The effect of caffeine on diethylnitrosamine-initiated hepatic altered foci in a mid-term induction system.

The modification potentials of caffeine on the development of preneoplastic hepatic enzyme altered foci were examined in an in vivo mid-term assay system. The number and area of glutathione S-transferase placental form-positive (GST-P+) hepatic foci was significantly reduced in rats given caffeine (0.1% or 0.2% in drinking water) followed by diethylnitrosamine (DEN) (200 mg/kg BW, IP) and DEN followed by caffeine as compared with the controls given carcinogen alone. Unscheduled DNA synthesis (USD) decreased approximately 70% in the hepatocytes treated with caffeine (200 mg/ml of medium). These results suggested that the antiinitiative effect of caffeine might be caused by the inhibition of the intracellular carcinogen accumulation and the antipromotive effect of caffeine might be associated with suppression of DNA repair.