Hepatic macromolecular covalent binding of the hepatocarcinogen 2,6-dinitrotoluene and its 2,4-isomer in vivo: modulation by the sulfotransferase inhibitors pentachlorophenol and 2,6-dichloro-4-nitrophenol.

Abstract

The sulfotransferase inhibitors 2,6-dichloro-4-nitrophenol and pentachlorophenol were used to investigate the role of sulfate ester formation during the in vivo bioactivation of 2,4- and 2,6-dinitrotoluene (DNT). Male F-344 rats were administered one of the sulfotransferase inhibitors (40 mu mol/kg i.p.) 45 min prior to oral administration of 28 mg/kg [ring-14C]-2,4-DNT or [3-3H]-2,6-DNT and killed 12 h later. Pentachlorophenol had no significant effect on the urinary excretion of the benzyl glucuronide or benzoic acid metabolites of 2,6-DNT. The sulfotransferase inhibitors decreased the total hepatic macromolecular covalent binding of 2,4-DNT by 33%, and of 2,6-DNT by 69%. Purification of hepatic DNA by hydroxylapatite chromatography indicated covalent binding of 2,4- and 2,6-DNT at levels of 45 and 94 pmol equivalents/mg DNA, respectively. The sulfotransferase inhibitors decreased the binding of the hepatocarcinogen 2,6-DNT to hepatic DNA by greater than 95%. 2,6-Dichloro-4-nitrophenol decreased the binding of 2,4-DNT to DNA by greater than 84% while the decrease due to pentachlorophenol was 33%. These results suggest that sulfation is important in the biotransformation of 2,4- and 2,6-DNT to reactive metabolites which covalently bind to DNA. 3H2O was detected in the urine of rats administered [3-3H]-2,6-DNT. Pentachlorophenol decreased 3H2O formation to the same extent as it decreased the total hepatic macromolecular covalent binding of 2,6-DNT, suggesting that 3H exchange at the 3 position of 2,6-DNT occurs following sulfate ester formation. These results are consistent with a nitrenium-carbonium ion resonance of the sulfate ester-derived reactive intermediate of 2,6-DNT.