The aim of this study was to find out whether Schizonepetin influences the pharmacokinetics of the main substrates drugs of CYP1A2, CYP3A1/2, CYP2E1, CYP2C19 and CYP2D6 in rats; the influence on the levels of CYP mRNA was also studied. Phenacetin, dapsone, chlorzoxazone, omeprazole and metoprolol were selected as probe substrates for CYP1A2, CYP3A1/2, CYP2E1, CYP2C19 and CYP2D6 respectively. HPLC methods were employed for the determination of these substrates in plasma and the pharmacokinetic parameters were calculated. Real-time RT-PCR was used to determine the effects of Schizonepetin on the mRNA expression of CYP3A1, CYP1A2 and CYP2E1 in the rat liver. After the rats were orally administrated with Schizonepetin once a day for seven consecutive days, there were significant differences in plasma concentration of phenacetin, dapsone, chlorzoxazone and metoprolol, but not omeprazole, as compared with pre-administration. In addition, Schizonepetin induced the expression of CYP3A1, CYP1A and CYP2E1 at dosages of 24 and 48 mg/kg. Our results indicated that Schizonepetin had significant induction effects on CYP3A1/2 and inhibition effects on CYP1A2, CYP2E1 or CYP2D6 as oriented from the pharmacokinetic profiles of the substrates. Moreover, in the mRNA expression levels, Schizonepetin could induce the mRNA expression of CYP3A1, CYP1A and CYP2E1. In conclusion, co-administration of some CYP substrates with Schizonepetin may lead to an undesirable herb-drug interaction.Keywords:Schizonepetin;Cytochrome P450;substrates drugs;pharmacokinetic parameters;mRNA;real-time RT-PCR
Human organic anion transporting polypeptide 1B3 (OATP1B3) and 1B1 are two liver-specific and highly homologous uptake transporters, whose structures consist of 12 transmembrane domains. The present study showed that OATP1B3 is more heavily N-glycosylated than OATP1B1 in extracellular loop 2 (EL2) and EL5. OATP1B3 has six N-glycosylation sites, namely N134, N145, N151, N445, N503, and N516, which is twice of that of OATP1B1. Single removal of individual N-glycans seems to have minimal influence on the surface expression and function of OATP1B3. However, simultaneous removal of all N-glycans will lead to OATP1B3's large retention in the endoplasmic reticulum and cellular degradation and thus significantly disrupts its surface expression. While N-glycosylation plays a crucial role in the surface expression of OATP1B3, it also has some effect on the transport function of OATP1B3 per se , which is not due to a decrease of substrate binding affinity but due to a reduced transporter's turnover number. Taken together, N-glycosylation is essential for normal surface expression and function of OATP1B3. Its disruption by some liver diseases such as NASH might alter the pharmacokinetic/pharmacodynamic properties of OATP1B3's substrate drugs.
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