med VL - 15 IS - 9 N2 - Some chemicals that contaminate our environment exert their toxic effects by virtue of their ability to form free radicals. In the absence of sufficient quenching reactions, these reactive radicals can attack biomolecules, resulting in their oxidative degradation. Biological membranes which contain polyunsaturated fatty acids are most susceptible to oxidative degradation (lipid peroxidation), although oxidation of DNA may have more severe biological consequences. Free radicals species can be generated by at least two mechanisms in vivo. The first, of which carbon tetrachloride (CCl4) is the classic example, is the biotransformation of the chemical to a free radical species. Metabolism of CCl4 to the trichloromethyl radical by the hepatic mixed-function oxidase system results in the initiation of lipid peroxidation, protein-lipid cross linkages, and trichloromethyl adducts with DNA, protein, and lipid. The second mechanism for forming free radicals involves their reduction to less stable free radical intermediates which are oxidized by molecular oxygen to give superoxide (O2-.). In the presence of transition metals, such as iron, O2-. can be converted to other oxygen radical species, such as the hydroxyl radical (.OH), an extremely powerful oxidant capable of cleaving DNA, oxidizing protein, and initiating lipid peroxidation. Under many conditions, lipid peroxidation appears not to be initiated by .OH, but rather by an iron-oxygen complex. Regardless of the identity of the initiating species, transition metals are required for most of the deleterious reactions of oxygen. Superoxide and certain organic radicals have been found to release iron from ferritin. SN - 0196-0644 UR - https://www.unboundmedicine.com/medline/citation/3526996/Free_radicals_and_environmental_toxins_ L2 - https://linkinghub.elsevier.com/retrieve/pii/S0196-0644(86)80132-9 DB - PRIME DP - Unbound Medicine ER -