Hepatic Biotransformation and Metabolite Profile during a 2-Week Depuration Period in Atlantic Salmon Fed Graded Levels of the Synthetic Antioxidant, Ethoxyquin

• Published in: Toxicological Sciences
• Main Authors: Berdikova Bohne, Victoria J., Hamre, Kristin, Arukwe, Augustine
• Format: Text
• Language: English
• Published: Oxford University Press 2006
• Subjects: BIOTRANSFORMATION AND TOXICOKINETICS; Atlantic salmon
• Online Access: http://toxsci.oxfordjournals.org/cgi/content/short/93/1/11; https://doi.org/10.1093/toxsci/kfl044

The synthetic antioxidant ethoxyquin (EQ) is increasingly used in animal feeds and has been candidate for carcinogenicity testing. EQ has the potential for toxicological and adverse health effects for both fish and fish consumers through “carryover” processes. The toxicological aspects of EQ have not been systematically investigated. The present study was performed to investigate the hepatic metabolism, metabolite characterization, and toxicological aspects of EQ in salmon during a 2-week depuration after a 12-week feeding period with 18 mg (low), 107 mg (medium), and 1800 mg/kg feed (high). The alteration in gene expressions and catalytic activities of hepatic biotransformation enzymes were studied using real-time polymerase chain reaction with specific primer pairs and by kinetics of two identified hepatic metabolites. Analysis of EQ metabolism was performed using high performance liquid chromatography (HPLC) method and showed the detection of four compounds of which two were quantified, parent EQ and EQ dimer (EQDM). Two metabolites were identified as de-ethylated EQ (DEQ) and quinone imine, but these were not quantified. The concentration of the quantified EQ-related compounds in the liver at day 0 showed a positive linear relationship with measured dietary EQ ( R 2 = 0.86 and 0.92 for parent EQ and EQDM, respectively). While the low–EQ-feeding group showed a time-specific increase of aryl hydrocarbon receptor (AhR) mRNA expression, the medium-dose group showed decreased AhR mRNA at depuration day 7. Expression of CYP1A1 was decreased during the depuration period. Consumption of dietary EQ produced the expression of CYP3A, glutathione S-transferase (GST), and uridine diphosphate glucuronosyl-transferase (UDPGT) mRNA during the depuration period. A similar pattern of effect was observed for both CYP3A and phase II genes and supports our previous postulation of common regulation of these enzymes by the same inducer, namely EQ metabolites. The increase of CYP3A, UDPGT, and GST gene expressions at day 7 was in ...