Regio-selective metabolism of benzo(a)pyrene by microsomes from rat and sea bass: Evidences for the occurrence of the 1-hydroxybenzo(a)pyrene as a major metabolite

The aim of the study was (i) to improve benzo(a)pyrene (BaP) metabolite analysis, (ii) and to establish that 1-hydroxybenzo(a)pyrene (1-phenol) is a major BaP metabolite produced by vertebrate xenobiotic metabolism. The species studied were sea bass (Discentrarcus labrax) and male wistar rat treated with 5-methylcholanthrene (MC). Comparison of the different conditions concerning the oxidized positions in the BaP molecule, was performed and supported by statistical calculations. BaP 9,10-, 4,5-, 7,8-diols, 1,6-, 3,6-, 6,12-quinones and 9-, 1-, 3-phenols in the elution order are the major BaP metabolites detected with both species. This was confirmed by the retention time of cold standards and by the measurement of the UV spectrum of the 9-, 1- and 3-phenols of BaP extracted from incubations of MC treated rat microsomes in the presence of 1,1,1-trichloro-2-propeneoxide (TCPO), an epoxide hydrolase inhibitor. These results support that cytochrome P450 is able to oxidize BaP in six positions, the 3>>6>1>9r5>7 in decreasing order.