硝克柳胺在大鼠和人肝脏的体外代谢研究

研究硝克柳胺在大鼠肝微粒体和胞浆中的代谢动力学，鉴定硝克柳胺在大鼠和人肝微粒体中的主要代谢产物及参与代谢的药物代谢酶。采用高效液相色谱-紫外检测(HPLC-UV)方法测定大鼠肝微粒体和胞浆中硝克柳胺浓度，应用选择性抑制剂鉴定参与硝克柳胺代谢的药物代谢酶类型，采用液相色谱-串联质谱联用(LC-MS/MS)法分离鉴定硝克柳胺在大鼠和人肝微粒体中的主要代谢产物。硝克柳胺在大鼠和人肝微粒体的主要代谢产物(M₁)为硝基还原产物［3-(3′-羧基-4′-羟基苯胺羰基)-6-氨基-7-羟基-8-甲基香豆素］，大鼠体内(血浆、尿液、胆汁及肝组织)主要代谢产物与M₁一致。硝克柳胺的体外代谢是依赖多个药物代谢酶参与的酶促反应，包括微粒体CYP450还原酶、细胞色素b₅还原酶和CYP2C6以及胞浆NAD(P)H脱氢酶和黄嘌呤氧化酶。     

雷公藤甲素在大鼠肝微粒体中代谢及酶促反应动力学研究

目的:研究雷公藤甲素在大鼠肝微粒体中代谢及酶促反应动力学。方法:将雷公藤甲素与5种不同诱导剂(地塞米松(DEX)、苯巴比妥(PB)、β-萘黄酮(β-NF)、吡啶(PD))诱导的大鼠肝微粒体进行体外共孵育;并与8种选择性CYP酶抑制剂(酮康唑、醋竹桃霉素、磺胺苯吡唑、二乙基二硫代氨基甲酸酯(盐)、奎尼丁、呋拉茶碱、毛果芸香碱、奥芬那君)在空白肝微粒体中共孵育。采用液相色谱-质谱联用技术测定孵育后剩余雷公藤甲素的含量。结果:酮康唑和醋竹桃霉素能明显抑制雷公藤甲素的代谢;磺胺苯吡唑和奥芬那君对其代谢也有一定抑制作用,但不及酮康唑和醋竹桃霉素。结论:雷公藤甲素在大鼠肝微粒体中代谢主要由CYP3A介导,其次由CYP2C和CYP2B介导。     

去氢厄弗酚在小鼠肝微粒体中代谢产物及CYP450酶亚型的鉴定

目的建立去氢厄弗酚(DHE)小鼠体外肝微粒体孵育方法,鉴定DHE在小鼠肝微粒体中的代谢产物及参与DHE代谢的CYP450酶亚型。方法采用UPLC-Q-TOF-MS/MS分析鉴定DHE在体外肝微粒体共温孵后的代谢产物,筛选7种CYP450酶亚型,并通过特异性化学抑制剂法,鉴别参与DHE代谢的主要CYP450酶亚型。结果在体外肝微粒体共温孵后,检测到4个代谢产物;所筛选的7种CYP450酶亚型中,CYP1A2、CYP2C8和CYP2D2对DHE体外肝微粒体代谢的参与度较高。结论在肝脏中,有多种代谢酶亚型参与DHE的代谢,表明DHE在临床上不易与其他药物产生相互作用。     

比阿培南在人肝微粒体、人肾S9和体外人血浆中的稳定性及其代谢产物鉴定

目的:考察比阿培南在人肝微粒体、人肾S9和体外人空白血浆中的代谢稳定性,并推测代谢产物的结构及可能的代谢途径.方法:采用高效液相色谱-串联质谱联用仪(HPLC-MS/MS)检测比阿培南分别与人肝微粒体、人肾S9和人空白血浆孵育后孵育液中剩余的比阿培南含量,比较代谢稳定性.此外,利用快速液相色谱-离子阱-飞行时间质谱联用...     

白及有效成分Militarine在肝微粒体中的体外代谢途径及其酶促动力学特征

目的:研究白及有效成分Militarine在肝微粒体中的体外代谢途径及其酶促反应动力学特征。方法:建立大鼠和人肝微粒体体外孵育体系,对Militarine进行体外孵育反应;采用超高效液相色谱-四极杆-飞行时间质谱联用技术,结合UNIFI数据库并参考文献对其代谢产物进行结构鉴定。同时,以葛根素为内标,采用超高效液相色谱-三重四极杆串联质谱联用技术对Militarine在大鼠肝微粒体中的代谢转化量进行定量分析,通过GraphPad Prism 5.0软件拟合代谢转化曲线,并计算在有/无还原性辅酶Ⅱ(NADPH)参与的反应条件下的Militarine酶促动力学参数[最大清除速率(v_(max))、米氏常数(k_m)、固有清除率(CL_(int))]。结果:Militarine在大鼠和人肝微粒体中孵育后,生成了1个化学式为C_(21)H_(29)O_(11)的化合物,推测其为Militarine的酯键水解代谢产物。酶促动力学研究显示,有/无NADPH参与的Militarine酶促反应的v_(max)分别为1.955、2.129 nmol/(h·mg),k_m分别为8.601、9.854 nmol/mL,CL_(int)分别为0.227 3、0.216 1 mL/(h·mg),两者无明显差异。结论:Militarine在肝微粒体中的主要代谢途径为C1或C4位酯键的水解;其代谢不依赖于由NADPH启动反应的细胞色素P_(450)酶代谢途径。     

甲基莲心碱在大鼠肝脏中的代谢产物及其途径

大鼠灌胃给予甲基莲心碱 20 mg·kg^-1，采用液相色谱-串联质谱联用法对大鼠肝脏中的代谢产物进行分析；并建立肝微粒体温浴及NADPH再生体系，采用高效液相色谱-紫外检测法研究CYP450亚型的特异性抑制剂对甲基莲心碱体外代谢的影响。在正离子检测方式下，除甲基莲心碱外共检测到4种代谢产物M₁、M₂(主要代谢产物)、M₃和M₄。其中，M₂和M₄通过与对照品的色谱和质谱比对，确认为莲心碱和异莲心碱，而M₁ 和M₃可能为去甲基莲心碱和去甲基异莲心碱。CYP3A1的特异性抑制剂酮康唑和CYP2D1的特异性抑制剂奎尼丁均可抑制甲基莲心碱在肝微粒体温孵液中的代谢，其主要代谢产物莲心碱的生成抑制率分别为25.7%和80.5%。因此提示，甲基莲心碱在肝脏中的主要代谢途径是苄基和喹啉环上的甲氧基脱甲基化，其主要代谢物为莲心碱，CYP2D1和CYP3A1均参与了其生物转化。     

苯环喹溴铵在大鼠肝微粒体中的代谢转化研究

目的:建立检测大鼠肝微粒体中苯环喹溴铵代谢产物的方法,验证其在大鼠体内的代谢途径。方法:采用大鼠肝微粒体体外温孵法,建立液相色谱-质谱法测定并分析肝微粒体中苯环喹溴铵及其代谢物。色谱及质谱条件如下:色谱柱为TSK-gelODS-80Ts,流动相为甲醇-40mmol·L-1的乙酸铵水溶液(含0.1%甲酸)梯度洗脱;正离子模式,扫描型离子检测。结果:在体外代谢系统中,根据质谱碎片信息检测出6个代谢产物,分别是苯环喹溴铵的二羟基、单羟基和氧化产物。结论:建立的液相色谱-质谱法能够准确灵敏地测定大鼠肝微粒体中苯环喹溴铵的代谢产物,验证了在大鼠体内苯环喹溴铵的代谢部位在环戊烷基上。     

倒千里光碱的反应性代谢产物与RNA形成双分子嘌呤共价结合物

目的 研究吡咯里西啶生物碱(pyrrolizidine alkaloids, PAs)中倒千里光碱(retrorsine, RTS)的反应性代谢产物在体外和体内与RNA的相互作用。方法 通过液相色谱-串联质谱法(LC-MS/MS)分析合成反应、肝微粒体孵育和给药RTS的小鼠中腺苷和鸟苷与RTS的反应性代谢产物形成的加合物。结果 在体外合成反应液,肝脏微粒体孵育液和给药RTS的小鼠肝脏组织中检测到了RTS的反应性代谢产物与腺苷和鸟苷形成的双分子嘌呤加合物,体内观察到的所有加合物的生成量呈剂量依赖性,并在给药后2 h达到峰值。结论 首次发现RTS的反应性代谢产物与RNA反应形成RNA双分子加合物,可能是RTS导致肝毒性的重要原因之一。     

基于UPLC-Q-exactive orbitrap-MS法的新型合成大麻素4CN-MDMB-BUTINACA体外代谢研究

为研究新型合成大麻素3,3-二甲基-2-[1-(4-氰基丁基)吲唑-3-甲酰氨基]丁酸甲酯(4CN-MDMB-BUTINACA)的体外代谢产物,本研究通过体外人肝微粒体孵育模型,采用高效液相色谱串联Q exactive质谱检测合成大麻素原形药及其代谢产物。肝微粒体实验发现4CN-MDMB-BUTINACA通过羟基化、酯水解、酯水解加羟基化、戊烷氧化为戊酸反应代谢物和酯水解加戊烷氧化为戊酸反应代谢物等代谢途径共产生7种代谢产物。本研究解析了合成大麻素体外代谢途径及其代谢产物,其中羟基化反应代谢产物(M1-a)、酯水解反应代谢产物(M2)以及戊烷氧化为戊酸反应代谢物(M4)为潜在的代谢标志物。研究结果为合成大麻素4CN-MDMB-BUTINACA的司法鉴定和吸食认定提供技术支撑。     

UPLC-MS/MS快速鉴定乔松素在人肝微粒体中的代谢产物

目的以超高效液相色谱质谱联用法(UPLC-MS/MS)快速鉴定乔松素在人肝微粒体中的代谢产物。方法以人肝微粒体体外孵育体系对乔松素进行代谢研究,以UPLC-MS/MS鉴定乔松素的体外代谢产物。结果建立了乔松素的体外代谢孵育体系,UPLC-MS/MS在6 min内检测到乔松素的4个代谢产物,分别鉴定为柚皮素、5,6,7-三羟基二氢黄酮、5,7,8-三羟基二氢黄酮和乔松素-7-葡萄糖醛酸苷,这4个代谢产物均为首次发现的乔松素人肝微粒体体外代谢产物。结论乔松素在人肝微粒体中的主要代谢途径为羟基化和葡萄糖醛酸化,5,7,8-三羟基二氢黄酮是其主要羟基化产物,乔松素-7-葡萄糖醛酸苷可能为乔松素的主要代谢失活形式。     

Metabolism of 2,4,5,2′,4′,5′-hexachlorobiphenyl (PCB153) in guinea pig

1. The in vitro and in vivo metabolism of 2,4,5,2′,4′,5′-hexachlorobiphenyl (PCB153) in guinea pig has been studied. 2. Seven metabolites were detected in the faeces of PCB153-treated animals and three were identical to those produced by dog liver microsomes. The detection of a metabolite where a chlorine atom was shifted from the 2- to 3-position strongly suggested the involvement of 2,3-arene oxide intermediate, and evidence for the concomitant formation of a 3,4-arene oxide intermediate was provided by identifying other two minor metabolites which were dechlorinated at the 4-position. 3. In vitro studies using liver microsomes from guinea pigs revealed that the 2,3-arene oxide and 3-hydroxylation pathways are the predominant metabolic routes compared with the 3,4-arene oxide pathway. Although the guinea pig is an another species that can metabolize PCB153 mainly to the 2,3-arene oxide intermediate, the rate of formation was only about one-tenth of the dog. 4. These results indicate that the ability to form this unusual 2,3-arene oxide intermediate may not be responsible for high excretion rate of this congener. Our data also suggest that the cytochrome P450-catalysed metabolism of PCB153 in the guinea pig and dog are similar, whereas for post-cytochrome P450 metabolism, the guinea pig resembles the rabbit.     

Specific metabolic pathway in vitro of pinazepam and diazepam by liver microsomal enzymes of different animal species.

The metabolic pathway of Pinazepam and Diazepam in vitro was studied with rat, guinea pig and dog liver microsomes using a chromatographic and spectrophotometric technique. Two main pathways were observed, N1-dealkylation and C3-hydroxylation. N1-dealkylation was shown to be the predominant reaction for Pinazepam in all the animal species studied, while C3-hydroxylation was the major metabolic pathway for Diazepam in the rat. No oxazepam was found when Pinazepam and Diazepam were incubated with liver microsomes.     

Metabolism of benzo[a]pyrene by guinea pig adrenal and hepatic microsomes

Studies were carried out to compare the metabolism of benzo[a]pyrene (BP) by adrenal and hepatic microsomes obtained from adult male guinea pigs. Adrenal microsomes produced fluorescent metabolites (primarily phenols) approximately three to four times more rapidly than hepatic microsomes, but the differences in the rates were considerably smaller when total BP metabolism was assessed using an isotopic assay. The apparent discrepancy between the two assays is attributable to differences in the profiles of BP metabolites produced by adrenal and liver. Separation of metabolites by high pressure liquid chromatography revealed that adrenal microsomes converted BP to primarily a phenolic metabolite with a retention time identical to that of 3-hydroxy-BP. Liver microsomes, by contrast, produced approximately equal amounts of compounds co-chromatographing with 3-hydroxy-BP and BP-4,5-dihydrodiol. Small amounts of other metabolites were also produced by adrenal and hepatic microsomes. Liver microsomes catalyzed the conversion of BP to metabolites that became covalently bound to exogenous DNA. The amount of binding was dependent upon the duration of incubation and concentration of microsomal protein. Adrenal microsomes, by contrast, did not promote BP binding to DNA. Inhibition of microsomal epoxide hydratase activity with trichloropropene oxide (TCPO) blocked the formation of dihydrodiol metabolites of BP by adrenal and liver microsomes. In the presence of TCPO, liver microsomes produced large amounts of a BP metabolite co-chromatographing with BP-4,5-oxide. TCPO also increased the rate of production of DNA-binding roetabolites by liver microsomes but had no effect on the formation of DNA-binding metabolites by adrenal microsomes. The results demonstrate major differences in the pathways of BP metabolism by guinea pig adrenal and hepatic microsomes. Although adrenal microsomes metabolize BP more rapidly than hepatic microsomes, far greater amounts of reactive metabolites are produced by the liver. Thus, adrenal metabolism of BP may be of little toxicological significance.     

Metabolism of prostaglandin E analogs in guinea pig and rat liver microsomes

Tritium-labelled 16,16-dimethyl-PGE2, 9-methylene-PGE2 (9-deoxo-16,16-dimethyl-9-methylene-prostaglandin E2) and tetranor-9-methylene-PGE2 were incubated with guinea pig liver microsomes. All three compounds were converted to omega-oxidized products in yields of a few per cent. In addition, from incubations with 9-methylene-PGE2 and tetranor-9-methylene-PGE2 were also obtained metabolites with the methylene group transformed into a dihydrodiol. In a comparative study with rat liver microsomes, it was found that these converted tetranor-9-methylene-PGE2 in a 50 per cent yield to omega-oxidized products. Finally, 20.000 X G supernatants from guinea pig and rat liver were compared with respect to omega-oxidation. The rat liver 20.000 X G supernatant was found to convert the substrate to the same extent as washed microsomes. By contrast, the guinea pig liver 20.000 X G supernatant was considerably more efficient than washed microsomes.     

Conversion of spironolactone to 7 alpha-thiomethylspironolactone by hepatic and renal microsomes

Recent observations indicate that 7 alpha-thiomethylspironolactone is an important circulating metabolite of the mineralocorticoid antagonist spironolactone (SL). Studies were carried out to determine possible sites and pathways of 7 alpha-thiomethyl-SL formation and, in particular, to evaluate SL metabolism by guinea pig hepatic and renal microsomal preparations. In the absence of S-adenosylmethionine (SAM), liver and kidney microsomes rapidly converted SL to 7 alpha-thio-SL as the only metabolite. The rate of 7 alpha-thio-SL production was greater in liver than kidney. In the presence of SAM, 7 alpha-thio-SL was further converted to 7 alpha-thiomethyl-SL by liver and kidney microsomes. The rates of methylation with 7 alpha-thio-SL as substrate were three to four times greater for liver than for kidney, but the Km values were similar (approximately 30 microM) in the two issues. Maximal enzyme activity was obtained with SAM concentrations of 25-200 microM. NADPH had no effect on SL or 7 alpha-thio-SL metabolism by liver or kidney microsomes. To determine if a pathway involving the C-S lyase enzyme might contribute to circulating 7 alpha-thiomethyl-SL levels in vivo, guinea pigs were treated with SL or its dethioacetylated derivative, canrenone, and plasma metabolites were analyzed by HPLC. Both 7 alpha-thiomethyl-SL and canrenone were found to be circulating metabolites in SL-treated animals, but only canrenone was identified in the plasma of canrenone-treated guinea pigs. The results indicate that the liver and kidney are potential sites of 7 alpha-thiomethyl-SL production and that its formation probably does not involve the C-S lyase pathway.     

Interspecies variability and drug interactions of loxapine metabolism in liver microsomes.

Loxapine is a dibenzoxazepine neuroleptic that is metabolized by the liver in humans. In the present study, we investigated first in vitro loxapine metabolism in liver microsomes from various species including rats, mice, guinea pigs, dogs, rabbits, monkeys and humans. This enables us to choose between species to further validate drug-drug interaction studies. We observed the formation of desmethyl- and hydroxy- metabolites of loxapine after incubation of the different species liver microsomes. Hydroxylation pathway was major in all species. Wide interspecies variability of loxapine metabolism was observed. Loxapine metabolism was similar in human, guinea pig and dog microsomes. We screened in vitro effects of 67 molecules, representative of 8 therapeutic classes, on loxapine metabolism. Loxapine (100 microM) was incubated with guinea pig liver microsomes (1 mg/ml) 30 min at 37 degrees C with and without the presence of interacting drug. We found that most of psychotropics (alimemazine, cyamemazine and levomepromazine), antifungal (ketoconazole), anticancer drugs (daunorubicin, pirarubicin) and analgesic (nefopam) inhibited more than 50% of hydroxyloxapine formation in vitro. Complementary clinical and pharmacokinetic studies should be performed to confirm these results.     

Biotransformation of mianserin in laboratory animals and man.

1. The biotransformation and excretion of the antidepressant mianserin were studied after oral administration of the labelled drug to rats, mice, rabbits, guinea pigs and humans. Mianserin was well absorbed and almost completely metabolized in all five species. 2. Major metabolic pathways of mianserin were p-oxidation of the N-substituted aromatic ring followed by conjugation, and oxidation and demethylation of the N-methyl moiety, followed by conjugation. Direct conjugation of the N-methyl moiety was observed as a metabolic pathway specific for man. 3. Conjugated metabolites were isolated by h.p.l.c. and identified by 1H-n.m.r. and FAB spectrometry. Novel metabolites such as an N-O-glucuronide in the guinea pig and an N-sulphonate in rat and guinea pig, were identified using these techniques. A quaternary N-glucuronide was found only in man.     

抗肿瘤药LS-177在大鼠和人肝微粒体中的代谢产物研究

目的：推测LS-177在大鼠和人肝微粒体中代谢产物的结构及其可能的体外代谢途径。方法：体外孵育大鼠和人肝微粒体代谢模型,采用超高效液相质谱联用（LC-MSⁿ）法,推测LS-177的体外代谢产物的结构。结果：通过质谱数据、保留时间和碎片离子,在肝微粒体中共检测到5个代谢产物,初步推测LS-1177在肝微粒体中可能的代谢途径。结论：建立LC-MSⁿ方法,初步推测LS-177在大鼠和人肝微粒体中代谢产物的结构,为其体内外代谢的进一步研究以及化学结构类似物的体外代谢研究提供一定的参考依据。     

Evidence for two catalytically different binding sites of liver microsomal cytochrome P-450: importance for species and sex differences in oxidation pattern of lidocaine

When the local anaesthetic drug lidocaine is added to liver microsomes biphasic type I spectral change titration curves can be observed. A high-affinity and a low-affinity phase is observed. In the present study we have found that microsomes from female rats have a dominant high-affinity phase, which can hardly be observed within microsomes from female guinea pigs. Male rats showed an intermediate phase. On incubation of lidocaine at concentrations of 1 micron or less with female rat liver microsomes a larger fraction of the drug was aromatically hydroxylated than deethylated. The opposite was true for guinea pig liver microsomes, and microsomes from male rats were intermediate. The ratio between the formation of deethylated and hydroxylated metabolites increased with the lidocaine concentration and at a lidocaine concentration of 10(-4)M deethylation was the dominant oxidation type in all microsomes. The data suggest that the two spectral phases represent two binding sites of cytochrome P-450 each having a certain "catalytic specificity" - the high affinity catalyzing aromatic hydroxylation and the "low-affinity site" deethylation. This hypothesis is further supported by the observed differential effects of pH and MgCl2 concentration on the two types of oxidation.     

Characterisation of the human liver in vitro metabolic pattern of artemisinin and auto-induction in the rat by use of nonlinear mixed effects modelling

Aims: The aims of the study were to characterise the metabolic pattern of artemisinin in human and rat liver microsomes and to assess the magnitude of auto‐induction in the rat. Methods: ¹⁴C‐artemisinin was incubated with human liver microsomes and with liver microsomes from rats pretreated with oral artemisinin or placebo. The metabolic fate of ¹⁴C‐artemisinin in microsomes from human B‐lymphoblastoid cell lines transformed with CYP2A6, CYP2B6 and CYP3A4 was also investigated. The human liver microsome data and the rat liver microsomes data were analysed by nonlinear mixed effects modelling and naïve pooling using NONMEM, respectively. Results: Four metabolites were radiometrically detected in experiments with rat liver microsomes. The model that best described the data involved three primary metabolites of which one metabolite was further metabolised to a secondary metabolite. The formation of the four metabolites was induced 2.8, 7.2, 4.8 and 2.5‐fold, respectively, in liver microsomes from rats pre‐treated with artemisinin. Three metabolites were formed in human liver microsomes; having the same retention times as three of the metabolites formed in the rat. The final model consisted of two primary metabolites and a secondary metabolite with CYP2B6 and CYP2A6 influencing the formation rates of the major and minor primary metabolites, respectively. Conclusions: CYP2B6 and CYP2A6 activities described variability in the formation of the major and minor primary metabolites, respectively, in human liver microsomes. All artemisinin metabolic pathways in rat liver microsomes were induced in artemisinin pretreated animals. We suggest modelling as a method for the discrimination and detection of more complex metabolic patterns from in vitro metabolism rate data. Copyright © 2002 John Wiley & Sons, Ltd.