The heterocyclic amines IQ and MeIQx show no promotive effect in a short-term in vivo liver carcinogenesis assay

The food-derived heterocyclic amines 2-amino-3-methyl-imidazo[4,5-f]quinoline (IQ) and 2-amino-3,8-dimethyl-imidazo[4,5-f]quinoxaline (MeIQx) are carcinogenic in rodents as well as in non-human primates (IQ). Using a short-term liver carcinogenesis model the compounds were found to be only weak initiators. It is also possible that these amines are involved in other phases of the carcinogenesis process. In an attempt to study the promotive effects of IQ and MeIQx, these heterocyclic amines were repeatedly given by gavage, over a period of 10 days, to Wistar rats previously initiated with diethylnitrosamine (DEN) and subjected to a partial hepatectomy. The rats were killed 1 month after DEN administration and their livers examined for glutathione-S-transferase positive (GST-P) foci. The positive control, 2-acetylaminofluorene, significantly increased the development of GST-P foci in the DEN-treated rats compared to the negative control, saline. However, neither the IQ- nor the MeIQx-treated groups differed from the controls and thus these amines do not promote the growth of DEN-initiated GST-P liver foci in this model.