Effects of fish cytochromes P450 inducers and inhibitors on difloxacin N-demethylation in kidney of Chinese idle (Ctenopharyngodon idellus)

Abstract

Cytochromes P450 (CYPs) play key roles in drug metabolism which are widely distributed in kidney in aquatic organisms. CYP(s) mainly catalyzed the N-demethylation reaction of difloxacin (DIF) biotransformation to sarafloxacin (SAR). However, limited information is available about CYP investigation in fish. In order to supply useful information on CYP(s) characterization for DIF N-demethylation, the present study assessed the effects of fish potent CYP inducers and inhibitors on DIF N-demethylation and the inductive and inhibitive enzyme kinetics in kidney of Chinese idle (Ctenopharyngodon idellus) by reversed-phase high-performance liquid chromatography (RP-HPLC). Results demonstrated that the amounts of SAR formation pretreated by β-naphthoflavone (BNF) increased by 1.1-fold and α-naphthoflavone (ANF) inhibited SAR formation level by 0.6-fold at the third day. Enzymatic parameters V(max) and Cl(int) of DIF N-demethylase were increased by 0.56- and 0.38-fold due to β-naphthoflavone (BNF) pretreatment. DIF N-demethylation inhibition by varying ANF concentrations represented a mixed-type inhibition with the value of the inhibition constants (K(i)) 12.9mg/kg. BNF and ANF are the separate typical inducer and inhibitor for CYP1A in fish. Thus, we suggest that CYP1A may be responsible for DIF N-demethylation in kidney. This study provides instructive information to ensure treatment success in fisheries medication with two or more drugs.