For cancer risk assessment of 1,3-butadiene from rodent cancer test data, the in vivo doses of formed 1,2:3,4-diepoxybutane (DEB) should be known. In vivo doses of DEB were measured through a specific reaction product with hemoglobin (Hb), a ring-closed adduct, N,N-(2,3-dihydroxy-1,4-butadiyl)valine (Pyr-Val), to N-terminal valines. An analytical method based on tryptic digestion of Hb and quantification of Pyr-modified heptapeptides by LC-MS/MS has been further developed and applied in vivo to DEB-treated rats. Furthermore, N-(2,3,4-trihydroxybutyl)valine adducts (THB-Val) to the N-terminal valine in Hb were measured in rats and mice treated with DEB and in a complementary experiment with 1,2-epoxy-3,4-butanediol (EBdiol), using a modified Edman degradation method and GC-MS/MS. In vitro reactions of hemolysate with DEB and EBdiol were used to measure reaction rates for adduct formation needed for calculation of doses and rates elimination in vivo. The results showed that the level of the Pyr-Val adduct per administered dose of DEB was approximately the same in rats as had earlier been observed in mice [Kautiainen et al. (2000) Rapid Commun. Mass Spectrom. 14, 1848-1853]. Levels of the THB-Val adduct after DEB treatment were 3-4 times higher in rat than in mouse, probably reflecting an enhanced hydrolysis of DEB to EBdiol catalyzed by epoxide hydrolase. After EBdiol treatment, the THB-Val adduct levels were about the same in rat and mouse. Calculations from in vitro data show that the Pyr-Val adduct is a relevant monitor for the in vivo dose of DEB and that THB-Val primarily reflects doses to EBdiol. The calculated rates of formation of adducts and rates of elimination agree with expectations. Procedures for quantification of Hb adducts as modified peptides as well as preparation and characterization of peptide standards have been evaluated.

Isoprene (2-methylbuta-1,3-diene) is a multi-site carcinogen in rodents. To evaluate the role of the diepoxide metabolite (1,2:3,4-diepoxy-2-methylbutane) in carcinogenesis, measurements of in vivo doses of the diepoxide are needed. The in vivo dose may be inferred from levels of reaction products with hemoglobin (Hb adducts). This report presents in vitro studies of the adduct formation by the diepoxide of isoprene with valinamide and oligopeptides as model compounds of N-terminal valines in hemoglobin (Hb). In the reaction with valinamide it was shown that isoprene diepoxide forms as the main product a ring-closed adduct, which is a pyrrolidine derivative [N,N-(2,3-dihydroxy-2-methyl-1,4-butadiyl)valinamide, MPyr-Val]. The analysis was performed by gas chromatography/mass spectrometry (GC/MS) (EI and PICI) after acetylation. The ring-closed adduct was also identified by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) as the main product in the reaction between isoprene diepoxide and standard hepta- or (2H8)octapeptides, corresponding to the N-terminal peptides of the alpha-chains in mouse and rat Hb. These peptides, alkylated with isoprene diepoxide, to be used as internal standards and calibration standards for quantification of MPyr-adduct levels in vitro and in vivo, were analyzed with respect to the degree of MPyr-alkylation by two independent methods, amino acid analysis and HPLC-UV; similar results were obtained using these methods. A method for measurement of Hb adducts as modified peptides, used earlier to measure a similar adduct to N-terminal valines in Hb from the diepoxide of 1,3-butadiene, has in the present work been tested for application to isoprene diepoxide. The method is based on tryptic degradation of globin and LC/ESI-MS analysis of N-terminal Pyr-heptapeptides of the Hb alpha-chain enriched by HPLC. MPyr-adduct levels in isoprene diepoxide alkylated hemolysate from mouse erythrocytes incubated with different concentrations of isoprene diepoxide (2 and 10 mM) for 1 h were quantified. The adduct level was about 50 nmol/g alpha-chain Hb per mM x h. From the adduct levels the rate constant of isoprene diepoxide for reaction with N-terminal valine was calculated to be about 1.6 times faster than for diepoxybutane.

Analytical methods facilitating studies of electrophilically reactive and genotoxic compounds in vitro and in vivo are needed. The strong nucleophile, cob(I)alamin, formed by reduction of Vitamin B12 [cob(III)alamin], may be used for trapping and analysis of 1,2-epoxides and other electrophiles. In the present study, cob(I)alamin is evaluated as an analytical tool for 1,2-epoxide metabolites (oxiranes) of 1,3-butadiene. Products of reaction of cob(I)alamin with 1,2-epoxy-3-butene (EB), 1,2:3,4-diepoxybutane (DEB), and 1,2-epoxy-3,4-butanediol (EBdiol) have been analyzed by reversed phase high performance liquid chromatography (HPLC) coupled on-line to electrospray ionization mass spectrometry (ESI-MS) and ultraviolet diode array detection (UV-DAD). It was shown that a specific alkyl-CbI complex is formed for each metabolite and that it was possible to discriminate between the products by HPLC-UV and by LC-MS. Quantification of DEB with the method by use of another 1,2-epoxide as an internal standard was successfully performed. The possibility of using cob(I)alamin for trapping and analysis of the three oxirane metabolites of 1,3-butadiene will facilitate quantitative comparisons of species in vitro with regard to metabolism of 1,3-butadiene.

Acrylamide is a probable human carcinogen with widespread exposure via food. The present study compared acrylamide intake measurements obtained from haemoglobin adduct levels and self-registered dietary consumption data in a group of 144 Norwegian healthy adults. Acrylamide adducts to N-terminal valine in haemoglobin were measured and used to estimate the intake via the internal dose approach which showed a median (interquartile range) of 0.24 (0.19–0.30) μg/kg bw/day. Data from weighed food records and food frequency questionnaires from the same individuals were used for probabilistic modelling of the intake of acrylamide. The median acrylamide intake was calculated to be 0.26 (0.16–0.39) and 0.30 (0.23–0.39) μg/kg bw/day, respectively from the two sources of self-registered dietary consumption data. Overall, a relatively good agreement was observed between the methods in pairwise comparison in Bland-Altman plots, with the methods disagreeing with 7% or less of the values. The intake estimates obtained with the two dietary consumption methods and one biomarker method are in line with earlier dietary estimates in the Norwegian population. The Margin of Exposure indicate a possible health risk concern from dietary acrylamide. This is the first study with a comparison in the same individuals of acrylamide intake estimates obtained with these methods.

1,3-Butadiene, a common air pollutant formed in the combustion of organic matter, has been assessed by the U.S. EPA to be a strongly carcinogenic compound. This risk assessment is very uncertain because of the lack of information on the dose of the powerful carcinogenic metabolite diepoxybutane (DEB). This report presents an analytical method for in vivo dose monitoring of a unique marker for DEB. For a large number of alkylating agents in vivo doses are monitored by measurement by gas chromatography/mass spectrometry (GC/MS) of adducts to N-terminal valine in hemoglobin (Hb), using a modified Edman degradation method. This method is applicable to monofunctional epoxides from butadiene. However, in reaction with N-terminal valine, DEB forms an adduct which is ring-closed to a pyrrolidine, N,N-(2,3-dihydroxy-1,4-butadiyl)valine, with a tertiary amino group that prevents detachment of the alkylated valine by the Edman reagent. Therefore a method has been developed based on the analysis by liquid chromatography/electrospray ionization mass spectrometry (LC/ESI-MS) of the N-modified N-terminal peptides enriched after trypsin digestion of globin. In this study Hb samples from mice injected intraperitoneally with (+/-)-DEB were examined qualitatively and quantitatively with regard to the ring-closed adduct. The N-terminal pyrrolidine-heptapeptide was identified in treated mice. The highest adduct levels were obtained in samples from animals given the highest dose of DEB and the adduct levels were below the detection level in control mice.

ArticlesThe Removal of Metallic Foreign Bodies by Surgical Operation under Direct X-Ray ControlC. Fred BaileyC. Fred BaileySearch for more papers by this authorPublished Online:18 Mar 2014https://doi.org/10.1259/are.1920.0020SectionsPDF/EPUB ToolsAdd to favoritesDownload CitationsTrack Citations ShareShare onFacebookTwitterLinked InEmail About Previous article Next article FiguresReferencesRelatedDetails Volume 25, Issue 3August 1920Pages: 65-96 Copyright © 1920, The British Institute of Radiology History Published onlineMarch 18,2014 Metrics Download PDF