The role of sulfation in the metabolic activation of N-hydroxy-4'-fluoro-4-acetylaminobiphenyl.

The role of sulfation in the metabolic activation of the liver carcinogen N-hydroxy-4'-fluoro-4-acetylaminobiphenyl (N-OH-FAABP) in male rat liver was investigated. N-OH-FAABP was a substrate for sulfotransferases in vitro and sulfation was inhibited by the sulfotransferase inhibitors pentachlorophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP). The main metabolite of N-OH-FAABP excreted in bile in vivo, and in the isolated perfused liver, was identified as the N-O-glucuronide conjugate. Inhibition of sulfation in vivo by PCP or DCNP, or in vitro by omission of inorganic sulfate, resulted in a large increase in the excretion of the N-O-glucuronide conjugate. It was estimated that at least 21% of the dose was sulfated in control animals. Inhibition of sulfation in vivo by PCP or DCNP prevented the covalent binding of N-OH-FAABP to liver (and kidney) macromolecules by 70% and 20% respectively. HPLC analysis of the fluorobiphenyl DNA and RNA adducts showed that the formation of both N-acetylated and deacetylated (deoxy)-guanosine adducts was prevented. Furthermore, omission of inorganic sulfate in the isolated perfused liver prevented the formation of all fluorobiphenyl DNA adducts by 70-80%. It is concluded that two sulfotransferase-dependent pathways exist for the metabolic activation of N-OH-FAABP in male rat liver: (i) direct sulfation of the hydroxamic acid, resulting, upon decomposition of the FAABP-N-sulfate ester, in the formation of N-acetylated DNA adducts and (ii) deacetylation followed by sulfation of the hydroxylamine to FABP-N-sulfate, leading to the formation of deacetylation DNA adducts.