Protein adducts of benzoquinone and benzene oxide: A study of the reactive metabolites of benzene
This work describes the use of protein binding to study the tissue doses of two classes of DNA-reactive metabolites resulting from administration of benzene to rats and mice. A desulfurization catalyst (Raney{reg_sign} nickel) formed the basis of a method to measure adducts of benzoquinones (BQ) with cysteinyl residues of proteins. Sulfur-bound adducts were cleaved by Raney{reg_sign} nickel, extracted, derivatized and analyzed by GC-ECD or GC-MS. Reactions of 1,4-BQ with whole blood of humans, rats and mice, in vitro, were undertaken to compare dose-related formation of BQ adducts. Rate constants for reactions of BQ with blood and blood proteins were estimated. Binding with hemoglobin (Hb) and bone-marrow proteins was used to compare in vivo reactions of four electrophilic metabolites of benzene, benzene oxide, 1,2-BQ, 1,4-BQ and 4,4{prime}-diphenoquinone, in F344 rats and B6C3F{sub 1} mice. Animals were given a single oral administration of [{sup 13}C{sub 6}] benzene and/or [{sup 14}C]benzene. The proportions of total protein binding were estimated for each reactive metabolite. Dose-related production of adducts of benzene oxide, 1,2-BQ and 1,4-BQ with Hb and bone-marrow proteins was seen in both species. Interestingly, large differences in adduct formation were observed between species and tissues. In the rat, benzene-oxide adducts of Hb predominated in the blood, whereas 1,2-BQ adducts were more prevalent in the marrow. In the mouse, adducts of 1,4-BQ were of greatest abundance with both Hb and bone-marrow proteins. The average blood concentrations of 1,4-BQ, estimated from the adduct levels and reaction-rate constants, were 2- to 4-fold higher in the mouse than in the rat. No adducts of 4,4{prime}-diphenoquionone were detected, in vivo. Background levels of 1,2-BQ and 1,4-BQ adducts were observed with proteins from humans, rats and mice, stemming from the dietary and endogenous sources of BQ precursors.
- Research Organization:
- North Carolina Univ., Chapel Hill, NC (United States)
- OSTI ID:
- 68639
- Country of Publication:
- United States
- Language:
- English
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