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 potency
mainly depends on its biotransformation fate. The hepatic biotransformation of ZEA in rainbow trout was
investigated in this study. Various concentrations of ZEA were separately incubated with the hepatic
microsomal and post-mitochondrial sub-fractions in the presence of NADPH, and the metabolites were
determined by means of HPLC. Moreover, the rate of glucuronidation for ZEA and its reduced metabolites
were estimated in the presence of uridine diphosphate glucuronic acid. β-zearalenol (β-ZOL) was found to be
the major metabolite of ZEA by both sub-cellular fractions. The enzymatic kinetics analyses indicated that
the 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 with
glucuronic acid at the lower concentrations. Data suggest that the hepatic biotransformation of ZEA in
rainbow trout resulted in its detoxification as the main metabolite tends to be β-ZOL with weak estrogenic
property. Moreover, at certain concentrations, the produced metabolites are entirely conjugated with
glucuronic acid, which may consequently cause a prolonged duration of action due to entero-hepatic cycle.