Pharmacokinetics And Quantitative Evaluation Of Cntcrohcpatic First-pass Metabolism Of SAMe In Rats

Objective: It has been widely hypothesized that intestinal apical secretion andmetabolism, people pay more attention and concern to preparation of oral biologicalagents and new drug. In this study, the proposed HPLC-UV method of SAMe rat plasmasamples, and by IVAP model to study the SAMe rat intestinal metabolic by giving thequantitative evaluation of different doses of SAMe, to study the liver and intestine,duodenum, portal vein and peripheral vein first pass metabolism level, and as tools fordrug CYP3A4and P-gp specific inhibitors ketoconazole and verapamil, preliminarystudy of intestinal CYP3A4and P-gp in SAMe intestinal first-pass metabolism. ExploreCYP3A4and P-gp in SAMe first-pass metabolism in the role, to provide experimentalbasis to improve the the SAMe oral bioavailability.Methods: The current study was performed using intestinal and vascular access ported（IVAP） rats to quantify and differentiate the components of intestinal and hepatic firstpass extraction of SAMe mediated by CYP3A and P-gp.The rat was feeded ofperipheral vein(70mg·kg^-1,140mg·kg^-1,280mg·kg^-1), portal vein(70mg·kg^-1,140mg·kg^-1,280mg·kg^-1), duodenal(140mg·kg^-1,280mg·kg^-1,560mg·kg^-1) by high,medium and low respectively, after administration of rat carotid0,1,10,20,30,40,60,90,120,180min blood0.3mL and put it into the heparinized tube, do thecentrifugation by the speed of10000r/min about5minutes, dissociate the plasma andkeep it for analysis at the temperature of-20℃, the plasma samples were treated byHPLC-UV to determine the concentration of SAMe in the plasma sample. Analysis andhandle the data by using the DAS2.0pharmacokinetic software and do the quantitativeanalysis of rat enterohepatic first-pass effect after confirming the pharmacokinetic parameters.Compared with the control group, to compare the effort of SAMepharmacokinetic to id (280mg·kg^-1) and iv (140mg·kg^-1)according to giveCYP3A4specific inhibitor ketoconazole (60mg·kg^-1) and P-gp specific inhibitorverapamil (9mg·kg^-1).Resalt: HPLC-UV is a method which has good specificity, high sensitivity andreliability to detect rat plasma concentration. SAMe can be completely separated fromthe linear range:10to2000μg· mL^-1, the regression equation was Y=30241X+256204, r=0.9991, the intraday precision RSD were2.6%,3.6%,3.9%; day RSDwere6.3%,4.9%,7.9%; recoveries were107%,101%,98.3%.In IVAP rat model, pharmacokinetic parameters of AUC and Cmax of SAMe wasincreased propotionally after id, ipv, and iv administration at various doses. After idadministration of various doses, all reached peak concentration within10min,pharmacokinetic parameters of AUCidwere68.60±19.54mg·L^-1·h,151.99±35.91mg·L^-1·h,449.19±27.53mg·L^-1·h, while AUCipvwere161.10±29.51mg·L^-1·h,457.86±106.83mg·L^-1·h,766.82±151.73mg·L^-1·h, and AUCivwere197.09±74.03mg·L^-1·h,577.25±161.61mg·L^-1·h,939.10±164.43mg·L^-1·h, respectively.When giving thesame dose of SAMe, lower than AUCivand AUCipv. Compared with the control group,the presence of ketoconazole or verapamil significantly increased AUC and Cmax ofid-administered SAMe, while it had no significant effect on those of SAMeadministered by iv ports. After id administration140mg·kg^-1and280mg·kg^-1SAMe.Thebioavalability of id were10.16±2.07%,17.77±5.41%repectly. EHwere18.73±2.42%,12.25±2.85%and EIwere84.82±3.74%,79.86±5.53%respectly.Conclusion:1. This method was proved to be simple and efficient with excellent specificity,sensitivity, precision, recovery and can be applied to pharmacokinetic investigation ofSAMe.2. SAMe has undergone a remarkable liver and intestinal metabolism, increasing thedrug dose may be a significant increase in SAMe. The SAMe may increase dose-dependently of iv and ipv, while that of SAMe may not increase with oral dose.3. Intestinal CYP3A4and P-gp-mediated transport processes are involved in the TheSAMe intestinal first-pass metabolism process, significant inhibition of intestinalCYP3A and P-gp function can increase SAMe oral bioavailability.4. The liver and intestinal metabolisms are the key reasons which lead to the lowbioavailability of the SAMe, but the effect is different.