乙醇摄入对小鼠肝生物转化酶活性及抗氧化功能的影响

观察摄入乙醇（２．５ ｇ·ｋｇ－ １ ｐｏ,每日１ 次）后小鼠肝脏药物代谢酶活性及抗氧化功能的变化,为临床安全用药提供实验依据． 结果表明乙醇摄入４ 周内可诱导苯胺羟化酶,谷胱甘肽Ｓ－转移酶的活性,氨基比林脱甲基酶活性无明显变化,４ 周后则可使上述药酶活性下降,提示长期乙醇摄入对药物代谢的抑制性影响;乙醇摄入早期肝各抗氧化成分无明显改变,４ 周后,谷胱甘肽还原酶,谷胱甘肽过氧化酶,超氧化物歧化酶活性及谷胱甘肽含量逐渐下降,但过氧化氢酶活性明显升高,至第８ 周末下降,谷胱甘肽含量恢复正常,表明乙醇对肝抗氧化功能影响与摄入时间有关．     

Alterations in hepatic Phase I and Phase II biotransformation enzymes by garlic oil in rats

Studies were conducted to examine the effect of a single and repeated administrations of garlic oil (diallyl sulfide) on Phase I and Phase II biotransformation enzymes in rats. Adult, male Sprague-Dawley rats treated with a single dose of garlic oil (500 mg/kg i.p.) showed a significant depression of hepatic cytochrome P-450, aminopyrine Ndemethylase and aniline hydroxylase while microsomal protein content, cytochrome b₅, NADPH-cytochrome c reducase, benzphetamine N-demethylase and cytosolic glutathione, S-transferase remained unaffected 24 h following the treatment. Although certain microsomal enzymes were depressed, there was no liver damage caused by garlic oil as judged by the putative serum enzyme test. On the other hand, daily administration of garlic oil (50 mg/kg) i.p. for 5 days) produced a significant increase in hepatic cytochrome P-450, aminopyrine N-demethylase and benzphetamine N-demethylase activities, but not in the rest of the aforementioned parameters of biotransformation reactions. These data indicate that the effect of garlic oil on the hepatic drug-metabolizing enzyme system is dose-dependent.     

Effects of human diets on biotransformation enzyme activity and metabolic activation of carcinogens in rat liver

We studied the effects of a complete human diet, based on mean consumption figures in The Netherlands, the heating of food, and the presence of vegetables and fruit in the diet on the drug metabolizing capacity of the rat liver and on metabolic activation of known carcinogens. Groups of five male and five female Wistar rats were given ad lib. one of six different diets for 3 months. Each diet contained 40 energy (E)% fat, 13 E% protein, 47 E% carbohydrate and 5% fibre (w/w). The diets were as follows: a control diet of semi-synthetic materials (A); a human diet of meat, bread and eggs without processing (B); diet B heated under usual household conditions (C); a diet representing a complete human meal including (summer) vegetables and fruit (D); diets consisting of winter vegetables (E) or summer vegetables (F) with fruit. Semi-synthetic components were added to diets B-F to achieve the desired composition. There were differences between male and female rats on the effects of the different diets on hepatic enzyme activity. In female rats, but not in males, ethoxyresorufin-O-deethylase activity was increased significantly (P less than 0.05) in groups C, D and E in comparison with the controls (group A). In male rats ethoxycoumarin-O-deethylase activity was enhanced in groups D, E and F, and glutathione-S-transferase was markedly induced in group F (P less than 0.01). In males, hepatic cytochrome P-450 was significantly (P less than 0.05) increased in groups B, C and E. There was no effect on aminopyrine-N-demethylase activity and almost no effect on UDP-glucuronyltransferase activity in either sex. Microsomes from rats fed heated food (C) markedly increased the mutagenicity of benzo[a]pyrene (B[a]P) in the Ames assay using Salmonella typhimurium strain TA98, in comparison with levels using microsomes from rats fed the raw food (B). Vegetables and fruit decreased B[a]P mutagenicity. All human diets except D decreased the mutagenicity of N-nitrosodimethylamine in tester strain TA100. The results indicate that the influence of components of human diets on rat-liver drug metabolism may have quite different effects on the biotransformation of carcinogens activated by different metabolic pathways.     

转运体和代谢酶在胆汁淤积性肝损伤中的作用机制

胆汁淤积性肝损伤是临床常见的肝脏疾病,主要由体内胆汁酸平衡失调引起,其发病机制与胆汁酸转运体、合成酶和代谢酶的表达和功能变化直接相关。核受体通过调控胆汁酸转运体及代谢酶的表达,在胆汁淤积所致的肝损伤中发挥重要作用。对肝脏转运体和代谢酶在胆汁淤积性肝损伤中的作用及核受体对转运体和代谢酶的调控机制作一综述。     

肝脏转运体和代谢酶在化学性肝损伤中的作用

肝脏是机体重要的代谢和解毒器官。肝细胞膜上存在多种功能性膜蛋白即肝脏药物转运体,它的功能是介导许多内源性及外源性物质如药物摄取进入肝脏,在肝脏内经过一定的代谢转化,最终将其从肝脏排入胆汁。研究发现,转运体和代谢酶在化学性肝损伤的发展过程中发挥重要的作用,其涉及的多种调控机制成为研究热点。就肝脏转运体和代谢酶的分类、转运体和代谢酶在化学性肝损伤中的变化及其调控机制作一综述。     

Radical accumulation in liver microsomal membranes during biotransformation of aromatic amines and nitro compounds

Summary Accumulation of aromatic nitroxide radicals in microsomal membranes of rabbit liver has been observed by ESR-spectroscopy in the course of biotransformation of 2-acetylaminofluorene, 2-aminofluorene, 2-aminonaphthalene, 4-aminostilbene, 4,4-diamincstilbene, 4-nitroquinoline-1-oxide.     

血清心肌酶水平与精神分裂症患者病情相关性研究

目的：探讨精神分裂症患者血清心肌酶谱的变化及其临床意义。方法测定405例精神分裂症患者入院时血清心肌酶（ CK、CK－MB、LDH、α－HBDH）水平,于入院治疗4周后复查血清心肌酶水平,分析其与病情的关系,并与100例健康人（对照组）进行对照。结果精神分裂症阳性症状组患者治疗前血清CK、CK－MB、LDH、α－HBDH分别为（1286．52±714．38） U／L、（40．72±27．38） U／L、（143．06±33．24） U／L、（115．75±22．74）U／L,CK、CK－MB均高于对照组（t ＝10．35、9．29,均 P＜0．01）;治疗4周后 CK、CK－MB、LDH、α－HBDH分别为（98．13±38．75）U／L、（12．87±5．73）U／L、（125．43±25．74）U／L、（102．15±26．86）U／L,呈下降趋势,与对照组比较,差异均无统计学意义（均P＞0．05）。结论急性发作期精神分裂症患者血清心肌酶CK、CK－MB升高可能与病情有关。     

Age related acute effects of microcystin-LR on Daphnia magna biotransformation and oxidative stress

As a result of eutrophication among other factors, bloom forming species of cyanobacteria frequently thrive and dominate communities in freshwater ecosystems. Cyanobacteria are considered as a nuisance and hazardous due to the production of toxins. The most potent and studied cyanobacterial toxins are the microcystins, especially the variant microcystin-LR (MC-LR). Daphnia magna plays a central role in freshwater pelagic food webs and its populations are negatively affected by cyanobacteria due to nutritional inadequacy, feeding interference and toxic effects on growth and reproduction. Biotransformation and antioxidant enzymes, amongst others enable D. magna capacity to cope with MC-LR up to a certain concentration. Aim of our study was to investigate the age related acute effects of MC-LR on D. magna biotransformation and antioxidant enzymes (glutathione S-transferase, GST and catalase, CAT), subsequent lipid peroxidation and furthermore to lactate and the enzyme lactate dehydrogenase (LDH). D. magna neonates (<3 days old) and young adults (7 days old), were exposed to increasing concentrations of MC-LR (up to 100 μg/L) for 24 and 48 h. D. magna sGST activities at both ages, but more pronounced in adults, increased at low MC-LR concentrations followed by decreased activities at the higher ones suggesting diminished ability to biotransform the cyanotoxin. Oxidative protection was more efficient in neonates, where CAT was elevated strongly and contributed to buffer oxidative stress, evidenced by the constant TBARS concentrations. LDH was negatively affected by MC-LR exposure leading to constant and low concentrations of lactate. As this enzyme is involved in the production of rapidly required energy, the findings suggest an energetic impairment due to MC-LR.     

外源性一氧化氮对大鼠肝脏抗氧化物酶和药物代谢酶活性的影响

用亚硝基铁氰化钠(SNP)作为NO生成前体,以 0, 1, 2, 4 和 8 mg·kg^-1 ip 给予大鼠,每日一次,连续 5 d,来研究外源性NO对大鼠肝脏细胞色素 P450, 苯胺羟化酶(AH), 谷胱甘肽S-转移酶(GST)等药物代谢酶和过氧化氢酶(Cat), 谷胱甘肽过氧化物酶(GSH-Px), 超氧化物歧化酶(SOD)等抗氧化物酶活性以及脂质过氧化的体内影响情况. 结果表明外源性NO能明显降低大鼠肝脏SOD, Cat, AH 的活性和细胞色素P450的含量(P<0.05),并且高剂量组还能明显促进脂质过氧化发生(P<0.05), 但对GSH-Px和GST的活性则无明显影响.     

外源性一氧化氮对大鼠肝脏抗氧化物酶和药物代谢酶活性的影响

用亚硝基铁氰化钠（ＳＮＰ）作为ＮＯ生成前体,以０,１,２,４和８ｍｇ·ｋｇ－１ｉｐ给予大鼠,每日一次,连续５ｄ,来研究外源性ＮＯ对大鼠肝脏细胞色素Ｐ４５０,苯胺羟化酶（ＡＨ）,谷胱甘肽Ｓ－转移酶（ＧＳＴ）等药物代谢酶和过氧化氢酶（Ｃａｔ）,谷胱甘肽过氧化物酶（ＧＳＨ－Ｐｘ）,超氧化物歧化酶（ＳＯＤ）等抗氧化物酶活性以及脂质过氧化的体内影响情况．结果表明外源性ＮＯ能明显降低大鼠肝脏ＳＯＤ,Ｃａｔ,ＡＨ的活性和细胞色素Ｐ４５０的含量（Ｐ＜０．０５）,并且高剂量组还能明显促进脂质过氧化发生（Ｐ＜０．０５）,但对ＧＳＨ－Ｐｘ和ＧＳＴ的活性则无明显影响     

Comparative incidence of oral ochratoxicosis and aflatoxicosis on the activity of drug-metabolizing enzymes in rat liver

Mycotoxicosis has been produced in the rat by daily oral administrations of ochratoxin A (1.5 mg/kg/day) or aflatoxin B1 (1 mg/kg/day). Hepatic microsomal cytochrome P-450 and b5 contents and many phase I and II biotransformation systems have been measured in the course of ochratoxicosis (4 to 15 dosings) and aflatoxicosis (1 to 8 dosings). In case of ochratoxicosis, decreases in cytochrome P-450 level, aminopyrine demethylase and aniline hydroxylase activities were observed in rats receiving 15 administrations of the toxin. Aflatoxicosis induced more severe decreases in cytochrome P-450, aminopyrine demethylase and ethoxycoumarin deethylase following 8 daily gavages. In the two studies, there was no significant change in activities of liver phase II biotransformation enzymes.     

氟喹诺酮类药对人肝药酶活性的影响

目的 :观察氟喹诺酮类 (FQs)药物对人肝微粒体药物代谢酶 (细胞色素P 4 5 0 )活性影响的差异。方法 :反应体系中微粒体蛋白终浓度为 0 .33～2 .0 g·L- 1,药物终浓度为 4 0 0mg·L- 1,测定药物代谢酶的活性。对照不加药。并测定不同底物浓度和不同环丙沙星浓度时乙基吗啡N 脱甲基酶的Vm和Km 值 ,求抑制常数Ki。结果 :FQs对酶活性的抑制强度为 :培氟沙星 (PFLX) >环丙沙星 (CPLX)>氧氟沙星 (OFLX) >左氧氟沙星 (LVLX)。FQs对戊巴比妥侧链羟化酶 (PSCH )、苯并芘羟化酶(BPH)、氨基比林N 脱甲基酶 (ADM )、乙基吗啡N 脱甲基酶 (EDM )和NADPH 细胞色素C还原酶的平均被抑制率分别为 :2 9% ,2 6 % ,19% ,17%和2 .3%。CPLX对EDM的抑制为竞争性抑制为主的混合性抑制 ,抑制常数Ki=2 5 0mg·L- 1。结论 :4种FQs对多种肝药酶活性均有不同程度的抑制 ,LVLX的抑制作用相对较弱。 5种肝药酶对药物的敏感性也各不相同。CPLX对EDM的抑制是竞争性抑制为主的混合性抑制。     

Variable activation of lovastatin by hydrolytic enzymes in human plasma and liver

Lovastatin, widely used to lower cholesterol, is a pro-drug that requires metabolic activation through hydrolysis by carboxyesterases. There appear to be at least three distinct esterases in humans capable of catalysing this reaction, one in plasma and two in the liver.The rate of lovastatin hydroxy acid formation was measured as 15.8 pmol · ml^–1 · min^–1 in plasma, 2.13 pmol · mg^–1 protein · min^–1 in hepatic microsomes and 0.92 pmol · mg^–1 protein · min^–1 in cytosol. The data suggest that on average the three esterases together are capable of activating about 220 nmol (90 g) lovastatin per minute per person, to which the esterases of plasma, liver microsomes and liver cytosol contribute approximately 18, 15 and 67%, respectively.All three esterases showed evidence of inter-individual variability. In one of 17 livers, both cytosolic and microsomal esterase activity was completely missing, while two other liver specimens lacked one esterase.Such variability must be expected to influence the therapeutic efficacy of the drug, and they might be related to its occasional toxicity.     

In vitro biotransformation of 2-methylpropene (isobutene): Epoxide formation in mice liver

Until now, no data are available concerning the biotransformation and toxicity of 2-methylpropene (or isobutene), a gaseous alkene widely used in industry (rubber, fuel additives, plastic polymers, adhesives, anti-oxidants). In this work, the biotransformation of 2-methyl-propene (MP) has been studied, using total liver homogenates of mice, supplemented with a NADPH-generating system. In analogy to other olefins, 2-methylpropene is metabolized to its epoxide 2-methyl-1,2-epoxypropane (MEP), as proved by the identification by gas chromatography coupled with mass spectrometry. The epoxidation is cytochromeP-450 dependent, as shown by experiments in the absence of the NADPH-generating system and in the presence of various concentrations of metyrapone and SKF 525-A, two known inhibitors of the mono-oxygenases. A simple gas chromatographic headspace method has been developed for the quantitative determination of the epoxide formed. The formation of MEP is never linear in function of time and it reaches a maximum after 20 min. Thereafter is decreases continuously to undetectable levels. This observation can be explained by the immediate action of epoxide hydrolase and glutathione S-transferase, converting the epoxide to 2-methyl-1,2-propanediol and to the glutathione conjugate respectively. The involvement of both enzymes has been demonstrated by the addition of 3,3,3-trichloropropene oxide and indomethacin. These inhibitors of, respectively, epoxide hydrolase and glutathione S-transferase increase the epoxide formation in a significant way. The actual concentration of MEP is therefore not only dependent on its formation by cytochromeP-450 dependent mono-oxygenases, but also on its conversion by epoxide hydrolase and glutathione S-transferase, both very active in liver tissue.     

An update on in vitro test methods in human hepatic drug biotransformation research: pros and cons

The liver is the predominant organ in which biotransformation of foreign compounds takes place, although other organs may also be involved in drug biotransformation. Ideally, an in vitro model for drug biotransformation should accurately resemble biotransformation in vivo in the liver. Several in vitro human liver models have been developed in the past few decades, including supersomes, microsomes, cytosol, S9 fraction, cell lines, transgenic cell lines, primary hepatocytes, liver slices, and perfused liver. A general advantage of these models is a reduced complexity of the study system. On the other hand, there are several more or less serious specific drawbacks for each model, which prevents their widespread use and acceptance by the regulatory authorities as an alternative for in vivo screening. This review describes the practical aspects of selected in vitro human liver models with comparisons between the methods.     

Purification and comparative studies of several mitochondrial aspartate aminotransferases from avian liver

A new purification method has been developed which only exploits the chromatographic behaviour of avian liver mitochondrial aspartate aminotransferase enzymes (m-AAT), and permits a rapid isolation of the protein (4 days) in large quantities with high yield and low cost. m-AAT from turkey, chicken and quail livers have been isolated by chromatography on CM-Sepharose, Sephadex G-100 and 5′ AMP-Sepharose using TEA-acetate buffer (pH 7.4), and specific activities (A.E.) of 311.6, 318.9, 320.1 I.U./mg respectively were obtained. Preparations were homogeneous as judged by various electrophoretic techniques and by size exclusion HPLC. The amino acid composition, Stokes Radius, subunit molecular weight and pI values have been determined and compared, finding no appreciable differences among them. In contrast, the absorption spectrum of the turkey enzyme differed from those of chicken and quail at both pH 7.4 and pH 5.0.     

Identification of the rat liver cytochrome P450 enzymes involved in the metabolism of the calcium channel blocker dipfluzine hydrochloride

This study aimed to identify the specific cytochrome P450 (CYP450) enzymes involved in the metabolism of dipfluzine hydrochloride using the combination of a chemical inhibition study, a correlation analysis and a panel of recombinant rat CYP450 enzymes. The incubation of Dip with rat liver microsomes yielded four metabolites, which were identified by liquid chromatography-coupled tandem mass spectrometry (LC/MS/MS). The results from the assays involving eight selective inhibitors indicated that CYP3A and CYP2A1 contributed most to the metabolism of Dip, followed by CYP2C11, CYP2E1 and CYP1A2; however, CYP2B1, CYP2C6 and CYP2D1 did not contribute to the formation of the metabolites. The results of the correlation analysis and the assays involving the recombinant CYP450 enzymes further confirmed the above results and concluded that CYP3A2 contributed more than CYP3A1. The results will be valuable in understanding drug–drug interactions when Dip is coadministered with other drugs.     

Xenobiotic-metabolizing enzymes in plants and their role in uptake and biotransformation of veterinary drugs in the environment

Many various xenobiotics permanently enter plants and represent potential danger for their organism. For that reason, plants have evolved extremely sophisticated detoxification systems including a battery of xenobiotic-metabolizing enzymes. Some of them are similar to those in humans and animals, but there are several plant-specific ones. This review briefly introduces xenobiotic-metabolizing enzymes in plants and summarizes present information about their action toward veterinary drugs. Veterinary drugs are used worldwide to treat diseases and protect animal health. However, veterinary drugs are also unwantedly introduced into environment mostly via animal excrements, they persist in the environment for a long time and may impact on the non-target organisms. Plants are able to uptake, transform the veterinary drugs to non- or less-toxic compounds and store them in the vacuoles and cell walls. This ability may protect not only plant themselves but also other organisms, predominantly invertebrates and wild herbivores. The aim of this review is to emphasize the importance of plants in detoxification of veterinary drugs in the environment. The results of studies, which dealt with transport and biotransformation of veterinary drugs in plants, are summarized and evaluated. In conclusion, the risks and consequences of veterinary drugs in the environment and the possibilities of phytoremediation technologies are considered and future perspectives are outlined.