Evidence for glucuronidation and sulfation of zeranol and metabolites (taleranol and zearalanone) by rat and pig hepatic subfractions.

Biochemical evidence is given of alpha-zearalanol (zeranol), zearalanone, and beta-zearalanol (taleranol) glucurono- and sulfoconjugation in the rat and pig. It is based on the use of liver microsomal and cytosolic fractions, incubation with labeled endogenous coupling substrates, i.e. UDP-glucuronic acid and sulfate, and HPLC profiling of the resulting incubates. It is proved that only monoconjugates are produced, while it is suggested that conjugation occurs on the aromatic ring. Whether it is the C-14 or C-16 hydroxyl group that is conjugated remains to be demonstrated. When comparing the metabolic profiles in vitro with those already obtained in pig plasma, it can be concluded that both glucurono- and sulfoconjugates are produced in vivo.