INVIVO FORMATION OF AFLATOXIN-B1 DNA ADDUCTS IN PARENCHYMAL AND NONPARENCHYMAL CELLS OF RAT-LIVER

The induction of hepatocellular carcinoma from liver parenchymal cells in laboratory animals by aflatoxin B1 (AFB1) is well documented. In contrast no tumours arising from the sinusoidal cell population have been reported after exposure to AFB1. The apparent resistance of the latter cell type was investigated at the level of DNA adduct formation in vivo in male Sprague-Dawley rats. Liver parenchymal and non-parenchymal cell populations were isolated from rats at 20 min and 1, 24 and 72 h after administration of 240-mu-Ci (0.6 mg) [G-H-3]AFB1/kg. AFB1-DNA binding was observed in both liver cell subpopulations and was 3- to 5-fold higher in parenchymal cells than in non-parenchymal cells. The major DNA adduct found in parenchymal cells at 1 h after AFB1 administration was 8,9-dihydro-8-(N7-guanyl)-9-hydroxyaflatoxin B1 (AFB1-gua), whereas at later time points the persistent secondary adduct, AFB1-formamido-pyrimidine, predominated. In contrast, AFB1-gua was not observed at any time in DNA from non-parenchymal cells and the secondary adducts predominated throughout. These observations are discussed with reference to the susceptibility of different liver cell types to AFB1-carcinogenesis and the possible roles of the major AFB1-DNA adduct species.