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Microsome-mediated covalent binding of 1,2-dichloroethane to lung microsomal protein and salmon sperm DNA
Abstract:
In order to determine whether the covalent binding of the carcinogen 1,2-dichloroethane to macromolecules is dependent on microsomes or cytosol, microsomes and cytosol from lungs of C57BL/6 X C3H/He F1 (hereafter called B6C3F1) mice and Osborne-Mendel rats were incubated with [1,2-14C]dichloroethane and salmon sperm DNA. 1,2-Dichlorothane binds covalently to microsomal protein and DNA only in the presence of microsomes, whereas cytosol has insignificant metabolic activation. The binding to macromolecules was significantly higher in the presence of native microsomes than denatured microsomes. The interaction of 1,2-dichloroethane with DNA was enhanced following pretreatment of the animals with phenobarbital and 3-methylcholanthrene. On the other hand, glutathione reduced the binding. The binding of 1,2- dichloroethane to lung microsomal protein of B6C3F1 mice and to DNA was three and five times higher, respectively, than that of Osborne-Mendel rat lung microsomal proteins. 1,2-Dichloroethane interacts 85% and 100% more with protein and DNA, respectively, in the presence of microsomes obtained from lung than from liver of B6C3F1 mice. These results suggest a correlation between the microsomally mediated binding and species and organ susceptibility to 1,2-dichloroethane-induced tumorigenesis.
Insights
1,2-dichloroethane binds to macromolecules via microsomes, not cytosol. This binding, influenced by enzymes and species, correlates with tumor susceptibility, highlighting the role of microsomes in carcinogenicity.
Area of Science:
- Toxicology
- Biochemistry
- Carcinogenesis
Background:
- 1,2-dichloroethane (DCE) is a known carcinogen.
- The metabolic activation of carcinogens is crucial for their toxic effects.
- Understanding the role of cellular components in carcinogen binding is essential.
Purpose of the Study:
- To investigate the role of microsomes and cytosol in the covalent binding of 1,2-dichloroethane to macromolecules.
- To compare the binding capacity between different species (mice and rats) and organs (lung and liver).
- To explore factors influencing DCE binding, such as enzyme induction and protective agents.
Main Methods:
- Incubation of microsomes and cytosol from B6C3F1 mice and Osborne-Mendel rats with [1,2-14C]dichloroethane and DNA.
- Comparison of binding in the presence of native versus denatured microsomes.
- Assessment of binding after animal pretreatment with enzyme inducers (phenobarbital, 3-methylcholanthrene) and with glutathione.
- Quantification of binding to protein and DNA in lung and liver tissues.
Main Results:
- 1,2-dichloroethane covalently binds to microsomal protein and DNA primarily in the presence of microsomes; cytosol shows minimal activation.
- Native microsomes facilitate significantly higher macromolecular binding than denatured ones.
- Enzyme inducers enhanced DCE-DNA interaction, while glutathione reduced it.
- B6C3F1 mice lung microsomes showed 3-5 times higher binding to protein and DNA, respectively, compared to rat lung microsomes.
- Lung microsomes from B6C3F1 mice exhibited 85% and 100% greater interaction with protein and DNA, respectively, than liver microsomes.
Conclusions:
- Microsomes are critical for the metabolic activation and covalent binding of 1,2-dichloroethane to macromolecules.
- Species and organ differences in microsomally mediated binding of DCE correlate with susceptibility to 1,2-dichloroethane-induced tumorigenesis.
- These findings provide insights into the mechanisms underlying DCE carcinogenicity and differential toxicity.