Bovine Hepatic Metabolism of Aflatoxin B1

Abstract

Differences in the expression and catalytic activity of hepatic biotransformation enzymes account for species differences in xenobiotic metabolism, including that of aflatoxin B1 (AFB1). The main objectives of this study were (1) to define the procedure for isolation and culture of bovine hepatocytes, (2) to characterize the biotransformation capacity of bovine hepatocytes for AFB1, and (3) to develop an HPLC method for the simultaneous analysis of AFB1 and its metabolites. Bovine hepatocytes were isolated and cultured in monolayers. Metabolic function of these hepatocytes was assessed by measuring total cytochrome P450 (CYP450) content, glutathione S-transferase (GST) activity, ethoxyresorufin O-deethylation (EROD), testosterone hydroxylation, and α-naphthol glucuronidation. When using these cultures to study the biotransformation of AFB1, the principal metabolites of AFB1 were AFM1 and AFB1-dihydrodiol (AFB1-dhd). Minor amounts of AFB1−glutathione conjugate (AFB1−GSH) and a polar metabolite were also detected. The polar metabolite was not specifically identified as a glucuronidation product of AFB1. No AFP1, AFQ1, AFB2a, or aflatoxicol (AFL) was detected. The HPLC method developed provided the simultaneous detection of AFB1 and the metabolites AFB1-dhd, AFM1, AFP1, AFQ1, AFL, and AFB1−GSH as well as AFB2a. Keywords: Bovine; hepatocytes; biotransformation; AFB1