Influence of Hydroxynaphthoquinone of Arnebia Euchroma (Royle) Johust. on Rat CYP2D6 Activity

OBJECTIVE To investigate the influence of hydroxynaphthoquinone of Arnebia Euchroma (Royle) Johust. (HNA) on CYP2D6 activity of Wistar rats. METHODS Liver microsomes of male Wistar rats were prepared after orally administrated HNA (5 and 60 mg·kg^-1·d^-1) or vehicle for 2 weeks. The CYP2D6 activity of rats was examined by the in vitro formation rate of dextrorphan metabolized from dextromethorphan. The effect of HNA on CYP2D6 was evaluated by comparing the data from administration groups with those from control group. RESULTS An accurate and rapid method was established to inspect CYP2D6 activity of rats by using dextromethorphan hydrobromide as a probe substrate. The study showed no significant differences on contents of microsome protein, cytochrome P450, cytochrome b5 and CYP2D6 activity among the administration groups and control group. CONCLUSION Oral administration of HNA for 2 weeks at dosage level ranging from 5 mg·kg^-1·d^-1 to 60 mg·kg^-1·d^-1 has no effect on CYP2D6 activity of Wistar rats. This result indicats that HNA orally administrated to rats has no significant inhibitory or inductive effect on CYP2D6 activity in liver microsome.