Relationship Between The Metabolism Of Neferine In Rat Liver Microsomes And Cytochrome P450

AIM: The metabolic character of neferine (Nef) in rat liver microsomes was studied in vitro and in vivo to identify which isoforms of cytochrome P450 were responsible for Nef metabolism in rats. METHODS: ① Wistar rats were untreated or treated with various inducers including dexamethasone (DEX)(50mg·kg~-1, ig×4d), phenobarbital (PB)(75 mg·kg~-1, ip×3d) and β–naphthoflavone(β-NF)(80mg·kg~-1, ip×3d).Liver microsomes were obtained from these rats and incubated with Nef in the presence of reduced form of nicotinamide adenine dinucleotide phosphate. A HPLC-UV method was developed to determine Nef and its metabolites ② The enzyme kinetics of the metabolism of Nef was investigated in rat liver microsomes. ③ Troleandomycin ,a CYP3A selective inhibitor ,was used to study its inhibition effect on the metabolism of Nef in vitro . ④ After the Wistar rats who had been treated with inducer, inhibitor, or untreated respectively, received administration of Nef (9.4mg·kg~-1 or 18.8mg·kg~-1,i.v.), blood samples were taken at different time points and the plasma concentration of Nef were determined by HPLC. Pharmacokinetic parameters of Nef were computed and compared. RESULTS: ① The metabolism of Nef in rat liver microsomes showed the characteristic of enzyme kinetics. ② The correlation between peak area of a metabolite and original concentration of Nef in rat liver microsomes solution was significant( r =0.993). ③ The disppearing rate of Nef in the incubation solutions of the rats liver microsomes, which treated with DEX or PB, were markedly quicker than that of control group (p<0.01)and the rate of DEX group was quicker than that of PB group (P<0.01), while no obvious difference between β-NF group and control group was observed (P>0.05).The average disappearing rate of Nef after incubation with differently treated rat liver microsomes were as follows: DEX,80.6±9.5%；PB,61.5±6.7%；β-NF,20.7±1.5%；Control, 19.9±1.6%； ④ Troleandomycin could significantly inhibit the metabolism of Nef in rat liver microsomes. ⑤ Both DEX and PB could speedup the metabolism of Nef in rats, which CL(s) were larger than that of the control group(DEX:0.363±0.063 L·min~-1·kg~-1 ,Control :0.151±0.019 L·min~-1·kg~-1,P<0.01； PB:0.250±0.051 L·min~-1·kg~-1,Control :0.151±0.019 L·min~-1·kg~-1,P<0.01), t1/2 were smaller than the control group(DEX:16.5±4.5 min,Control :59.7±14.7min,P<0.01； PB:32.5±5.3min,Control :59.7±14.7min,P<0.01),and the induction effect of DEX on the metabolism of Nef was stronger than that of PB. By contraries, TAO could inhibit the metabolism of Nef in rats, which CL(s) was smaller than the control group(TAO:0.083±0.014 L·min~-1·kg~-1,Control :0.151±0.019 L·min~-1·kg~-1,P<0.01), t1/2 was larger than the control group(TAO:94.2±24.5min,Control :59.7±14.7min,P<0.01). CONCLUSION: Our results suggest that both CYP3A and CYP2B are involved in Nef metabolism in rats, and CYP3A plays a major role.