title: Studies on guanine adducts excreted in rat urine after benzene exposure.
abstract: Investigations with [14C]benzene indicate the formation of base adducts in vivo. Experiments to separate adducts from urine of [14C]benzene-exposed rats suggest the excretion of eight labeled compounds different from benzene metabolites. In order to obtain information about their structure we synthesized N7-, O6-, C8- and N2-phenylguanine. With regard to their chromatographic properties we compared these phenylguanines with products obtained by alkylation of guanine by metabolites of unlabeled and 14C-labeled benzene in vivo with HPLC with UV detection and liquid scintillation counting. Furthermore GC/MS and ELISA techniques were used to detect N7-phenylguanine. Phenylguanines could not be identified in collected DNA fractions. The labeled compounds detected in urine of [14C]benzene-exposed rats also showed deviations from the HPLC elution patterns of our reference substances. Even N7-phenylguanine, formerly suspected to be a urinary metabolite of benzene in the rat, could not be detected with these refined HPLC methods. With GC/MS a compound was found in trace amounts in concentrated rat urine samples, which had a similar fragmentation pattern to N7-phenylguanine. These data could not be confirmed by a sensitive immunological assay (ELISA). No N7-phenylguanine was detected in purified rat urine samples. The results suggest the excretion of a hydroxylated phenylguanine which may be formed in liver or bone marrow DNA by highly reactive hydroxylated intermediates. The OH group might be lost because of the high temperatures during GC/MS measurements. A hydroxy group at the phenyl-ring of N7-phenylguanine will cause other elution properties in HPLC compared to N7-phenylguanine.
authors.affiliation: Institut für Hygiene und Arbeitsmedizin, Universitäts-Klinikum, Essen, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Krewet
authors.forename: C
authors.initials: C
authors.lastname: Verkoyen
authors.forename: G
authors.initials: G
authors.lastname: Müller
authors.forename: C
authors.initials: C
authors.lastname: Schell
authors.forename: W
authors.initials: W
authors.lastname: Popp
authors.forename: K
authors.initials: K
authors.lastname: Norpoth
mesh_terms: D000818:Animals; D001554:Benzene / Q000378:metabolism / Q000493:pharmacokinetics / Q000633:toxicity*; D002250:Carbon Radioisotopes; D002851:Chromatography, High Pressure Liquid; D004247:DNA / Q000378:metabolism / Q000652:urine*; D004249:DNA Damage; D004797:Enzyme-Linked Immunosorbent Assay; D008401:Gas Chromatography-Mass Spectrometry; D006147:Guanine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000652:urine*; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet
chemical_list: D002250:Carbon Radioisotopes; C056235:N(7)-phenylguanine; D006147:Guanine; D004247:DNA; D001554:Benzene