[DNA methylation characteristics of different fetal and maternal body tissues in rats administered 1,2-dimethylhydrazine].

A high rate of DNA methylation in the liver and large colon mucosa was registered 6 hrs after dimethylhydrazine (SDMH) treatment of rats with 19-day gestations. However, in fetal liver, a low concentration of methylated guanine (7-methyl guanine) derivatives was found, while in large colon and brain, these substances were not detected at all. It is suggested that the resistance of embryonal tissues to the transplacental effect of SDMH is due to the underdeveloped enzymatic system of the fetus.