title: Metabolism of N²-(4-hydroxyphenyl)guanine, a DNA adduct formed from p-benzoquinone, in rat.
abstract: Among numerous adducts formed by reaction of DNA with p-benzoquinone (p-BQ), an electrophilic metabolite of benzene, only N2-(4-hydroxyphenyl)guanine (N2HPG) has been confirmed in vivo. If excreted in urine N2HPG would be a candidate non-invasive biomarker of the DNA damage caused by benzene. To test this hypothesis, biotransformation of N2HPG was studied in rats. Unchanged N2HPG in urine amounted to 8.0 ± 2.2% and 9.1 ± 1.7% (mean ± SE) at the dose of 2 mg/kg excreted within 1 and 2 days after ip dosage, respectively. After acidic hydrolysis of the urine a slight but consistent increase in urinary N2HPG to 9.5 ± 3.2% and 11 ± 2.6% of dose was found within 1 and 2 days, respectively, indicating formation of hydrolysable conjugates. An oxidised metabolite was detected by LC-ESI-MS and identified by comparison with authentic standard as N2-(4-hydroxyphenyl)-8-oxoguanine (N2HPOG). Its excretion amounted to 2.7 ± 0.2% of dose and increased to 12.0 ± 2.7% of dose when N2HPOG was released from its conjugates by acidic hydrolysis. Glucuronides and sulphates of both N2HPG and N2HPOG were confirmed in urine by LC-ESI-MS and by enzymatic treatment with glucuronidase/sulphatase. These results indicate an extensive metabolism of N2HPG in vivo, which must be taken into account when considering N2HPG as a possible biomarker of exposure to benzene.
authors: Department of Organic Chemistry, Faculty of Chemical Technology, Institute of Chemical Technology, Prague, Technická 1905, CZ-166 28 Prague, Czech Republic. linharti@vscht.cz
authors: Igor
authors: I
authors: Linhart
authors: Petr
authors: P
authors: Mikeš
authors: Antonín
authors: A
authors: Králík
authors: Jaroslav
authors: J
authors: Mráz
authors: Emil
authors: E
authors: Frantík
mesh_terms: D000818:Animals; D016227:Benzoquinones / Q000378:metabolism*; D015415:Biomarkers / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D001711:Biotransformation; D002273:Carcinogens / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D018736:DNA Adducts / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics* / Q000652:urine; D005966:Glucuronidase / Q000378:metabolism; D020719:Glucuronides / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D006147:Guanine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000493:pharmacokinetics / Q000652:urine; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008297:Male; D010084:Oxidation-Reduction; D051381:Rats; D017208:Rats, Wistar; D021241:Spectrometry, Mass, Electrospray Ionization; D013429:Sulfatases / Q000378:metabolism; D013431:Sulfates / Q000737:chemistry / Q000378:metabolism / Q000652:urine; D053719:Tandem Mass Spectrometry
chemical_list: D016227:Benzoquinones; D015415:Biomarkers; D002273:Carcinogens; D018736:DNA Adducts; D020719:Glucuronides; C561484:N2-(4-hydroxyphenyl)-8-oxoguanine; C561483:N2-(4-hydroxyphenyl)guanine; D013431:Sulfates; D006147:Guanine; D013429:Sulfatases; D005966:Glucuronidase