In vitro reduction of zearalenone to β-zearalenol by rainbow trout (Oncorhynchus mykiss) hepatic microsomal and post-mitochondrial subfractions

Mycoestrogen zearalenone (ZEA) is found in human foods and animal feeds. Its estrogenic potencymainly depends on its biotransformation fate. The hepatic biotransformation of ZEA in rainbow trout wasinvestigated in this study. Various concentrations of ZEA were separately incubated with the hepaticmicrosomal and post-mitochondrial sub-fractions in the presence of NADPH, and the metabolites weredetermined by means of HPLC. Moreover, the rate of glucuronidation for ZEA and its reduced metaboliteswere estimated in the presence of uridine diphosphate glucuronic acid. β-zearalenol (β-ZOL) was found to bethe major metabolite of ZEA by both sub-cellular fractions. The enzymatic kinetics analyses indicated thatthe α-ZOL and β-ZOL production by microsomal fraction were 8- and 2-fold higher than those by postmitochondrial fraction, respectively. High percentages of ZEA and its metabolites are conjugated withglucuronic acid at the lower concentrations. Data suggest that the hepatic biotransformation of ZEA inrainbow trout resulted in its detoxification as the main metabolite tends to be β-ZOL with weak estrogenicproperty. Moreover, at certain concentrations, the produced metabolites are entirely conjugated withglucuronic acid, which may consequently cause a prolonged duration of action due to entero-hepatic cycle.