The binding of N-hydroxy-2-acetylaminofluorene to DNA and repair of the adducts in primary rat hepatocyte cultures

Primary cultures of rat hepatocytes were exposed to ring-³H]-N-hydroxy-2-acetylaminofluorene(N-OH-AAF) for 4 h, and the RNA and DNA nucleoside adducts wereisolated and identified by h.p.l.c. The DNA adducts were shownto be N-(deoxyguanosin-8-yl)-2-acetylaminofluorene (dG-C8-AAF),N-(deoxyguanosin-8-yl)-2-aminofluorene (dG-C8-AF), and 3-(deoxy-guanosin-8-yl)-2-acetylaminofluorene(dG-N2-AAF), while the RNA adducts were N-(guanosin-8-yl)-2-acetyl-aminofluorene,and N-(guanosin-8-yl)-2-aminofluorene. The removal of theseadducts was measured up to 38 h following the cessation of exposureof the hepatocytes to N-OH-AAF. The dG-C8-AAF adduct was removedwith a half-life of approximately 10 h, while dG-N²-AAF anddG-C8-AF remained constant for 14 h, followed by a slow rateof removal. The dG-C8-AAF adduct initially composed about 60%of the total DNA adducts of primary hepatocytes in contrastto the 20% found in liver in vivo. The formation of the 3 DNAadducts and the different rates of repair indicate that primarycultured rat hepatocytes may be a valuable system to study initiationof liver carcinogenesis by N-OH-AAF.