DETECTION OF 1,N-6-ETHENOADENINE IN RAT URINE AFTER CHLOROETHYLENE OXIDE EXPOSURE

The four etheno adducts of vinyl chloride formed in DNA, 1,N-6-ethenoa denine (epsilon A), 3,N-4-ethenocytosine, 1,N-2-ethenoguanine and N-2, 3-ethenoguanine were previously reported to be released from DNA by a family of enzymes in the base-excision repair pathway (Dosanjh et al., Proc. Natl Acad, Sci, USA, 91, 1024-1028, 1994; Hang et al., Carcinog enesis, 17, 155-157, 1996; Hang et al., Proc, Natl Acad Sci, USA, 94, 12869-12874, 1997). Adducts excised from DNA by glycosylases are usual ly excreted in urine and have been reported to be potential biomarkers of DNA damage in exposed individuals. In this study, we report the de tection of epsilon A in the urine of rats exposed to chloroethylene ox ide (CEO) using immunoaffinity columns made with specific monoclonal a ntibodies for enrichment, followed by quantitation by HPLC with fluore scence detection. Chemical analysis of urine samples revealed the pres ence of a compound chromatographically identical to authentic epsilon A standard, This compound was confirmed by mass spectral analysis. eps ilon A was present in urine of control and CEO-treated rats, with the latter having up to 50-fold greater amounts. The cumulative excretion of epsilon A reached a plateau between 24 and 48 h post-exposure. Whil e it is clear that CEO treatment results in increased excretion of eps ilon A, the exact source of the adduct is unknown. When rats were admi nistered epsilon A i.v., similar to 10% of the administered dose was e xcreted in urine. This research demonstrates that urinary excretion of epsilon A may be a potential biomarker for in vivo alkylation of DNA and nucleotide pools.