Enhancement of Spontaneous Hepatic Tumorigenesis in C3H Mice by Dietary Phenobarbital2

Male and female C3H mice, housed 1/cage or 5/cage, were fed a control diet or one containing 0.05% phenobarbital. After 12 months the mice were examined for spontaneous liver tumors. In mice fed the control diet, tumor incidence was higher in males than in females, and higher in mice housed 1/cage than in those housed 5/cage. Phenobarbital in the diet increased the incidence of liver tumors, irrespective of population density or sex, but did not decrease the degree of differentiation of the tumors. Phenobarbital apparently accelerated the expression of spontaneous hepatic tumorigenesis in C3H mice.