Early appearance of histochemically altered hepatocyte foci and liver tumors in female rats treated with carcinogens one day after birth.

A single i.p. injection of diethylnitrosamine (DEN) or benzo[a]pyrene (BAP) in 1-day-old female rats produced a high incidence of gamma-glutamyltranspeptidase-(GGT)-positive hepatocyte foci within 4 weeks after the rats were weaned onto a 0.05% phenobarbital diet; the injection of benzo[e]pyrene did not produce foci under these conditions. Liver tumors appeared in rats treated with DEN within 8 weeks after weaning and in BAP-treated rats within 16 weeks after weaning. The results suggest that the treatment protocol used in this study may increase the utility of the liver tumorigenesis model as a broadly applicable in vitro system for the rapid detection of tumorigenic potential in environmental contaminants.