hydroxymethylvinyl-ketone and 3-butene-1-2-diol

1,2:3,4-Diepoxybutane is hypothesized to be the main intermediate involved in mutagenicity following exposure to low levels of 1,3-butadiene (BD) in mice, while metabolites of 3-butene-1,2-diol (BD-diol) are thought to become involved in both rats and mice at higher exposures. BD-diol is biotransformed to hydroxymethylvinyl ketone (HMVK), a potentially mutagenic metabolite, and 3,4-epoxy-1,2-butanediol (EB-diol), a known mutagen. To determine the relative importance of HMVK and EB-diol in BD-diol associated mutagenesis, we have examined the dosimetry of a HMVK derived DNA adduct, as well as EB-diol derived DNA and hemoglobin adducts, in rodents exposed to BD-diol. We previously demonstrated similarities in the shapes of the dose-response curves for EB-diol derived DNA adducts, hemoglobin adducts, and Hprt mutant frequencies in BD-diol exposed rodents, indicating that EB-diol was involved in the mutagenic response associated with BD-diol exposure. To examine the role of HMVK in BD-diol mutagenicity, a method to quantify the alpha-regioisomer of HMVK derived 1,N(2)-propanodeoxyguanosine (alpha-HMVK-dGuo) was developed. The method involved enzymatic hydrolysis of DNA, HPLC purification, and adduct measurement by liquid chromatography - tandem mass spectrometry. Intra- and inter-experimental variabilities were determined to be 2.3-18.2 and 4.1%, respectively. The limit of detection was approximately 5 fmol of analyte standard injected onto the column or 5 fmol/200 microg DNA. The method was used to analyze liver DNA from control female F344 rats and female F344 rats exposed to 36 ppm BD-diol. In addition, liver samples from female Sprague-Dawley rats exposed to 1000 ppm BD were analyzed. alpha-HMVK-dGuo was not detected in any of the samples analyzed. Several possible explanations exist for the negative results including the possibility that alpha-HMVK-dGuo may be a minor adduct or may be efficiently repaired. Alternatively, HMVK itself may be readily detoxified by glutathione (GSH) conjugation. While experiments must be conducted to understand the exact mechanism(s), these results, in addition to published EB-diol derived adduct dosimetry and existing HMVK derived mercapturic acid data, suggest that EB-diol is primarily responsible for BD-diol induced mutagenicity in rodents.

Topics: Animals; Butanones; Butylene Glycols; Chromatography, High Pressure Liquid; Chromatography, Liquid; DNA Adducts; Dose-Response Relationship, Drug; Female; Glycols; Hydrolysis; Hypoxanthine Phosphoribosyltransferase; Liver; Mass Spectrometry; Mice; Mutagenesis; Mutagenicity Tests; Rats; Rats, Inbred F344; Rats, Sprague-Dawley; Reference Standards; Reproducibility of Results; Stereoisomerism

3-Butene-1,2-diol (BDD), a major metabolite of 1,3-butadiene (BD), can readily be oxidized to hydroxymethylvinyl ketone (HMVK), a Michael acceptor. In previous studies, 4-(N-acetyl-l-cystein-S-yl)-1,2-dihydroxybutane (DHB), a urinary metabolite of BD that was used to assess human BD exposure, was suggested to be a metabolite of HMVK, but DHB formation from BDD and the formation of the DHB precursor 4-(N-acetyl-l-cystein-S-yl)-1-hydroxy-2-butanone (HB) have not been previously investigated. In the current study, four HMVK-derived mercapturic acids [DHB, HB, 3-(N-acetyl-l-cystein-S-yl)propan-1-ol (POH), and 3-(N-acetyl-l-cystein-S-yl)propanoic acid (PA)] were identified in the urine of mice and rats given BDD (284-2272 micromol/kg, i.p.) based on GC/MS analyses and comparisons with synthetic standards after esterification and silylation of the carboxyl and hydroxyl groups, respectively. The combined amounts of the mercapturic acids excreted after BDD exposure were dose-dependent and were mostly similar between mice and rats given equivalent doses of BDD. The mercapturic acids accounted for a greater fraction of the administered BDD dose as the dose was lowered, suggesting that HMVK formation represents a prominent route for BDD metabolism in both mice and rats. The major mercapturic acid excreted by mice was DHB, whereas rats excreted equivalent amounts of DHB and HB. The levels of POH or PA were significantly lower in both species relative to DHB or HB. The observed species differences in the excretion of DHB and HB were thought to be due to differences in the capacity of mice and rats to reduce HB to DHB.

Topics: Acetylcysteine; Animals; Butadienes; Butanones; Gas Chromatography-Mass Spectrometry; Glycols; Male; Mice; Rats; Rats, Sprague-Dawley