In vivo methylation of guanine by the organophosphorus insecticide tetrachlorvinphos1

Abstract
The in vivo methylating capability of the organophos‐phorus insecticide tetrachlorvinphos, assayed by the formation of 7‐methyl‐guinine in mouse liver, was investigated. Following intraperitoneal injection of male mice with different doses of the 14C‐insecticide, labelled at the OCH3 groups, the total and specific radioactivity of nucleic acids and protein were determined. The 14C‐labelling in the isolated macromolecules reached its maximum 24 hours following administration of the insecticide. Analysis of the acid hydrolysate of DNA and of RNA on Dowex‐50 WX‐12 revealed the presence of (7‐14C) methylguanine. At maximum 14C‐labelling, the amount of radioactive 7‐MeGu, calculated as fraction of total dose, was around 9 x 10‐5 and 39 x 10‐5 for DNA and RNA, respectively.