Relationship between the genetically determined acetylator phenotype and DNA damage induced by hydralazine and 2-aminofluorene in cultured rabbit hepatocytes.

Abstract

The relationship between acetylation rates of rabbit hepatocytes and their susceptibility to genotoxicity by DNAdamaging chemicals that undergo N-acetylation was studied in primary cultures of hepatocytes from New Zealand White rabbits that have a genetically determined difference in acetylation rates. Hepatocytes from rapid and slow acetylator rabbits maintained in culture the difference in acetylation rates that existed in viva DNA repair, an index of DNA damage, was produced by hydralazine in hepatocytes from slow acetylator rabbits but not in those from rapid acetylators. In contrast to these results, hepatocytes from rapid acetylators were more sensitive than those from slow acetylators to toxicity from the carcinogen 2-aminofluorene and displayed greater amounts of DNA repair. The amount of DNA repair measured with either chemical was dose dependent. These phenotype-dependent differences in the genotoxicity of two DNAdamaging chemicals provide evidence for the role of the acetylation polymorphism as a factor in determining susceptibility to toxicity, and perhaps carcinogenicity, of these chemicals. N-Acetylation rates of xenobiotics are under polymorphic genetic control in both humans and rabbits, resulting in individuals being either rapid or slow acetylators (1-5). This trait has been linked to toxicity and damage to DNA by chemicals of the aromatic amine or hydrazine type (6). For example, slow acetylator individuals are more likely than rapid acetylators to develop drug-related systemic lupus erythematosus (6-8). Individuals that develop this reaction have antinuclear antibodies as well as antibodies to DNA and nucleoproteins (6)(7)(8)(9)(10)(11)(12)(13). In vitro studies have also demonstrated interaction of systemic lupus erythematosus-inducing drugs with DNA (11,14,15).In the metabolism ofxenobiotics, N-acetylation is a step that can be followed by reactions such as N-hydroxylation and esterification, resulting in the generation of reactive metabolites that undergo covalent binding with cellular macromolecules, including DNA (16,17). Chemicals that can be acetylated and that also form covalent adducts with DNA include procainamide (18,19), isoniazid (20), and hydralazine (15), as well as the aromatic amine carcinogens, benzidine (21, 22), 2-aminofluorene, and 4-aminobiphenyl (23). Adduct formation by chemicals can be mediated by the enzymatic removal of the N-acetyl moiety (24,25), and evidence in the rabbit suggests that this reaction and the initial acetylation step are properties of the same enzyme (26).Because a difference in the acetylation rate can alter the proportion ofspecific metabolites that are formed (27), it is possible that genotoxicity-i. e., damage to DNA (28)-by substrates of N-acetyltransferase could be affected by the amount of acetylation. In order to investigate this possibility, we developed a model system that permitted measurement of both N-acetyltransferase activity and DNA damage in the same cells, using hepatocytes, which represent a major tissue of acetylation (...

The hepatocyte primary culture/DNA repair test using hepatocytes from several species

“…Hydralazine induced DNA repair in rat and rabbit hepatocytes McQueen et al, 1982), but no DNA repair was observed in hepatocytes from C57B1/6 mice. Additionally, genetically determined differences in the biotransformation of hydralazine resulted in a difference in the susceptibility of the cells from the same species to the genotoxic effect of the chemical.…”

“…The method for isolating rat hepatocytes (Williams, 1976;Williams et al, 1982) has been modified for use with mouse, hamster, rabbit and guinea pig (McQueen et al, , 1982(McQueen et al, , 1983aMaslansky and Williams, 1985a). Cells are isolated from young adult animals by a two-step in situ perfusion of the liver.…”

“…The rat HPC/DNA repair test has also been extended to utilize hepatocytes from other species (McQueen et al, , 1982(McQueen et al, , 1983aMcQueen and Williams, 1983;Barfknecht, 1983, 1984a,b;Mori et al, 1984;Strom et al, 1982;Butterworth et al, 1983;Maslansky and Williams, 1985a). In addition to rat, hepatocytes from mouse, hamster, rabbit, guinea pig, monkey and human have been used in the HPC/DNA repair test.…”

Modulation of genotoxic and cytotoxic effects of aromatic amines in monolayers of rat hepatocytes

“…Various enzyme systems, such as cytochrome P-450-dependent N-hydroxylase (Miller and Miller, 1969;Felton et al, 1976), sulfotransferase (De Braun et al, 1970;Meerman et al, 1981), Nacetyltransferase (Brouns et al, 1981, McQueen et al, 1982, N-O-acetyltransferase (Weeks et al, 1978, King andGlowinski, 1983), deacetylase (Schut et al, 1978), UDP-glucuronyl-transferase (Irving, 1971), prostaglandin endoperoxide synthetase (Boyd et al, 1983) and peroxidase (Walker and Floyd, 1979) have all been proposed to be important in the conversion of AAF and AF to their ultimate carcinogenic forms. Many of the apparent discrepancies regarding the relative importance of these enzymes in the activation of AAF and AF which have been reported may possibly be due to the different endpoints used in the various studies.…”

Effect of intra‐articular glucocorticoids on the disposition of sulphadimidine in chronic osteoarthritis patients.

“…Firstly, it may have direct application in diseases such as ulcerative colitis and rheumatoid arthiris where steroids and sulphasalazine are frequently coprescribed. Secondly, it may influence the genotoxicity of several arylamines which are metabolically activated by NAT (Glowinski et al, 1978;McQueen et al, 1982McQueen et al, , 1983. In the present communication, we have investigated the effect of intra-articular corticosteroids on the disposition of sulphadimidine in patients with osteoarthritis.…”