Interactions of caffeine and phenobarbital on sister chromatid exchanges in rat liver epithelial cell lines treated with 2-acetyl-aminofluorene and N-acetoxy-2-acetylaminofluorene.

Using "Fluorescence plus Giemsa" technique, sister chromatid exchanges (SCE) were determined on second-division metaphases in rat liver epithelial cell lines treated with 2-acetylaminofluorene (2-AAF), the procarcinogen, and N-acetoxy-2-AAF (N-OAc-2AAF), an ultimate carcinogen analog. The SCE frequency was found decreased after some conditions of 2-AAF treatment and increased with N-OAc-2-AAF. Phenobarbital (PB) decreased also the SCE frequency but cancelled the 2-AAF action when incubated after the procarcinogen. The addition of caffeine (Caf) cancelled the action of 2-AAF but not of phenobarbital. It is suggested that the mechanism of SCE may have several origins.