Retention of promutagenic O6-ethylguanine in the DNA of various rat tissues following transplacental inoculation with ethylnitrosourea.

Pregnant Fischer rats at their 20th day of gestation were inoculated intravenously with [14C]ENU (75 mg/kg). The O6-ethylguanine content of liver, kidney, and brain DNA from both fetuses (offspring) and adults were quantitatively determined 3 h and 7 days after carcinogen treatment. Removal of O6-ethylguanine from the DNA of brain (target) was much slower than from liver (non-target) and kidney (low-target). Retention of O6-ethylguanine was found to be relatively similar in adult and fetal brains, although 100% of the offspring transplacentally exposed to 75 mg/kg ENU were shown to develop tumors of the nervous system, whereas the inoculated pregnant dams did not.