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Coumarin chemoprotection against aflatoxin B 1 ‐induced gene mutation in a mammalian cell system: A species difference in mutagen activation and protection with chick embryo and rat liver S9
Author(s) -
Goeger Douglas E.,
Anderson Karl E.,
Hsie Abraham W.
Publication year - 1998
Publication title -
environmental and molecular mutagenesis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1
H-Index - 87
eISSN - 1098-2280
pISSN - 0893-6692
DOI - 10.1002/(sici)1098-2280(1998)32:1<64::aid-em8>3.0.co;2-b
Subject(s) - aflatoxin , coumarin , carcinogen , mutagen , metabolite , biology , biochemistry , embryo , mutant , cytotoxicity , chemistry , microbiology and biotechnology , in vitro , gene , genetics , food science , botany
Coumarin (1,2‐benzopyrone), a natural food constituent, prevents polycyclic aromatic hydrocarbon‐induced neoplasms in rats and mice, but has not been studied with other chemical carcinogens. We examined coumarin chemoprotection against aflatoxin B 1 using the 6‐thioguanine resistance mutation assay in two different Chinese hamster ovary cell lines (K 1 BH 4 and AS52) with liver S9 from rats and 19‐day‐old chick embryos for aflatoxin B 1 bioactivation. Laboratory rodents metabolize coumarin through 3‐hydroxylation, whereas 7‐hydroxylation predominates in chick embryos and humans. Chick embryo liver S9 was approximately 25‐fold more effective in activating aflatoxin B 1 to the mutagenic and cytotoxic metabolite(s) than rat liver S9. Coumarin added at 50 and 500 μM with chick embryo liver S9 reduced the mutant frequency of 1 μM aflatoxin B 1 by 40 and 85%, respectively. Coumarin up to 500 μM had no effect on aflatoxin B 1 mutagenicity with rat liver S9. When liver S9 from chick embryos pretreated with coumarin was used for aflatoxin B 1 bioactivation, mutant frequency and cytotoxicity were decreased compared to liver S9 from vehicle‐treated controls. Liver S9 from coumarin‐treated rats did not significantly affect mutant frequency or cytotoxicity. HPLC analysis of chick embryo liver S9 incubated with 1 μM aflatoxin B 1 showed a dose‐dependent decrease by coumarin of aflatoxin B 1 activation to the 8,9‐epoxide ranging from 70% of controls at 5 μM coumarin to 4% of controls at 500 μM coumarin. In contrast, coumarin produced a dose‐dependent increase in 20 μM aflatoxin B 1 activation by rat liver S9, reaching twice the control levels at 500 μM coumarin. These findings, using a mammalian cell system as a mutagenic endpoint, demonstrate marked species differences in chemoprotection by coumarin. Environ. Mol. Mutagen. 32:64–74, 1998 © 1998 Wiley‐Liss, Inc.