In vitro metabolism of zeranol: evaluation of covalent binding to microsomal protein.

Using an in vitro system (i.e. bovine liver microsomes), the authors have studied the metabolism of zeranol. The oxidation of zeranol into zearalanone by NADPH-dependent monooxygenases has been measured. The rate of metabolic activation and the level of covalent binding to microsomal proteins of zeranol metabolites have been evaluated. They were found to be very low. A possible detoxication effect of glutathione and glutathione-S-transferases was undetectable.