速效救心丸对大鼠体内CYP450酶活性影响的研究

目的采用Cocktail探针药物法研究速效救心丸对大鼠体内药物代谢酶CYP2E1和CYP3A4的影响,为临床用药提供参考。方法 Wistar大鼠,随机分为,①实验组:灌胃给予速效救心丸(给药体积0.5mL/100g,给药剂量64.8mg·kg-1);②对照组:灌胃给予等体积的纤维素钠混悬液。采用高效液相色谱法(HPLC)测定探针底物氯唑沙宗和咪达唑仑的血药浓度,计算其药代动力学参数,考察大鼠体内CYP2E1及CYP3A4酶的活性。结果实验组氯唑沙宗的代谢无显著性差异,咪达唑仑的代谢明显减慢。结论速效救心丸对大鼠的CYP2E1酶活性无明显影响,对CYP3A4酶活性有抑制作用。     

酒精性肝损伤大鼠细胞色素P450 CYP2E1和细胞色素P450 CYP3A的代谢活性

目的观察酒精性肝损伤对大鼠细胞色素P450CYP3A(CYP3A)和细胞色素P450CYP2E1(CYP2E1)代谢活性的影响。方法采用ig给予白酒制备大鼠酒精性肝损伤模型,检测血清中谷丙转氨酶(GPT)和谷草转氨酶(GOT)活性,采用HE染色法光镜下观测酒精对肝脏损伤程度。大鼠ip给予CYP3A探针药物咪达唑仑10mg·kg-1或ig给予CYP2E1探针药物氯唑沙宗50mg·kg-1后,采用高效液相色谱法测定不同时间点大鼠血浆中咪达唑仑和氯唑沙宗的血药浓度,并应用3P87软件计算其药代动力学参数,以考察CYP2E1和CYP3A的代谢活性的变化。大鼠ig给予氯唑沙宗80mg·kg-1后,热板方法测定大鼠添足次数和添足反射潜伏期。结果酒精性肝损伤可致大鼠肝小叶结构不清,肝索排列紊乱,肝细胞体积增大,呈弥漫性中度水变性,肝窦受压,大部分肝细胞胞浆内见大小不等的脂肪空泡;与正常对照组相比,酒精性肝损伤组大鼠GPT和GOT活性分别增加了16.0%和20.0%(P<0.05,P<0.01)。酒精性肝损伤致大鼠CYP2E1对探针药物氯唑沙宗的代谢活性增强,AUC,t1/2和cmax分别降低了38.0%,30.5%和35.0%(P<0.05);酒精肝损伤组大鼠氯唑沙宗镇痛效果明显降低;酒精性肝损伤致大鼠CYP3A对探针药物咪达唑仑的代谢活性增强,AUC,t1/2和cmax分别降低了122.6%,54.9%和56.9%(P<0.01,P<0.05)。结论酒精性肝损伤可使大鼠CYP2E1和CYP3A代谢活性增强。     

丹参-红花药对配伍前后对大鼠肝药酶亚型CYP1A2、CYP2E1和CYP3A4活性的影响

目的 研究丹参、红花药对配伍前后对大鼠肝药酶亚型CYP1A2、CYP2E1和CYP3A4活性的影响。方法 分别选用咖啡因、氯唑沙宗和咪达唑仑作为CYP1A2、CYP2E1和CYP3A4的探针药物。将大鼠随机分为4组,即空白对照组、丹参（1.2 g生药/kg）组、红花（0.4 g生药/kg）组、丹参（1.2 g生药/kg）+红花（0.4 g生药/kg）组,按上述剂量ig给药7 d。于末次给药后30 min,尾iv探针药物咖啡因、氯唑沙宗和咪达唑仑溶液,在不同的时间点取血进行检测;以甲硝唑为内标,采用HPLC法检测探针药物咖啡因、氯唑沙宗和咪达唑仑的量,评价各药物组对大鼠CYP3A4、CYP2E1和CYP1A2活性的影响。结果 与空白对照组比较,丹参组咖啡因、氯唑沙宗和咪达唑仑的清除率（CL）有所增强,曲线下面积（AUC）减少,其半衰期（t_1/2）有减少趋势,但差异均不显著;红花组咖啡因和氯唑沙宗的CL有所降低,但差异不显著,咪达唑仑的CL显著降低（P<0.01）,氯唑沙宗的AUC增加,但差异不显著,咖啡因和咪达唑仑的AUC明显增加（P<0.05、0.01）;丹参+红花组咖啡因和氯唑沙宗的CL明显降低（P<0.05）,曲线下面积（AUC）明显增加（P<0.05）,其t_1/2有延长趋势,但差异不显著。结论 丹参、红花配伍后对CYP450亚型CYP1A2和CYP2E1有抑制作用,这可能是丹参、红花配伍协同增效的作用机制之一。     

混合探针法评价白香丹胶囊对大鼠体内CYP450酶活性的影响

目的：建立同时测定大鼠血浆中6种CYP450探针药物的方法,并采用Cocktail法研究白香丹胶囊对大鼠CYP450酶活性的影响。方法：选用茶碱（CYP1A2）、氯唑沙宗（CYP2E1）、甲苯磺丁脲（CYP2C6）、右美沙芬（CYP2D2）、奥美拉唑（CYP2D1）、咪达唑仑（CYP3A2）作为探针药物。大鼠随机分为对照组和给药组,给药组每天灌胃白香丹胶囊0.675 g·kg-1,对照组灌胃等量生理盐水,连续给药14 d。第15天均灌胃给予6个探针药物,于不同时间点眼眶取血,采用LC-MS/MS法测定各探针药物浓度,计算药动学参数并进行组间t检验。结果：与对照组相比,给药组茶碱（P<0.01）、氯唑沙宗（P<0.01）、甲苯磺丁脲（P<0.05）代谢显著加快;右美沙芬、奥美拉唑、咪达唑仑代谢无显著性差异。结论：白香丹胶囊对大鼠 CYP1A2有中强诱导作用,对CYP2E1、CYP2C6有弱诱导作用。     

Cocktail法评价白香丹胶囊对大鼠体内CYP450酶活性的影响

目的：建立同时测定大鼠血浆中6种CYP450探针药物的方法,并采用Cocktail法研究白香丹胶囊对大鼠CYP450酶活性的影响。方法：选用茶碱(CYP1A2)、氯唑沙宗(CYP2E1)、甲苯磺丁脲(CYP2C6)、右美沙芬(CYP2D2)、奥美拉唑(CYP2D1)、咪达唑仑(CYP3A2)作为探针药物。大鼠随机分为对照组和给药组,给药组每天灌胃白香丹胶囊0.675 g?kg-1,对照组灌胃等量生理盐水,连续给药14天。第15天均灌胃给予6个探针药物,于不同时间点眼眶取血,采用LC-MS/MS法测定各探针药物浓度,计算药动学参数并进行组间t检验。结果：与对照组相比,给药组茶碱(P < 0.01)、氯唑沙宗(P < 0.01)、甲苯磺丁脲(P < 0.05)代谢显著加快,右美沙芬、奥美拉唑、咪达唑仑代谢无显著性差异。结论：白香丹胶囊对大鼠CYP1A2有中强诱导作用,对CYP2E1、CYP2C6有弱诱导作用。     

豆腐果苷对人肝微粒体CYP450酶体外抑制作用研究

目的:通过评价豆腐果苷在体外对人肝微粒体CYP450酶的7种亚型酶活性的影响,预测服用豆腐果苷可能出现的食物-药物及药物-药物代谢的影响。方法:将豆腐果苷与CYP450酶7种亚型的特异性探针底物咖啡因(CYP1A2)、右美沙芬(CYP2D6)、甲苯磺丁脲(CYP2C9)、S-美芬妥因(CYP2C19)、氯唑沙宗(CYP2E1)、香豆素(CYP2A6)及咪达唑仑(CYP3A4)与人肝微粒体进行孵育反应,采用HPLC和LC-MS/MS法测定对应的7种代谢产物(1,7-二甲基黄嘌呤、去甲右美沙芬、4-羟基甲苯磺丁脲、4-羟基美芬妥因、6-羟基氯唑沙宗、7-羟基香豆素和1-羟基咪达唑仑)的浓度,与对照组比较,确定豆腐果苷对以上7种亚酶活性的影响。结果:豆腐果苷在1～100μmol.L-1时对7种酶的抑制作用均无明显统计学意义(P>0.05)。结论:豆腐果苷可能不会引起有临床意义的CYP450酶抑制现象的发生。     

Cocktail探针药物法评价胃炎灵颗粒对大鼠体内CYP450活性的影响

目的研究胃炎灵颗粒对大鼠体内细胞色素P450酶活性的影响。方法分别以右美沙芬(CYP2D6)、咪达唑仑(CYP3A4)、奥美拉唑(CYP2C19)、茶碱(CYP1A2)、氯唑沙宗(CYP2E1)和甲苯磺丁脲(CYP2C9)作为探针底物,大鼠6只,每日灌胃胃炎灵颗粒4 g/kg,采用LC-MS/MS测定给药前后大鼠体内6种探针药物的血药浓度。结果胃炎灵颗粒连续给药10 d后,与给药前相比,大鼠体内的右美沙芬(P <0. 01)、甲苯磺丁脲(P <0. 01)代谢减慢,氯唑沙宗(P <0. 01)代谢加快,奥美拉唑、咪达唑仑、茶碱的代谢无显著差异。结论胃炎灵颗粒在大鼠体内对CYP2D6酶产生中强抑制作用,对CYP2C9酶产生弱抑制作用,对CYP2E1酶产生轻微诱导作用,对CYP3A4、CYP2C19和CYP1A2基本没有影响。     

HPLC 法同时测定大鼠血浆中 CYP450酶探针药物氯唑沙宗、甲苯磺丁脲和咪达唑仑浓度

目的：建立同时测定大鼠血浆中细胞色素 P450（CYP450）酶探针药物氯唑沙宗、甲苯磺丁脲和咪达唑仑浓度的高效液相色谱法。方法色谱柱采用 Diamonsil C18（250 mm ×4．6 mm,5μm）,流动相为甲醇与磷酸二氢铵缓冲液（61∶39,V ／V）,流速1 mL·min －1,检测波长230 nm,带宽4 nm,柱温35℃,以地西泮为内标,同时检测氯唑沙宗、甲苯磺丁脲和咪达唑仑的大鼠血浆药物浓度。结果氯唑沙宗、甲苯磺丁脲和咪达唑仑均在0．1～50 mg·L －1（r ＝0．9995）的范围内线性关系良好;低、中、高3个浓度下,3种探针药物精密度试验中相对标准偏差为4．78％～9．78％,回收率为92．71％～109．79％。结论该方法操作简便,灵敏度高,重现性好,符合生物样品分析要求,适用于同时测定3种 CYP450酶亚型探针药物氯唑沙宗、甲苯磺丁脲和咪达唑仑的大鼠血浆药物浓度,可为 CYP450酶活性测定提供分析方法学参考。     

无梗五加果实提取物对大鼠CYP450活性的影响

目的研究无梗五加果实提取物对大鼠CYP450亚型CYP1A2、CYP2C19、CYP2E1、CYP3A4活性的影响。方法以咖啡因、奥美拉唑、氯唑沙宗和咪达唑仑作为CYP1A2、CYP2C19、CYP2E1和CYP3A4特异性探针药物,配制cocktail混合探针溶液,建立同时测定4种探针药物血药浓度的高效液相色谱法。将SD大鼠随机分为无梗五加果实70%乙醇提取物组、水提取物组和对照组,每天分别ig无梗五加果实70%乙醇提取物溶液、水提取物溶液和溶剂10 mL/kg,连续给药1周,于第8天ip混合探针药物10 mL/kg,分别在给药0、0.083、0.25、0.417、0.583、0.833、1、2、3、5、8、11、12 h于大鼠眼眶静脉丛采血,采用HPLC法对血浆样品进行分析,对给药组和对照组探针药物的药动学参数生物半衰期(t_(1/2))进行比较。结果与对照组比较,无梗五加果实水提取物组和70%乙醇提取物组咖啡因、咪达唑仑的t_(1/2)显著降低,奥美拉唑、氯唑沙宗的t_(1/2)显著增加,差异均具有统计学意义(P0.05、0.01)。结论无梗五加果实70%乙醇提取物和水提取物对大鼠的CYP2C19、CYP2E1有抑制作用,对大鼠的CYP1A2、CYP3A4有诱导作用。     

五味子甲素对CYP3A活性的影响及其体内外相关性研究

目的:通过"探针"法探讨五味子甲素体内、外对大鼠肝微粒体CYP3A活性的影响及其相关性。方法:选取咪达唑仑作为CYP3A探针,用高效液相色谱法测定五味子甲素体外孵育给药和体内灌胃给药后大鼠肝微粒体酶CYP3A活性,通过药动学参数K_m确定其体内、外作用的相关性。结果:体外试验结果表明,五味子甲素非竞争性抑制咪达唑仑的代谢,其K_i为5.5μmol·L^-1,体内试验亦证实了五味子甲素能显著抑制肝微粒体CYP3A酶活性（P<0.01）并呈剂量依赖性,其体内给药的K_i值为30.67 mg·kg^-1。体内外K_m值十分接近。结论:五味子甲素在体内和体外均可非竞争性抑制大鼠肝微粒体酶CYP3A活性,其对CYP3A影响的体内、体外结果具有良好的相关性。     

Molecular modelling of CYP1 family enzymes CYP1A1, CYP1A2, CYP1A6 and CYP1B1 based on sequence homology with CYP102

Molecular modelling of a number of CYP1 family enzymes from rat, plaice and human is described based on amino acid sequence homology with the haemoprotein domain of CYP102, a unique bacterial P450 of known structure. The interaction of various substrates and inhibitors within the putative active sites of rat CYP1A1, human CYP1A2, a fish CYP1 enzyme CYP1A6 (from plaice) and human CYP1B1, is shown to be consistent with P450-mediated oxidation in each example or, in the case of inhibitors, mechanism of inhibition. It is reported that relatively small changes between the enzymes' active site regions assist in the rationalization of CYP1 enzyme preferences for particular substrate types, and a template of superimposed CYP1A2 substrates is shown to fit the putative active site of the human CYP1A2 enzyme.     

Effect of eurycomanone on cytochrome P450 isoforms CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2E1 and CYP3A4 in vitro

Eurycomanone, an active constituent isolated from Eurycoma longifolia Jack, was examined for modulatory effects on cytochrome P450 (CYP) isoforms CYP1A2, CYP2A6, CYP2C8, CYP2C9, CYP2C19, CYP2E1 and CYP3A4 using in vitro assays. The IC₅₀ value was determined to assess the potencies of modulation for each CYP isoform. Our results indicated that eurycomanone did not potently inhibit any of the CYP isoforms investigated, with IC₅₀ values greater than 250 μg/ml. Hence there appears to be little likelihood of drug–herb interaction between eurycomanone or herbal products with high content of this compound and CYP drug substrates via CYP inhibition.     

Pharmacogenomics of CYP2A6, CYP2B6, CYP2C19, CYP2D6, CYP3A4, CYP3A5 and MDR1 in Vietnam

Aim  The aim of this study was to obtain pharmacogenetic data in a Vietnamese population on genes coding for proteins involved in the elimination of drugs currently used for the treatment of malaria and human immunodeficiency virus/acquired immunodeficiency syndrome. Method  The main polymorphisms on the cytochrome P450 (CYP) genes, CYP2A6, CYP2B6, CYP2C19, CYP2D6, CYP3A4 and CYP3A5, and the multi-drug resistance 1 gene (MDR1) were genotyped in 78 healthy Vietnamese subjects. Pharmacokinetic metrics were available for CYP2A6 (coumarin), CYP2C19 (mephenytoin), CYP2D6 (metoprolol) and CYP3As (midazolam), allowing correlations with the determined genotype. Results  In the CYP2 family, we detected alleles CYP2A6*4 (12%) and *5 (15%); CYP2B6*4 (8%), *6 (27%); CYP2C19*2 (31%) and *3 (6%); CYP2D6*4, *5, *10 (1, 8 and 44%, respectively). In the CYP3A family, CYP3A4*1B was detected at a low frequency (2%), whereas CYP3A5 *3 was detected at a frequency of 67%. The MDR1 3435T allele was present with a prevalence of 40%. Allele proportions in our cohort were compared with those reported for other Asian populations. CYP2C19 genotypes were associated to the S-4′-OH-mephenytoin/S-mephenytoin ratio quantified in plasma 4 h after intake of 100 mg mephenytoin. While CYP2D6 genotypes were partially reflected by the α-OH-metroprolol/metoprolol ratio in plasma 4 h after dosing, no correlation existed between midazolam plasma concentrations 4 h post-dose and CYP3A genotypes. Conclusions  The Vietnamese subjects of our study cohort presented allele prevalences in drug-metabolising enzymes that were generally comparable with those reported in other Asian populations. Deviations were found for CYP2A6*4 compared to a Chinese population (12 vs. 5%, respectively; P = 0.023), CYP2A6*5 compared with a Korean population (15 vs. <1%, respectively; P < 0.0001), a Malaysian population (1%; P < 0.0001) and a Chinese population (1%; P < 0.0001); CYP2B6*6 compared with a Korean population (27 vs. 12%; P = 0.002) and a Japanese population (16%; P = 0.021). Pharmacokinetic metrics versus genotype analysis reinforces the view that the predictive value of certain globally common variants (e.g. CYP2D6 single nucleotide polymorphisms) should be evaluated in a population-specific manner.     

Time-dependent CYP inhibition

Time-dependent inhibition (TDI) of CYP refers to a change in potency during an in vitro incubation or dosing period in vivo. Potential mechanisms include the formation of inhibitory metabolites and mechanism-based inhibition (MBI). In vitro experiments are configured to assess TDI and MBI is inferred, at least initially. MBI is more profound after multiple-dosing and the recovery period is independent of continued drug exposure. Advances in in vitro-in vivo extrapolations for competitive inhibition and the potential relationship between MBI and reactive metabolite-mediated toxicity, have redirected emphasis to CYP TDI. In contrast, with reversible inhibition, strategies for projecting the risks from TDI are less developed and the traditional I/K(i) model often yields a dramatic underprediction. This review explores the contribution of TDI to drug-drug interactions and idiosyncratic drug toxicity.     

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.     

CYP3 phylogenomics: evidence for positive selection of CYP3A4 and CYP3A7

OBJECTIVE: CYP3A metabolizes 50% of currently prescribed drugs and is frequently involved in clinically relevant drug interactions. The understanding of roles and regulations of the individual CYP3A genes in pharmacology and physiology is incomplete. METHODS: Using genomic sequences from 16 species we investigated the evolution of CYP3 genomic loci over a period of 450 million years. RESULTS: CYP3A genes in amniota evolved from two ancestral CYP3A genes. Upon the emergence of eutherian mammals, one of them was lost, whereas, the other acquired a novel genomic environment owing to translocation. In primates, CYP3A underwent rapid evolutionary changes involving multiple gene duplications, deletions, pseudogenizations, and gene conversions. The expansion of CYP3A in catarrhines (Old World monkeys, great apes, and humans) differed substantially from New World primates (e.g. common marmoset) and strepsirrhines (e.g. galago). We detected two recent episodes of particularly strong positive selection acting on primate CYP3A protein-coding sequence: (i) on CYP3A7 early in hominoid evolution, which was accompanied by a restriction of its hepatic expression to fetal period and (ii) on human CYP3A4 following the split of the chimpanzee and human lineages. In agreement with these findings, three out of four positively selected amino acids investigated in previous biochemical studies of CYP3A affect the activity and regioselectivity. CONCLUSIONS: CYP3A7 and CYP3A4 may have acquired catalytic functions especially important for the evolution of hominoids and humans, respectively.     

CYP2A13-catalysed coumarin metabolism: comparison with CYP2A5 and CYP2A6

1. We investigated the total metabolism of coumarin by baculovirus (BV)-expressed CYP2A13 and compared it with metabolism by BV-expressed CYP2A6. The major coumarin metabolite formed by CYP2A13 was 7-hydroxycoumarin, which accounted for 43% of the total metabolism. The product of 3,4-epoxidation, o-hydroxyphenylacetaldehyde (o-HPA), accounted for 30% of the total metabolites. 2. The K(m) and V(max) for CYP2A13-mediated coumarin 7-hydroxylation were 0.48+/-0.07 micro m and 0.15+/-0.006 nmol min(-1) nmol(-1) CYP, respectively. The V(max) of coumarin 7-hydroxylation by CYP2A13 was about 16-fold lower than that of CYP2A6, whereas the K(m) was 10-fold lower. 3. In the mouse, there were two orthologues for CYP2A6: CYP2A4 and CYP2A5, which differed by only 11 amino acids. However, CYP2A5 is an efficient coumarin 7-hydroxylase, where as CYP2A4 is not. We report here that BV-expressed CYP2A4 metabolizes coumarin by 3,4-epoxidation. Two products of the 3,4-epoxidation pathway, o-HPA and o-hydroxyphenylacetic acid (o-HPAA), were detected by radioflow HPLC. 4. The K(m) and V(max) for the coumarin 3,4-epoxidation by CYP2A4 were 8.7+/-3.6 micro m and 0.20+/-0.04 nmol min(-1) nmol(-1) CYP, respectively. Coumarin 7-hydroxylation by CYP2A5 was more than 200 times more efficient than 3,4 epoxidation by CYP2A4.     

Genetic polymorphisms of the CYP3A4, CYP3A5, CYP3A7 and CYP1A2 among the Jordanian population

Cytochromes P450 (CYP450) plays an extremely vital role in oxidation, reduction, and peroxidation of numerous endogenous and exogenous compounds, like drugs and procarcinogens. Mainly, expression occurs in the liver, in varying polymorphic forms. Therefore, proposed as biomarkers of susceptibility to carcinogenicity and toxicity. The objective of this study was to find the allelic frequencies of CYP3A5*2,*3,*4,*5,*6,*7, CYP3A4*1B, CYP3A7*1C and CYP1A2*1C, *1D, *1E, *1F enzymes in Jordanians, and to compare them with other ethnic groups. We used polymerase chain reaction-restriction fragment length (PCR-RFLP) to genotype alleles, and we calculated frequencies using Hardy Weinberg's equation (HWE). Allelic frequencies results were: CYP3A5*2 (0.2%), CYP3A5*3 (86.6%), CYP3A5*6 (1.7%), CYP*3A5*4,*5*7 not detected, CYP3A4*1B (11.7%), CYP3A7*1C (1.7%). Finally 6.5%, 18.2%, 6.0%, 67.3% were the results of CYP1A2*1C, 1D, 1E and 1F, respectively. In conclusion, genotyping method and results of this study can be adopted or used in pharmacotherapy, toxicity and carcinogenic studies in Jordan.     

Comparative metabolic capabilities of CYP3A4, CYP3A5, and CYP3A7.

The human cytochromes P450 (P450) CYP3A contribute to the biotransformation of 50% of oxidatively metabolized drugs. The predominant hepatic form is CYP3A4, but recent evidence indicates that CYP3A5 contributes more significantly to the total liver CYP3A than was originally thought. CYP3A7 is the major fetal form and is rarely expressed in adults. To compare the metabolic capabilities of CYP3A forms for 10 substrates, incubations were performed using a consistent molar ratio (1:7:9) of recombinant CYP3A, P450 reductase, and cytochrome b5. A wide range of substrate concentrations was examined to determine the best fit to kinetic models for metabolite formation. In general, K(m) or S(50) values for the substrates were 3 to 4 times lower for CYP3A4 than for CYP3A5 or CYP3A7. For a more direct comparison of these P450 forms, clearance to the metabolites was determined as a linear relationship of rate of metabolite formation for the lowest substrate concentrations examined. The clearance for 1'-hydroxy midazolam formation at low substrate concentrations was similar for CYP3A4 and CYP3A5. For CYP3A5 versus CYP3A4, clearance values at low substrate concentrations were 2 to 20 times lower for the other biotransformations. The clearance values for CYP3A7-catalyzed metabolite formation at low substrate concentrations were substantially lower than for CYP3A4 or CYP3A5, except for clarithromycin, 4-OH triazolam, and N-desmethyl diltiazem (CYP3A5 - CYP3A7). The CYP3A forms demonstrated regioselective differences in some of the biotransformations. These results demonstrate an equal or reduced metabolic capability for CYP3A5 compared with CYP3A4 and a significantly lower capability for CYP3A7.