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Quantitative comparison of covalent aflatoxin-DNA adducts formed in rat and mouse livers and kidneys
Abstract:
The covalent interactions between aflatoxin B1 (AFB1) and DNA were investigated in the inbred F344 rat and noninbred CD -1 Swiss mouse. A good correlation was found between the level of covalent modification of DNA, species sensitivity, and organ specificity, to the toxic effects of AFB1. The patterns of AFB1 acid hydrolysis products from DNA isolated from the livers and kidneys of both species were examined. The principal acid hydrolysis product in all cases was identified as 2,3-dihydro-3-hydroxy-(N7-guanyl)AFB1. Minor products consisted of adducts formed by the chemical transformation of the AFB1-N7-substituted guanine moiety forming putative formamidopyrimidine derivatives and the activation of AFB1 metabolites, which also modified the N-7 guanine atom. These last-mentioned products were present in greater amounts in resistant tissues. In vitro studies on the activation of AFB1 by microsomal fractions of mouse and rat livers found that mouse liver microsomes were rapidly inactivated.
Insights
Aflatoxin B1 (AFB1) covalently modifies DNA, with levels correlating to toxicity and organ specificity in rats and mice. Researchers identified key AFB1-DNA adducts, revealing insights into species resistance mechanisms.
Area of Science:
- Toxicology
- Molecular Biology
- Biochemistry
Background:
- Aflatoxin B1 (AFB1) is a toxic compound known to interact with DNA.
- Understanding these interactions is crucial for assessing toxicity and organ specificity.
Purpose of the Study:
- To investigate the covalent interactions between AFB1 and DNA in rats and mice.
- To correlate DNA modification levels with species sensitivity and organ specificity of AFB1 toxicity.
- To identify and characterize AFB1-DNA adducts formed in vivo.
Main Methods:
- Comparative analysis of AFB1-DNA adducts in inbred F344 rats and CD-1 Swiss mice.
- Acid hydrolysis of DNA isolated from liver and kidney tissues.
- Identification of AFB1 hydrolysis products using chromatographic and spectroscopic methods.
- In vitro studies using liver microsomal fractions to assess AFB1 activation.
Main Results:
- A strong correlation was observed between DNA covalent modification, species sensitivity, and organ specificity to AFB1 toxicity.
- The primary AFB1-DNA adduct identified was 2,3-dihydro-3-hydroxy-(N7-guanyl)AFB1 in both species.
- Minor adducts, including formamidopyrimidine derivatives, were found, particularly in resistant tissues.
- Mouse liver microsomes showed rapid inactivation of AFB1 activation in vitro.
Conclusions:
- Species-specific differences in AFB1-DNA adduct formation and metabolism contribute to variations in toxicity and organ targeting.
- The identified adducts provide a molecular basis for understanding AFB1-induced toxicity and resistance mechanisms.
- Further research into AFB1 metabolism and detoxification pathways is warranted.