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Arch Toxicol (2013) 87:15451556 DOI 10.1007/s00204-013-1054-0
TOXICOKINETICS AND METABOLISM
Toxicokinetics of acrylamide in primary rat hepatocytes: coupling to glutathione is faster than conversion to glycidamide
Nico Watzek Denise Scherbl Markus Schug
Jan G. Hengstler Matthias Baum Michael Habermeyer
Elke Richling Gerhard Eisenbrand
Received: 7 February 2013 / Accepted: 26 March 2013 / Published online: 9 April 2013 Springer-Verlag Berlin Heidelberg 2013
Abstract Acrylamide (AA), classied as class 2A carcinogen (probably carcinogenic to humans) by the International Agency for Research on Cancer (IARC), is formed during heating of food from reducing carbohydrates and asparagine by Maillard reaction chemistry. After dietary uptake, AA is in part metabolically converted into the proximate genotoxic phase I metabolite glycidamide (GA). GA reacts with nucleophilic base positions in DNA, primarily forming N7-(2-carbamoyl-2-hydroxyethyl)guanine (N7-GA-Gua) adducts. In a competing phase II biotrans-formation pathway AA, as well as its phase I metabolite GA, is coupled to glutathione (GSH). The GSH coupling products are further biotransformed and excreted via urine as mercapturic acids (MA), N-acetyl-S-(2-carbamoylethyl)cysteine (AAMA), and N-acetyl-S-(2-hydroxy-2-carbamoylethyl)cysteine (GAMA). In the present study, hepatic biotransformation pathways and DNA adduct formation were studied in primary rat hepatocytes, incubated with AA (0.22,000 lM) for up to 24 h. Contents of AA
GSH, GA, AAMA, and GAMA were measured in the cell culture medium after solid phase extraction (SPE). N7-GAGua adducts in DNA of hepatocytes were determined by HPLCESIMS/MS after lysis of the cells and neutral thermal hydrolysis. Formation of AA-GSH was linear with AA concentration and incubation time and became
detectable already at 0.2 lM (4 h). In contrast to AA, GA was not detected before 16 h incubation at 10-fold higher AA concentration (2 lM). In summary, the rate of AA
GSH formation was found to be about 1.53 times higher than that of GA formation. N7-GA-Gua adducts were found only at the highest AA concentration tested (2,000 lM).
Keywords Acrylamide Glycidamide Glutathione
adducts DNA adducts Mercapturic acids Detoxication
Introduction
Acrylamide (AA) is an a,b-unsaturated aliphatic carbonyl compound generated during heating of food. AA is formed predominantly from asparagine in the presence of reducing sugars in the course of the Maillard reaction (Zyzak et al. 2003). AA has been found in heat processed potato products, with some preference in fried potatoes or potato crisps, bread, cereals,...