Reduction and enhancement by phenobarbital of hepatocarcinogenesis induced in the rat by 2-acetylaminofluorene.

Summary The effects of dietary phenobarbital on hepatocarcinogenesis in rats fed 2-acetylaminofluorene (AAF) were studied. The simultaneous feeding of AAF and phenobarbital reduced the hepatocarcinogenic effects of AAF. In contrast, the sequential feeding of AAF and phenobarbital resulted in a significant increase in the incidence of hepatomas. No ill effects were observed in rats fed phenobarbital alone. AAF and phenobarbital each stimulated the proliferation of hepatocytes, but, whereas the effect of AAF was maintained for the duration of exposure, the effect of phenobarbital was short lived. Phenobarbital fed simultaneously with AAF decreased the effect of AAF on liver cell proliferation.