Effects of harman and norharman on the metabolism and genotoxicity of 2-acetylaminofluorene in cultured rat hepatocytes

Abstract

Monolayers of rat hepatocytes metabolize 0.25 mM 2-acetylaminofluorene (AAF) to various ether-extractable, water-soluble as well as covalently bound products. The major ether-extractable metabolite formed is 2-aminofluorene (AF), followed by 7-OH-AAF and 9-OH-AAF. Pretreatment of rats with the inducer Aroclor 1254 (PCB) increased the metabolism of AAF and caused an increased DNA repair synthesis in hepatocytes exposed to AAF or AF. With N-OH-AAF, a decreased genotoxic response in PCB-treated cells compared to control cells was seen. The addition of harman and norharman decreased the metabolism of AAF to ether-extractable metabolites, water-soluble metabolites and metabolites covalently bound to macromolecules. In contrast, the DNA-repair synthesis caused by the same concentrations of AAF was increased by harman. One explanation for this apparent discrepancy could be that the aromatic amines changed the metabolism of harman and norharman in such a way that these compounds were converted into genotoxic metabolites.

Gas chromatography-mass spectrometry analysis of tert.-butyldimethylsilyl derivatives of 2-acetylaminofluorene and metabolites in isolated rat hepatocytes

“…The m/z [M -57] ÷ ion [M -C(CH3)3] + was significant for each tBDMS derivative (Corey and Venkateswarlu, 1972;Quilliam and Westmore, 1978;Quilliam et al, 1980;Woollard, 1983) and Biosynthesis of2-AAF Metabolites. Hepatocytes in suspension (Dybing et al, 1979;Smith and Thorgeirsson, 1981) Spilman and Byard, 1981;Holme et al, 1985;Holme et al, 1986;McQueen et al, 1986) have already been used for the study of the metabolism of 2-AAF. One advantage of using intact hepatocytes rather than subcellular preparations is that both activating and detoxifying enzymes are functional (Billings et al, 1977;Croci and Williams, 1985).…”