Abstract
The cytostatic drug procarbazine has previously been shown to be a potent transplacental neurotropic carcinogen in rats. Following a single IP administration of (14C-methyl)procarbazine (110 mg/kg) on day 22 of gestation, methylation products with cellular DNA were determined in fetal and maternal rat organs. The concentration of the major adduct N7-methylguanine was highest in the maternal liver (224 mumol/mol guanine). Fetal and nonhepatic maternal tissues exhibited significantly lower levels, but differed little from each other. In brain, lung, intestines, and placenta the O6-methylguanine/N7-methylguanine ratio was close to 0.11, indicating that procarbazine, like other methylating carcinogens, initiates malignant transformation via methyldiazonium hydroxide as the ultimate reactant. Following a single dose of (14C-methyl)procarbazine to newborn animals, methylpurine values were 30-60 times lower than after prenatal administration. This suggests that DNA alkylation in nonhepatic tissues occurs by systemic distribution of a proximate carcinogen formed in the adult rat liver.