MN9202在Beagle犬肝微粒体酶中的代谢动力学

目的研究MN9202在Beagle犬肝微粒体酶中的代谢。方法差速离心法制备Beagle犬肝微粒体酶，0.4 μmol·L^-1的MN9202与1.0 g·L^-1的肝微粒体酶在37 ℃水浴中孵育30 min，加入0.5 mL碱化液终止反应，然后采用RP-HPLC法测定孵育液中MN9202原形药物的浓度。根据所测浓度与反应速度做Lineweave-Brurk双倒数曲线，推导出药物的米氏常数K_m和最大反应速度V_max,并计算机体内在清除率。同时观察不同浓度和不同种类的人肝微粒体酶(CYP450)抑制剂对MN9202代谢的影响。结果MN9202在Beagle犬肝微粒体酶中的K_m为(22.6±8.0) μmol·L^-1；V_max为(0.54±0.17) μmol·g^-1·min^-1；CL_int为(0.024 2±0.000 9) L·g^-1·min^-1。醋竹桃霉素(Tro)和酮康唑(Ket)能够显著抑制MN9202的代谢；反苯环丙胺(Tra)对MN9202的代谢也有一定的抑制作用，而其他CYP450抑制剂对MN9202的代谢无明显影响。结论CYP3A和CYP2C19参与了MN9202的代谢，人CYP3A和CYP2C19的抑制剂可能使MN9202的代谢受到抑制，造成药物的药效或毒性的增加。     

利福平及异烟肼对家兔体内地西泮药代动力学的影响

用HPLC测定方法,研究了家兔多次ig利福平(100mg·kg^-1·d^-1×4)及异烟肼(50mg·kg^-1×4)后,对iv地西泮的药代动力学。结果表明,给药后利福平组肝微粒体细胞色素P-450含量增加98.1%,使地西泮的T_1/2β由98.77±19.38min减少到40.08±17.75min;AUC由143.52±41.41mg·min·L^-1减少到79.10±11.46mg·min·L^-1;CL由22.41±8.12ml·min^-1·kg^-1增加到43.96±10.38ml·kg^-1·min^-1。异烟肼组则表现出相反的作用。而利福平与异烟肼合用组对P-450含量及地西泮的动力学均无显著影响。提示利福平诱导家兔肝药酶的作用可加速地西泮的体内代谢过程,异烟肼抑制肝药酶减低地西泮的代谢。     

用β-escin穿孔膜片技术研究粉防己碱对豚鼠心室肌钙电流的作用

目的用β-escin穿孔膜片(PPR)技术研究粉防己碱(tetrandrine,Tet)对I_Ca,L和I_Ca,T的作用。方法用PPR和全细胞记录(WCR)模式记录心室肌细胞I_Ca,L和I_Ca,T。结果25 μmol·L^-1 β-escin可在心室肌细胞形成稳定的PPR模式,用此模式记录的I_Ca,L衰减明显减慢。在PPR模式下1～300 μmol·L^-1 Tet浓度依赖性地减小I_Ca,L幅值。3,30和300 μmol·L^-1 Tet对I_Ca,T的抑制率分别为(16±5)%,(40±7)%和(75±11)%。结论用25 μmol·L^-1 β-escin在豚鼠心室肌细胞能得到较稳定的PPR模式,在此模式下Tet浓度依赖性地抑制I_Ca,L和I_Ca,T。     

III类抗心律失常药RP58866对豚鼠及犬内向整流及瞬时外向钾电流的作用

目的:研究III类抗心律失常药RP58866 对I_K1 ,瞬时外向钾电流(Ito) 的作用。方法:用豚鼠和犬离体心肌细胞及全细胞电压钳技术。结果:在- 100 m V 时,RP58866 以浓度依赖方式明显减少了豚鼠心室肌细胞I_K1,其IC₅₀为(3-4±0-8) μmol·L^-1。在犬心室肌细胞,RP58866 可明显抑制Ito( 在100 μmol·L^-1 时减少87% ±2-1% ),其IC₅₀为(2-3±0-5) μmol·L^-1 。结论:RP58866 对心肌细胞的IK1 和Ito 均有抑制作用,而不是一种特殊的IK1抑制剂。     

苄基四氢巴马汀对豚鼠心室肌细胞快激活延迟整流钾电流的作用

目的研究苄基四氢巴马汀(BTHP)对心室肌细胞快激活(I_kr)延迟整流钾电流的作用。方法 用全细胞膜片钳技术记录豚鼠心室肌细胞钾离子通道电流。结果BTHP在1～100 μmol·L^-1以浓度依赖性方式阻滞I_kr,其IC₅₀为13.5 μmol·L^-1(95%可信范围:11.2～15.8 μmol·L^-1)。30 μmol·L^-1 BTHP可使I_kr及I_kr,tail分别降低(31±4)%和(36±5)% (N=6,P<0.01)。与多数III类抗心律失常药物不同,BTHP可频率依赖性地抑制I_kr。该药主要改变I_kr的失活过程,可使I_kr的失活时间常数(τ)从(238±16) ms降至(196±14) ms,而对I_kr的激活动力学影响不大。结论BTHP对I_kr有明显的抑制作用,且其阻滞作用呈现频率依赖性特征。     

银杏叶提取物对低氧复氧、H2O2和谷氨酸损伤时谷氨酸引起的大鼠星形胶质细胞［Ca2+］i变化的影响

目的研究银杏叶提取物对低氧复氧、H₂O₂和L-谷氨酸损伤时谷氨酸升高大鼠星形胶质细胞［Ca²⁺］_i的影响。方法钙荧光探针Fluo-3/AM标记胞浆内游离钙离子，激光扫描共聚焦显微镜测定［Ca²⁺］_i的变化。结果 在低氧复氧、H₂O₂以及高浓度的L-谷氨酸损伤后，外源性谷氨酸（27 μmol·L^-1）均不能引起培养乳大鼠星形胶质细胞正常的［Ca²⁺］_i升高，反而使［Ca²⁺］_i分别降低(3.3±1.6)%，(81±11)%和(81±7)%；损伤前预先给予GbE（10 mg·L^-1）不能明显改善星形胶质细胞的谷氨酸反应，但预先给予GbE（100 mg·L^-1）后，27 μmol·L^-1谷氨酸可使损伤的星形胶质细胞［Ca²⁺］_i分别升高(135±98)%，(117±93)%和(89±36)%。结论低氧复氧、H₂O₂以及高浓度的L-谷氨酸均能损伤星形胶质细胞的谷氨酸反应，影响神经细胞与胶质细胞的双向交流。GbE能明显逆转不同损伤后谷氨酸诱导星形胶质细胞［Ca²⁺］_i的异常变化，使星形胶质细胞在不同损伤时能维持正常功能，该作用可能与GbE的脑保护作用有关。     

中国人肝微粒体体外代谢奥美拉唑的酶促反应动力学

采用中国成人肝微粒体建立了体外孵育代谢奥美拉唑的酶促反应,应用反相HPLC法测定孵育体系中奥美拉唑的两种主要代谢物羟奥美拉唑和奥美拉唑砜的含量。该方法灵敏度高、简便、快速、可靠。实验结果表明,人肝微粒体主要通过羟化和S原子氧化代谢奥美拉唑。其羟化反应的最大反应速率(Vmax)和米氏常数(Km)分别为42.90 nmol·min^-1·mg^-1和6.49μmol·L^-1,而S原子氧化代谢为6.63nmol·min^-1·mg^-1和11.80μmol·L^-1。消旋美芬妥英、地西泮、去甲西泮及罂粟碱对奥美拉唑体外代谢的实验结果表明,上述药物对奥美拉唑的羟化代谢均有不同程度的抑制作用,其中美芬妥英、地西泮、去甲西泮为奥美拉唑羟化代谢的竞争性抑制剂,罂粟碱为反竞争性抑制剂。同时,这4种药物对奥美拉唑的S原子氧化代谢亦有一定的影响。     

马蔺子素的单扫描示波极谱法测定

目的建立测定马蔺子素的极谱法。方法单扫描示波极谱法。结果在8.0×10^-3 mol·L^-1 Na₂B₄O₇-1.6×10^-2 mol·L^-1 KH₂PO₄ (pH 7.7)支持电解质中,马蔺子素有一灵敏的极谱还原波,其峰电位E_p=-1.23 V(vs SCE),二阶导数峰电流i_p″与马蔺子素浓度为1.5×10^-7～5.2×10^-6 mol·L^-1呈良好线性关系(γ=0.9992,N=9),检出限为6.0×10^-8 mol·L^-1。13次测量2.0×10^-6 mol·L^-1马蔺子素还原波二阶导数峰峰电流,相对标准偏差RSD为0.87%。结论该方法灵敏、简便、快速,可用于原料药及胶囊中马蔺子素含量的测定。     

非手性与手性色谱法研究尼莫地平及其对映体在大鼠体内的药代动力学及组织分布

目的研究尼莫地平及其对映体在大鼠体内药代动力学及组织分布特性。方法生物样品在碱性条件下,经正己烷-醋酸乙酯(1∶1)提取。非手性色谱分析用ODS柱(150 mm×4.6 mm ID),以甲醇-水(70∶30)为流动相;手性色谱分析用Chiralcel OJ柱(250 mm × 4.6 mm ID),以正己烷-无水乙醇(85∶15)为流动相;检测波长为236 nm。结果尼莫地平及其对映体分别在非手性及手性色谱系统中分离良好,在血浆及组织匀浆液中线性关系、最低检测限、精密度和准确度均满足分析要求。对映体间主要药动学参数T_max,C_max,AUC和CL_s,S-(-)-尼莫地平为:(2.1±0.3) h,(197±5) μg·L^-1,(656±18) μg·h·L^-1和(0.30±0.03) mL·min^-1,r-(+)-尼莫地平为:(1.7±0.5) h,(128±4)μg·L^-1,(381±8) μg·h·L^-1和(0.53±0.03) mL·min^-1;在主要的效应器官中S-(-)-尼莫地平的浓度高于r-(+)-尼莫地平,在主要消除器官中r-(+)-尼莫地平浓度高于S-(-)-尼莫地平的浓度。结论尼莫地平对映体在大鼠体内药代动力学及组织分布存在着立体差异性。     

氮烯乙茶在大鼠、犬、猴肝亚细胞成分中的生物转化

目的:利用肝亚细胞成分研究I类抗癌新药氮烯乙茶的生物转化及其种属差异。方法:以高效液相色谱法检测肝9 000 ×g 上清液(S-9) 和微粒体中氮烯乙茶及其代谢产物的浓度。结果:大鼠、犬、猴肝S-9中氮烯乙茶的固有清除率(CL_int) 分别为14-9,10-4,30-4 μL·min^-1·mg^-1 protein,代谢产物为7-乙基-8-氨基茶碱(7-ethyl-8-aminotheophylline,EAT),氮烯乙茶在肝的生物转化部位在微粒体。结论:预计氮烯乙茶在生物转化途径上的种属差异较小;肝亚细胞成分是研究药物代谢及种属差异的较好体外模型。     

五味子甲素对大鼠肝微粒体CYP3A活性的影响

目的：通过体外药物代谢实验探讨五味子甲素对CYP3A活性的影响。方法：以大鼠肝微粒体为载体,选取咪达唑仑（MDZ）作为药物“探针”,建立高效液相色谱（HPLC）检测方法,体外给药测定五味子甲素对MDZ的IC50值以及相关酶动力学参数。结果：孵育体系内源性物质不干扰测定,方法快捷、稳定、灵敏度高。在肝微粒中,五味子甲素对MDZ的IC50浓度为6．26μmol／mL,相关酶动力学参数：Km=15．77μmol／L,Ki=5．50μmol／mL。结论：五味子甲素对大鼠肝微粒体CYP3A活性具有抑制作用,其抑制作用为混合型,即：非竞争与反竞争抑制。     

染料木黄酮在雌雄大鼠肝微粒体中的代谢差异

目的研究染料木黄酮在♀、♂大鼠肝微粒体中的代谢差异。方法制备♀、♂大鼠肝微粒体,确定染料木黄酮代谢的酶动力学条件,分别用CYP1A2抗体和选择性CYP1A2抑制剂呋喃茶碱与大鼠肝微粒体和染料木黄酮共同温孵,测定染料木黄酮在♀、♂大鼠肝微粒体中的代谢速率,评价♀、♂大鼠CYP1A2的相对百分比活性。结果在CYP1A2抗体浓度为1∶400,孵育时间为30 m in条件下,♂大鼠肝微粒体代谢染料木黄酮的相对代谢率为(20.95±2.13)%,♀动物为(13.73±1.26)%。在选择性CYP1A2抑制剂呋喃茶碱浓度为3.125μmol.L-1,孵育时间为30 m in条件下,♂动物为(58.02±3.35)%,而♀大鼠肝微粒体代谢染料木黄酮的相对代谢率为(43.82±2.65)%,两者之间差异有显著性(P<0.01)。结论染料木黄酮在♂大鼠肝微粒体中代谢较♀大鼠快,提示♂大鼠肝微粒体CYP1A2酶活性高于♀大鼠。     

五味子甲素对大鼠肝微粒体CYP3A活性的影响

目的：通过体外药物代谢实验探讨五味子甲素对CYP3A活性的影响。方法：以大鼠肝微粒体为载体,选取咪达唑仑（MDZ）作为药物“探针”,建立高效液相色谱（HPLC）检测方法,体外给药测定五味子甲素对MDZ的IC50值以及相关酶动力学参数。结果：孵育体系内源性物质不干扰测定,方法快捷、稳定、灵敏度高。在肝微粒中,五味子甲素对MDZ的IC50浓度为6．26μmol／mL,相关酶动力学参数：Km=15．77μmol／L,K1=5．50μmol／mL。结论：五味子甲素对大鼠肝微粒体CYP3A活性具有抑制作用,其抑制作用为混合型,即：非竞争与反竞争抑制。     

氟他胺在大鼠肝微粒体经细胞色素P450 1A2代谢的性别差异

目的体外研究大鼠肝微粒体细胞色素P450 1A2(CYP1A2)对氟他胺(flutamide Flu)代谢的性别差异影响。方法制备正常♀♂大鼠肝微粒体,用CYP1A2抗体与氟他胺(2 mg·L^-1)共同温孵,测定氟他胺主要代谢产物2-羟基氟他胺(2-hydroxyflutamide, HF)和原药的浓度比(HF/Flu),评价氟他胺在大鼠肝微粒体代谢的性别差异。结果在CYP1A2抗体浓度为1∶400,孵育时间为30 min条件下,氟他胺在♂大鼠肝微粒体中的HF/Flu为(1.5±0.6),而♀动物为(0.9±0.4)。不同性别大鼠肝微粒体对氟他胺的代谢存在性别差异(P<0.01)。结论Flu在♂大鼠肝微粒体中代谢快,而在♀大鼠肝微粒体中代谢较慢。♂大鼠体内的CYP1A2酶活性高于♀大鼠。     

The 1'-hydroxylation of Rac-bufuralol by rat brain microsomes.

The 1'-hydroxylation of rac-bufuralol, which is catalyzed by polymorphic CYP2D6 in humans, was studied in brain microsomes from male and female Wistar rats and from the female Dark Agouti rat, a model of the CYP2D6 poor metabolizer phenotype. The kinetics of the 1'-hydroxylation of bufuralol (1-1500 microM) by brain microsomes were biphasic. The activity of the high-affinity site of metabolism was consistent with Michaelis-Menten kinetics (apparent K(m1) = 0. 61-1.42 microM, V(max1) = 4.3-4.8 fmol/min/mg of protein), whereas the low-affinity activity was better described by a Hill function (K(50%(2)) = 253-258 microM, V(max2) = 817-843 fmol/min/mg of protein, n = 1.2-1.3). Values for kinetic constants were similar in all rat strains. Quinine was only a weak inhibitor of both the high- (apparent K(i) = 90 microM) and low-affinity (210 microM) sites of metabolism. In contrast, the kinetics of 1'-hydroxylation of bufuralol by rat liver microsomes were best described by a two-site Michaelis-Menten function. V(max) values were 3 to 5 orders of magnitude greater compared with those for brain microsomes (male and female Wistar), and liver microsomes from female Dark Agouti rats were significantly less active than those from Wistar rats. These data, together with the known potent inhibitory effect of quinine on bufuralol 1'-hydroxylation by rat liver microsomes, indicate tissue-specific differences in the enzymology of this reaction. The role of brain CYP2D enzymes remains to be clarified.     

CYP3A catalyses schizandrin biotransformation in human,minipig and rat liver microsomes

1. Schizandrin is recognized as the major absorbed effective constituent of Fructus schisandrae, which is extensively applied in Chinese medicinal formula. The present study aimed to profile the phase I metabolites of schizandrin and identify the cytochrome P450 (CYP) isoforms involved.

2. After schizandrin was incubated with human liver microsomes, three metabolites were isolated by high-performance liquid chromatography (HPLC) and their structures were identified to be 8(R)-hydroxyl-schizandrin, 2-demethyl-8(R)-hydroxyl-schizandrin, 3-demethyl-8(R)-hydroxyl-schizandrin, by liquid chromatography-mass spectrometry (LC-MS), ¹H-nuclear magnetic resonance (NMR), and ¹³C-NMR, respectively. A combination of correlation analysis, chemical inhibition studies, assays with recombinant CYPs, and enzyme kinetics indicated that CYP3A4 was the main hepatic isoform that cleared schizandrin. Rat and minipig liver microsomes were included when evaluating species differences, and the results showed little difference among the species.

3. In conclusion, CYP3A4 plays a major role in the biotransformation of schizandrin in human liver microsomes. Minipig and rat could be surrogate models for man in schizandrin pharmacokinetic studies. Better knowledge of schizandrin’s metabolic pathway could provide the vital information for understanding the pharmacokinetic behaviours of schizandrin contained in Chinese medicinal formula.

     

大豆苷元在人肝微粒体中的单羟化代谢机制大豆苷元在人肝微粒体中的单羟化代谢机制

目的探讨大豆苷元在人肝微粒中羟基化代谢所涉及的肝细胞色素P450(CYP)同工酶，为研究其在人体内的代谢提供基础。方法通过分析大豆苷元在肝微粒体中和重组CYP酶中形成的单羟化代谢物的酶促动力学,分析其酶学模型，然后用不同CYP同工酶选择性抑制剂或底物进行抑制实验，初步筛选出介导大豆苷元单羟化代谢所涉及的CYP同工酶。结果代谢物的形成动力学符合米氏方程单酶模型。CYP1A2选择性抑制剂呋喃茶碱和CYP1A2单克隆抗体均能明显抑制3种单羟化代谢物的形成。而其他CYP选择性的抑制剂对3种代谢物的形成没有或较小产生抑制作用。用重组酶实验得出相同结果。结论体外肝微粒体研究表明，大豆苷元的单羟基代谢主要由CYP1A2所介导。     

Identification of cytochrome P4503A as the major subfamily responsible for the metabolism of roquinimex in man

1. Roquinimex, a novel immunomodulator, is metabolized in liver microsomes from mouse and rat via cytochrome P450s to four hydroxylated and two demethylated metabolites (R1-6). The study investigated which cytochrome P450 enzyme(s) is responsible for the metabolism of roquinimex in man. 2. Enzyme kinetic analysis demonstrated an apparent Km = 1.28-7.00 mM and Vmax = 50-159 pmol x mg(-1) microsomal protein x min(-1) for the primary metabolites in human liver microsomes. The sum of Cl(int) for the primary pathways was 0.167 microl x mg(-1) microsomal protein x min(-1). 3. A correlation between the formation rate of R1-6 and 6beta-hydroxylation of testosterone was obtained within a panel of liver microsomes from 11 individuals (r2 = 0.72-0.97). Furthermore, significant inhibition (>90%) of roquinimex primary metabolism was demonstrated by ketoconazole and troleandomycin, specific inhibitors of CYP3A4 as well as with anti-CYP3A4 antibodies. Moreover, a similar metabolite pattern was produced from roquinimex by incubation with cDNA-expressed CYP3A4 as by human liver microsomes. 4. In conclusion, these data indicate a major role for CYP3A4 in the formation of roquinimex primary metabolites in human liver microsomes.     

Metabolism of dipropyl disulfide by rat liver phase I and phase II enzymes and by isolated perfused rat liver.

The metabolism of dipropyl disulfide (DPDS), an Allium sulfur compound, was investigated in rat liver cell subfractions and in an isolated perfused rat liver. DPDS is oxidized to dipropyl thiosulfinate (DPDSO) by rat microsomes. The contribution of cytochrome P450 enzymes (CYPs) or flavin-containing monooxygenases (FMO) to the formation of DPDSO from its precursor was investigated. In rat microsomes, the reaction followed Michaelis-Menten kinetics with a K(m) = 0.52 +/- 0.1 mM and a V(max) = 5.91 +/- 0.5 nmol/min/mg of protein, respectively (mean +/- S.E., n = 4). Both FMOs and CYPs were involved in DPDS oxidation, although the contribution of CYPs was predominant. Liver microsomes from phenobarbital-treated rats showed a 3.2-fold increase in the rate of formation of DPDSO. Among many CYP isoform-specific inhibitors, only CYP2B1/2 inhibitors decreased the formation of DPDSO and the best correlation between the rate of DPDS oxidation with specific monooxygenase activities was found with a marker of CYP2B1/2 activity. The action of phase II enzymes on DPDS metabolism was studied by incubating DPDS or DPDSO with liver cytosols or microsomes. Two metabolites were formed from DPDS: propylglutathione sulfide conjugate and propylmercaptan, whereas with DPDSO, only the glutathione conjugate was observed. No conjugate compound was detected in the presence of UDP-glucuronyl transferases. When isolated rat liver was perfused with DPDS, different metabolites were obtained in the output and in the liver tissues: propylmercaptan appeared in the output, whereas methylpropyl sulfide, methylpropyl sulfone, and propylglutathione sulfide were detected in the liver tissue.