Bovine hepatic metabolism of aflatoxin B1

Differences in the expression and catalytic activity of hepatic biotransformation enzymes account for species differences in xenobiotic metabolism, including that of aflatoxin B-1 (AFB(1)). 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 AFB(1), and (3) to develop an HPLC method for the simultaneous analysis of AFB(1) 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 alpha-naphthol glucuronidation. When using these cultures to study the biotransformation of AFB(1), the principal metabolites of AFB(1) were AFM(1) and AFB(1)-dihydrodiol (AFB(1)-dhd). Minor amounts of AFB(1)-glutathione conjugate (AFB(1)-GSH) and a polar metabolite were also detected. The polar metabolite was not specifically identified as a glucuronidation product of AFB(1). No AFP(1), AFQ(1), AFB(2a), or aflatoxicol (AFL) was detected. The HPLC method developed provided the simultaneous detection of AFB1 and the metabolites AFB(1)-dhd, AFM(1), AFP(1), AFQ(1), AFL, and AFB(1)-GSH as well as AFB(2a).