The role of sulfation and/or acetylation in the metabolism of the cooked-food mutagen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine in Salmonella typhimurium and isolated rat hepatocytes

Journal Article · · Chemical Research in Toxicology; (United States)

DOI:https://doi.org/10.1021/tx00038a005· OSTI ID:7035657

Malfatti, M A; Buonarati, M H; Turteltaub, K W; Shen, N H; Felton, J S ^[1]

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1. Lawrence Livermore National Lab., CA (United States)

Mutagenic activity of the cooked-food mutagen/carcinogen 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is highly dependent upon cytochrome P450 activation to the N-hydroxylated intermediate. The present study investigated the bioactivation pathways of PhIP in Salmonella typhimurium and isolated rat hepatocyte preparations. In the Ames/S. typhimurium assay, the acetyltransferase and sulfotransferase enzyme inhibitors pentachlorpophenol (PCP) and 2,6-dichloro-4-nitrophenol (DCNP) were used to modulate mutagenicity. DCNP, but not PCP, produced a concentration-dependent decrease in mutagenic activity of 2-(hydroxyamino)-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-hydroxy-PhIP). In rat hepatocyte preparations, PCP and DCNP, as well as the cytochrome P450 IA1 and IA2 inhibitor [alpha]-naphthoflavone (ANF), were used to modulate metabolite, protein adduct, and DNA adduct formation. Incubations of [[sup 3]H]PhIP (100 [mu]M) with Aroclor 1254-induced or uninduced hepatocytes resulted in the formation of several metabolites, including 4[prime]-(2-amino-1-methylimidazo[4,5-b]pyrid-6-yl)phenyl sulfate (4[prime]-PhIP-sulfate), 2-amino-1-methyl-4[prime]-hydroxy-6-phenylimidazo[4,5-b]pyridine, and other uncharacterized metabolites. While PCP or DCNP pretreatment produced a significant decline in sulfate-dependent conjugation of 4[prime]-hydroxy-PhIP to 4[prime]-PhIP-sulfate, these inhibitors produced only slight decreases in PhIP-dependent covalent binding to proteins in hepatocytes derived from either Aroclor 1254-induced or uninduced rats. PhIP DNA adduct levels were relatively unchanged by PCP or DCNP pretreatment of Aroclor 1254-induced hepatocytes. DNA adducts from hepatocytes dosed with N-hydroxy-PhIP, however, resulted in a decrease in adduct levels from cells pretreated with PCP or DCNP. Pretreatment of cells with ANF reduced the formation of all detectable metabolites by at least 50%, yet increased DNA adduct levels by nearly 4-fold. 36 refs., 6 figs., 2 tabs.

• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 7035657
• Journal Information: Chemical Research in Toxicology; (United States), Vol. 7:2; ISSN 0893-228X
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
CYTOCHROMES
METABOLIC ACTIVATION
PICOLINES
BIOLOGICAL PATHWAYS
MUTAGENESIS
BIOCHEMICAL REACTION KINETICS
DNA ADDUCTS
ENZYME INHIBITORS
LIVER CELLS
RATS
SALMONELLA TYPHIMURIUM
ADDUCTS
ANIMAL CELLS
ANIMALS
AZINES
BACTERIA
HETEROCYCLIC COMPOUNDS
KINETICS
MAMMALS
MICROORGANISMS
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PIGMENTS
PROTEINS
PYRIDINES
REACTION KINETICS
RODENTS
SALMONELLA
SOMATIC CELLS
VERTEBRATES
550200* - Biochemistry
550500 - Metabolism