水飞蓟宾非对映异构体在大鼠肝微粒体中葡萄糖醛酸化代谢的酶动力学比较研究

目的比较水飞蓟宾A(silybin A,sa)和水飞蓟宾B(silybin B,sb)在大鼠肝微粒体中葡萄糖醛酸化代谢的酶动力学特性。方法将系列浓度的水飞蓟宾(sa和sb的质量比为45∶53)加入到大鼠肝微粒体孵育液中进行孵育,采用HPLC法分别测定β-葡萄糖苷酸酶水解前和水解后孵育液中sa和sb的浓度,据此计算sa和sb的葡萄糖醛酸结合物的浓度,绘制酶动力学曲线,并计算酶动力学参数。结果 sa和sb的最大反应速率(vmax)分别为(2.80±0.14)mmol·min~(-1)·kg~(-1)和(4.21±0.31)mmol·min~(-1)·kg~(-1),米氏常数(Km)分别为(36.66±7.52)μmol·L-1和(89.78±23.08)μmol·L-1,内在清除率(Clint)分别为76.38 L·min~(-1)·kg~(-1)和46.89 L·min~(-1)·kg~(-1)。结论水飞蓟宾在大鼠肝微粒体中的葡萄糖醛酸化代谢具有立体选择性,sb的代谢速率快于sa。     

辛伐他汀对大鼠肝微粒体药物代谢酶活性的影响

目的 研究辛伐他汀(simvastatin, SV)对大鼠肝脏药物代谢酶活性的影响。方法 大鼠口服给予SV,qd×7,超速离心法分离肝微粒体,一氧化碳示差光谱法测定细胞色素P450(CYP)含量,以红霉素、苯胺、CDNB、利尿酸、7-羟基-4-甲基香豆素和对羟基联苯为底物分别测定肝微粒体红霉素脱甲基酶(CYP3A4)、苯胺羟化酶(CYP2E1)、谷胱甘肽-S-转移酶(glutathione S transferase, GST)及其π亚型 (πGST)、尿苷二磷酸葡萄糖醛酸转移酶(uridine diphosphoglucuronyl transferase, UGT1和UGT2)活性。结果 大鼠口服给予SV可明显降低大鼠肝微粒体CYP含量及CYP3A4活性,对CYP2E1则没有显明影响。同时,SV 则可显著增高大鼠肝微粒体GST、πGST及UGT1和UGT2活性。结论 SV可降低大鼠肝微粒体CYP3A4活性,而增高肝微粒体Ⅱ相代谢酶的活性。     

大黄素在大鼠肝微粒体酶动力学及胡椒碱对其代谢的影响

目的分别研究大黄素在雌性和雄性大鼠肝微粒体中酶促动力学及胡椒碱对其代谢的影响。方法将系列浓度的大黄素分别与雌性或雄性大鼠肝微粒体进行体外共孵育,采用HPLC法测定孵育液中大黄素的浓度,并计算酶动力学参数。另将不同浓度的胡椒碱与大黄素在大鼠肝微粒体中进行共孵育,计算胡椒碱对大黄素代谢的抑制常数(Ki),进一步探讨其代谢抑制类型,并推测其对大黄素体内代谢的影响。结果大黄素在雌性和雄性大鼠肝微粒体中代谢的最大反应速率(Vmax)分别为(84.49±9.62)和(32.97±7.37)μmol·min~(-1)·mg protein~(-1),米氏常数(Km)分别为(60.50±8.71)和(34.48±4.96)μmol·L~(-1),内在清除速率(CLint)分别为(1 406±112)和(965±73.7)μL·min~(-1)·mg protein~(-1),雌性和雄性大鼠的Ki值分别为0.35和0.31μmol·L~(-1)。结论大鼠肝微粒体中胡椒碱抑制大黄素的葡萄糖醛酸代谢呈浓度依赖性,根据图形推断其抑制类型为混合性抑制,并推测合用胡椒碱后,大黄素在大鼠体内的血药浓度显著增加,为其进一步开发研究提供了参考依据。     

辛伐他汀对大鼠肝微粒体药物代谢酶活性的影响

目的研究辛伐他汀(simvastatin, SV)对大鼠肝脏药物代谢酶活性的影响。方法大鼠口服给予SV,qd×7,超速离心法分离肝微粒体,一氧化碳示差光谱法测定细胞色素P450(CYP)含量,以红霉素、苯胺、CDNB、利尿酸、7-羟基-4-甲基香豆素和对羟基联苯为底物分别测定肝微粒体红霉素脱甲基酶(CYP3A4)、苯胺羟化酶(CYP2E1)、谷胱甘肽-S-转移酶(glutathione S transferase, GST)及其π亚型 (πGST)、尿苷二磷酸葡萄糖醛酸转移酶(uridine diphosphoglucuronyl transferase, UGT1和UGT2)活性。结果大鼠口服给予SV可明显降低大鼠肝微粒体CYP含量及CYP3A4活性,对CYP2E1则没有显明影响。同时,SV 则可显著增高大鼠肝微粒体GST、πGST及UGT1和UGT2活性。结论SV可降低大鼠肝微粒体CYP3A4活性,而增高肝微粒体Ⅱ相代谢酶的活性。     

柠檬苦素在大鼠肝微粒体中代谢的性别差异

目的：研究柠檬苦素在大鼠肝微粒体中代谢的性别差异以及引起性别差异的可能的CYP450亚型。方法：柠檬苦素与雌雄大鼠肝微粒体共同孵育,抑制实验为在肝微粒体中加入特异性CYP450抑制剂后,再加入柠檬苦素共同孵育,温孵后的样品乙醚提取后进行HPLC分析。结果：柠檬苦素在雌雄大鼠肝微粒体中代谢的表观酶动力学参数分别为：米氏常数K㎡：（12±3）、（16±4）ug／mL,最大反应速度Vmax：（49±6）、（93±14）ng·min^-1·mg^-1。柠檬苦素在雌雄大鼠肝微粒体中孵育30min的代谢率分别为（33．9±4．7）9／6和（53．8±2．8）％,代谢速度分别为（4．46±0．62）和（7．08±0．37）ng·min^-1·mg^-1。CYP3A2特异性抑制剂酮康唑、CYP2C11特异性抑制剂西咪替丁对柠檬苦素的代谢抑制作用明显,CYPlA2特异性抑制剂a-萘黄酮和CYP2D1特异性抑制剂奎尼丁对柠檬苦素的代谢也有不同程度的抑制作用。结论：柠檬苦素在大鼠肝微粒体中代谢存在明显的性别差异,CYP3A2和CYP2C11在雌雄大鼠肝微粒体中的性别差异可能是引起代谢性别差异的主要原因。     

白屈菜碱在大鼠肝微粒体中代谢的酶动力学及CYP450酶特异性抑制剂对其代谢的影响

目的研究白屈菜碱在大鼠肝微粒体中代谢的酶动力学及CYP450酶特异性抑制剂对其代谢的影响。方法将系列浓度的白屈菜碱与大鼠肝微粒体进行体外共孵育,采用HPLC法测定孵育液中剩余白屈菜碱的浓度,利用Graph Pad Prism 6.0软件进行数据拟合并计算酶动力学参数;分别将5种CYP450酶的特异性抑制剂与白屈菜碱进行共孵育,考察抑制剂对白屈菜碱代谢的影响,探讨参与其代谢的酶亚型。结果在大鼠肝微粒体中,白屈菜碱的Vmax为(3.52±0.18)mmol·min-1·kg-1;Km为(12.02±2.92)μmol·L-1;CLint为292.4 L·min-1·kg-1;CYP450酶特异性抑制剂酮康唑、α-萘黄酮、氟康唑和奎尼丁可以显著地抑制白屈菜碱的代谢,而噻氯匹定对白屈菜碱的代谢没有明显影响。结论白屈菜碱在大鼠肝微粒体中广泛代谢,CYP3A4、CYP1A2、CYP2D6、CYP2C9是参与其代谢的主要代谢酶。     

水黄皮素在大鼠肝微粒体中的代谢研究

目的 研究水黄皮素在大鼠肝微粒体中的代谢稳定性,确定水黄皮素的代谢酶表型.方法 将水黄皮素与大鼠肝微粒体于37℃孵育,应用UPLC-MS/MS法检测孵育液中水黄皮素的含量,考察水黄皮素的代谢稳定性.将水黄皮素与各细胞色素P450(CYP)酶中的各同工酶CYP2E1、2C19、1A2、2D6、2C9和3A4的特异性抑制剂共孵育,确定其代谢酶表型.结果 在大鼠肝微粒体中,水黄皮素的t1/2=1.97 h、Cl =0.70 mL·h-1 ·mg-1,CYP1 A2是其主要代谢酶.结论 水黄皮素在大鼠肝微粒体中是由多个CYP同工酶介导代谢的,其中,CYP1 A2酶的介导作用最强.     

山姜素在人肝微粒体的葡萄糖醛酸化反应研究

目的研究体外肝微粒体孵育体系中山姜素的葡萄糖醛酸化代谢情况,鉴定参与山姜素葡萄糖醛酸化代谢的UGT亚型。方法用体外肝微粒体孵育体系,用HPLC-UV检测方法,检测山姜素的葡萄糖醛酸化代谢情况。将代谢产物进行纯化后,用质谱(MS)和核磁共振(NMR)法进一步鉴定其结构。用商业化重组表达的UGT单酶,鉴定代谢产物的结构和归属可能参与山姜素葡萄糖醛酸化代谢反应的葡萄糖醛酸转移酶(UGTs)亚型。结果山姜素葡萄糖醛酸代谢产生一个代谢产物,经结构鉴定为山姜素-氧-单葡萄糖醛酸化产物。人肝微粒体代谢山姜素的动力学行为,符合米方程且动力学参数:Vmax=(101.9±3.0)nmol·min-1·mg-1·pro,Km=(40.6±3.6)μmol·L-1。UGT1A1、UGT1A3、UGT1A9和UGT2B15均参与了山姜素的葡萄糖醛酸化反应。结论山姜素在人肝微粒体孵育体系中会被代谢成为一个单葡萄糖醛酸化产物,且归属了参与的UGT酶。     

补骨脂酚的体外肝微粒体代谢及代谢减毒作用的种属比较

目的研究补骨脂酚在人、比格犬和大鼠肝微粒体的体外代谢动力学及种属差异,评价不同种属肝微粒体对补骨脂酚人肾近曲小管上皮细胞(HK-2)的减毒作用。方法应用MTT法检测HK-2细胞的存活率来评价补骨脂酚对HK-2细胞的毒性作用以及不同种属肝微粒体对其毒性的影响。应用HPLC法分析补骨脂酚在3个种属肝微粒体孵育液中的剩余浓度,研究其在肝微粒体中的代谢稳定性和代谢动力学。结果在3个种属肝微粒体分别作用下,补骨脂酚的HK-2细胞毒性明显降低。补骨脂酚在人肝微粒体中的代谢最慢,在大鼠肝微粒体中的代谢最快,人、犬和大鼠的代谢动力学参数Km、Vmax、T21和CLint分别为:(81.66±3.41),(89.35±4.32)和(31.89±2.60)μmol.L-1;(0.47±0.01),(0.57±0.01)和(1.88±0.09)μmol.L-1.min-1;(44.14±1.13),(53.31±0.29)和(6.79±0.39)min;(39.38±1.04),(65.16±0.35)和(365.92±20.01)ml.min-1.kg-1。结论肝微粒体降低补骨脂酚的HK-2细胞毒性,这一减毒作用与补骨脂酚经肝微粒体酶的代谢相关。补骨脂酚的体外肝代谢动力学性质存在着一定的种属差异;犬肝微粒体对高浓度补骨脂酚所致的HK-2细胞毒性的降低作用要弱于人和大鼠肝微粒体。     

头花蓼水提取物对CYP450酶诱导和抑制作用研究

目的考察头花蓼水提取物对人肝微粒体CYP450 5种亚型酶的体外抑制作用和对小鼠的体内诱导作用,从而预测发生药物相互作用的可能性,为临床合理用药提供科学依据。方法以探针底物代谢物生成法,考察头花蓼水提取物体外对人肝微粒体主要I相代谢酶CYP1A2、CYP2E1、CYP2C9、CYP2C19和CYP3A4活性的影响;采用微粒体体外孵育法,考察小鼠经高、低剂量(1.16、0.58 g·kg-1)头花蓼水提取物分别连续灌胃7 d和14 d后,小鼠肝微粒体中主要I相代谢酶活性的变化,以评价头花蓼水提取物对小鼠肝微粒体主要CYP450酶是否有诱导作用。结果头花蓼水提取物对人肝微粒体中主要的CYP450 I相代谢酶的抑制作用均不强,IC50值在849.6~2 287 mg·L-1;与空白对照组比较,1.16 g·kg-17 d组小鼠CYP2C9和CYP3A4活性分别增加了49.9%和21.1%(P<0.01和P<0.05),0.58 g·kg-114 d组小鼠CYP2C9和CYP3A4活性分别增加了27.6%和15.5%(P<0.01和P<0.05),1.16 g·kg-114 d组小鼠CYP2C9和CYP3A4活性分别增加了67.5%和32.1%(P<0.01),头花蓼提取物对其余CYP亚型活性未见明显影响。结论在临床剂量下,头花蓼水提取物对人肝微粒体CYP1A2、CYP2E1、CYP2C9、CYP2C19和CYP3A4无明显抑制作用,对小鼠肝微粒体CYP2C9和CYP3A4显示诱导作用。     

Interaction of estrone and estradiol with DNA and protein of liver and kidney in rat and hamster in vivo and in vitro

[6,7-³H] Estrone (E) and [6,7-³H]estradiol-17 (E₂) have been synthesized by reduction of 6-dehydroestrone and 6-dehydroestradiol with tritium gas. Tritiated E and E₂ were administered by oral gavage to female rats and to male and female hamsters on a dose level of about 300 g/kg (54 mCi/kg). After 8 h, the liver was excised from the rats; liver and kidneys were taken from the hamsters. DNA was purified either directly from an organ homogenate or via chromatin. The radioactivity in the DNA was expressed in the units of the Covalent Binding Index, CBI = (mol chemical bound per mol DNA-P)/(mmol chemical administered per kg b.w.). Rat liver DNA isolated via chromatin exhibited the very low values of 0.08 and 0.09 for E and E₂, respectively. The respective figures in hamster liver were 0.08 and 0.11 in females and 0.21 and 0.18 in the males. DNA isolated from the kidney revealed a detectable radioactivity only in the female, with values of 0.03 and 0.05 for E and E₂, respectively. The values for male hamster kidney were < 0.01 for both hormones. The minute radioactivity detectable in the DNA samples does not represent covalent binding to DNA, however, as indicated by two sets of control experiments. (A) Analysis by HPLC of the nucleosides prepared by enzyme digest of liver DNA isolated directly or via chromatin did not reveal any consistent peak which could have been attributed to a nucleoside-steroid adduct. (B) All DNA radioactivity could be due to protein contaminations, because the specific activity of chromatin protein was determined to be more than 3,000 times higher than of DNA. The high affinity of the hormone to protein was also demonstrated by in vitro incubations, where it could be shown that the specific activity of DNA and protein was essentially proportional to the concentration of radiolabelled hormone in the organ homogenate, regardless of whether the animal was treated or whether the hormone was added in vitro to the homogenate.Carcinogens acting by covalent DNA binding can be classified according to potency on the basis of the Covalent Binding Index. Values of 10³–10⁴ have been found for potent, 10² for moderate, and 1–10 for weak carcinogens. Since estrone is moderately carcinogenic for the kidney of the male hamster, a CBI of about 100 would be expected. The actually measured limit of detection of 0.01 places covalent DNA binding among the highly unlikely mechanisms of action. Similar considerations can be made for the liver where any true covalent DNA binding must be below a level of 0.01. It is concluded that an observable tumor induction by estrone or estradiol is unlikely to be due to DNA binding.Paper presented at the Satellite Symposium of the European Society of Toxicology, Rome, March 29, 1983     

Metabolic interaction between imipramine and carbamazepine in vivo and in vitro in rats

Summary The pharmacokinetic consequences of the combination of carbamazepine with imipramine in male Wistar rats have been investigated. It was found that a 2-week treatment with the combination resulted in the increase of the concentrations of the parent compounds and a simultaneous decrease in their metabolites in blood plasma i.e. carbamazepine inhibited imipramine demethylation in the side chain while imipramine inhibited carbamazepine 10,11-epoxidation. The velocity of imipramine 2-hydroxylation and 10,11-epoxy-carbamazepine hydration did not seem to be changed by the combination. On the basis of studies in vitro it is concluded that the observed metabolic interaction between carbamazepine and imipramine is due to the competition of the drugs for the active centre of cytochrome P 450 and to a certain qualitative alteration of the enzyme by imipramine as can be deducted from the decrease of carbamazepine binding to the cytochrome. Send offprint requests to K. J. Netter     

Nicotine metabolism and urinary elimination in mouse: in vitro and in vivo

This study aimed at elucidating the in vivo metabolism of nicotine both with and without inhibitors of nicotine metabolism. Second, the role of mouse CYP2A5 in nicotine oxidation in vitro was studied as such information is needed to assess whether the mouse is a suitable model for studying chemical inhibitors of the human CYP2A6. The oxidation of nicotine to cotinine was measured and the ability of various inhibitors to modify this reaction was determined. Nicotine and various inhibitors were co-administered to CD2F1 mice, and nicotine and urinary levels of nicotine and four metabolites were determined. In mouse liver microsomes anti-CYP2A5 antibody and known chemical inhibitors of the CYP2A5 enzyme blocked cotinine formation by 85-100%, depending on the pre-treatment of the mice. The amount of trans-3-hydroxycotine was five times higher than cotinine N-oxide, and ten times higher than nicotine N-1-oxide and cotinine. Methoxsalen, an irreversible inhibitor of CYP2A5, significantly reduced the metabolic elimination of nicotine in vivo, but the reversible inhibitors had no effect. It is concluded that the metabolism of nicotine in mouse is very similar to that in man and, therefore, that the mouse is a suitable model for testing novel chemical inhibitors of human CYP2A6.     

Nicotine metabolism and urinary elimination in mouse: in vitro and in vivo

This study aimed at elucidating the in vivo metabolism of nicotine both with and without inhibitors of nicotine metabolism. Second, the role of mouse CYP2A5 in nicotine oxidation in vitro was studied as such information is needed to assess whether the mouse is a suitable model for studying chemical inhibitors of the human CYP2A6. The oxidation of nicotine to cotinine was measured and the ability of various inhibitors to modify this reaction was determined. Nicotine and various inhibitors were co-administered to CD2F1 mice, and nicotine and urinary levels of nicotine and four metabolites were determined. In mouse liver microsomes anti-CYP2A5 antibody and known chemical inhibitors of the CYP2A5 enzyme blocked cotinine formation by 85–100%, depending on the pre-treatment of the mice. The amount of trans-3-hydroxycotine was five times higher than cotinine N-oxide, and ten times higher than nicotine N-1-oxide and cotinine. Methoxsalen, an irreversible inhibitor of CYP2A5, significantly reduced the metabolic elimination of nicotine in vivo, but the reversible inhibitors had no effect. It is concluded that the metabolism of nicotine in mouse is very similar to that in man and, therefore, that the mouse is a suitable model for testing novel chemical inhibitors of human CYP2A6.     

Penetration and action of edoxudine in vitro and in vivo

The penetration of 5-ethyl-2'-deoxyuridine (edoxudine, Aedurid) from gel base with and without the addition of urea and other adjuvant has been studied in an in vitro model using guinea pig skin. The formulation of 3% edoxudine gel with 5% urea showed the best results. In vivo experiments on hairless mice infected intracutaneously with herpes simplex virus type 1 also showed this formulation's good efficacy as compared to other formulations.     

Buprenorphine and naloxone alone and in combination in opioid-dependent humans

Subjective, physiological and behavioral effects of subcutaneously administered hydromorphone (6 mg), naloxone (0.2 mg), buprenorphine (0.2 and 0.3 mg), and two buprenorphine-naloxone combinations (buprenorphine 0.2 mg plus naloxone 0.2 mg and buprenorphine 0.3 mg plus naloxone 0.2 mg) were assessed under double-blind conditions in six opioid-dependent volunteers. Physiologic measures and subject- and observer-rated behavioral responses were measured before dosing and for 120 min after drug administration. Hydromorphone decreased pupil diameter and respiration, increased blood pressure and increased scores on subjective measures indicating opioid-like effects. Buprenorphine given alone had no significant effect on any variable measured. Naloxone given alone produced opioid abstinence-like effects which were measurable on subject- and observer-rated behavioral measures and physiological measures. Buprenorphine in combination with naloxone somewhat attenuated the naloxone-precipitated withdrawal response. Overall, the naloxone-buprenorphine combinations produced effects which were qualitatively similar to the effects of naloxone alone, suggesting a low potential for abuse of the combination product by opioid-dependent individuals.Supported by a grant from Reckitt and Colman Pharmaceutical Division and USPHS Grants DA-00050 and DA-04089 from the National Institute on Drug Abuse     

Cadmium in milk and mammary gland in rats and mice

The purpose of the present investigation was to study the uptake of cadmium in mammary tissue, effects on milk secretion and composition, and lactational transport of cadmium to the sucklings. Cadmium exposure during lactation resulted in retention of cadmium in the mammary tissue in mice and rats. The uptake of cadmium in the mammary tissue was rapid, as shown in lactating mice by whole-body autoradiography 4 h after an intravenous injection of a tracer dose of (109)CdCl(2). Retention of cadmium in kidneys of suckling pups was observed in the autoradiograms at 7 days after exposure of the dams. Lactating rats were intravenously infused with (109)CdCl(2) in 0.9% saline via osmotic minipumps from day 3 to day 16 after parturition. The cadmium dose given was 0, 8.8, 62 and 300 microg Cd/kg body wt. per day. Plasma and milk were collected at day 10 and 16 after parturition. Plasma cadmium levels in dams increased from day 10 to day 16. Cadmium levels were higher in milk than in plasma, with milk/plasma ratios varying from 2 to 6. Zinc levels in milk were positively correlated to cadmium levels in milk (r(2)=0.26; P=0. 03). In milk, (109)Cd was distributed in fat (46-52%), casein fraction (40-46%), and whey fraction (6-8%). There was a high correlation between cadmium concentrations in pups' kidney and cadmium concentrations in dam's milk (r(2)=0.98; P < 0.001). Of the cadmium dose given to the dams <0.05% was retained in the litters on day 16 of lactation. No effects were observed due to cadmium exposure on body weight in pups or dams. Cadmium treatment did not cause any effect on the lactose or protein concentration in milk, the concentrations of DNA, RNA or the ratio RNA/DNA in the mammary gland. Histological evaluation of mammary tissue did not reveal any abnormalities at any dose level. (109)Cd was bound to metallothionein in mammary tissue. The fraction of radiolabelled cadmium bound to metallothionein increased in a dose-dependent manner in both the liver (88-98%) and mammary tissue (57-80%). The present results indicate a low transfer of cadmium to the suckling pup, which might be due to binding of cadmium to metallothionein in the mammary tissue. However, during the susceptible developmental period even a low cadmium exposure may be of concern.     

Circulating nucleic acids in plasma and serum: roles in diagnosis and prognosis in diabetes and cancer

The presence of DNA and RNA circulating in human plasma and serum is described. The possible sources of the DNA/RNA in blood, their ability to enter other cells and to express in the recipient cells are discussed and the relationship with metastases considered. The possible role(s) of the DNA/RNA in clinical diagnosis, in monitoring treatment and in prognosis are considered for diabetes and oncology.     

SalB stimulates neurogenesis and angiogenesis in vitro and in vivo

Aims： Previous studies suggested that Salvianolic acid B （SalB） has strong protective effect against cerebral ischemia. Recently, Sal B has been reported to enhance angiogenesis in vitro. Based on the information above, in this study we are interested in the effect of SalB on neurogenesis and angiogenesis. Methods：In vitro study, we used embryonic mouse （El6） primary cortical neural cultures. Neuron was recognized by anti-MAP2 with immunocytochemistry. Neurogenesis was tested with BrdU incorporation by ELSA method. SalB（ 10 -6 -10 -8M） or vehicle was added to the culture medium 24 hrs before BrdU addition. In vivo, middle cerebral artery occlusion （MCAO） rats were used as focal cerebral ischemia model.