Are there thresholds for carcinogens carcinogenicity?

DOI 19 References
  • FUKUSHIMA Shoji
    Japan Bioassay Research Center, Japan Industrial Safety and Health Association
  • WEI Min
    Department of Pathology, Osaka City University Medical School
  • KAKEHASHI Anna
    Department of Pathology, Osaka City University Medical School
  • WANIBUCHI Hideki
    Department of Pathology, Osaka City University Medical School

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  • 発がん物質にも閾値が存在する

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Abstract

A food-derived, genotoxic hepatocarcinogen, 2-amino-3,8-dimethylimidazo[4,5-f ] quinoxaline (MeIQx) low-dose carcinogenicity was examined in the rat liver using a medium term bioassay for carcinogens. MeIQx was shown to form DNA adducts at very low doses, but did not induce 8-hydroxy-2′-deoxyguanosine formations, lacI gene mutations or an initiation activity. Glutathione S-transferase placental form (GST-P)-positive foci which are preneoplastic lesions occurred at higher dose. Furthermore, N-nitroso compounds, such as N-nitrosodiethylamine and N-nitrosodimethylamine were found not to induce GST-P-positive foci in the rat liver at very low doses. A genotoxic colon carcinogen, 2-amino-1-methyl-6-phenolimidazo [4,5-b] pyridine (PhIP) induced PhIP-DNA adducts at very low dose with no-effect level and aberrant crypt foci as a surrogate marker of preneoplastic lesions appeared at relatively high doses.These results imply the existence of thresholds, at least practical ones for the carcinogenicities of these genotoxic carcinogens. A non-genotoxic carcinogen, phenobarbital showed hormetic phenomenon in rat hepatocarcinogenicity, indicating the real threshold for the carcinogenicity.

Journal

  • JSM Mycotoxins

    JSM Mycotoxins 58 (2), 119-128, 2008

    Japanese Society of Mycotoxicology

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