白细胞介素-2引起离体大鼠主动脉环舒张及其作用机制

本文旨在研究白细胞介素－2（interleukin-2,IL-2）以离体大鼠胸主动脉环收缩张力的作用及其可能机制。采用累积加药法,检测IL－2对去氧肾上腺素（PE）和KCl预收缩的胸主动脉环收缩张力的影响。结果表明,IL－2（1、10、100、1000U／ml）对PE（10μmol/L）预收缩的内皮完整血管环产生浓度依赖性的舒张作用,而对KCl (120mmol/L）预收缩的血管无作用,去除内皮后,IL－2的舒张作用被取消。用一氧化氮合酶抑制剂L－NAME（0.1mmol/L）和鸟苷酸环化酶抑制剂亚甲蓝（10μmol/L）预处理,均可阻断IL－2的舒张血管作用。用环氧合酶抑制剂吲哚美辛（Indo,10μmol/L）预处理可阻断IL－2的血管舒张作用。从上述观察结果推论,IL－2通过NO－鸟苷酸环化酶和环氧合酶途径产生内皮依赖的血管舒张作用。     

CYP4A抑制剂HET0016对小鼠离体主动脉血管张力的影响

为研究CYP4A抑制剂HET0016对小鼠离体主动脉血管张力的影响,对雄性C57BL/6J小鼠进行脱臼处死后,取主动脉并剪成3~4 mm长的血管环,固定于微血管测定仪的浴槽内,分别用高钾溶液(KCl 60 mmol/L)和去氧肾上腺素(Phe 1μmol/L)进行血管功能性检测,发现二者均能让离体主动脉环产生持续性收缩;然后采用累积给药法观察1μmol/L Phe处理组、60 mmol/L高钾处理组、eNOS抑制剂L-NAME(100μmol/L)和L-钙通道阻滞剂nifedipine(1μmol/L)单独或共同孵育后Phe(1μmol/L)预收缩处理组中不同浓度HET0016对小鼠离体主动脉环张力的影响,并探讨其可能的作用机制。结果发现,高浓度的HET0016可以舒张高钾和Phe预收缩的内皮完整的主动脉环;对于L-NAME单独孵育后Phe预收缩的内皮完整的主动脉环,只有高浓度的HET0016有显著舒张作用;而对于nifedipine单独孵育以及L-NAME和nifedipine共同孵育后Phe预收缩的主动脉环,HET0016的舒张作用呈明显的浓度依赖性。这些结果显示,HET0016这种舒张作用是多通道的,呈部分的内皮依赖性,但也不是主要通过L-电压门控钙通道产生,只有在高浓度的情况下才开始影响L-电压门控钙通道。     

大、小动脉内皮细胞乙酰胆碱作用靶标药理学特性的比较

目的 :比较大、小动脉内皮细胞乙酰胆碱作用靶标药理学特性的差异。方法 :采用大鼠尾动脉螺旋状血管条和主动脉离体血管环两种组织 ,对比观察乙酰胆碱 (ACh)诱发大、小动脉内皮依赖性舒张反应特征的差异 ,从而进一步研究小动脉内皮细胞乙酰胆碱作用靶标的药理学特性。结果 :氯化钾 (6 0mmol/L)预致血管收缩的尾动脉和主动脉对不同浓度ACh (10 -8～ 10 -4mol/L)产生内皮依赖性舒张反应 ,且呈剂量依赖性。L Nω 硝基精氨酸甲酯 (L NAME :10 -4mol/L)或美蓝 (MB :10 -5mol/L)与吲哚美辛 (Indo :10 -4mol/L)联用仅可部分地阻断ACh诱发尾动脉内皮依赖性舒张反应 ;而L NAME或MB可完全阻断ACh诱发主动脉内皮依赖性舒张反应。结论 :ACh激活大、小动脉上内皮细胞乙酰胆碱作用靶标诱发内皮依赖性舒张反应的药理学性质不同 ,在小动脉上 ,除了NO和PGI2介导外 ,还有一种非NO和非PGI2 的舒血管因子参与 ;在大动脉上 ,内皮依赖性舒张反应主要由NO介导     

胍丁胺对离体大鼠主动脉张力的影响及其受体机制

采用离体血管环灌流方法,观察了胍丁胺（agmatine,Agm)对大鼠胸主动脉张力的影响,并探讨其受体机制,实验结果如下：（1）在苯肾上腺素PE,10^-6mol/L)引起血管预收缩的 基础上,Agm(10^-7-10^-2mol/L)剂量依赖性地舒张大鼠胸主动脉。（2）上述舒张反应在去除内皮和应用NOS抑制剂N^-G-mnitro-L-arginine methyl ester(L-NAME,0.5mmol/L)后依然存在,提示Agm的舒血管作用为非内皮依赖性,并无NO的参与。（3）在高Ca^2 (3mmol/L)引起血管预收缩的基础上,Agm也可剂量依赖性地舒张大鼠主动脉。（4）预先应用α2－肾上腺素能受体（α2－adrenergic receptor,α2－AR）和咪唑啉受体（IR）阻断剂idazoxan(10^-4mol/L)则可完全阻断Agm的上述作用。（5）应用α2－AR拮抗剂yohimbine(10^-4mol/L)可部分阻断Agm对大鼠主动脉的舒张反应,以上结果表明,Agm对大鼠主动脉血管的舒张作用是由α2－AR和IR共同介导。     

超氧阴离子抑制大鼠肠系膜阻力血管内皮依赖性舒张功能

目的:研究超氧阴离子对大鼠肠系膜阻力血管内皮细胞超极化因子(EDHF)和一氧化氮(NO)引起的血管舒张作用的影响及其可能机制.方法:雄性Sprague-Dawley大鼠,取肠系膜血管三级分支约2 mm长血管环,置于DMT 610 M系统,记录张力变化.血管环浴液中加入焦酚建立超氧阴离子损伤模型.结果:焦酚(10,100,300和1 000 μmol/L)可浓度依赖性地引起乙酰胆碱(ACh)诱导的肠系膜阻力血管舒张功能减弱;其中,300 μmol/L焦酚显著减弱肠系膜血管环由ACh诱导的EDHF和NO介导的内皮依赖性血管舒张效应,但对硝普钠和吡那地尔引起的内皮非依赖性的血管舒张作用无明显影响.结论:超氧阴离子可减弱阻力血管内皮依赖性舒张反应,其机制可能与超氧阴离子抑制了阻力血管内皮细胞EDHF和NO的作用有关.     

Apelin对大鼠离体肺动脉环的舒张作用及与一氧化氮的关系

目的：探讨新的小分子活性肽Apelin对大鼠离体肺动脉环的舒张作用及与一氧化氮（NO）途径的关系,并比较低氧大鼠的肺动脉环对Apelin的舒张反应与正常大鼠的差异。方法：36只大鼠随机分为正常组与低氧组;采用离体血管环灌流法,检测Apelin对去甲肾上腺素（NE）预收缩的大鼠离体肺主动脉环的舒张效应,观察去内皮或用一氧化氮合酶抑制剂（L-NAME）、可溶性鸟苷酸环化酶（sGC）抑制剂（ODQ）孵育后该舒张率的变化。结果：①在正常组大鼠肺动脉环,Apelin（0.01~100 nmol/L）具有浓度依赖性的舒张效应。去除内皮后,Apelin对NE预先收缩的肺血管舒张效应明显减弱（P〈0.01）。L-NAME或ODQ预孵育后,Apelin的舒张效应均明显减弱（P均〈0.01）。②低氧组大鼠的肺动脉环对Apelin的舒张反应明显低于正常组大鼠,在最大浓度100 nmol/L时,Apelin的效应低60.45%（P〈0.01）,而两组EC50相比差异无显著性（P〉0.05）。结论：Apelin具有内皮依赖性的舒张肺动脉环的作用,该效应与NO-sGC-cGMP信号途径有关;低氧大鼠的离体肺动脉环对Apelin的舒张反应减弱。     

美皂异黄酮非内皮依赖性血管舒张作用及其机制

目的:探讨植物雌激素美皂异黄酮舒张血管的可能机制。方法:采用MedLab生物信号采集系统记录灌流大鼠胸主动脉环张力变化。结果:美皂异黄酮(10-9~10-4mol/L)对苯肾上腺素(PE,10-5mol/L)预收缩的内皮完整或去内皮血管环均产生浓度依赖性的舒张作用;美皂异黄酮对高浓度氯化钾(KCl,6×10-2mol/L)预收缩的血管环也产生浓度依赖性的舒张作用;四乙胺(TEA,5×10-3mol/L)或格列苯脲(3×10-6mol/L)预处理对美皂异黄酮诱导的去内皮动脉环舒张作用具有明显的抑制效应;在无钙液中,美皂异黄酮抑制PE引起的去内皮主动脉环的短暂收缩。结论:美皂异黄酮的非内皮依赖性血管舒张作用的机制可能涉及血管平滑肌细胞的Ca2+激活K+通道和ATP敏感性K+通道的激活,以及肌浆网内钙离子释放的减少。     

香青兰总黄酮对大鼠离体胸主动脉的舒张作用

香青兰(Dracocephalum MoldavicaL.)为传统维吾尔族药材,具有补益心脑之功效,现代研究表明其对冠心病、心绞痛等病具有治疗作用。该文作者采用大鼠离体胸主动脉灌流技术,观察了香青兰总黄酮的血管舒张作用,旨在为阐明其活性物质基础和作用机制提供依据。结果表明:1)10.0～40.0mg/L香青兰总黄酮对内皮完整和去内皮大鼠主动脉环的基础张力没有明显影响。2)10.0～40.0mg/L香青兰总黄酮对去甲肾上腺素(NE,10μmol/L)所致的内皮完整和去内皮血管均有浓度依赖性的舒张作用,对内皮完整血管的舒张作用更强;一氧化氮合酶抑制剂左旋硝基精氨酸甲酯L-NAME(0.1mmol/L)、鸟苷酸环化酶抑制剂亚甲蓝(10μmol/L)和环氧合酶抑制剂吲哚美辛(10μmol/L)预处理均可一定程度上抑制香青兰总黄酮的血管舒张作用,表明血管内皮合成的一氧化氮(NO)信号通路和前列环素(PGI2)信号通路参与了香青兰总黄酮的血管舒张作用。3)香青兰总黄酮预处理去内皮血管环可以抑制细胞外钙内流所致的血管收缩,但对细胞内钙释放所致的血管收缩没有影响,香青兰总黄酮对高钾(60mmol/L KCl)所致血管收缩没有...     

NO在CCK—8减轻肿瘤坏死因子诱导兔肺动脉反应性变化中的作用

为探讨八肽胆囊收缩素（CCK－8）缓解内毒素休克时肺动脉高压的作用机制,应用离体血管环张力测定技术及一氧化氮合酶（NOS）检测方法,观察了一氧化氮（NO）在CCK－8减轻肿瘤坏死因子－α（tumor necrosis factor-al-pha,TNF-α）的抑制肺动脉内皮依赖性舒张反应中的作用。结果显示：TNF－α（4000U／ml）孵育2h时,肺动脉对10^-6mol/L苯肾上腺素(phenylephrine,PE）和10^-6mol/L乙酰胆碱（ACh）的收缩反应及内皮依赖性舒张反应均无明显变化。TNF－α孵育7或14h时,肺动脉对10^-6mol/L ACh介导的内皮依赖性舒张反应降低,CCK－8（0.5μg/ml）可逆转TNF－α的上述作用,CCK－8本身对正常肺动脉反应性无明显影响。TNF－α、CCK－8对PE引起的收缩反应无显著影响。L－精氨酸（L－Arg）可使TNF－α7h内皮依赖性舒张作用恢复。氨基胍（AG）不影响各组肺动脉对10^-6mol/L ACh的内皮依赖性舒张反应,而使TNF－α组肺动脉环对10^-6mol/L PE的收缩反应显著增加。L－硝基精氨酸（L－NNA）使各组肺动脉环对10^-6mol/L ACh反应由舒张变为收缩,对10^-6mol/L PE的收缩反应显著增强。检测7h各组NOS活性,TNF－α组、TNF－α＋CCK－8组均较对照组显著增加,CCK－8组与对照组比较无显著差异。上述结果提示,CCK－8可逆转TNF－α对内皮依赖性舒张反应的抑制作用,此作用可能与NO有关。     

一氧化碳对大鼠离体肺动脉的舒张作用

本研究观察了一氧化碳 (CO)对离体大鼠肺动脉的舒张作用。制备Wistar大鼠肺动脉环 ,作出ACh浓度效应曲线之后 ,肺动脉环用一氧化氮合成酶抑制剂L NAME 3 0 μmol/L (n =10 )或血红素氧化酶抑制剂ZnPPIX 10μmol/L +L NAME 3 0 μmol/L (n =10 )孵育 3 0min ,再制备一个ACh的浓度效应曲线 ,观察ZnPPIX对ACh的浓度效应曲线的影响。另取一组肺动脉环 ,分为内皮完整组和去内皮组 ,观察外源性CO对肺动脉环张力的影响。结果表明 ,用L NAME孵育后 ,ACh的血管舒张反应受抑 ,最大抑制率为 5 0 4± 9 2 % ;用ZnPPIX +L NAME孵育后 ,ACh的血管舒张反应进一步受抑 ,最大抑制率为 84 4± 11 2 %。外源性CO无论对内皮完整组还是去内皮组肺动脉都有舒张作用。本研究提示 ,ZnPPIX可抑制ACh的内皮依赖性肺动脉舒张反应 ,CO是一个内皮源性的血管舒张因子 ,外源性CO可舒张肺动脉     

葛根素对抗高糖诱导的血管低反应性的作用及其机制

目的：研究葛根素是否可对抗高糖引起的血管低反应性,并探讨其作用机制。方法：采用血管环离体灌流装置,观察SD大鼠胸主动脉环的收缩反应;测定主动脉胆红素生成量反映血红素加氧酶-1（heme oxygenase-1,HO-1）的活性。结果：①与空白对照组（含11 mmol/L葡萄糖）相比,经44 mmol/L葡萄糖（高糖）孵育血管4 h后,主动脉环对苯肾上腺素（PE）引起的血管收缩反应下降;且该作用通过内皮依赖性途径实现。②葛根素（10-10~10-8mol/L）与高糖联合孵育,可剂量依赖性地改善高糖诱导的血管PE收缩反应的下降。③葛根素孵育血管后可引起血管HO-1活性增高;用ZnPP抑制HO-1的活性后,葛根素抗高糖损伤的作用被取消。结论：葛根素具有对抗高糖引起的血管收缩功能下降的作用,其机制可能是通过诱导HO-1活性增加实现的。     

乙酰胆碱不依赖NO的释放引起耳蜗螺旋动脉平滑肌细胞的超极化

目的：乙酰胆碱（ACh）不仅是神经递质,也是一种有效的血管舒张物质参与许多血管床的调节活动。本实验观察ACh引起耳蜗螺旋动脉平滑肌细胞超极化的离子机制以及NO在超极化反应中的可能作用。方法：在豚鼠离体耳蜗螺旋动脉标本上,运用细胞内微电极技术记录外源性的ACh引起的反应。结果：在保持灌流液中含有5mmol／L K^＋以及最小纵向张力的情况下,ACh（0．1—10μmol／L）引起低静息膜电位细胞明显的超极化反应,而引起高静息膜电位细胞明显的去极化反应。ACh引起的平滑肌细胞超极化反应是浓度依赖性的（ACh的浓度是1μmol／L和10／μmol／L时,分别引起超极化的幅度是22和30mV,n=7）。ACh引起的超极化反应能被阿托品（atropine,0．1～1μmol／L,n=6）或DAMP（50～100nmol／L,n=6,一种选择性的地受体的拮抗剂）所阻断,同时也可被BAPTA—AM（10μmol／L,n=7,一种可通过细胞膜的Ca^2＋螯合剂）或eharybdotoxin＋apamin（50-100nmol／L,n=4,两种Ca^2＋激活K^＋通道的阻断剂）所阻断,但是Nω-nitro-L-arginine methyl ester（L-NAME,300μmol／L,n=8,一种NO合成酶的完全抑制剂,n≥5）或glipizide（10μmol／L,ATP敏感性的K^＋通道阻断剂,n=4）或indomethacin（10μmol／L,环氧合酶的抑制剂,n=4）不能阻断ACh引起的超极化反应。结论：ACh通过激活内皮细胞的M3受体,开放钙依赖的钾通道．进而引起耳蜗螺旋动脉平滑肌细胞产生超极化反应,并且这一超极化反应与内皮细胞NO的产生和释放无关。     

Iptakalim ameliorates relaxation to acetylcholine in thoracic aortic rings impaired by microvesicles derived from hypoxia/reoxygenation-treated HUVECs

Objective: To investigate the effect of Iptakalim(Ipt) preventing injury of endothelial microvesicles(EMVs) derived from hypoxia/reoxygenation(H/R)-treated HUVECs on the relaxation of rat thoracic aortic rings and explore the underlying mechanism. Methods: H/R injury model was established to release H/R-EMVs from HUVECs. H/R-EMVs from HUVECs were isolated by ultracentrifugation from the conditioned culture medium. H/R-EMVs were characterized by using Transmission Electron Microscope(TEM). Thoracic aortic rings of rats were incubated with 10~(-7)-10~(-3 )mol/L Ipt and co-cultured with 10 μg/ml H/R-EMVs for 4 hours, and their endothelium- dependent relaxation in response to acetylcholine(ACh) was recorded in vitro. The nitric oxide(NO) production of ACh-treated rat thoracic aortic rings was measured by using Griess reagent. The expression of endothelial NO synthase(e NOS), phosphorylated e NOS(p-e NOS, Ser-1177), serine/threonine kinas(Akt) and phosphorylated Akt(p-Akt, Ser-473) in the thoracic aortic rings of rats was detected by Western blotting. Results: H/R-EMVs were induced by H/R-treated HUVECs and isolated by ultracentrifugation. The isolated H/R-EMVs subjected to TEM revealed small, rounded vesicles(100–1 000 nm) surrounded by a membrane. H/R-EMVs impaired relaxation induced by ACh of rat thoracic aortic rings significantly. Compared with H/R-EMVs treatment individually, relaxation and NO production of rat thoracic aortic rings were increased by Ipt treatment in a concentration-dependent manner(P0.05, P0.01). The expression of total e NOS(t-e NOS) and total Akt(t-Akt) was not affected by Ipt or H/R-EMVs. However, the expression of p-e NOS and p-Akt increased after treated with Ipt(P0.01). Conclusion: Based on H/R-EMVs treatment, ACh induced endothelium-dependent relaxation of rat thoracic aortic rings was ameliorated by Ipt in a concentration-dependent manner. The mechanisms involved the increase in NO production, p-e NOS and p-Akt expression.     

肾上腺髓质素2的降压作用及其机制

目的:研究肾上腺髓质素2(ADM2)拮抗血管紧张素Ⅱ(AngⅡ)发挥舒张血管的作用及机制。方法:将18只180~200 g雄性SD大鼠随机分为3组(n=6):对照组、AngⅡ(150 ng/(kg·min))组和AngⅡ(150 ng/(kg·min))+ADM2(500 ng/(kg·h))组,采用皮下埋植微量渗透泵的方法给药。2周后颈动脉插管法测量大鼠血压,测定血浆一氧化氮(NO)含量和内皮型一氧化氮合酶(eNOS)活性。DHE染色法检测大鼠动脉壁活性氧产生。制备大鼠离体血管环,观察ADM2的舒血管作用。培养人脐静脉内皮细胞系EA.hy 926,用DCFH-DA荧光探针检测AngⅡ和ADM2对血管内皮细胞活性氧释放的影响。结果:与AngⅡ组相比,ADM2显著降低了大鼠血压,血浆中eNOS活性提高、NO含量增加,血管壁活性氧产生减少。ADM2呈浓度依赖性和内皮依赖性舒张血管环,并明显抑制了AngⅡ引起的血管内皮细胞活性氧产生。结论:ADM2可能通过拮抗AngⅡ诱导的血管内皮氧化应激效应,改善内皮功能,发挥舒张血管、降低血压的作用。     

Evaluation of the mechanism of endothelial dysfunction in the genetically-diabetic BB rat

Endothelial dysfunction is known to occur in chemically-induced animal models of diabetes. The BB diabetic rat is a genetic diabetes-prone model which more closely resembles Type I diabetes mellitus. In this study, we examined the role of Superoxide anion radical and cyclooxygenase activity on endothelial dysfunction in aorta of the spontaneous diabetic BB rat. Vascular endothelial function was studied in vitro in aortic rings from 8-wk diabetic rats and agematched nondiabetic littermates. There was no alteration in reactivity to norepinephrine as a result of diabetes. Relaxation to acetylcholine (but not nitroglycerin) was impaired in diabetic rings. Relaxation to acetylcholine was abolished by 100 μM L-nitroarginine but unaltered by an equimolar concentration of aminoguanidine (an inducible nitric oxide synthase inhibitor) in both control and diabetic rings. Incubation with 10 μM indomethacin did not alter relaxation to acetylcholine in either control or diabetic rings. In contrast, addition of 20 U/ml Superoxide dismutase enhanced relaxation to acetylcholine in diabetic rings but had no effect on relaxation to acetylcholine in control rings. Thus, nitric oxide-mediated, endothelium-dependent relaxation is diminished in aortic rings of the genetic diabetic BB rat. Furthermore, Superoxide anion radicals but not cyclooxygenase products play an important role in endothelial dysfunction in this genetic diabetic model.     

Vasorelaxant effect of the flavonoid galangin on isolated rat thoracic aorta

Here we investigated the effect of the flavonoid galangin in isolated rat thoracic aortic rings. Galangin (0.1-100 microM) induced relaxation in rings pre-contracted with phenylephrine (PE 1 microM) or with KCl (100 mM) or pre-treated with the nitric oxide synthase inhibitor Nomega-nitro-L-arginine methyl ester (L-NAME, 100 microM), the cyclooxygenase inhibitor indomethacin (10 microM) and the adenylate cyclase inhibitor, SQ 22,536 (100 microM). In another set of experiments, rat aortic rings were incubated with galangin (1-100 microM) and the contractile responses to PE (0.001-3 microM) or to KCl (60 mM) were evaluated. We also evaluated the effect of galangin (100 microM) on PE (10 microM)-induced contraction in a Ca2+-free medium. Galangin relaxed aortic rings with or without endothelium. Galangin effect was significantly inhibited by L-NAME. Galangin inhibited the contractile response to PE, either in presence or in absence of external calcium, and to KCl. In the end, we also found that galangin caused nitric oxide (NO) release from aortic rings and abolished the increase in [Ca2+]i triggered by PE or KCl in aortic smooth muscle cells, either in presence and in absence of external Ca2+. Our results suggest that galangin reduces the contractility of rat aortic rings through an endothelium-dependent mechanism, involving NO, and also through an endothelium-independent mechanism, inhibiting calcium movements through cell membranes.     

黄芪苷Ⅳ对微囊泡损伤的大鼠胸主动脉环舒张功能的保护作用

目的：以缺氧/复氧诱导人脐静脉内皮细胞（HUVECs）释放的微囊泡（H/R-EMVs）处理大鼠胸主动脉环,造成其舒张功能损伤,探究黄芪苷Ⅳ（AST）对大鼠胸主动脉环舒张功能的影响及相关机制。方法：采用缺氧12 h/复氧4 h的方法诱导体外培养的HUVECs产生MVs,H/R-EMVs保存于D-Hank's液中备用。雄性Wistar大鼠开胸取出胸主动脉,制备3~4 mm宽、内皮完整的胸主动脉环。实验分为6组：H/R-EMVs组,在孵育胸主动脉环的培养基中加入H/R-EMVs,使其终浓度为10μg/ml;不同剂量AST组分别采用10、20、40、60 mg/L AST与10μg/ml H/R-EMVs共同孵育胸主动脉环;对照组给予等体积的D-Hank's溶液。孵育时间为4 h,每组各测定5个血管环。观察AST对舒张功能的影响,检测一氧化氮（NO）含量及t-eNOS、p-eNOS、t-Akt、p-Akt、ERK1/2和p-ERK1/2蛋白质水平。结果：H/R-EMVs对大鼠胸主动脉环舒张功能有明显的抑制作用（P<0.01）。与H/R-EMVs组相比,AST 20、40和60 mg/L组剂量依赖性地提高大鼠胸主动脉环的舒张率（P<0.01）,使NO含量增加（P<0.05,P<0.01）;t-eNOS、t-Akt和ERK1/2蛋白质水平不变,p-eNOS、p-Akt和p-ERK1/2蛋白质水平增高（P<0.01）。结论：AST可显著改善H/REMVs损伤的大鼠胸主动脉环的舒张功能,其机制与提高NO含量及增加p-eNOS、p-Akt和p-ERK1/2蛋白质水平有关。     

The effect of oxidative stress on endothelium-dependent and nitric oxide donor-induced relaxation: implications for nitrate tolerance.

Increased inactivation of nitric oxide (NO) by superoxide has been implicated in nitrate tolerance. Here, we set out to compare the inhibitory effect of superoxide on endothelium-dependent, acetylcholine (ACh)-mediated vascular relaxation with that on the endothelium-independent effects of glyceryl trinitrate (GTN) and another NO donor drug, S-nitrosoglutathione (GSNO). Rings of thoracic aorta from adult male Wistar rats (350-450 g) were precontracted with phenylephrine (approximately EC(90)) prior to cumulative additions (10 nM/L-10 microM/L) of GTN, GSNO, or ACh. Rings were then treated with the superoxide generator pyrogallol (300 micromol/L) alone or following pretreatment with the Cu/Zn superoxide dismutase inhibitor diethyldithiocarbamate (DETCA; 100 micromol/L), and cumulative additions of the vasodilators were repeated. All experiments were conducted in the presence of catalase (3000 U/ml) to prevent accumulation of hydrogen peroxide. Relaxation to ACh was abolished by pyrogallol-derived superoxide. Relaxation to GSNO was significantly inhibited by superoxide (P < 0.05, n = 8) and was more pronounced at lower GSNO concentrations. However, GTN was relatively resistant to inhibition by superoxide with modest inhibition only occurring in rings pretreated with DETCA prior to pyrogallol (P < 0.05; n = 8). In contrast to GSNO, the inhibitory effect was more pronounced with high concentrations of GTN, suggesting that the mechanism underlying superoxide-mediated inhibition is different for the two NO donor drugs. Further experiments showed that vascular responses to ACh were not inhibited (P > 0.05, n = 6) in aortic rings made tolerant to GTN (10 micromol/L, 2-h incubation) and that treatment of vessels with the antioxidant vitamin C (1 mmol/L) successfully prevented the development of tolerance. Taken together, these results suggest that superoxide is not a major factor in tolerance in vitro and imply that the protective actions of vitamin C are unrelated to its antioxidant activity in this setting.     

氧化应激在高原重体力劳动过程中急性高原反应发生中的作用

目的：观察氧化应激在高原重体力劳动过程中急性高原反应（AHAR）发生中的作用。方法：由低海拔（1500m）快速进入高原（3700m）并从事重体力劳动的男性官兵96名,年龄18～35岁。根据AHAR症状评分,分为重度AHAR组（A组,n=24）、轻中度AHAR组（B组,n=47）和无AHAR组（C组,n=25）,在该高度逗留50d后下撤前及返回低海拔（1500m）后12h、15d分别测定血清8．异前列腺素F2a（8-iso-PGF2a）、超氧化物歧化酶（SOD）、丙二醛（MDA）,并与低海拔（1500m）50名健康官兵（D组）比较。结果：A组血清8-iso-PGF2a、MDA[分别为（9．53±0．47）μg／L、（8．91±0．39）μmol／L]水平显著高于B组[分别为（8．34±O．42）μg／L、（7．31±0．32）μmol／L]、C组[分别为（7．02±0．48）μg／L、（6．41±0．23）μmol／L和D组[分别为（5．13±0．56）μg／L、（5．48±0．33）μmol／L]（均P〈0．01）,SOD（52．08±3．44）μ／mL水平显著低于B组（62．27±2．54）μ/mL、C组（71．99±3．35）μ/mL和D组（80．78±3．44）μ/mL,（均P〈0．01）,B组与c组之间和C组与D组之间亦有显著性差异（均P〈0．01）。海拔3700mAHAR总计分与血清8-iso-PGF2α、ⅣⅡ）A呈显著正相关（均P〈0．01）,与血清SOD显著负相关（P〈0．01）;8-iso-PGF2α、MDA与SOD显著负相关（均P〈0．01）。海拔3700m50d,血清8-iso-PGF2α、MDA水平显著高于,SOD水平显著低于海拔1500m12h、15d和D组（均P〈0．01）,海拔1500m12h与15d之间有显著性差异（均P〈0．01）,海拔1500m 15d与D组之间无显著性差异。结论：人体在高原低氧并重体力时氧化应激和氧化．抗氧化失衡与AHAR的发病和程度有密切关系,氧化应激和氧化．抗氧化失衡越严重,AHAR越重。返回低海拔后12h有显著改善,15d恢复到正常水平。