Liver ornithine decarboxylase during phenobarbital promotion of nitrosamine carcinogenesis

The incidence of liver tumors induced in rats by N-diethylnitrosamine was increased by the feeding of phenobarbital. Liver ornithine decarboxylase activity did not increase in animals receiving phenobarbital in the diet, and the concentration of polyamines in the liver was similarly unchanged. No relationship between the promotion of N-nitrosamine-induced liver tumors by phenobarbital and the ornithine decarboxylase activity of the liver was indicated by these experiments.