烷化剂环磷酰胺和异环磷酰胺对大鼠肝微粒体CYP2C19酶活性的影响

目的探讨烷化剂环磷酰胺和异环磷酰胺对CYP2C19酶活性的影响,为临床合理用药提供理论依据。方法利用高效液相色谱法测定大鼠体外培养体系中肝微粒体CYP2C19酶的活性,以5-羟基奥美拉唑(5-OHOMZ)与奥美拉唑(OMZ)的比值表示,比较加入和不加入环磷酰胺和异环磷酰胺CYP2C19酶活性的变化。结果加入环磷酰胺与异环磷酰胺时,CYP2C19酶活性分别降低20.7%±3.47%、12.63%±6.32%。结论环磷酰胺与异环磷酰胺对CYP2C19酶活性具有较显著的抑制作用,故应注意代谢性相互作用对药物疗效的影响,以达到临床合理用药的目的。     

高效液相色谱法测定大鼠肝微粒体CYP3A酶的活性

目的 以咪达唑仑为探针药用HPLC法测定大鼠肝微粒体CYP3A酶活性.方法 用ZORBAX SB-C18色谱柱分离;流动相为乙腈-水-0.1％三氟乙酸;流速为1 mL· min-1;柱温40℃;检测波长为230 nm.肝微粒体加入咪达唑仑孵育5 min后,用乙腈终止反应,加入内标溶液50 μL,混匀后离心10 min,取上清进行HPLC分析;计算Km和Vmax.结果 1-羟基咪达唑仑浓度在0.06～3.00 mg· L-1内线性关系良好;日内、日间精密度均＜10％,回收率＞75％.咪达唑仑羟化反应的Km =7.32μmol· L-,Vmax=0.59 nmol·min-1·mg-1 pro.结论 本方法稳定可靠,能准确反映CYP3A酶的活性.     

以普罗帕酮为探针测定人肝微粒体中CYP2D6的活性

目的:测定普罗帕酮(PPF)和5-羟基普罗帕酮(5-OHP)的比值以表达人肝微粒体中CYP2D6的活性.方法:以1g·L-1微粒体蛋白浓度37℃孵育PPF 1 h,以HPLC测定PPF和5-OHP的含量.结果:PPF和5-OHP的线性方程分别为Y=0.452 0 C 0.003 0,r=0.999 7;Y=0.749 4 C-0.020 5,r=0.997 5.结论:人肝微粒体CYP2D6酶的活性可以通过测定5-OHP与PPF的比值进行预测.     

高效液相色谱法测定鼠肝微粒体中CYP1A2酶的活性及动力学考察

目的:建立以非那西丁为探针的高效液相色谱-紫外检测的实验方法,测定大鼠肝微粒体中CYP1A2酶活性并对其进行动力学考察。方法:采用Shimadzu Shim-Pack VP-ODS柱(150 mm×4.6 mm,5μm),流动相为:100 mmol·L-1磷酸二氢钠缓冲液(pH 4.3)和乙腈,梯度洗脱,流速为1.0 mL·min-1,柱温为室温,检测波长245 nm。非那西丁与大鼠肝微粒体在37℃温孵60 min,加入冰甲醇终止,12000 r.min-1离心10 min,取上清进行HPLC分析,以Lineweaver-Burk作图计算Vmax与Km值。结果:非那西丁、对乙酰氨基酚及其内标间乙酰氨基酚三者分离良好且无内源性干扰。对乙酰氨基酚最低检测限50 nmol·L-1,线性范围0.1～10μmol·L-1。日内日间精密度均小于10%。回收率大于75%。动力学考察表明选择甲醇作为终止试剂效果较好,非那西丁在0.2 mg·mL-1大鼠肝微粒体体系中孵育60 min,测得动力学参数Vmax为0.21 nmol·min-1.mgprotein-1,Km为20.39μmol·L-1。结论:该方法稳定,结果能准确地反映CYP1A2酶的活性,可以用于相关动力学研究。     

CYP2C19基因型和CYP2C9对人肝微粒体中氟西汀N-去甲基代谢的影响(英文)

目的:本实验旨在研究CYP2C19基因型人肝微粒体中氟西汀N-去甲基代谢的酶促动力学特点并鉴定参与此代谢途径的细胞色素P-450酶。方法:测定基因型CYP2C19肝微粒体中去甲氟西汀形成的酶促动力学。鉴定氟西汀N-去甲基酶活性与细胞色素P-450 2C9,2C19,1A2和2D6酶活性的相关性,同时应用各种细胞色素P-450酶的选择性抑制剂和化学探针进行抑制实验,从而确定参与氟西汀N-去甲基代谢的细胞色素P-450酶。结果:去甲氟西汀生成的酶促动力学数据符合单酶模型,并具有Michaelis-Menten动力学特征。当底物浓度为氟西汀25μmol/L和100μmol/L时,去甲氟西汀(N-FLU)的生成率分别与甲磺丁脲3-羟化酶活性显著相关(r_1=0.821,P_1=0.001;r_2=0.668,P_2=0.013),当底物浓度为氟西汀100μmol/L时,N-FLU的生成率与S-美芬妥因4’-羟化酶活性显著相关(r=0.717,P=0.006)。PM肝微粒中磺胺苯吡唑和醋竹桃霉素对氟西汀N-去甲基代谢的抑制作用显著大于EM(73％vs 45％,P<0.01)。结论:在生理底物浓度下,CYP2C9是催化人肝微粒体中氟西汀N-去甲基代谢的主要CYP-450酶;而高底物浓度时,以CYP2C19的作用为主。     

紫草羟基萘醌对大鼠肝微粒体CYP2D6的影响

目的研究紫草羟基萘醌（HNA）对大鼠肝微粒体CYP2D6的影响。方法 Wistar大鼠,♂,口服给予不同剂量的HNA（5,60 mg.kg-1.d-1）或等量的空白溶媒,连续给药2周后制备肝微粒体。以体外探针药物右美沙芬的代谢物右啡烷的生成速率来反映CYP2D6的活性,通过比较给药组与空白溶媒组酶活性的差异来评价HNA对大鼠肝微粒体CYP2D6的影响。结果建立了一种以右美沙芬为探针底物评价大鼠肝微粒体CYP2D6活性的方法。口服给予HNA两周后,两个剂量组大鼠的肝微粒体蛋白含量、细胞色素P450总量、b5含量以及CYP2D6的活性与空白溶媒组相比差异均无统计学意义。结论 5 mg.kg-1.d-1和60 mg.kg-1.d-1剂量的紫草羟基萘醌口服2周对Wistar大鼠肝微粒体CYP2D6的活性均无显著影响,没有明显的诱导或抑制作用。     

奥拉西坦对肝微粒体酶CYP2C9活性的影响研究

目的:考察奥拉西坦对肝微粒体酶CYP2C9活性的影响。方法:将大鼠随机分为对照组和实验组,每组18只,对照组每天灌胃蒸馏水,实验组每天灌胃奥拉西坦80 mg/kg,每日2次,连续8 d。第8天灌胃后两组大鼠均立即灌胃给予CYP2C9的探针药物甲苯磺丁脲50 mg/kg,并于给予甲苯磺丁脲后0.25、0.5、0.75、1、1.5、2、3、4、6、10、12、24 h内眼内眦取血。采用高效液相色谱法测定血药浓度,拟合药动学参数,并对两组药动学参数进行比较。结果:对照组与实验组主要药动学参数t1/2分别为(5.45±1.98)、(6.54±1.45)h,cmax分别为(169.12±58.14)、(146.19±49.44)mg/L,AUC0-24 h分别为(1 113.01±264.32)、(1 120.14±208.91)mg·h/L,Vd分别为(0.77±0.32)、(0.91±0.40)L/kg,CL分别为(0.08±0.03)、(0.08±0.02)L/(h·kg),两组间比较差异无统计学意义(P>0.05)。结论:奥拉西坦对甲苯磺丁脲在大鼠体内的药动学未见明显影响,初步认为奥拉西坦对经CYP2C9代谢的药物的药动学无明显影响。     

大鼠肝微粒体中有机锡抗癌化合物DBDCT的测定与酶促动力学研究

目的 建立测定大鼠肝微粒体中有机锡抗癌化合物DBDCT的方法并研究其相应的酶促动力学。方法 采用HPLC测定DBDCT在体外代谢系统中的酶促动力学,用Eadie-Hofstee法分析数据,求算酶促动力学参数Km和Vmax以及肝代谢速率Clin。结果 在体外代谢系统中,DBDCT代谢酶促动力学参数Km=159.07 μmol·L^-1,Vmax=2.813 μmol·(min·mg)^-1以及肝清除率Clin=V_max/Km=0.017 L·(min·mg)^-1。结论 此分析方法符合方法学验证要求且简单准确,可满足DBDCT体外代谢的研究。     

大鼠肝微粒体中有机锡抗癌化合物DBDCT的测定与酶促动力学研究

目的 建立测定大鼠肝微粒体中有机锡抗癌化合物DBDCT的方法并研究其相应的酶促动力学。方法 采用HPLC测定DBDCT在体外代谢系统中的酶促动力学,用Eadie-Hofstee法分析数据,求算酶促动力学参数Km和Vmax以及肝代谢速率Clin。结果 在体外代谢系统中,DBDCT代谢酶促动力学参数Km=159.07 μmol·L^-1,Vmax=2.813 μmol·(min·mg)^-1以及肝清除率Clin=V_max/Km=0.017 L·(min·mg)^-1。结论 此分析方法符合方法学验证要求且简单准确,可满足DBDCT体外代谢的研究。     

高效液相色谱法检测人肝微粒体CYP3A活性

目的：测定普罗帕酮和N 去丙基普罗帕酮的比值以表达人肝微粒体中CYP3A的活性。方法：以1 mg·mL 1微粒体蛋白浓度37℃孵育普罗帕酮1 h，以HPLC测定普罗帕酮和N 去丙基普罗帕酮的含量。结果： 普罗帕酮和N 去丙基普罗帕酮的线性方程分别为Y＝0.452 0X＋0.003 029(r＝0.999 7)；Y＝1.137 3X＋0.012 740(r＝0.998 5)。结论：N 去丙基普罗帕酮与普罗帕酮的最大比值为1.54，CYP3A具有饱和性。     

细胞色素氧化酶CYP2C9的诱导机制及研究进展

细胞色素P4 5 0 2C9(CYP2C9)是表达在人类肝脏中的一类重要的药物代谢酶 ,能催化许多临床常用药物 ,还包括一些治疗指数低的药物。该文主要从CYP2C9的基因结构 ,诱导机制 ,基因的多态性及其功能意义 ,人群的分布综述CYP2C9的研究进展。     

Polymorphism of CYP2D6, CYP2C19, CYP2C9 and CYP2C8 in the Faroese population

Objective The purpose of the study was to study the distribution of poor and extensive metabolizers of CYP2C19 and CYP2D6 and to genotype for CYP2C8 and CYP2C9 among 312 randomly selected Faroese.Methods and results The participants were phenotyped for CYP2D6 with the use of sparteine. The distribution of the sparteine metabolic ratio (sparteine/didehydrosparteines) was bimodal, and 14.5% (n=44; 95% CI: 10.7–18.9%) of the subjects were phenotyped as poor metabolizers. The frequency of poor metabolizers was higher (P=0.0002; ² test) among the Faroese than in other European populations (7.4%). Genotype analyses for the CYP2D6*3, *4, *6 and *9 alleles were performed using real-time polymerase chain reaction (PCR) (TaqMan, Foster City, CA, USA), and we found 14.6% (n = 45) (95% CI: 10.8–19.0%) with deficient CYP2D6 genes (*3/*4, *4/*4, *4/*6, *6/*6) in the Faroese population. The subjects were phenotyped for CYP2C19 with the use of mephenytoin and 10 subjects, i.e., 3.2% (95% CI: 1.6–5.9%) were phenotyped as poor metabolizers. Genotype analysis for the CYP2C19*2 and *3 alleles was performed by means of PCR analysis, and 2.9% (n=9) (95% CI: 1.3–5.4%) of the Faroese were found to have a deficient CYP2C19 gene all explained by the CYP2C19*2/*2 genotype. The allele frequencies of the CYP2C9*2 and CYP2C9*3 alleles were 8.8% (95% CI: 6.7–11.4%) and 5.3% (95% CI: 3.7–7.4%), respectively, while the CYP2C8*3 allele frequency was 6.9% (95% CI: 5.0–9.2%). Real-time PCR (TaqMan) was used for both CYP2C9 and CYP2C8 genotype analyses.Conclusion The frequency of CYP2D6 poor metabolizers is twofold higher among the Faroese population than other Caucasians, while the frequencies of Faroese subjects with decreased CYP2C19, CYP2C8 and CYP2C9 enzyme activity are the same as seen in other Caucasian populations. A possible consequence might be a higher incidence of side effects among Faroese patients taking pharmaceuticals that are CYP2D6 substrates.     

In vitro comparative inhibition profiles of major human drug metabolising cytochrome P450 isozymes (CYP2C9, CYP2D6 and CYP3A4) by HMG-CoA reductase inhibitors

Objective: The affinity of (+)-, (−)- and (±)-fluvastatin, a new synthetic HMG-CoA reductase inhibitor developed as a racemate, for specific human P450 monooxygenases in liver microsomes was compared with that of the pharmacologically active acidic forms of lovastatin, pravastatin and simvastatin. Methods: Affinity was determined as the inhibitory potency for prototype reactions for 3 major drug metabolising enzymes: diclofenac 4′-hydroxylation (CYP2C9), dextromethorphan O-demethylation (CYP2D6), and midazolam 1′-hydroxylation (CYP3A4). Results: Lovastatin acid, pravastatin and simvastatin acid displayed moderate affinity for all three P450 isozymes (estimated K_i > 50 μmol⋅l⁻¹). Racemic and (+)- and (−)-fluvastatin showed moderate affinity (estimated K_i > 50 μmol⋅l⁻¹) for CYP2D6 and CYP3A4, whereas their affinity for CYP2C9 was high (estimated K_i < 1 μmol⋅l⁻¹). Diclofenac 4′-hydroxylation was competitively and stereoselectively inhibited, with measured K_i’s of 0.06 and 0.28 μmol⋅l⁻¹ for (+)- and (−)-fluvastatin, respectively. Conclusion: Fluvastatin selectively inhibits a major drug metabolising enzyme (CYP2C9), the (+)-isomer (pharmacologically more active) showing 4–5 fold higher affinity. As already reported for lovastatin and simvastatin, in vivo drug interactions by inhibition of liver oxidation of CYP2C9 substrates (e.g. hypoglyceamic sulphonylureas and oral anticoagulants) may be expected. Received: 9 June 1995/Accepted in revised form: 7 November 1995     

Microsomal prediction of in vivo clearance of CYP2C9 substrates in humans

AIMS: To assess the utility of human hepatic microsomes for predicting in vivo intrinsic clearance (CLint ) via the use of four cytochrome P450 2C9 substrates: phenytoin, tolbutamide (S)-ibuprofen (two pathways) and diclofenac, and to examine the role of exogenous albumin within the microsomal incubation. METHODS: V max, Km and CLint (defined as V max/Km ratio) were estimated under initial rate conditions for five pathways of metabolism in a bank of 15 human hepatic microsomal samples and were scaled to in vivo units using the microsomal protein index. Non-metabolic related binding in microsomes was measured for phenytoin and tolbutamide in the presence and absence of albumin. RESULTS: Microsomal CLint values differed by over two orders of magnitude, with the means ranging from 0.18 (phenytoin) to 40.70 (diclofenac) microl min-1 mg-1 microsomal protein. When these data were scaled and compared with published in vivo studies a similar rank order was obtained, however, the actual CLint tended to be underpredicted. While the in vivo unbound Km for phenytoin, 1-5 micron is substantially lower than the value determined in microsomes based on total concentrations (56 micron), correction for the in vitro binding reduces this value to 20 micron and 6 micron in the absence and presence of albumin, respectively. Similar trends were seen with tolbutamide Km. CONCLUSIONS: An appreciation of the utility of in vitro prediction can be best achieved when the range of CLint values predicted from the individual hepatic microsomal samples are compared with the range of individual in vivo CLint values reported in the literature. The degree of underprediction is less evident using the range than the mean data and no consistent advantage in adding albumin to the incubation media is apparent.     

Effect of Water-miscible Organic Solvents on CYP450-mediated Metoprolol and Imipramine Metabolism in Rat Liver Microsomes

The catalytic activity of cytochrome P450 enzymes is known to be affected by presence of organic solvents in in vitro assays. However, these effects tend to be variable and depend on the substrate and CYP450 isoform in question. In the present study, we have investigated effect of ten water miscible organic solvents (methanol, ethanol, propanol, isopropanol, acetone, acetonitrile, dimethylsulphoxide, dimethylformamide, dioxane and PEG400) on water soluble substrates of CYP450, metoprolol and imipramine, at 0, 0.1, 0.25, 0.5, 0.75 and 1% v/v concentration in rat liver microsomes. Organic solvents studied had a concentration dependent inhibitory effect on the metoprolol and imipramine metabolism activity. Metoprolol metabolism was found to be more susceptible to the organic solvents, almost all the ten solvents had more or less inhibitory effect compared to imipramine metabolism. Except acetone, PEG400 and dimethylsulphoxide, all solvents had ~50% inhibition of total metoprolol metabolism activity, while in case of imipramine metabolism activity, only n-propanol, isopropanol and PEG400 had ~50% inhibition at 1% v/v. Interestingly, methanol, dimethylsulphoxide and acetonitrile had negligible effect on the imipramine metabolism (less than 10% inhibition at 1% v/v) while, total metoprolol metabolism activity was substantially inhibited by these solvents (MeOH 52%, DMSO 29% and ACN 47% at 1% v/v). In both cases, dioxane was found to be the most inhibitory solvent (~90% inhibition at 1% v/v).     

新疆维吾尔族健康人群细胞色素P450基因多态性研究

目的了解CYP2C9基因多态性在新疆维吾尔族健康人群中的分布以及与其他不同民族之间的差异。方法采用序列特异性引物聚合酶链反应和限制性内切酶反应(PCR-RFLP)技术对197名乌鲁木齐地区维吾尔族健康个体CYP2C9*2和CYP2C9*3位点进行了检测,计算其基因型和等位基因频率,并与国外多个民族CYP2C9基因多态性分布进行比较。结果国内首次在新疆维吾尔族健康人群中发现CYP2C9*2等位基因,新疆维吾尔族健康人群中共检测到3种等位基因:CYP2C9*1、CYP2C9*2、CYP2C9*3,等位基因频率分别为80%、3%、17%。新疆维吾尔族健康人群CYP2C9共检测到5种基因型,以CYP2C9*1*1常见,基因型频率为77%,其次为CYP2C9*3*3,基因型频率为15%。CYP2C9*1*2、CYP2C9*1*3和CYP2C9*2*2的基因型频率分别为4%、3%和1%。结论新疆维吾尔族CYP2C9基因多态性的分布与欧美人群接近,而与日本、韩国以及国内报道的汉族人群CYP2C9基因多态性分布有较大差异。     

CYP2C9、CYP2C19、CYP3A4基因多态性对磺脲类降糖药代谢的影响

磺脲类口服降糖药在人体内主要经过肝脏代谢。肝脏中的细胞色素氧化酶P450是一种重要的药物代谢酶系统,在人群中存在基因多态性,导致药物疗效和不良反应在个体间存在着较大的差异。本文将对CYP450中的几种重要的代谢酶亚型CYP2C9、CYP2C19、CYP3A4的基本结构、基因多态性、种族差异及其对磺脲类降糖药代谢的影响作一综述。     

Influences of cytochrome b5 expression and its genetic variant on the activity of CYP2C9, CYP2C19 and CYP3A4

The objective of the present study was to investigate the effects of cytochrome b5 (cytb5) on the drug metabolism catalyzed by CYP2C9, CYP2C19 and CYP3A4. Activities of CYP2C9, CYP2C19, and CYP3A4 were determined by using the prototypical substrates tolbutamide, omeprazole and midazolam, respectively. Cytb5 protein and mRNA contents showed large inter-individual variations with 11- and 6-fold range, respectively. All of three P450s showed an increased activity in proportion to the amount of cytb5 expression. Particularly, CYP3A4 showed the strongest correlation between cytb5 protein amount and the activity, followed by CYP2C9 and CYP2C19. The putative splicing variant, c.288G>A (rs7238987) was identified and was screened in 36 liver tissues by direct DNA sequencing. Liver tissues having a splicing variant exhibited unexpected sizes of cytb5 mRNA and a decreased expression tendency of cytb5 protein compared to the wild-type. A decreased activity in the metabolism of the CYP2C19 substrate omeprazole was observed in liver tissues carrying the splicing variant when compared to the wild-type Cytb5 (P < 0.05). The present results propose that different expression of cytb5 can cause variations in CYP mediated drug metabolism, which may explain, at least in part, the inter-individual difference in drug responses in addition to the CYP genetic polymorphisms.