Formation of 2-amino-α-carbolines in pan-fried poultry and 32 P-postlabelling analysis of DNA adducts

Abstract

Amino-α-carbolines are food-derived genotoxic heterocyclic aromatic amines (HAAs) that have been shown to be carcinogenic in rodents, to induce preneoplastic foci in rat liver and to be active in a number of genotoxicity tests, inducing gene mutations, DNA strand breaks and cell transformation. 2-Amino-α-carboline (AαC) has been estimated to account for about 20% of the carcinogenic HAAs that are ingested with the diet. Using the tandem cartridge solid-phase extraction procedure we were able to show that in pan-fried poultry the proportion of AαC and its 3-methyl derivative (MeAαC) account for 15% of the HAA fraction. Covalent DNA adducts are considered to be the primary lesions in chemical carcinogenesis. Both AαC and MeAαC have been shown to induce covalent DNA adducts in vitro and in vivo. Formation of DNA adducts was investigated by 32P-postlabelling analysis in vitro in primary rat hepatocytes treated with 10–500 μM AαC or MeAαC. While for MeAαC-derived adducts the highest response was obtained with the nuclease P1 enhancement procedure, AαC adducts were most efficiently detected upon 32P-postlabelling preceded by a cartridge enrichment step. Adduct levels detected were dose dependent but decreased for the higher doses due to cytotoxic effects. We have characterised the major DNA adducts of AαC and MeAαC as deoxyguanosine derivatives with the amino-α-carboline bound via the 2-amino group to the C8 position of guanine.