Metabolism of benz[ a]anthracene by human liver microsomes

The metabolism of benz[ a]anthracene (BA) by human hepatic microsomes was investigated. Only dihydrodiols were observed when BA was the substrate. No tetrahydrotetrols were detected, indicating lack of diol epoxide formation. The BA-dihydrodiols identified by GC-MS analysis and comparison to authentic standards were BA-8,9-dihydrodiol (42.4% of total metabolites), BA-5,6-dihydrodiol (25%), BA-10,11-dihydrodiol (24.8%), BA-3,4-dihydrodiol (5.3%), and BA-1,2-dihydrodiol (< 1.5%). BA-dihydrodiols were also used individually as substrates. Only BA-1,2-dihydrodiol, the least abundant isomer produced from BA, was converted efficiently to a tetrahydrotetrol (> 72% conversion). BA-10,11-dihydrodiol was converted to BA-8,9,10,11-tetrahydrotetrols in < 12% yield. BA-10,11- and BA-3,4-dihydrodiols were not converted to tetrahydrotetrols.