4-(2-amino-1-methylimidazo pyrid-6-yl)[4,5-b]phenyl sulfate—a major metabolite of the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b] (PhIP) in the rat

Abstract

Isolated rat hepatocytes (4 × 10⁶ cells/ml metabolized the food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) (100 μM) to at least eight different metabolites in a 4 h duration. The major metaboilte formed was 4-(2-amino-1-methylimldazo[4,5-b]pyrid-6-yl) sulfate (4′-PhIP sulfate). Its rate of formation was increased in hepatocytes from PCB pretreated animals in comparison to hepatocytes from untreated animals. One of the other metabolites was the unconjugated derivative of the sulfate (4′-OH-PhIP). This metabolite was also found after in-vitro incubations of rat liver microsomes from PCB or β-naphtho flavone pretreated animals. The evidence for the proposed structure of the major metabolite is based on [¹H]NMR and UV spectroscopy, incorporation of radiolabelled sulfate and arylsulfatase-labilhty. The formation of 4′-PhIP sulfate was inhibited by the P-450 inhibitors α-naphthoflavone and metyrapone and when incubated in sulfate-free medium added the sulfotransferase Inhibitor pentachlorophenol. 4′-PhIP sulfate was also the major metabolite of PhIP in the urine of exposed rat.