Phenobarbital as a promoter in the initiation/selection process of experimental rat hepatocarcinogenesis.

Supplementary introduction of a phenobarbital (PB) promotion step after the Solt and Farber procedure dramatically increases the number of phenotypically-altered hepatocytes. These hepatocytes occupy approximately 40% of the liver volume after one week of PB treatment. These areas constitute a relatively uniform cellular population with altered histological phenotype and with distinct histochemical markers used by other authors for the detection of premalignancy. This procedure leads to the appearance of numerous hepatocellular carcinomas at approximately the 36 weeks stage. It was suggested that the early hepatocellular alterations after the initiation/selection procedure followed by PB might correspond to the hyperplasia of phenotypically-altered epidermal cells at the conversion step of mouse skin tumor promotion.