Cysteine and methionine-precursors of methyl sulphone metabolites of 2,4',5-trichlorobiphenyl in mice.

In order to account for the origin of the sulphur atom in methyl sulphones derived from polychlorinated biphenyls (PCB), groups of mice were treated with 2,4'-5-trichlorobiphenyl and [35S]cysteine or [35S]methionine, respectively. Control animals received the labelled amino acids only. The radioactive substances extracted from lung tissue were characterized by partition between hexane and sulphuric acid, thin-layer radiochromatography (TLRC), gas chromatography (GC) and mass fragmentography (MF). In lung extracts of both experimental groups sulphuric acid soluble metabolites were present: Their Rf-values on TLRC were identifical with that of 4-methylsulphonyl-2,4'-5-trichlorobiphenyl and their identity was confirmed by GC and GC-MF, which also indicated the presence of a minor sulphone isomer. The study shows that both cysteine and methionine could function as donors of the sulphur atom in the methyl sulphone metabolites derived from PCB.