3-(3,4-Dihydroxyphenyl)adenine, a urinary DNA adduct formed in mice exposed to high concentrations of benzene

ABSTRACT Metabolism of benzene, an important environmental and industrial carcinogen, produces three electrophilic intermediates, namely, benzene oxide and 1,2‐ and 1,4‐benzoquinone, capable of reacting with the DNA. Numerous DNA adducts formed by these metabolites in vitro have been reported in the literature, but only one of them was hitherto identified in vivo. In a search for urinary DNA adducts, specific LC‐ESI‐MS methods have been developed for the determination in urine of six nucleobase adducts, namely, 7‐phenylguanine, 3‐phenyladenine, 3‐hydroxy‐3,N4‐benzethenocytosine, N2‐(4‐hydroxyphenyl)guanine, 7‐(3,4‐dihydroxyphenyl)guanine and 3‐(3,4‐dihydroxyphenyl)‐adenine (DHPA), with detection limits of 200, 10, 260, 50, 400 and 200 pg ml−1, respectively. Mice were exposed to benzene vapors at concentrations of 900 and 1800 mg m−3, 6 h per day for 15 consecutive days. The only adduct detected in their urine was DHPA. It was found in eight out of 30 urine samples from the high‐exposure group at concentrations of 352 ± 146 pg ml−1 (mean ± SD; n = 8), whereas urines from the low‐exposure group were negative. Assuming the DHPA concentration in the negative samples to be half of the detection limit, conversion of benzene to DHPA was estimated to 2.2 × 10−6% of the absorbed dose. Thus, despite the known high mutagenic and carcinogenic potential of benzene, only traces of a single DNA adduct in urine were detected. In conclusion, DHPA is an easily depurinating adduct, thus allowing indication of only high recent exposure to benzene, but not long‐term damage to DNA in tissues. Copyright © 2012 John Wiley & Sons, Ltd. Low concentrations of 7‐(3,4‐dihydroxyphenyl)guanine and 3‐(3,4‐dihydroxyphenyl)adenine (DHPA), an easily depurinating DNA adduct derived from 1,2‐benzoquinone, was detected in the urine of mice repeatedly exposed to benzene vapours at 1800 mg m−3, 6 h per day. It was found in eight out of total 30 urine samples at concentrations of 352 ± 146 pg ml−1. Conversion of benzene to DHPA was estimated to 2.2 × 10−6 % of the absorbed dose. Search for the other five nucleobase adducts derived from benzene was negative.