[PCB methylsulfone accumulated in muscle of mink dosed with PCB (Clophen A50)].

The structural requirements of the parent PCBs for the formation of the retained PCB methylsulfones (MeSO2-CBs) were investigated in mink (Mustela vison) exposed to PCB (Clophen A50). Muscle was analyzed for the MeSO2-CBs, which were determined by comparison of synthesized reference compounds. Major unmetabolized CBs such as 2, 4, 5, 2', 4'-pentaCB, 2, 4, 5, 2', 3', 4'-hexaCB, 2, 4, 5, 2', 4', 5'-hexaCB and 2, 3, 4, 5, 2', 4', 5'-heptaCB were determined in high concentrations in the mink muscle. All these PCBs are substituted in the 2, 4, 5-positions of at least one of the phenyl rings. On the other hand, CBs with free meta/para-positions were readily metabolized. Thus, at least 25 MeSO2-CBs were detected at concentration of 16 micrograms/g in extracted lipids from the muscle, corresponding to one tenth of PCB levels. Most of the methyl sulfone metabolites were 3- and 4-MeSO2-CB isomers of PCBs known to be rapidly metabolized, e.g. 2, 4, 2', 5'-tetraCB, 2, 3, 6, 4'-tetraCB, 2, 5, 3', 5'-pentaCB, 2, 4, 5, 2', 5'-pentaCB, 2, 3, 4, 2', 5'-pentaCB, 2, 3, 6, 3', 4'-pentaCB, 2, 3, 6, 2', 4', 5'-hexaCB and 2, 3, 6, 2', 3', 4'-hexaCB. 3-MeSO2-2, 5, 2', 5'-tetraCB and 3-MeSO2-2, 5, 6, 2', 5'-pentaCB were also found to be retained in the muscle, but their isomeric 4-MeSO2-CBs were not detected. Both the 3- and 4-MeSO2-2, 5, 6, 2', 4', 5'-hexaCB isomers were identified in the muscle extracts while no MeSO2-CB metabolite originating from 2, 3, 2', 4', 5'-pentaCB were detected in the muscle. These results show the PCBs with at least one phenyl ring with 2, 5-dichloro- and 2, 3, 6-trichloro-substitution are strongly favored and may be considered a criterion for the formation of MeSO2-CBs accumulated in mink muscle. These observations are in accordance with MeSO2-CBs detected also in other mammals.