【作者】 付云峰；

【导师】 熊燕；

【作者基本信息】 中南大学 ， 药理学， 2003， 硕士

【摘要】 卡托普利对同型半胱氨酸损伤内皮功能的保护作用 研究背景和目的 高同型半胱氨酸(Hcy)血症是动脉粥样硬化等心血管疾病发生发展的一个独立而重要的危险因子。高同型半胱氨酸血症的病人和动物模型均存在有明显的血管内皮依赖性舒张功能的损害。最近研究发现给高同型半胱氨酸血症的患者和动物补充B族维生素和／或叶酸可降低血中Hcy的浓度，但并不能改善血管内皮依赖性舒张功能、阻止动脉粥样硬化病变的发生发展。因此寻找一种药物对抗同型半胱氨酸的血管损伤作用，对防治与高同型半胱氨酸血症有关的心血管疾病具有十分重要的理论与实际意义。研究发现，血管紧张素转化酶抑制药(ACEI)能改善动脉粥样硬化和高血压所引起的血管内皮依赖性舒张功能的损害，并被广泛用于防治心血管疾病。然而，ACEI对高同型半胱氨酸血症引起的血管内皮功能损害及血管疾病是否有保护作用尚未见国内外文献报道。因此，本实验拟从离体和在体两个层次探讨ACEI卡托普利对Hcy损伤大鼠胸主动脉内皮依赖性舒张功能的保护作用及其机制。 方法 实验分为离体和在体两个部分。 在离体实验中用不同浓度的Hcy(0.3～3mmol/L)孵育大鼠离体胸主动脉环30min诱导血管内皮损伤，观察卡托普利(3～30gmol／L)对HCy损伤血管内皮依赖性舒张功能的影响。另外，为了探讨卡托普利的保护作用是否与清除氧自由基和促进内皮细胞合成、释放一氧化氮有关，我们比较了氧自由基清除剂超氧化物歧化酶旧OD，200U加l）或研一氧化氮的合成前体卜精氨酸G mmol／L）对Hey损伤血管内皮依赖性舒张功能的影响。 在在体实验中给正常大鼠尾静脉注射 10 m叭g／d同型半肤氨酸4w诱导血管内皮损伤，观察卡托普利治疗臼 mgthg伯，i．v．）4 w对 Hey损伤血管内皮的影响及其与内源性一氧化氮合酶抑制物非对称性二甲基精氨酸（ADMA）的关系。用胸主动脉环方法来检测各组动物的血管舒张功能；检测各组大鼠血清中内源性ADMA和一氧化氮（NO）代谢产物NO厂的含量，测定血中脂质过氧化产物丙二醛的浓度和肝组织SOD的活性，并检测血清血管紧张素转化酶（ACE）的活性和血肌鼾囱水平。 结 果 离体实验结果显示，用 Hey①．3－3 mmol几）体外孵育大鼠的离体胸主动脉环呈浓度依赖性损伤乙酚胆碱诱导的内皮依赖性血管舒张反应，但不影响硝普钠诱导的内皮非依赖性血管舒张反应。用卡托普利门－3 0 pmol几）预孵育血管环 15 min，再与 Hey 门）共同孵育 3 0 min，明显改善 Hey对血管内皮依赖性舒张反应的损害，并呈浓度依赖性。此外，用氧自由基清除剂SODQ00 U／mL）或一氧化氮的合成前体卜精氨酸门 mmol／L）分别处理血管环，也能部分减轻比 门）对内皮依赖性舒血管功能的损害。然而，用 I互 人SOD和 L－精氨酸共同孵育血管环，可完全逆转 Hey门 几）对内皮依赖性舒血管功能的损害，这一作用与 30 pmol／L的卡托普利相＜。 在体实验的结果表明，给正常大鼠尾静脉注射同型半肤氨酸4W后其离体胸主动脉环内皮依赖性舒张反应明显降低，伴随血中内源性NOS抑制物ADMA含量明显升高和血清NO含量显著降低，以及血中脂质过氧化产物丙二醛浓度增加和肝组织SOD活性下降。用ACEI卡托普利治疗4 W后可阻止血中内源性ADMA的升高，同时增加血中＊0的含量：降低血中丙二醛的浓度，升高肝组织”D活性；并改菩离体血管的内皮依赖性舒张功能。卡托普利的这些作用可能不是通过抑制ACE产生的，因为HCy模型组大鼠与正常组大鼠血清ACE的活性没有明显区别。此外3组动物血肌酚含量也没有明显区别。 结 论 卡托普利对同型半脐氨酸所引起的血管内皮依赖性舒张功能的损害具有明显的保护作用，该作用可能与卡托普利抑制内源性NOS抑制物ADMA的蓄积、抗氧化，促进内皮细胞合成、释放一氧化氮有关。更多还原

【Abstract】 Hyperhomocysteinemia is an independent risk factor for cardiovascular diseases. A number of studies have demonstrated impaired endothelium-dependent vasodilatation in animals and humans with hyperhomocysteinemia. Supplementation of B vitamins and / or folic acid has been shown to reverse hyperhomocysteinemia but is not sufficient to improve vascular endothelial dysfunction or atherosclerotic lesions in hyperhomocysteinemic animals and humans. Therefore, it is important to search for an effective pharmacological approach to the prevention of homocysteine-induced vascular diseases.Angiotensin converting enzyme inhibitors (ACEIs) have achieved widespread usage in the treatment of cardiovascular diseases. Furthermore, ACEIs have been shown to improve endothelial dysfunction in hypertension and atherosclerosis. However, it is unclear whether ACEI can improve the impairment of endothelium-dependent relaxation due to homocysteine. In the present study, we sought to examine whether captopril may exert beneficial effects on homocysteine-induced impairment of endothelium-dependent relaxation in rat aorta.METHODSThe present experiment comprised two parts, in vitro and in vivo In vitro, rat aortic rings were incubated with various concentrations of homocysteine (0.3 ~ 3 mmol/L) for 30 min in organ-bath to induce endothelial damage. In the captopril groups, aortic rings were pre-incubated with captopril (3~30 umol/L) for 15 min and then exposed to homocysteine for another 30 min in the presence of captopril. In order to determine whether scavenging oxygen free radicals and enhancing NO production contribute to the beneficial effect of captopril, we compared effects of superoxide dismutase (200 U/ml) or L-arginine (3 ~ 10 mmol/L) alone or in combination of superoxide dismutase (200 U/ml) and L-arginine (3 mmol/L) on the inhibition of homocysteine in isolated aortic rings with those of captopril. After these incubations, the endothelium-dependent relaxation response to acetylcholine and the endothelium-independent relaxation response to sodium nitroprusside were examined at the plateau phase of phenylephrine-contraction, respectively.In vivo, rats were given tail vein injections with homocysteine (10 mg/kg/d) or with homocysteine plus captopril (3 mg/kg/d, i.v.) for 4 weeks. Isometric tension recordings were used to assess inhibitory effects of homocysteine and protective effects of captopril on endothelium-dependent and -independent relaxation of aortic rings. Inthree groups, serum levels of endogenous inhibitor of nitric oxide synthase asymmetric dimethylarginine (ADMA) and NO2~ were measured. Moreover, serum malondialdehyde, derived from lipid peroxidation, and SOD activity in liver tissue were determined. In addition, serum angiotensin converting enzyme activity and serum creatinine level were assayed.RESULTSExposure of aortic rings to homocysteine (0.3 ~ 3 mmol/L) for 30 min induced a significant concentration-dependent inhibition of endothelium-dependent relaxation response to acetylcholine, but did not affect endothelium-independent relaxation response to sodium nitroprusside. Pre-incubation of aortic rings with captopril (3 ~ 30 umol/L) for 15 min and co-incubation of aortic rings with homocysteine (1 mmol/L) for another 30 min attenuated the inhibition of homocysteine in a dose-dependent manner. Moreover, superoxide dismutase (SOD, 200 U/ml), a scavenger of superoxide anions, reduced homocysteine-induced inhibition. L-arginine (3 mmol/L), a precursor of nitric oxide (NO), also attenuated the impairment of vasorelaxation induced by homocysteine. But in the combined presence of SOD and L-arginine, the inhibitory effect of homocysteine was reversed, which was very similar to the effect of 30 umol/L captopril.Administration of Hey (10 mg/kg/d) to normal male Sprague-Dawleyrats for 4 weeks significantly elevated serum concentration of endogenous ADMA and decreased serum content of NO compared with control group. This elevation of endogenous ADMA in serum of Hcy-更多还原