ERK1/2参与自发性高血压大鼠离体血管环对apelin-13舒张反应性降低作用

研究自发性高血压大鼠(spontanously hypertensive rat,SHR)离体血管环对G蛋白偶联受体APJ的内源性配体apelin-13的血管收缩与舒张反应及其与一氧化氮(NO)和ERK1/2通路关系．采用离体血管环体外灌流方法用Power-Lab生物信息采集仪检测血管环的张力．实验分组如下：新福林(Phenylephrine,PE)组,乙酰胆碱(acetylcholine,Ach)组,apelin-13组,apelin-13 + PE组,apelin-13 + Ach组,PD98059(ERK1/2抑制剂) + PE组,PD98059 + Ach组,LNNA(L-nitro-arginine,硝基左旋精氨酸,一氧化氮合酶抑制剂) + PE组,LNNA+Ach组,apelin-13(预孵育) + PD98059 + PE组,apelin-13(预孵育)+PD98059+ Ach组,apelin-13(预孵育) + LNNA + PE组和apelin-13(预孵育) + LNNA + Ach组,以WKY大鼠血管环为对照组．培养大鼠血管平滑肌细胞,Western blot检测ERK1/2蛋白表达．结果显示：a．apelin-13对于有内皮的血管表现出浓度依赖性舒张作用,血管舒张百分比SHR < WKY大鼠,而对于去除内皮血管,apelin-13则表现出收缩血管的作用,且收缩张力SHR>WKY大鼠,apelin-13预孵育,能减少SHR和WKY大鼠血管对新福林的缩血管反应性,增加对乙酰胆碱的舒张反应性;b．NOS抑制剂LNNA阻断NO形成后,血管环对apelin-13的舒张反应明显抑制,且SHR组较WKY组对apelin的舒张反应减少更明显,提示apelin-13的舒血管效应至少部分依赖NO通路,而SHR高血压大鼠NO通路障碍减弱了apelin对血管的舒张作用;c．ERK1/2抑制剂PD98059预孵育后血管环对apelin-13表现出浓度依赖性的收缩,与去除内皮后apelin-13的收缩血管效应趋势一致,血管收缩张力SHR＞WKY大鼠,PD98059逆转了apelin-13引起的血管舒张效应;d．Apelin-13促大鼠VSMCs ERK1/2磷酸化增加并呈剂量依赖性和时间依赖性,ERK1/2抑制剂PD98059可以减少apelin-13诱导ERK1/2的磷酸化．结果表明,自发性高血压大鼠离体血管环对apelin-13舒张反应性降低, NO通路和ERK1/2通路介导了apelin-13的舒张血管作用．     

慢性缺氧对自发性高血压大鼠血液动力学和血管反应性的影响

本研究观察了鼠龄10周的自发性高血压大鼠(SHR)在慢性缺氧条件下(模拟海拔5000m,15d)体动脉压(SBP)、平均肺动脉压(MPAP)、左、右心室收缩指数(LVIC、RVIC)和舒张指数(LVIR、RVIR)以及血管反应性的变化。结果表明,慢性缺氧明显阻抑SHR大鼠SBP升高(P<0.05),但使SHR大鼠MPAP升高(P<0.001)。慢性缺氧还可增大SHR大鼠LVIC和LVIR,增强SHR大鼠胸主动脉对乙酰胆碱(ACh)的舒张反应,减弱其对5-羟色胺(5-HT)的收缩反应。SHR大鼠肺动脉对ACh和5-HT的反应则与主动脉相反。实验结果提示,慢性缺氧阻抑SHR大鼠血压升高与血管反应性的改变有关。     

蛋白激酶C对大鼠离体肺动脉环张力及其反应性的调节作用

目的 :观察蛋白激酶C(PKC)对大鼠离体肺动脉环张力及反应性的调节作用。方法 :取Wistar大鼠肺动脉 ,观察在离体情况下PKC激活剂PMA及PKC抑制剂RO3 182 2 0对肺动脉环张力的直接作用 ;对氯化钾 (KCl)、5 羟色胺 (5 HT)和缺氧引起的收缩反应的影响 ;以及PMA对乙酰胆碱 (ACh)介导的内皮依赖性舒张 (EDR)和硝普钠(SNP)介导的内皮非依赖性舒张 (EIDR)反应的影响。结果 :①PMA(5 0 0nmol/L)使肺动脉环产生缓慢增强、持久的收缩 ,随PMA浓度增加而增强 ,RO3 182 2 0 (5 μmol/L)可完全阻断PMA的上述作用 ;②PMA可增强肺动脉对KCl、5 HT的收缩反应 ,该作用随PMA浓度增加而增强 ;③RO3 182 2 0 (5 μmol/L)几乎可以完全阻断离体肺动脉环对缺氧的第二相收缩反应 ;④PMA(10nmol/L)在 10min内完全逆转ACh(10 μmol/L)介导的EDR ,PMA(10nmol/L)还可使ACh的浓度一反应显著减弱 ,达到最大舒张反应的一半时对应的ACh浓度 (EC50 )显著增加 ,最大舒张反应明显减小 ;而PMA对SNP介导的EIDR无显著影响。结论 :PKC在与肺动脉张力及反应性的调节有关的细胞内生物信号传递过程中具有重要作用。     

褪黑素改善内毒素血症大鼠血管反应性

观察褪黑素(melatonin,MT)对脂多糖(lipopolysaccharide,LPS)诱导的体循环和肺循环血管反应性失调的影响,并探讨可能的作用机制。实验分为溶剂对照组、LPS组、LPS+MT组和MT组。制备离体胸主动脉环和肺动脉环,应用血管张力检测技术检测各组血管环对苯肾上腺素(phenylephrine,PE)和乙酰胆碱(acetylcholine,ACh)的反应性并绘制累积剂量反应曲线;制备各组血管组织匀浆,测定丙二醛(malondialhyde,MDA)和超氧化物歧化酶(superoxidedismutes,SOD)含量变化。结果显示:与对照组相比,LPS6h后胸主动脉对PE的收缩反应减弱(P<0.01),对PE(1×10–8~1×10–5mol/L)累积剂量反应曲线下移;而肺动脉对ACh的舒张反应显著下降(P<0.01),对ACh(1×10–8~1×10–5mol/L)累积剂量反应曲线下移。加用MT可显著改善LPS诱导的胸主动脉对缩血管剂PE的低反应性,同时可逆转LPS对肺动脉舒张反应的抑制,LPS+MT组胸主动脉对PE的累积剂量反应曲线和肺动脉对ACh的累积剂量反应曲线位于对照组和LPS组之间;MT还可对抗LPS导致的脂质过氧化,使MDA含量减少,提高抗氧化酶SOD的活性。上述结果提示,MT可改善内毒素血症大鼠的血管反应性失调,抗氧化途径可能是其发挥保护作用的机制之一。     

慢性心力衰竭大鼠主动脉舒缩功能的变化及其机制

为探讨心力衰竭诱导的血管舒缩功能紊乱的相关机制,本实验对心梗后大鼠慢性心力衰竭(chronic heart failure,CHF)模型胸主动脉血管环的舒缩功能变化及可能的病理学机制进行了研究。将Sprague-Dawley大鼠随机分为两组:假手术(sham)组和慢性心衰(CHF)组。通过冠脉结扎法制作大鼠CHF模型。手术10周后,检测大鼠血流动力学指标及相关参数,之后迅速取出心脏并称重,TTC染色法检测心梗面积。制备大鼠胸主动脉环,利用敏感的肌张力描记技术,比较sham组和CHF组胸主动脉环的舒缩功能,观察血管环对KCl、CaCl2、苯肾上腺素(phenyle phrine,PE)和咖啡因(caffeine)的收缩反应以及对乙酰胆碱(acetylcholine,ACh)的舒张反应。并进一步研究一氧化氮合酶(nitricoxide synthase,NOS)抑制剂N-硝基-L-精氨酸甲酯(N-nitrl-L-arginine methylester,L-NAME)和非选择性环氧合酶(cyclooxy genase,COX)抑制剂吲哚美辛(indomethacin,Indo)对两组胸主动脉环ACh的反应曲线的影响。结果显示:(1)与sham组相比,CHF组大鼠胸主动脉环对血管收缩剂KCl(5～100mmol/L)和PE(1×10-8～3×10-4mol/L)的反应性明显提高,对血管舒张剂ACh(1×10-12～1×10-4mol/L)的反应性显著性降低(P0.01,P0.05);(2)L-NAME(1mmol/L)预处理后,CHF组血管对ACh(1×10-7～1×10-4mol/L)介导的内皮依赖性收缩明显增强(P0.05),加入Indo(10μmol/L)后该现象消失;(3)与Indo未处理组相比,Indo(10μmol/L)预处理后,CHF组血管对ACh(1×10-12～1×10-4mol/L)介导的舒张反应明显增强(P0.05);(4)在无钙K-H液中,与sham组相比,CHF组血管对CaCl2(1×10-4～3×10-2mol/L)介导的钙依赖性收缩曲线明显左移(P0.05);caffeine(30mmol/L)诱导的血管收缩未见显著性变化。以上结果表明,CHF大鼠的胸主动脉血管环收缩异常与内皮功能障碍有关,其机制可能是通过血管内皮细胞COX途径提高内皮收缩因子,和(或)通过电压依赖性钙通道增加外钙流入引起血管收缩性能提高。     

罗格列酮对胰岛素抵抗高血压大鼠主动脉功能的影响

为探讨罗格列酮(rosiglitazone,ROSI)对胰岛素抵抗高血压大鼠(insulin resistant-hypertensive rats,IRHR)主动脉功能的影响及其可能机制,用高果糖饲养Sprague-Dawley大鼠8周,制备IRHR模型,并通过相关指标的检测判断造模是否成功。随后采用血管环灌流方法,观察各实验组动物离体胸主动脉环对新福林(L-phenylephrine,PE)、氯化钾(KCl)的收缩反应和对乙酰胆碱(acetylcholine,ACh)、硝普钠(sodium nitroprusside,SNP)的舒张反应：以及用一氧化氮合酶(nitric oxide synthase,NOS)的抑制剂N-硝基-L-精氨酸甲酯(N^ω-nitro-L-arginine methyl ester,L-NAME)预孵育血管30min后,主动脉环对ACh的舒张反应：同时对各实验组血清一氧化氮(nitric oxide,NO)的含量进行测定。结果显示：(1)罗格列酮能降低IRHR的收缩压、血清胰岛素水平,改善胰岛素抵抗。(2)高果糖组动物主动脉对PE、KCl的收缩反应明显增强,对ACh的舒张反应明显减弱,ROSI可逆转上述作用。(3)用L-NAME预处理后,高果糖组动物主动脉对ACh的舒张反应进一步减弱,ROSI可部分对抗上述作用。(4)各组大鼠离体主动脉对SNP的舒张反应无显著性差异。(5)ROSI对对照组大鼠主动脉功能的影响不明显。(6)与对照组相比,高果糖组动物血清NO含量显著降低,用ROSI处理后,血清NO含量显著增加。上述结果表明,ROSI能改善IRHR主动脉的舒张功能,其作用的机制可能是部分通过NOS途径促进内皮NO释放,或是通过降低血压、血清胰岛素水平,以及改善胰岛素抵抗等作用,导致血管舒张。     

抗氧化剂丹酚酸A对缺氧鼠肺内动脉ACh舒张反应的影响

应用微量生物测定法观察了丹酚酸A(salvinolic acid A,Sal.A)对慢性缺氧(5000m,10d)大鼠(200～300g)肺内动脉ACh舒张反应的影响,并对其机制进行了初步探讨。实验发现,慢性缺氧可明显减弱大鼠肺内动脉ACh(10~(-8)～10~(-4)mol/L)舒张反应(P<0.01～0.001),在浴槽内先加入Sal.A(10~(-4)mol/L),缺氧鼠肺内动脉ACh舒张反应明显增强(P<0.01),而在浴槽内同时加入血管内皮舒张因子(EDRF)灭活剂phenidon(5×10~(-5)mol/L),则Sal.A上述增强缺氧鼠肺内动脉ACh舒张反应的作用消失。此外,本实验还发现,在以黄嘌呤(X,10~(-4)mol/ L)-黄嘌呤氧化酶(XO,0.01U/ml)系统产生氧自由基损伤正常大鼠肺内动脉ACh舒张反应的基础上,Sal.A(10~(-4)mol/L)同样可明显减弱氧自由基对大鼠肺内动脉ACh舒张反应的损伤作用。结果表明,Sal.A可消除氧自由基对肺血管内皮细胞释放的EDRF的破坏作用而具有保护慢性缺氧鼠肺内动脉ACh舒张反应的作用。     

有氧运动上调Agtr1a基因甲基化改善高血压肠系膜动脉ACE1-AT1R收缩轴功能

血管紧张素Ⅱ 1A受体(angiotensin Ⅱ type 1A receptor, AT1aR)是Ang Ⅱ的主要受体亚型。AT1aR基因(Agtr1a)启动子区DNA甲基化水平的变化是调控AT1aR表观遗传的重要机制。为明确运动是否通过调节Agtr1a基因启动子区甲基化水平而减弱ACE1-AT1R收缩轴功能,从而起到改善高血压血管功能的作用,本研究选用3月龄自发性高血压大鼠(spontaneously hypertensive rat, SHR)和正常血压对照组大鼠(Wistar-Kyoto, WKY),随机分为正常血压安静组WKY-C、正常血压有氧运动组WKY-E、高血压安静组SHR-C、高血压有氧运动组SHR-E,各组n=24。12周跑台运动结束后,有氧运动显著减低运动组大鼠血压和体重(P0.05);采用微血管环张力测定技术测定肠系膜动脉对去甲肾上腺素(norepinephrine, NE)、血管紧张素Ⅱ(angiotensin Ⅱ, Ang Ⅱ)的反应性。结果显示,有氧运动显著减弱高血压大鼠肠系膜动脉对血管收缩因子NE、AngⅡ的收缩反应(P0.05);高效液相色谱法(high performance liquid chromatography, HPLC)测定血浆中ACE1-AT1R收缩轴主要活性肽血管紧张素原(angiotensinogen, AGT)、AngⅡ的水平。结果显示,有氧运动显著减弱高血压大鼠肠系膜动脉对血管收缩因子NE、AngⅡ的收缩反应(P0.05);免疫印迹法和q-PCR技术测定肠系膜动脉ACE1、AT1R蛋白质和AT1aR的mRNA水平相对含量。结果显示,有氧运动显著降低高血压大鼠肠系膜动脉ACE1、AT1R蛋白质和AT1aR mRNA水平(P0.05);亚硫酸氢盐测序BSP法测定Agtr1a基因的启动子区甲基化水平。结果显示,有氧运动显著上调高血压大鼠肠系膜动脉Agtr1a基因启动子区甲基化水平(P0.05)。本研究表明,有氧运动通过上调高血压肠系膜动脉Agtr1a基因启动子区甲基化水平,即而减弱RAS系统ACE1-AT1R收缩轴功能,从而抑制高血压血管张力增高,缓解血压增高。     

慢性缺氧对大鼠肺动脉内皮依赖性舒张反应及cGMP含量的影响

本实验观察了慢性缺氧对大鼠肺动脉内皮依赖性舒张反应和肺动脉内环磷酸鸟苷(cGMP)含量的影响。乙酰胆碱(ACh)和三磷酸腺苷(ATP)可使正常大鼠的离体肺动脉产生内皮依赖性舒张反应,其舒张作用不受消炎痛的影响,但被甲烯蓝完全抑制。慢性缺氧明显减低了 ACh 和 ATP 诱发的大鼠肺内和肺外动脉的内皮依赖性舒张反应。当 ACh 浓度为10~(-6)mol/L 时,缺氧组大鼠肺内和肺外动脉舒张百分数分别为对照组的61.3%和59.2%;当 ATP浓度为1.8×10~(-5)mol/L 时,缺氧组大鼠肺内和肺外动脉舒张反应分別为对照组的64.9%和55.3%。慢性缺氧也减低了硝普钠(SNP)诱发的大鼠肺动脉非内皮依赖性舒张反应。慢性缺氧显著减低了大鼠肺动脉内 cGMP 的含量。缺氧组和对照组大鼠肺动脉内 cGMP 的基础含量分别是51.9±5.7 pmol/g wet wt.(n=14)和84.9±9.7 pmol/g wet wt.(n=14),p<0.01;经 10~(-7)mol/L ACh 刺激后分别是91.4±7.3 pmol/g wet wt.(n=5)和240.8±30.6pmol/g wet wt.(n=5),p<0.01。慢性缺氧可能抑制了肺动脉平滑肌细胞胞浆中可溶性鸟苷酸环化酶,从而减低了肺动脉对内皮舒张因子和 SNP 的舒张反应性。     

雷米普利对自发性高血压大鼠脑动脉缝隙连接蛋白43表达的影响

本文旨在探讨血管紧张素转换酶抑制剂雷米普利(Ramipril)是否通过调节脑动脉血管细胞缝隙连接蛋白43 (connexin43, Cx43)的表达发挥其降压及保护脑动脉的作用。Wistar-Kyoto (WKY)和自发性高血压大鼠(spontaneously hypertensive rat,SHR)随机分为4组:WKY组、WKY+Ramipril组、SHR组、SHR+Ramipril组(n=8)。运用无创尾动脉测压仪测量收缩压;采用苏木素-伊红染色观察脑动脉病理学改变;应用压力肌动图技术检测各组脑动脉血管收缩率;应用免疫荧光和免疫组织化学技术分析脑动脉上Cx43的分布及表达;采用real-time PCR和Western blot技术分别检测脑动脉上Cx43 mRNA及蛋白表达。结果显示:(1) SHR组收缩压显著高于WKY组(P 0.01, n=8);SHR+Ramipril组收缩压明显低于SHR组(P 0.01, n=8)。(2)相比于WKY组,SHR组脑动脉管壁增厚明显(P 0.01, n=8),而SHR+Ramipril组相比于SHR组,动脉管壁厚度明显减少。(3) SHR组脑动脉收缩率高于WKY组(P 0.05, n=8);SHR+Ramipril组脑动脉收缩率低于SHR组(P 0.05, n=8)。应用2-APB (Cx43非特异性阻断剂)或Gap26 (Cx43特异性阻断剂)预孵育后,SHR+Ramipril组动脉收缩率显著下降(P 0.05, n=8);给予Cx43非特异性激动剂AAP10预孵育后,SHR+Ramipril组动脉收缩率显著升高(P 0.05, n=8)。(4) SHR组脑动脉上Cx43 mRNA及蛋白表达水平高于WKY组(P 0.05, n=8);SHR+Ramipril组脑动脉上Cx43 mRNA及蛋白表达水平明显低于SHR组(P 0.05, n=8)。以上结果提示,雷米普利能够下调SHR脑动脉血管细胞间Cx43 mRNA和蛋白的表达,降低血压,改善高血压诱发的脑动脉重塑以及血管功能障碍。     

Development of vasomotor responses in fetal mesenteric arteries

Changes in mesenteric arterial diameters were studied using intravital microscopy in chick fetuses at days 13 and 17 of incubation, corresponding to 0.6 and 0.8 fetal incubation time, both during 5 min of hypoxia followed by 5 min of reoxygenation and after topical administration of increasing concentrations (10(-6)-10(-2) M) of norepinephrine (NE) and acetylcholine (ACh). Baseline diameters of second-order mesenteric arteries increased from 56 microm at 0.6 incubation to 75 microm at 0.8 incubation. Acute hypoxia induced a reduction in arterial diameter to 87 +/- 4.4% of baseline at 0.6 incubation and to 44 +/- 6.7% at 0.8 incubation (P < 0.01). During reoxygenation, mesenteric arteries dilated to 118 +/- 6.5% and 121 +/- 7.5% of baseline at 0.6 and 0.8 fetal incubation time, respectively. Phentolamine did not affect the vasoconstriction during hypoxia at 0.6 incubation, whereas this alpha-adrenergic antagonist significantly attenuated the vasoconstrictor response at 0.8 incubation (to 93 +/- 2.7% of baseline, P < 0.01). Topical NE induced maximal vasoconstriction to 71 +/- 3% of baseline at 0.6 incubation and to 35 +/- 3.8% at 0.8 incubation (P < 0.01). Maximal vasodilation to topical ACh was 113 +/- 4.4% and 122 +/- 4.8% of baseline at 0.6 and 0.8 incubation, respectively. These in vivo findings show that fetal mesenteric arteries constrict in response to acute hypoxia and that the increase in magnitude of this vasoconstrictor response from 0.6 to 0.8 of fetal development results from an increase in adrenergic constrictor capacity.     

消痰化瘀利窍方对慢性间歇性低氧大鼠肠系膜动脉损伤的改善作用

目的:观察消痰化瘀利窍方对慢性间歇性低氧(CIH)大鼠肠系膜动脉功能损伤的作用,并探讨其可能机制。方法:48只雄性SD大鼠随机分为4组(n=12),常氧对照组(Normoxia)、慢性间歇性低氧组(CIH)、慢性间歇性低氧中药干预组(Formula+CIH)、中药对照组(Formula)。CIH与Formula+CIH组置于间歇性低氧装置,通过充入氮气、氧气使O2含量在9%至21%间循环,每循环3min;Normoxia和Formula组则充入空气。其中,Formula+CIH与Formula组于每日造模前中药水煎液灌胃(24g/kg),而CIH组与Normoxia组给予等量生理盐水。造模结束后,应用HE染色观察各组大鼠肠系膜动脉的组织病理学改变,通过微血管环技术观察ACh、L-Arg诱导的肠系膜动脉舒张反应,通过ELISA技术检测大鼠造模前及造模21d血清一氧化氮(NO)的含量并应用Westernblot技术测定肠系膜动脉eNOS和p-eNOS的蛋白水平。结果:与Normoxia组相比,CIH组大鼠肠系膜动脉内皮明显损伤、中膜增厚,ACh、L-Arg诱导的肠系膜动脉舒张反应明显减弱,血清中NO水平及肠系膜动脉p-eNOS/eNOS比值显著降低。消痰化瘀利窍方干预能够减轻大鼠肠系膜动脉的内膜与中膜病理损伤,改善肠系膜动脉舒张功能,提高血清NO含量及肠系膜动脉eNOS磷酸化水平。而单纯给予消痰化瘀利窍方大鼠与Normoxia组相比各指标均未发现显著变化。结论:消痰化瘀利窍方可以减轻慢性间歇性低氧引起的大鼠肠系膜动脉功能损伤,其机制与提高NO的生物利用度有关。     

Endothelium-dependent vasodilation induced by Hancornia speciosa in rat superior mesenteric artery

The vasodilator effect of the ethanolic extract of leaves from Hancornia speciosa Gomes (HSE) was evaluated in superior mesenteric artery rings. HSE produced a concentration-dependent vasodilation (IC50 = 10.8 +/- 4.0 microg/mL) in arterial rings pre-contracted with phenylephrine, which was completely abolished in endothelium-denuded vessels. Endothelium-dependent vasodilation induced by HSE was strongly reduced by L-NAME (100 microM), a nitric oxide (NO) synthase inhibitor, but neither by atropine, a muscarinic receptor antagonist (1 microM), nor by indomethacin (10 microM), a cyclooxygenase inhibitor. In rings pre-contracted with 80 mM KCl, the vasodilator effect of HSE was shifted to the right and was completely abolished in the presence of L-NAME (100 microM). Similar effects were obtained in mesenteric rings pre-contracted with phenylephrine in the presence of KCl 25 mM alone or in addition to 100 microM L-NAME. In addition, BaCl2 (1 mM) dramatically reduced the vasodilation induced by HSE. Together, these findings led us to conclude that HSE induces an endothelium-dependent vasodilation in rat mesenteric artery, by a mechanism dependent on NO, on the activation of potassium channels and endothelium-derived hyperpolarizing factor release. Rutin, identified as a major peak in the HPLC fingerprint obtained for HSE, might contribute for the observed vasodilator effect, since it was able to induce an endothelium-dependent vasodilation in rat superior mesenteric arteries.     

Pregnancy-associated increase in rat systemic arteries endothelial nitric oxide production diminishes vasoconstrictor but does not enhance vasodilator responses

Late pregnancy in rats is characterized by a decrease in arterial pressure and in isolated arterial vessels response to vasoconstrictors. In uterine arteries the pregnancy-associated attenuation of the response to vasoconstrictors has been attributed to an increase in basal and agonist-induced endothelial NO production. However, the role of NO in pregnancy-associated changes of systemic arteries reactivity to vasoactive agents remains to be fully elucidated. We examined whether pregnancy influences the reactivity of systemic arteries to vasodilator or vasoconstrictor agents through NO-dependent mechanisms. Thoracic aortic rings and mesenteric arterial bed of late pregnant rats showed refractoriness to phenylephrine-induced vasoconstriction that was abolished by NO synthase inhibition. The potency of L-NNA to enhance tension of aortic rings preconstricted with phenylephrine (10–20% of their maximal response) was significantly lower in preparations from pregnant animals. In phenylephrine-contracted aortas and mesenteric bed, the effects of the endothelium-dependent vasodilators acetylcholine, A23187 and bradykinin, were not influenced by pregnancy. Similarly, pregnancy did not affect the vasodilator responses of adenosine, isoproterenol, capsaicin, nitroprusside, forskolin, and Hoe234 in the mesenteric bed. NO synthase activity measured by determining the conversion of L−[³H]-arginine to L−[³H]-citrulline in aorta and mesenteric arteries homogenates was not altered by pregnancy. These findings show that endothelial-dependent and -independent vasodilators action as well as NO synthase activity in systemic arteries is uninfluenced by pregnancy, whereas pregnancy-associated hyporeactivity of systemic arteries to vasoconstrictors is related to an enhanced endothelial NO production either spontaneous or elicited directly or indirectly by vasoconstrictor agents. This interpretation implies that the enhanced NO production observed in systemic arteries during late pregnancy involves cellular pathways other than the ones involved in the response to endothelium-dependent vasodilators such as acetylcholine.     

Nociceptin: An endogenous agonist for central opioid like1 (ORL1) receptors possesses systemic vasorelaxant properties

The purpose of the present study was to investigate the effects of nociceptin on peripheral arterial rings from the cat. When feline renal, mesenteric, carotid and femoral rings with intact endothelium were precontracted with phenylephrine (100 nanomolar), nociceptin (3 × 10⁻¹¹ − 3 × 10⁻⁶ M) decreased tension in a concentration-dependent manner. The present datasuggest nociceptin possesses biologic activity outside the CNS and may contribute to the regulation of systemic blood pressure and regional blood flow.     

Modulation of temperature-induced tone by vasoconstrictor agents.

One of the primary cardiovascular adjustments to hyperthermia is a sympathetically mediated increase in vascular resistance in the viscera. Nonneural factors such as a change in vascular tone or reactivity may also contribute to this response. Therefore, the aim of this study was to determine whether vascular smooth muscle tone is altered during heating to physiologically relevant temperatures >37 degrees C. Gradually increasing bath temperature from 37 degrees C (normothermia) to 43 degrees C (severe hyperthermia) produced graded contractions in vascular ring segments from rat mesenteric arteries and thoracic aortae. In untreated rings these contractions were relatively small, whereas hyperthermia elicited near-maximal increases in tension when rings were constricted with phenylephrine or KCl before heating. In phenylephrine-treated mesenteric arterial rings, the contractile responses to heating were markedly attenuated by the Ca2+ channel antagonists nifedipine and diltiazem. Diltiazem also blocked the contractile responses to heating in thoracic aortic rings. These results demonstrate that hyperthermia has a limited effect on tension generation in rat vascular smooth muscle in the absence of vascular tone. However, in the presence of agonist-induced tone, tension generation during heating is markedly enhanced and dependent on extracellular Ca2+. In conclusion, these data suggest that local regulation of vascular tone can contribute to the hemodynamic adjustments to hyperthermia.     

Calcium-sensitive potassium channel inhibitors antagonize genistein- and daidzein-induced arterial relaxation in vitro

Estradiol-17beta relaxes rabbit coronary artery rings via large conductance Ca2+-activated K+-channels (K(Ca)). Genistein and daidzein are plant-derived estrogen-like compounds. The aim of the present study was to investigate whether potassium channels participate in the genistein- and daidzein-induced arterial relaxation like they do in the case of estradiol-17beta. Endothelium-denuded superior mesenteric arterial rings from non-pregnant Wistar female rats were used. At a concentration of 10 microM, estradiol-17beta, genistein and daidzein relaxed noradrenaline precontracted arterial rings, (58 +/- 4%, 45 +/- 5% and 31 +/- 3%, respectively; (n=6-8)). Genistein- and daidzein-induced relaxations were inhibited both by iberiotoxin (1-10 nM) and charybdotoxin (30 nM), the antagonists of large conductance Ca2+-activated K+-channels (K(Ca)). Estradiol-17beta-induced relaxation was reduced by iberiotoxin (30 nM). Estradiol-17beta- and daidzein-induced relaxations were also decreased by apamin (0.1-0.3 microM), an antagonist of small conductance Ca2+-activated K+-channels. The antagonists of voltage-dependent K+-channels (K(V)) (4-aminopyridine), ATP-sensitive K+-channels (K(ATP)) (glibenclamide), or inward rectifier K+-channels (KIR) (barium) had no effect on the relaxation responses of any of the compounds studied. Estrogen receptor antagonist tamoxifen did not inhibit the relaxations. In conclusion, in the noradrenaline precontracted rat mesenteric arteries, the relaxations caused by estradiol-17beta, genistein and daidzein were antagonized by large and small conductance K(Ca)-channel inhibitors, suggesting the role of these channels as one of the relaxation mechanisms.     

血管内皮舒张因子在氧自由基所致慢性缺氧大鼠肺内动...

The role of endothelium-derived relaxing factor (EDRF) on the effect of oxygen-derived free radicals (generated by xanthine-xanthine oxidase system) on intrapulmonary arterial in chronic hypoxic rats was studied by a microbioassay method. Intrapulmonary artery rings with intact or denuded endothelium of hypoxic (5,000 m, 10 days) and normoxic rats were prepared for observation of oxygen-derived free radicals induced contraction. It was shown that oxygen-derived free radicals induced contractions of intrapulmonary arterial rings with intact endothelium were obviously augmented in hypoxic rats than in normoxic controls. The augmented responses could be further potentiated by the addition of EDRF inactivator reduced hemoglobin (RHb), but diminished or even abolished by applying superoxide dismutase (Cu-Zn SOD). However, no effect on denuded rings was observed when RHb or SOD was added. It is concluded that chronic hypoxia may attenuate the action of EDRF in the enhancement of the reactivity of intrapulmonary artery to oxygen-derived free radicals.     

Inhibition of superoxide anion-mediated impairment of endothelium by treatment with luteolin and apigenin in rat mesenteric artery

This study was designed (i) to test the hypothesis that the endothelium-derived hyperpolarizing factor (EDHF) component of ACh-induced vasorelaxation and hyperpolarization of smooth muscle cells (SMCs) are impaired following exposure to superoxide anion, and (ii) to further investigate whether luteolin and apigenin induce vasoprotection at the vasoactive concentrations in rat mesenteric artery. Rat mesenteric arterial rings were isolated for isometric force recording and electrophysiological studies. Perfusion pressure of mesenteric arterial bed was measured and visualization of superoxide production was detected with fluorescent dye. 300 microM pyrogallol significantly decreased the relaxation and hyperpolarization to ACh. Luteolin and apigenin both induced vasoprotection against loss of the EDHF component of ACh-induced relaxation and attenuated the impairment of hyperpolarization to ACh. Oxidative fluorescent microtopography showed that either luteolin or apigenin significantly reduced the superoxide levels. The results suggest that superoxide anion impairs ACh-induced relaxation and hyperpolarization of SMC in resistance arteries through the impairment of EDHF mediated responses. Luteolin and apigenin protect resistance arteries from injury, implying that they may be effective in therapy for vascular diseases associated with oxidative stress.     

Acidic reoxygenation protects against endothelial dysfunction in rat aortic rings submitted to simulated ischemia

Ischemia-reperfusion causes endothelial dysfunction. Prolongation of acidosis during initial cardiac reperfusion limits infarct size in animal models, but the effects of acidic reperfusion on vascular function are unknown. The present work analyzes the effects of acidic reoxygenation on vascular responses to different agonists in rat aortic rings. Arterial rings obtained from Sprague-Dawley rat aorta were placed in organ baths containing a Krebs solution oxygenated at 37 degrees C (pH 7.4). After equilibration (30 mN, 1 h), the effects of acidosis (pH 6.4) on aortic responses to acetylcholine and norepinephrine were initially assessed under normoxic conditions. Thereafter, the effects of acidosis during hypoxia (1 h) or reoxygenation on aortic responses to acetylcholine, norepinephrine, or sodium nitroprusside were analyzed and compared with those observed in control rings. Acidosis did not modify aortic responses to acetylcholine or adrenaline during normoxia. In contrast, rings submitted to hypoxia and reoxygenated at pH 7.4 showed a reduction in vasodilator responses to acetylcholine and in contractions to norepinephrine with no change in responses to sodium nitroprusside. Reoxygenation at pH 6.4 did not modify the depressed response to norepinephrine but enhanced the recovery of acetylcholine-induced vasorelaxation. Cumulative concentration-response curves to acetylcholine showed an increased responsiveness to this drug in rings reoxygenated at a low pH. This functional improvement was associated with the preservation of aortic cGMP content after stimulation of reoxygenated rings with acetylcholine. In conclusion, acidic reoxygenation preserves endothelial function in arterial rings submitted to simulated ischemia, likely through the preservation of cGMP signaling.