Abstract
The modifying potentials of two heterocyclic amines, harman and norharman, as well as sodium nitrite (NaNO2), on 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx)-induced rat liver carcinogenesis were investigated using a medium-term liver bioassay system. Harman (500 ppm in diet), norharman (500 ppm in diet) or NaNO2 (0.1% in drinking water) were given with or without MeIQx (300 ppm in diet) for 6 weeks after initiation with a single dose of dimethylnitrosamine (DEN). The appearance of MeIQx-induced glutathione S-transferase placental form positive foci in the liver was significantly decreased in the harman and norharman cases (p< 0.001), but it was significantly increased by NaNO2 (p< 0.001). These chemicals, however, did not modify DEN-liver carcinogenesis in the absence of MeIQx. Neither harman nor norharman affected mRNA expression of CYP1A1 and 1A2 in the liver, with or without MeIQx administration, whereas NaNO2 significantly enhanced CYP1A1 mRNA levels together with MeIQx.
