Carcinogenesis vol.9 no.10 pp.1835-1841, 1988 Metabolism of acetylaminofluorene in primary cultures of human hepatocytes: dose-response over a four-log range

3To whom reprint requests should be sent The metabolism of acetylaminofluorene (AAF) in human hepatocyte cultures from different donors was investigated for a four-log concentration range (500, 50, 5.0 and 0.5 /iM) or at 3, 8 and 24 h at 500 nM. The metabolite profile was dependent on the concentration to which the cells were exposed. The hepatocyte cultures varied in the degree to which they metabolized AAF predominantly because of different levels of deacetylation. Ring-hydroxylation was the predomi-nant pathway for AAF metabolism at low concentrations (5.0 and 0.5 /tM) but saturated in three of four human cases at high concentrations of AAF; N-hydroxylation did not appear to become saturated. Human hepatocytes catalyzed the covalent binding of AAF metabolites to their DNA. A linear increase in DNA binding was observed when increasing concentrations of AAF were added to hepatocyte cultures; however, the increase in AAF metabolites binding to DNA was not proportional to the dose. While the concentration of AAF in the media was increased over a four-log range, both the production of N-hydroxy AAF and binding of metabolites to hepatocellular DNA increased over approximately a three-log range. These results with cultured human hepatocytes indicate that the pathways of AAF metabolism are qualitat-ively similar to those identified in experiments with rat hepatocytes as well as experiments conducted in vivo with human subjects. These studies confirm that the cultured human hepatocyte is a useful model for the investigation of human xenobiotic metabolism and indicate that the concen-tration of the xenobiotic used in the experiments is an important determinant of the metabolitic profile produced