DNA adducts of ethylene dibromide: Aspects of formation and mutagenicity
1,2-Dibromoethane (ethylene dibromide, EDB), a potential human carcinogen, undergoes bioactivation by the pathway of glutathione (GSH) conjugation, which generates a reactive intermediate capable of alkylating DNA. The major DNA adduct formed is S-[2-(N[sup 7]-guanyl)ethyl]GSH. This dissertation examined the bioactivation of EDB and the formation of DNA adducts. The selectivity of purified rat and human GSH S-transferases for EDB was examined in vitro. An assay was developed to measure the formation of S,S[prime]-ethylene-bis(GSH). The [alpha] class of the GSH S-transferases was responsible for the majority of EDB-GSH conjugation with both the rat and human enzymes. Human tissue samples for a victim of EDB poisoning were analyzed for S-[2-(N[sup 7]-guanyl)ethyl]GSH utilizing electrochemical detection. No adducts were detected in samples of brain, heart, or kidney. The pattern of alkylation of guanines in fragments of plasmid pBR322 DNA by S-(2-chloroethyl)GSH and related compounds was determined. Alkylation varied approximately ten-fold in intensity and was strongest in runs of guanines. Few differences were observed in the alkylation patterns generated by the different compounds tested. The spectrum of mutations caused by S-(2-chloroethyl)GSH was determined using an M13 bacteriophage forward mutation assay. The majority of mutations (70%) were G:C to A:T transitions. Participation of the N[sup 7]-guanyl adduct in the mutagenic process is strongly implicated. The sequence selectivity of alkylation in the region of M13 sequenced in the mutation assay was determined. Comparison of the sequence selectivity with the mutation spectrum revealed no obligate relationship between the extent of adduct formation and the number of mutations which resulted at different sites. Sequence context appears to exert a strong influence on the processing of lesions. These studies strongly implicate S-[2-(N[sup 7]-guanyl)-ethyl]GSH as a mutagenic lesion formed by EDB.
- Research Organization:
- Vanderbilt Univ., Nashville, TN (United States)
- OSTI ID:
- 5579984
- Resource Relation:
- Other Information: Thesis (Ph.D)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
GENE MUTATIONS
BROMIDES
BIOLOGICAL PATHWAYS
DNA ADDUCTS
ETHYLENE
ALKYLATION
GLUTATHIONE CONJUGATES
MAN
MUTAGENESIS
RATS
ADDUCTS
ALKENES
ANIMALS
BROMINE COMPOUNDS
CHEMICAL REACTIONS
HALIDES
HALOGEN COMPOUNDS
HYDROCARBONS
MAMMALS
METABOLITES
MUTATIONS
ORGANIC COMPOUNDS
PRIMATES
RODENTS
VERTEBRATES
560300* - Chemicals Metabolism & Toxicology
550400 - Genetics
550200 - Biochemistry