Formation of 7-methylguanine by dichlorvos in bacteria and mice

The methylating capability of dichlorvos, as assayed by the formation of labelled 7-methylguanine from dichlorvos radioactively labelled in the methyl groups, has been studied in an Escherichia coli test system and in mice. Labelled 7-methylguanine is present in both DNA and RNA isolated from E. coli exposed to dichlorvos. Mice exposed to dichlorvos by inhalation as well as by i.p. injection excrete in the urine labelled 7-methylguanine which most likely originates from the non-enzymatic methylation of guanine moieties. The methylating capability of dichlorvos is less, by a factor of 10 to 100, than that of strongly genotoxic methylating compounds.