Studies on the displacement of methylthio groups by glutathione.

1. 14C-Methylthio-labelled 2-methylthio-4-ethylamino-6-tert-butylamino-sym-triazine (terbutryn), pentachlorothioanisole (PCTA), and 1,4-bis(methylthio)tetrachloro-benzene (bis-MTTCB) and their methylthio-oxidation congeners were reacted with glutathione (GSH) in the presence and absence of immobilized liver microsomal enzymes. 2. 13C-Methylthio-labelled terbutryn sulphoxide and terbutryn sulphone were used to study displacement of the methylthio moiety by GSH using 13C-n.m.r. 3. Methanesulphinic acid was identified as the group displaced by GSH from the methyl sulphones in vitro. 4. Methanesulphenic acid is proposed to be the group displaced by GSH from methyl sulphoxides forming methyl mercaptan, methyl glutathionyl disulphide and methane-sulphinic acid in vitro. 5. Rats given 14C-methylthio-labelled terbutryn, PCTA, bis-MTTCB, and their methylthio-oxidation congeners excreted 14CO2 and 14C-methanesulphinic acid in varying amounts. These results were compared to the in vitro data.