Anaerobic metabolism and nuclear binding of the carcinogen 2-amino-4-(5-nitro-2-furyl)thiazole (ANFT)

Abstract

The anaerobic reductive metabolism of the urinary tract carcinogen 2-amino-4-(5-nitro-2-furyl)-[2-14C]-thiazole ([14C]ANFT) was examined in vitro using rabbit liver and kidney microsomes. The intermediate(s) produced during the reduction binds to tRNA, DNA, and protein. ANFT reduction was inhibited by oxygen, required NADPH and was not inhibited by SKF-525A or allopurinol. No binding to tRNA or DNA was observed if the nucleic acids were added at the end of the incubation. The covalent binding of an ANFT metabolite(s) to nucleic acids and protein was inhibited by the antioxidants vitamin E and butylated hydroxytoluene. The stoichiometry of microsomal reduction shows 3 mol of NADPH were used/mol of ANFT reduced. In inner medullary microsomes, the apparent Km and Vmax were 0.05 mM and 0.92 nmol/mg/min, respectively. Two metabolites from the anaerobic incubation of ANFT were isolated. The metabolites were tentatively identified as 1-(2-amino-4-thiazolyl)-3-cyano-1-propanone and 2-amino-4-(5-hydroxyl-amino-2-furyl)thiazole.