The effect of the dose of diethylnitrosamine on the initiation of altered hepatic foci in neonatal female rats

The dose—response characteristics of initiation of hepatocarcinogenesisby diethylnitrosamine (DEN) was investigated in the neonatalfemale rat by means of the quantitative stereologic estimationof altered hepatic foci (AHF) expressing multiple markers. At5 days of age, female Sprague—Dawley rats were given asingle i.p. dose of DEN (0.1–30 mg/kg body wt) or thevehicle (trioctanoin). The semisynthetic AIN-76A diet was providedto half of the rats in each treatment group, while the remainderreceived this diet containing 500 mg phenobarbital (PB)/kg for8 months from weaning until the animals were killed. To ascertainmore exactly the dose—response relationship for initiationby DEN, the number, volume percentage and phenotypes of theresulting AHF were determined by quantitative stereologicalanalysis on serial sections of frozen tissue, each stained forone of four markers of preneoplasia. A linear relationship wasobserved between the dose of DEN (0–30 mg/kg) and thenumber and volume percentage of AHF detected, with each singlemarker or the total number of AHF detected when the placentalisozyme of glutathione S transferase,