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Analysis of N-nitrosamines for genotoxicity in primary hepatocytes derived from various species
P Schmezer1, B L Pool, R Preussmann
1Institute for Toxicology and Chemotherapy, German Cancer Research Center, Heidelberg.
Abstract:
DNA single-strand breaks (SSB) were induced in metabolically competent primary hepatocytes from rats, hamsters and pigs by a series of N-nitrosamines with organ-specific activities. Both hepatotrophic and nonhepatotropic carcinogens were genotoxic in the liver cells of all three species. Nonhepatotropic compounds were active at relatively lower doses than liver carcinogens in all species tested, substantiating many previous findings that organ-specific activation is not the primary determining factor of organ susceptibility to cancer. In 11 experiments of almost identical quality, the degree of SSB induced by 6.25 mumol N-nitrosodimethylamine varied by 75%. This high interindividual variability, even among hepatocytes derived from a single rat strain, indicates that the slight differences seen between rat, hamster and pig hepatocytes are not necessarily due to differences in species susceptibility.
Insights
This study investigated DNA damage in liver cells from rats, hamsters, and pigs exposed to N-nitrosamines. Results show high variability in DNA single-strand breaks (SSB), suggesting species susceptibility differences may be less significant than previously thought.
Area of Science:
- Toxicology
- Genotoxicity
- Carcinogenesis
Background:
- Organ-specific carcinogens often exhibit differential activity across species.
- Understanding interspecies variations in genotoxicity is crucial for risk assessment.
Purpose of the Study:
- To assess DNA single-strand breaks (SSB) in primary hepatocytes from rats, hamsters, and pigs.
- To evaluate the genotoxic effects of N-nitrosamines with varying organ-specific activities.
Main Methods:
- Primary hepatocytes from rats, hamsters, and pigs were exposed to N-nitrosamines.
- Induction of DNA single-strand breaks (SSB) was measured as a genotoxicity endpoint.
Main Results:
- Both hepatotrophic and nonhepatotropic carcinogens induced genotoxicity in hepatocytes of all three species.
- Nonhepatotropic compounds were generally more potent at lower doses.
- Significant interindividual variability (up to 75%) in SSB induction was observed, even within the same species.
Conclusions:
- Organ-specific activation may not be the primary determinant of cancer susceptibility.
- High interindividual variability in DNA damage response complicates species comparison.
- Observed differences between rat, hamster, and pig hepatocytes might be due to variability rather than inherent species susceptibility.