N-hydroxy-2-acetylaminofluorene sulfotransferase: its probable role in carcinogenesis and in protein-(methion-S-yl) binding in rat liver.

Abstract

Summary 1- and 3-Methylmercapto-2-acetylaminofluorene (1- and 3-methylmercapto-AAF) were identified as degradation products of hepatic protein-bound methionyl derivatives in rats given AAF or N-hydroxy-AAF. The same derivatives were shown previously to be products of the in vitro reaction of free or peptide-bound methionine with various synthetic esters of N-hydroxy-AAF, including the very reactive O-sulfonate (AAF-N-sulfate). The amounts of o-methylmercapto-AAF obtained from liver protein were proportional to the dose of N-hydroxy-AAF given i.p. and appear to be a measure of the amount of ester-like metabolites of the carcinogen formed in vivo. 1- and 3-Methylmercapto-2-aminofluorene were not obtained as degradation products of the liver proteins of rats or other animals given N-hydroxy-AAF or of rats given N-hydroxy-2-aminofluorene. The soluble proteins of rat liver contain sulfotransferase(s) which synthesize AAF-N-sulfate from N-hydroxy-AAF and 3′-phosphoadenosine 5′-phosphosulfate; magnesium and manganous ions stimulate the system. Under a variety of conditions, the N-hydroxy-AAF sulfotransferase activity in rat liver, as assayed in vitro, paralleled the amounts of o-methylmercapto-AAF which could be released from the livers of similarly treated rats after administration of N-hydroxy-AAF and the susceptibility to liver tumor induction by N-hydroxy-AAF. Adult male rat liver, which is highly susceptible to carcinogenesis with N-hydroxy-AAF, contained considerably more N-hydroxy-AAF sulfotransferase activity and formed considerably more protein-bound 1- and 3-(methion-S-yl)-AAF in vivo than did the livers of female rats or of male mice, hamsters, rabbits, or guinea pigs. Female rats and the latter species are relatively resistant to hepatic carcinogenesis with N-hydroxy-AAF. Similarly, the increased hepatic carcinogenicity of 2-aminofluorene derivatives in female gonadectomized rats given testosterone and the marked inhibition of hepatocarcinogenesis with N-hydroxy-AAF in hypophysectomized or thyroidectomized male rats were mirrored by corresponding changes in hepatic sulfotransferase activity for N-hydroxy-AAF and the formation of protein-bound methionyl-AAF derivatives in vivo. The results strongly suggest that AAF-N-sulfate is at least one of the ultimate reactive and carcinogenic metabolites of AAF and N-hydroxy-AAF in rat liver. Syntheses of the following new compounds are described: N-methoxy-AAF, potassium 4-acetylaminobiphenyl-N-sulfate, 3-methylmercapto-4-acetylaminophenyl, and 3-methylmercapto-4-aminobiphenyl hydrochloride.