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Variability in fecal water genotoxicity, determined using the Comet assay, is independent of endogenous N-nitroso compound formation attributed to red meat consumption

Lookup NU author(s): Dr Hazel Greetham


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Red meat consumption causes a dose-dependent increase in fecal apparent total N-nitroso compounds (ATNC). The genotoxic effects of these ATNCs were investigated using two different Comet assay protocols to determine the genotoxicity of fecal water samples. Fecal water samples were obtained from two studies of a total of 21 individuals fed diets containing different amounts of red meat, protein, heme, and iron. The first protocol incubated the samples with HT-29 cells for 5 min at 4°C, whereas the second protocol used a longer exposure time of 30 min and a higher incubation temperature of 37°C. DNA strand breaks were quantified by the tail moment (DNA in the comet tail multiplied by the comet tail length). The results of the two Comet assay protocols were significantly correlated (r = 0.35, P = 0.003), however, only the second protocol resulted in detectable levels of DNA damage. Inter-individual effects were variable and there was no effect on fecal water genotoxicity by diet (P > 0.20), mean transit time (P = 0.588), or weight (P = 0.705). However, there was a highly significant effect of age (P = 0.019). There was no significant correlation between concentrations of ATNCs in fecal homogenates and fecal water genotoxicity (r = 0.04, P = 0.74). ATNC levels were lower in fecal water samples (272 g/kg) compared to that of fecal homogenate samples (895 g/kg) (P < 0.0001). Failure to find dietary effects on fecal water genotoxicity may therefore be attributed to individual variability and low levels of ATNCs in fecal water samples.

Publication metadata

Author(s): Cross JA, Greetham HL, Pollock JRA, Rowland IR, Bingham SA

Publication type: Article

Publication status: Published

Journal: Environmental and Molecular Mutagenesis

Year: 2006

Volume: 47

Issue: 3

Pages: 179-84

ISSN (print): 0893-6692

ISSN (electronic): 1098-2280

Publisher: John Wiley & Sons, Inc.


DOI: 10.1002/em.20181

PubMed id: 16304669


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