MUTAGENIC POTENTIAL OF BINARY AND COMPLEX-MIXTURES USING DIFFERENT ENZYME-INDUCTION SYSTEMS

A series of experiments was conducted to investigate the mutagenic pot ential of binary and complex mixtures in the presence and absence of i nducible liver enzyme systems prepared with several different chemical inducers. Liver homogenate (S9, or 9000 x g supernatant) fractions we re obtained from Sprague-Dawley rats induced with either Aroclor 1254 (AR), phenobarbital (PB), 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), or corn oil (UI). The muta genic potential of test samples was measure d with Salmonella typhimurium strain TA98 using each of the various S9 fractions. Test samples included benzo[a]pyrene (BaP), pentachlorophe nol (PCP), a binary mixture of BaP and PCP, two five-component mixture s, a methylene chloride extract of wood preserving waste-amended soil, and a methanol extract of coal gasification waste. At a dose of 25 mu g/plate, BaP produced 55, 83, 217, and 161 net revertants per plate w ith UI-, PB-, AR-, and TCDD-induced S9, respectively. The complex mixt ure extracted from the wood preserving waste-amended soil induced appr oximately equal responses with all four S9 mixes. Ar a close of 250 mu g/plate, the methanol extract of a coal gasification waste produced 5 6 net revertants using the uninduced S9; however, when AR- and TCDD-in duced S9 was used, 129 and 67 net revertants were observed, respective ly. These data demonstrate the relative importance of the various indu ced cytochrome P-450 isozymes for the metabolism of mutagenic chemical s and complex mixtures.