二苯乙烯苷对人脐静脉内皮细胞一氧化氮合酶及其基因的调节作用

目的探讨二苯乙烯苷（THSG）对人脐静脉内皮细胞（HUVECs）一氧化氮（NO）含量及内皮型一氧化氮合酶（eNOS）活性的影响及其机制。方法培养HUVECs,分为阴性对照组和THSG 1,10,100 μmol•L－1组,用分光光度比色法检测HUVECs上清液中NO含量和eNOS活性,RT PCR法检测HUVECs eNOS mRNA水平,Western Blot检测HUVECs eNOS蛋白表达。结果与阴性对照组比较,THSG各剂量组HUVECs中NO含量和NOS活性显著提高,eNOS mRNA和蛋白表达上调（P＜0.05）,并呈剂量依赖性。结论THSG可通过上调血管内皮细胞中eNOS表达来增加NO量,从而发挥舒张血管作用。     

氧化应激在乙醇诱导内皮细胞凋亡中的作用

目的 观察乙醇诱导的内皮细胞凋亡及氧化应激所起的作用.方法 体外培养人内皮细胞株EA.hy926,实验分对照组、实验组（ 0.6% 乙醇）、N-乙酰半胱氨酸（NAC）组（0.6% 乙醇＋ 10 mmol•L^-1 NAC）,各组以相应药物孵育12 h,采用四甲基偶氮唑蓝法检测细胞抑制率,流式细胞仪检测细胞活性氧（ROS）和凋亡率,相应试剂盒测定超氧化物歧化酶（SOD）活力及丙二醛（MDA）水平.结果与对照组相比,实验组内皮细胞增殖受到明显抑制,SOD活力从(40.8±2.9 )U•mg^-1蛋白降至（29.2±4.0） U•mg^-1蛋白、MDA水平由（46.5±3.8） nmol•mg^-1蛋白升至（89.5±5.6） nmol•mg^-1蛋白、ROS荧光强度从（93.69±7.58）升高到（162.30±18.85）,凋亡率由（0.49± 0.16）% 增至（5.31±0.54）% (均P＜0.01);而NAC组凋亡率、ROS和MDA水平较实验组均降低（P＜0.01),SOD活力显著恢复.结论 乙醇引起的氧化应激在其诱导的内皮细胞凋亡中起重要作用.     

白藜芦醇对纤维蛋白上调大鼠脑血管内皮细胞白介素6表达的影响

目的观察白藜芦醇（resveratrol,Res）对体外大鼠脑血管内皮细胞与纤维蛋白共培养高表达白介素6（interleukin 6,IL 6）转录及蛋白水平的影响。方法大鼠脑血管内皮细胞分离后培养,加入1.0 mg•mL 1纤维蛋白和不同浓度白藜芦醇,通过RT PCR检测脑血管内皮细胞中IL 6转录水平,应用酶联免疫方法（ELISA）定量检测培养基中的IL 6水平。结果加入不同浓度（0,1,5,10,25和50 μmol•L 1）的白藜芦醇24 h后,25和50 μmol•L 1白藜芦醇组培养基中IL 6水平显著降低（均P＜0.01）;RT PCR结果显示,25和50 μmol•L 1白藜芦醇组大鼠脑血管内皮细胞中IL 6 mRNA显著下调（均P＜0.01）。结论白藜芦醇可降低纤维蛋白导致的大鼠脑血管内皮细胞中IL 6的表达。     

左旋单甲基精氨酸对大鼠肾小球清蛋白通透性的影响

目的探讨一氧化氮(NO)合成酶抑制药对大鼠体外肾小球清蛋白通透性的影响及可能的作用机制。方法用标准筛技术游离正常雄性SD大鼠肾小球,应用视频显微术通过肾小球体积变化计算肾小球清蛋白的通透性（Palb）。大鼠体外肾小球分别与不同浓度（0.5,1.0,2.0 mmol•L 1）NO 单甲基 L 精氨酸(L NMMA)培养30 min;与2.0 mmol•L 1L NMMA培养不同时间（15,30,45 min）。体外肾小球与2.0 mmol•L 1L NMMA及500 μmmol•L 1NO供体diethylenetriamine NONOate（DETA NONOate)培养45 min;与2.0 mmol•L 1L NMMA 及5 mmol•L 1超氧化物歧化酶（SOD）培养45 min。观察不同情况下Palb。结果与对照组比较,大鼠体外肾小球与0.5 mmol•L 1L NMMA培养30 min对Palb无明显影响,与1.0或2.0 mmol•L 1L NMMA培养导致Palb显著增加（P＜0.01）,且2.0 mmol•L 1L NMMA对Palb影响更为显著。体外肾小球与2.0 mmol•L 1L NMMA培养15,30,45 min,Palb均较对照组明显增加（均P＜0.01）,且随时间延长Palb逐渐增加,培养45 min时Palb最大。体外肾小球与L NMMA及DETA NONOate一起培养45 min,Palb无明显增加;与L NMMA及SOD一起培养45 min,Palb亦无明显增加。结论 NO是肾小球清蛋白滤出的调节因子,生成减少导致Palb增加,过氧化物活性可能参与NO合成酶抑制药引起的清蛋白排泄增加。     

连芪消渴胶囊对糖尿病肾病模型大鼠晚期糖基化终末产物与氧化应激损伤的影响

［摘要］目的通过观察连芪消渴胶囊对糖尿病肾损害大鼠晚期糖基化终末产物（AGEs）及氧化应激反应的影响,探讨该药对糖尿病大鼠肾损害的干预作用和初步机制。方法大鼠高糖高脂饲料喂养4周并腹腔注射低剂量（30 mg•kg 1）链脲佐菌素(STZ),诱发糖尿病大鼠肾损伤模型,分为正常对照组,模型组,连芪消渴胶囊低、中、高剂量（2, 4, 8 g•kg 1•d 1）组,二甲双胍组（0.2 g•kg 1•d 1）,治疗8周取血、留尿、取肾组织,检测大鼠血糖、尿微量清蛋白（U mALB）、肾组织超氧化物歧化酶（SOD）、丙二醛（MDA）、血AGEs、生长转化因子（TGF β1）、肿瘤坏死因子（TNF α）等,肾组织苏木精 伊红（HE）染色的病理变化。结果连芪消渴胶囊组血糖（18.67±2.52） mmol•L 1,MDA（1.78±0.39） nmol•g 1,U mALB（41.84±8.23） μg•L 1,血AGEs（116.91±19.96） ng•mL 1,TGF β1（33.22±9.94） ng•mL 1,TNF α（54.01±17.55） pg•mL 1,均较模型组下降（P＜0.05）;SOD（190.11±15.88） U•mg 1,比模型组升高（P＜0.05）;肾功能和肾组织病理得到改善,其中连芪消渴胶囊大剂量组治疗效果显著。结论高糖高脂饲料联合低剂量STZ成功制备大鼠糖尿病肾病模型;连芪消渴胶囊能明显降低AGEs水平,减轻糖尿病肾损害,其机制可能与抑制AGEs的产生、降低氧化应激反应、抑制炎症因子等作用有关。     

七氟烷对兔心肌缺血-再灌注心律失常及NADPH氧化酶亚单位p22phox表达的影响

目的探讨七氟烷对兔心肌缺血-再灌注心律失常及还原型烟酰胺腺嘌呤二核苷酸磷酸（NADPH）氧化酶亚单位p22phox表达的影响。方法将兔随机分成3组,假手术组、模型组和七氟烷预处理组。制备兔心肌缺血-再灌注模型,硫代巴比妥酸反应产物（TBARS）显色分光光度比色法测定脂质过氧化物水平,免疫印迹法检测NADPH氧化酶亚单位p22phox表达。结果模型组室性心律失常发生率（90%）和持续时间［（158.82±18.86） s］均较假手术组明显增加（0%,0 s,P＜0.01,P＜0.01）;模型组心肌脂质过氧化物水平［（2.12±0.36） μg•g－1］显著高于假手术组［（0.89±0.11） μg•g－1,P＜0.01］,且p22phox亚单位表达显著上调。与模型组比较,七氟烷预处理组室性心律失常发生率（70%）和持续时间［（39.65±5.27） s］、心肌脂质过氧化物水平［（1.35±0.20） μg•g－1］及p22phox表达均显著下调。结论七氟烷可抑制兔心肌缺血 再灌注诱导的心律失常,其机制可能与下调p22phox表达进而抑制组织脂质过氧化物水平有关。     

川芎嗪对顺铂所致大鼠肾氧化损伤的保护作用

目的探讨川芎嗪（TMP）对顺铂（DDP）所致大鼠肾氧化损伤影响。方法将32只SD大鼠随机分成4组各8只：DDP+TMP 50 mg•kg－1•d－1组和DDP+TMP 100 mg•kg－1•d－1组分别腹腔注射TMP 50和100 mg•kg－1•d－1,连续5 d;对照组和DDP组给予0.9%氯化钠溶液,均5 mL•kg－1。给药第3天,除对照组外,其他3组腹腔注射DDP,8 mg•kg－1。实验第5天收集代谢笼中大鼠24 h尿,测尿蛋白含量;处死大鼠后测血清尿素氮（BUN）、肌酐（SCr）、24 h尿蛋白、肾皮质丙二醛（MDA）、还原型谷胱甘肽（GSH）、过氧化物歧化酶（SOD）、谷胱甘肽 S 转移酶（GST）活性及肾皮质一氧化氮（NO）含量、一氧化氮合酶（NOS）活性。结果与DDP组比较,DDP+TMP50 mg•kg－1•d－1组和DDP+TMP100 mg•kg－1•d－1组大鼠24 h尿蛋白分别下降41.45%和65.33%;BUN分别下降18.12%和57.51%;SCr分别下降14.39%和48.89%（P＜0.05或P＜0.01）;与DDP组比较,DDP+TMP 100 mg•kg－1•d－1组大鼠肾皮质MDA、NO含量及NOS活力分别降低36.73%,45.39%,22.86%（P＜0.05）,GSH含量和SOD、GST活性分别为DDP组的1.33,1.66,1.57倍（P＜0.05）。结论TMP对DDP所致大鼠肾氧化性损伤具有保护作用。     

普罗布考联合阿托伐他汀预防对比剂肾损害80例

目的探讨普罗布考联合阿托伐他汀防治冠状动脉介入性诊断及治疗术后急性肾损害的疗效。方法接受冠状动脉造影和介入治疗的患者250例,随机分为3组。联合预防组80例,术前及术后3 d服用普罗布考500 mg,bid;阿托伐他汀20 mg,qd;普罗布考组85例,术前及术后3 d服用普罗布考500 mg,bid;阿托伐他汀组85例,术前及术后3 d服用阿托伐他汀20 mg,qd。所有患者术后立即接受水化治疗12 h（1 mL•kg－1•h－1）。3组均给予防治冠心病标准用药,如肠溶阿司匹林、氯吡格雷、低分子肝素、β受体阻断药、血管紧张肽转化酶抑制药或血管紧张肽Ⅱ受体拮抗药。观察术前及术后3 d尿素氮（BUN）、肌酐清除率（Ccr）的变化并计算对比剂急性肾损害（CIAKI）发生率。结果联合预防组手术后BUN水平升高（3.12±0.54）mmol•L－1,Ccr水平升高（8.41±2.13） mL•min－1,CIAKI发生率3.75%,均明显优于其他两组［普罗布考组：（6.22±0.82） mmol•L－1,（17.14±2.29） mL•min－1,12.94%;阿托伐他汀组：（7.02±1.13） mmol•L－1,（22.09±2.38） mL•min－1,15.29%］（P＜0.05）。3组患者均无明显不良反应。结论普罗布考联合阿托伐他汀可显著降低CIAKI发生率,无明显不良反应。     

川芎嗪对大鼠肾缺血-再灌注后核因子-κB表达与一氧化氮合酶活性的影响

目的 研究川芎嗪对肾脏缺血－再灌注后肾功能、核因子-κB（NF-κB）的表达及一氧化氮合酶（NOS）活性的影响.方法 将30只SD大鼠随机分为假手术组、缺血－再灌注模型组和川芎嗪处理组,化学法检测血清肌酐（Cr）和尿素氮（BUN）浓度以及左肾组织中一氧化氮合酶活性,HE染色后镜下观察肾脏病理变化,免疫组化测定肾组织NF-κB的表达水平.结果川芎嗪15,30,45 mg•kg-1剂量于缺血前静脉注射均能降低再灌注时肾脏组织中NF-κB的表达,抑制诱生型NOS（iNOS）活性、降低尿素氮和肌酐水平,其中以15 mg•kg-1作用最为显著.结论 川芎嗪15,30,45 mg•kg-1剂量均能减轻肾缺血损伤, 其机制可能与抑制NF-κB的表达、降低iNOS活性有关,且该作用与川芎嗪的剂量相关,以15 mg•kg-1剂量的效果最好.     

野百合碱对培养的肺动脉内皮细胞NO含量、eNOS蛋白表达及肺动脉平滑肌细胞收缩性的影响

目的研究野百合碱(monocrotaline pyrrole,MCTP)对培养的牛肺动脉内皮细胞(calf pulmonary artery endothelial cells,CPAEs)一氧化氮(NO)含量、内皮型一氧化氮合酶(eNOS)蛋白表达及肺动脉平滑肌细胞收缩的影响。方法采用荧光共聚焦激光显微镜检测培养的牛肺动脉内皮细胞的NO含量;Western blot检测eNOS蛋白表达;胶原凝胶实验分析肺动脉平滑肌细胞收缩性。结果经野百合碱处理的牛肺动脉内皮细胞NO含量和eNOS蛋白表达较对照组明显减少、肺动脉平滑肌细胞收缩性增强。结论MCTP可抑制eNOS蛋白表达,肺动脉内皮细胞NO产生受到抑制,使肺动脉平滑肌细胞收缩性增强,这些改变与肺动脉高压的形成可能存在一定关系。     

Uncoupling of eNOS contributes to redox-sensitive leukocyte recruitment and microvascular leakage elicited by methylglyoxal

Elevated levels of the glycolysis metabolite methylglyoxal (MG) have been implicated in impaired leukocyte–endothelial interactions and vascular complications in diabetes, putative mechanisms of which remain elusive. Uncoupling of endothelial nitric oxide synthase (eNOS) was shown to be involved in endothelial dysfunction in diabetes. Whether MG contributes to these effects has not been elucidated. By using intravital microscopy in vivo, we demonstrate that MG-triggered reduction in leukocyte rolling velocity and increases in rolling flux, adhesion, emigration and microvascular permeability were significantly abated by scavenging reactive oxygen species (ROS). In murine cremaster muscle, MG treatment reduced tetrahydrobiopterin (BH4)/total biopterin ratio, increased arginase expression and stimulated ROS and superoxide production. The latter was significantly blunted by ROS scavengers Tempol (300 μM) or MnTBAP (300 μM), by BH4 supplementation (100 μM) or by NOS inhibitor N^G-nitro-l-arginine methyl ester (l-NAME; 20 μM). In these tissues and cultured murine and human primary endothelial cells, MG increased eNOS monomerization and decreased BH4/total biopterin ratio, effects that were significantly mitigated by supplementation of BH4 or its precursor sepiapterin but not by l-NAME or tetrahydroneopterin, indicative of MG-triggered eNOS uncoupling. MG treatment further decreased the expression of guanosine triphosphate cyclohydrolase I in murine primary endothelial cells. MG-induced leukocyte recruitment was significantly attenuated by supplementation of BH4 or sepiapterin or suppression of superoxide by l-NAME confirming the role of eNOS uncoupling in MG-elicited leukocyte recruitment. Together, our study uncovers eNOS uncoupling as a pivotal mechanism in MG-induced oxidative stress, microvascular hyperpermeability and leukocyte recruitment in vivo.     

The effects of modulating eNOS activity and coupling in ischemia/reperfusion (I/R)

The in vivo role of endothelial nitric oxide synthase (eNOS) uncoupling mediating oxidative stress in ischemia/reperfusion (I/R) injury has not been well established. In vitro, eNOS coupling refers to the reduction of molecular oxygen to L-arginine oxidation and generation of L-citrulline and nitric oxide NO synthesis in the presence of an essential cofactor, tetrahydrobiopterin (BH(4)). Whereas uncoupled eNOS refers to that the electron transfer becomes uncoupled to L-arginine oxidation and superoxide is generated when the dihydrobiopterin (BH(2)) to BH(4) ratio is increased. Superoxide is subsequently converted to hydrogen peroxide (H(2)O(2)). We tested the hypothesis that promoting eNOS coupling or attenuating uncoupling after I/R would decrease H(2)O(2)/increase NO release in blood and restore postreperfused cardiac function. We combined BH(4) or BH(2) with eNOS activity enhancer, protein kinase C epsilon (PKC ε) activator, or eNOS activity reducer, PKC ε inhibitor, in isolated rat hearts (ex vivo) and femoral arteries/veins (in vivo) subjected to I(20 min)/R(45 min). When given during reperfusion, PKC ε activator combined with BH(4), not BH(2), significantly restored postreperfused cardiac function and decreased leukocyte infiltration (p?相似文献   

Cell type-specific recycling of tetrahydrobiopterin by dihydrofolate reductase explains differential effects of 7,8-dihydrobiopterin on endothelial nitric oxide synthase uncoupling

(6R)-5,6,7,8-Tetrahydro-l-biopterin (BH4) availability regulates nitric oxide and superoxide formation by endothelial nitric oxide synthase (eNOS). At low BH4 or low BH4 to 7,8-dihydrobiopterin (BH2) ratios the enzyme becomes uncoupled and generates superoxide at the expense of NO. We studied the effects of exogenously added BH2 on intracellular BH4/BH2 ratios and eNOS activity in different types of endothelial cells. Incubation of porcine aortic endothelial cells with BH2 increased BH4/BH2 ratios from 8.4 (controls) and 0.5 (BH4-depleted cells) up to ∼20, demonstrating efficient reduction of BH2. Uncoupled eNOS activity observed in BH4-depleted cells was prevented by preincubation with BH2. Recycling of BH4 was much less efficient in human endothelial cells isolated from umbilical veins or derived from dermal microvessels (HMEC-1 cells), which exhibited eNOS uncoupling and low BH4/BH2 ratios under basal conditions and responded to exogenous BH2 with only moderate increases in BH4/BH2 ratios. The kinetics of dihydrofolate reductase-catalyzed BH4 recycling in endothelial cytosols showed that the apparent BH2 affinity of the enzyme was 50- to 300-fold higher in porcine than in human cell preparations. Thus, the differential regulation of eNOS uncoupling in different types of endothelial cells may be explained by striking differences in the apparent BH2 affinity of dihydrofolate reductase.     

内皮型一氧化氮合酶脱偶联的研究进展

血管内皮功能障碍(endothelial dysfunction)是多种心脑血管疾病的共同病理机制,其突出表现为内皮依赖性血管舒张功能障碍,主要由NO减少及氧自由基增加所致。最新研究发现,内皮型一氧化氮合酶脱偶联(eNOS uncoup ling)是导致NO水平下降和氧自由基水平升高的重要机制,是高血压、糖尿病、动脉粥样硬化等疾病中内皮功能障碍的重要原因。通过纠正eNOS脱偶联可有效改善内皮功能,有望为保护血管内皮功能提供有效途径。     

普罗布考对高血压合并脑梗死患者氧化型低密度脂蛋白水平的影响*

【摘要】 目的 探讨急性脑梗死患者氧化型低密度脂蛋白(ox-LDL)水平的特点及ox-LDL致脑梗死的发病机制,评价普罗布考对ox-LDL及血管功能的改善作用。方法 120例急性脑梗死患者根据是否合并高血压分为血压正常组和合并高血压组各60例,再将2个病例组分别随机分为干预组和未干预组,每组30例,干预组患者在常规治疗的基础上加用普罗布考治疗,所有患者分别于治疗前,治疗后2周、12周检测ox-LDL、内皮型一氧化氮合酶(eNOS)及NO水平。结果脑梗死合并高血压组的ox-LDL高于正常血压组,eNOS、NO水平低于正常血压组。对于脑梗死正常血压患者,普罗布考干预治疗12周后,TC、HDL、ox-LDL水平降低,eNOS升高(P<0.05)。对于脑梗死合并高血压患者,普罗布考干预治疗12周后,TC、TG、LDL、ox-LDL水平降低,eNOS、NO升高(P<0.05)。结论 普罗布考除具有调脂作用外,还可降低ox-LDL水平,改善血管内皮功能,稳定斑块,有利于防止发生动脉粥样硬化。     

Genistein ameliorated endothelial nitric oxidase synthase uncoupling by stimulating sirtuin-1 pathway in ox-LDL-injured HUVECs

Endothelial nitric oxidase synthase (eNOS) uncoupling plays a causal role in endothelial dysfunction in atherosclerosis. Genistein consumption has been associated with the prevention of atherosclerosis. However, the effect of genistein on eNOS uncoupling has not been reported. A model of oxidized low-density lipoprotein (ox-LDL)-induced injury on human umbilical vein endothelial cells (HUVECs) was established to evaluate the effect of genistein on eNOS uncoupling. We investigated the effect of genistein on NADPH oxidase-dependent superoxide production, NOX4 expression, BH4 synthesis and oxidation, the expression of GTP cyclohydrolase 1 (GCH1) and dihydrofolate reductase (DHFR). The results showed that genistein decreased superoxide production and NOX4 expression, enhanced the ratio of BH4/BH2, augmented the expressions of GCH1 and DHFR. Accompanied with genistein ameliorating eNOS uncoupling, genistein elevated the expression of sirtuin-1; furthermore, the effects of genistein on eNOS uncoupling were blunted with sirtuin-1 siRNA. The present study indicated that genistein ameliorated eNOS uncoupling was concerned with sirtuin-1 pathway in ox-LDL-injured HUVECs.     

Understanding eNOS for pharmacological modulation of endothelial function: a translational view

Knowledge about the function of endothelial nitric oxide synthase (eNOS), and its regulation in pathophysiological states has tremendously increased. It is now clear that diminished activity of nitric oxide (NO) contributes to endothelial dysfunction, which is a characteristic of impeding atherosclerosis. This review aims to summarize the available knowledge about the impact of important cardiovascular risk factors on NO production by eNOS. There are 4 principle causes of diminished NO bio-activity: decreased expression and/or activity of the eNOS enzyme, eNOS uncoupling, enhanced breakdown or scavenging of NO and impaired transmission of NO-mediated signaling events (failure of the effector mechanisms). From the analysis, it becomes clear, that several aspects of eNOS functionality have only scarcely been tested under conditions of increased (experimental) cardiovascular risk. These aspects include palmitoylation, myristoylation and phosphorylation of the eNOS enzyme. Clear is that enhanced production of reactive oxygen species (ROS) and eNOS uncoupling are relatively important causes of reduced NO-bioactivity in cardiovascular disease states. Ideally, eNOS is sufficiently expressed, produces NO sufficiently and not abundantly, does not produce superoxide and is not scavenged by ROS; the produced NO then reaches its signaling target, mainly soluble guanylyl cyclase (sGC) and elicits a cellular response. Considering which aspects of eNOS are now assessable in a clinical setting and which therapeutic measures are available, there is a great challenge ahead.     

一氧化氮参与非诺贝特抗高糖高胰岛素诱导的心肌肥大

目的研究过氧化物酶体增殖物激活受体-α(peroxi-some proliferator-activated receptor-α,PPAR-α)特异性激动剂非诺贝特(fenofibrate,FF)在高糖高胰岛素(high glucose and insulin,HGI)所致心肌细胞肥大中的作用及其与一氧化氮(nitric oxide,NO)途径的关系。方法乳鼠心肌细胞培养,以细胞表面积、蛋白含量和心房利钠因子mRNA表达为心肌肥大反映指标,观察FF对HGI致肥大作用的影响。利用Real-time PCR和Western blot方法检测mRNA及蛋白水平的表达;比色法和硝酸还原法分别检测细胞培养液中一氧化氮合酶(nitric oxide synthase,NOS)的活性和NO的浓度。结果FF浓度依赖性地抑制HGI诱导的心肌细胞肥大(P<0.01);FF0.3μmol·L-1明显上调HGI导致的PPAR-α以及内皮型一氧化氮合酶(endothelial nitric oxide synthase,eNOS)mRNA和蛋白表达的降低(P<0.05);并增加HGI降低的NOS活性和NO浓度(P<0.01)。PPAR-α阻断剂MK886可完全取消FF的上述作用(P<0.05)。L-精氨酸的作用与FF相似(P<0.01)。结论FF可能通过激活PPAR-α,从而促进eNOS的表达及NO的释放,产生抗HGI诱导心肌肥大的作用。     

Stress and vascular responses: oxidative stress and endothelial dysfunction in the insulin-resistant state

Although insulin-resistant states have been associated with endothelial dysfunction due to increased vascular oxidative stress, the underlying mechanisms are pooly understood. Recent experimental evidence suggests that tetrahydrobiopterin (BH(4)), the natural and essential cofactor of NO synthases (NOS), plays a crucial role not only in increasing the rate of NO generation by NOS but also in controlling the formation of superoxide anion (O(2)(-)) in endothelial cells. Because insulin resistance has been suggested to be a significant contributing factor in the development of abnormal pteridine metabolism and endothelial dysfunction, we investigated pteridine content and NO/O(2)(-) production with the use of isolated thoracic aortas obtained from fructose-induced insulin-resistant rats. Under insulin-resistant conditions where BH(4) levels are suboptimal, the production of O(2)(-) by NOS leads to endothelial dysfunction. Furthermore, oral supplementation of BH(4) restores endothelial function and relieved oxidative tissue damage, at least in part, through activation of endothelial NOS (eNOS) in the aorta of insulin-resistant rats. These results indicate that insulin resistance may be a pathogenic factor for endothelial dysfunction through impaired eNOS activity and increased oxidative breakdown of NO due to enhanced formation of O(2)(-), which are caused by relative deficiency of BH(4) in vascular endothelial cells.