咪达唑仑对大鼠离体胸主动脉环的舒张机制研究

目的观察咪达唑仑对大鼠离体胸主动脉环张力的影响,并探讨其作用机制。方法采用离体血管张力试验方法。观察咪达唑仑在3×10-6mol/L、1×10-5mol/L、3×10-5mol/L、1×10-4mol/L浓度时,对去甲肾上腺素（NE,1×10-6mol/L）、氯化钾（KCl,60 mmol/L）诱发大鼠离体胸主动脉环收缩的影响。观察Na＋/Ca2＋交换体阻断剂KB-R7943（1×10-6mol/L）、KV通道阻断剂4-AP（4-AP,1×10-3mol/L）、KATP通道阻断剂格列苯脲（Gli,1×10-5mol/L）、KCa通道阻断剂四乙胺（TEA,1×10-2mol/L）、KiR通道阻断剂氯化钡（BaCl2,1×10-3mol/L）对咪达唑仑作用的影响。结果各浓度咪达唑仑对预收缩的大鼠离体胸主动脉环有舒张作用。用KB-R7943、4-AP、TEA及BaCl2预处理的血管环对咪达唑仑的舒张反应与未经处理时比较无统计学意义（P〉0.05）。Gli可减弱咪达唑仑对血管环的舒张作用（P〈0.05）。结论咪达唑仑对大鼠胸主动脉环具有浓度依赖性的舒张作用,其舒张反应与Na＋/Ca2＋交换体、KV通道、KCa通道和KiR通道无关,可能与KATP通道有关。     

Ca^2＋、pH值、温度对氯化钾预收缩猪离体冠状动脉的影响

目的观察Ca^2＋、pH值、温度对氯化钾预收缩的猪冠状动脉环收缩效应的影响。方法利用猪冠状动脉条的离体实验法,观察理化因素对其收缩的影响。观察不同浓度Ca^2＋对KCl预收缩猪冠脉血管环张力的影响以及KCa通道阻断剂四乙胺（TEA,1×10-2mol/L）、Na＋/Ca^2＋交换体阻断剂KB-R7943（1×10^-6mol/L）对3.0 mmol/L Ca^2＋所致血管张力的影响。研究不同pH值对KCl预收缩猪冠脉血管环张力的影响以及KATP通道阻断剂格列苯脲（Gli,1×10^-5mol/L）对pH值为6.5所致血管张力的影响。比较不同温度对KCl预收缩猪冠脉血管环张力的影响。结果 30 mmol/L KCl为猪冠脉的最适收缩浓度。Ca^2＋浓度为0.5 mmol/L,1.0mmol/L,1.5 mmol/L,2.5 mmol/L的30 mmol/L KCl对猪冠脉血管环产生浓度依赖性收缩,增加钙浓度至3.0 mmol/L产生明显的舒张作用。高钙的舒张作用可以被TEA所阻断（P〈0.05）,而KB-R7943对其无影响。34℃、31℃、28℃时30 mmol/L KCl诱发的收缩幅度均比37℃时低,差异有统计学意义（P〈0.05）。结论 Ca^2＋、pH值、温度对氯化钾预收缩的猪冠状动脉环收缩效应均有影响。高钙所致的猪冠脉血管环舒张可能是与KCa通道有关。     

黄芩素对大鼠离体胸主动脉的舒张作用及其机制

目的:研究黄芩素(BAI)对去甲肾上腺素(NE,1×10-6mol· L-1)和氯化钾(KCl,6×10-2 mol·L-1)预收缩健康成年雄性大鼠胸主动脉环的舒张作用,并探讨其作用机制.方法:应用离体血管环技术观察BAI对大鼠胸主动脉环张力的作用,记录NE预收缩的离体大鼠胸主动脉环张力变化.采用一氧化氮合酶(eNOS)抑制剂L-硝基精氨酸甲酯(L-NAME,1×10-4mol·L-1)、环氧合酶抑制剂吲哚美辛(INDO,1×10-5mol· L-1)和鸟苷酸环化酶抑制剂亚甲蓝(MB,1×10-5mol· L-1)和不同的钾通道阻滞剂预孵后观察BAI对血管环张力改变的影响,并观察对NE诱发的内钙释放和CaCl2引起的外钙内流的影响.结果:BAI对NE或KCl预收缩的内皮完整和去内皮大鼠离体胸主动脉环均产生明显的舒张作用,与溶剂组相比差异有统计学意义.预先用L-NAME,MB,KV通道阻断剂四氨基吡啶(4-AP,1×10-4mol· L-1),KC.通道阻断剂四乙胺(TEA,1×10-3mol· L-1),Kir通道阻断剂氯化钡(BaCl2,1×10-4mol·L-1)孵育后,BAI对预收缩的血管张力的改变与无阻断药时比较,差异均无统计学意义;预先用KATP通道阻断剂格列苯脲(Gli,1×10-5mol·L-1)和INDO孵育后,BAI的舒张血管作用减弱,与无阻断药比较差异有统计学意义(P＜0.05);且BAI对NE外钙内流引起的收缩有明显的抑制作用.结论:黄芩素可明显降低由NE诱发的血管环张力的升高,且其作用具有浓度依赖性,此作用有内皮依赖性和非内皮依赖性的特点.内皮依赖性收缩可能与前列环素(PGI2)途径有关,非内皮依赖机制与KATP通道和钙离子通道有关.     

替米沙坦对大鼠离体胸主动脉环的舒张机制研究

目的观察替米沙坦对大鼠离体胸主动脉环张力的影响,并探讨其作用机制。方法采用离体血管张力实验方法。观察替米沙坦在1×10^-9mol／L,1×10^-9mol／L,1×10^-9mol／L,1×10^-9mol／L,1×10^-9mol／L浓度时,对去甲肾上腺素（NE,1×10^-9mol／L）、氯化钾（KCl,60mmol／L）诱发大鼠离体胸主动脉环收缩的影响。观察Na＋／Ca2＋交换体阻断剂KB—R7943（1×10^-5mol／L）、Kv通道阻断剂四胺基吡啶（4-AP,1×10^-3mol／L）、KATP通道阻断剂格列苯脲（Gli,1×10^-5mol／L）、Kca通道阻断剂四乙胺（TEA,1×10mol／L）、K．R通道阻断剂氯化钡（BaCl2,1×10^-3mol／L）对替米沙坦作用的影响。结果替米沙坦对KCl（60mmol／L）预收缩的离体胸主动脉环张力无影响,对NE（1×10^-6mol／L）预收缩的离体胸主动脉环产生浓度依赖性的舒张作用。用KB—R7943、4-AP、Gli预处理的血管环对替米沙坦的舒张反应与未经处理时比较无统计学意义（P〉0．05）。TEA及BaCl2可减弱替米沙坦对血管环的舒张作用（P〈O．05）。结论替米沙坦对NE预收缩的大鼠胸主动脉环具有浓度依赖性的舒张作用,其舒张反应与Na＋／Ca2＋交换体、Kv通道和KATP通道无关,可能与Kca通道及KR通道有关。     

Militarine对离体大鼠胸主动脉环的舒张作用及机制研究

目的:研究从手掌参中分离的Militarine对离体大鼠胸主动脉环的舒张作用并探讨其可能的机制。方法:记录去甲肾上腺素(NE)和KCl预收缩的离体大鼠主动脉环张力变化,观察Militarine的舒血管作用及不同工具药对其作用的影响。结果:Militarine可以抑制去甲肾上腺素(NE,1×10-4mol·L-1)和KCl(1.8 mol·L-1)引起去内皮和内皮完整的离体大鼠胸主动脉环的收缩作用,但二者有明显差别;L-硝基精氨酸甲酯(LNAME,1×10-4mol·L-1)、亚甲蓝(MB,1×10-5mol·L-1)、吲哚美辛(INDO,1×10-5mol·L-1)均能一定程度抑制Militarine对胸主动脉环的舒张作用;钾离子通道阻断剂四乙基胺(TEA,1×10-3mol·L-1)、格列苯脲(glibenclamide,1×10-5mol·L-1)、Ba Cl2(1×10-4mol·L-1)可明显减弱Militarine对血管环的舒张作用;在无钙环境下,预孵育Militarine对去甲肾上腺素引起的血管环收缩有明显抑制作用。结论:Militarine有内皮依赖性和非内皮依赖性的血管舒张作用,其作用机制可能涉及激活内皮细胞中NO/c GMP通路,开放钾离子通道和抑制钙离子内流。     

金鸡菊对大鼠主动脉的舒张作用及钾通道机制

目的:研究金鸡菊(Coreopsis tinctoria Nuff.)乙醇提取物对离体血管平滑肌张力影响,同时探讨其作用机制。方法:采用大鼠离体胸主动脉灌流,应用金鸡菊提取物(0.25、0.50、0.75和1.00 mg/ml)记录张力变化,观测其对Sprague Dawley(SD)大鼠离体胸主动脉环的作用,L-NAME及不同钾通道阻滞剂的影响。结果:金鸡菊提取物0.50¹.00 mg/ml对氯化钾(60 mmol/L)和苯肾上腺素(0.3μmol/L)预收缩的血管环具有浓度依赖的舒张作用,对内皮完整和去内皮血管环舒张作用无差异,该舒张作用为非内皮依赖性。在KCl预收缩基础上,加入一氧化氮合酶抑制剂(L-NAME,100μmol/L)和内向整流钾通道阻断剂钾通道阻断剂氯化钡(BaCl2,30μmol/L)均不能抑制金鸡菊提取物提取物的舒血管效应,非选择性钾通道阻断剂(TEA,10mmol/L)、电压依赖性钾通道阻断剂四氨基吡啶(4-AP,1 mmol/L)、ATP敏感钾通道阻断剂(Gli,10μmol/L)及大电导激活钾通道阻断剂(IbTX,100 nmol/L)能抑制金鸡菊提取物提取物对血管的舒张作用。结论:金鸡菊提取物提取物舒张血管的作用具有浓度依赖性,其作用机制可能与激活KATP、BKca和Kv有关。     

天麻素对离体大鼠胸主动脉环的舒张作用及其机制

目的:研究天麻素对离体大鼠胸主动脉环的舒张作用并探讨其可能的机制。方法:记录去甲肾上腺素(NE)和KCl预收缩的离体大鼠主动脉环张力变化,观察天麻素的舒血管作用及不同工具药对其作用的影响。结果:天麻素对去甲肾上腺素(NE,1×10-6mol.L-1)和KCl(6×10-2mol.L-1)引起的去内皮和内皮完整胸主动脉环的收缩均有舒张作用,二者没有显著差别;L-硝基精氨酸甲酯(L-NAME,1×10-4mol.L-1)、亚甲蓝(MB,1×10-5mol.L-1)、吲哚美辛(INDO,1×10-5mol.L-1)并不能抑制天麻素对胸主动脉环的舒张作用;钾离子通道阻断剂4-氨基吡啶(4-AP,1×10-4mol.L-1)、四乙基胺(TEA,1×10-3 mol.L-1)、格列苯脲(glibenclamide,1×10-5mol.L-1)、BaCl2(1×10-4mol.L-1)均能抑制天麻素对血管环的舒张作用;在无钙环境下,预孵育天麻素对去甲肾上腺素收缩有明显抑制作用。结论:天麻素有浓度依赖性的血管舒张作用,此作用不依赖血管内皮,与钾离子通道及抑制血管平滑肌细胞内质网储存钙的释放和外钙内流有关系。     

Kv和BK_(Ca)通道阻断剂对家兔离体Oddi括约肌肌环张力的作用及芍药甙的调控作用

目的探讨电压依赖性钾通道(Kv)、大电导钙激活钾通道(BKCa)阻断剂对家兔离体Oddi括约肌(SO)肌环张力的作用及中药芍药的有效成分芍药甙对其调控作用。方法制备离体兔Oddi括约肌肌环标本,放置于平滑肌恒温灌流浴槽中,观察Kv通道阻断剂4-aminopyridine(4-AP)、BKCa通道阻断剂tetraethylammonium chloride(TEA)对家兔离体SO肌环的收缩作用;观察芍药甙对4-AP和TEA引起的收缩作用的影响。结果 4-AP、TEA均可以引起SO肌环收缩,且随4-AP、TEA浓度增加,收缩程度也在增强。4-AP和TEA对SO肌环的收缩作用可以被芍药甙抑制。结论在离体条件下,Kv通道和BKCa通道对维持SO细胞的静息膜电位起主要作用。芍药甙可能通过对Kv通道和BKCa通道的调控,实现了对SO细胞的舒张反应。     

丹酚酸B对大鼠离体胸主动脉环张力的影响

目的:研究丹酚酸B(salvianolic acid B,Sal B)对离体大鼠胸主动脉收缩张力的作用及其机制探讨。方法:SD大鼠,采用大鼠离体胸主动脉灌流模型,通过累积加药法加入Sal B使终浓度递增为1×10-8,1×10-7,1×10-6,1×10~(-5),1×10~(-4)mol·L~(-1),观察血管张力的变化,观察1×10~(-5),1×10~(-4)mol·L~(-1)Sal B对去甲肾上腺素(NE)和氯化钾(KCl)预收缩的胸主动脉环收缩张力的影响。结果:Sal B对内皮完整和内皮损伤的离体大鼠主动脉环基础张力的作用不明显;Sal B对NE预收缩的血管环有明显舒张作用,但对KCl预收缩的血管环无舒张作用;用一氧化氮合酶抑制剂左旋硝基精氨酸甲酯(L-NAME)和环氧酶抑制剂吲哚美辛(Indo)处理血管后,对Sal B舒张血管效应阻断作用不明显,使用电压依赖性的K+通道阻断剂4-AP,Ca2+敏感性的K+通道阻断剂四乙胺(TEA)以及ATP敏感性的K+通道阻断剂格列苯脲处理后,对Sal B舒张血管效应的阻断作用不明显,使用β受体阻断药普萘洛尔处理后,对Sal B舒张血管效应的阻断作用亦不明显;而Sal B对Ca2+引起的收缩有抑制作用,抑制内钙收缩作用比外钙收缩作用更强。结论:Sal B舒张血管作用机制可能与阻断受体依赖性钙通道、电压依赖性钙通道引起的外钙内流和阻断三磷酸肌醇(IP3)受体引起的内钙释放有关,而与NO-鸟苷酸环化酶途径,环氧合酶途径,K+通道和β受体无关。     

pH值改变对大鼠离体冠状动脉静息张力的影响及机制

目的研究在基础张力状态下,不同pH对大鼠冠状动脉血管静息张力的影响并探讨机制。方法采用离体血管张力记录方法,大鼠冠状动脉环的张力舒缩状态采用PowerLab和DMT系统记录。观察pH值梯度改变对大鼠冠脉血管环张力的影响。观察内外钙、Na＋/Ca2＋交换体抑制剂KB-R7943（1×10-6 mol/L）、氯离子通道阻断剂NPPB（3×10-5 mol/L）、钙通道阻断剂维拉帕米（1×10-5 mol/L）、Na＋/H＋交换体抑制剂氨氯吡咪（AM,3×10-5 mol/L）、Na＋-K＋-ATP酶抑制剂哇巴因（1×10-6 mol/L）、NO合酶抑制剂L-NAME（1×10-4 mol/L）对浴液pH6.4时冠脉张力的影响。结果随胞外pH值逐渐降低,大鼠离体冠脉血管环的静息张力逐渐增强。外钙内流和内钙释放均参与pH6.4时的冠脉收缩,钙通道阻断剂Verapamil可部分阻断冠脉收缩幅度的升高。与对照组相比,KB-R7943、哇巴因对pH6.4时冠脉收缩幅度无显著影响（P〉0.05）;NPPB、氨氯吡咪均可抑制pH6.4时冠脉收缩幅度的升高（P〈0.05）;L-NAME可增强pH6.4时冠脉收缩幅度（P〈0.05）。结论酸中毒时,随胞外pH值降低,大鼠冠脉的静息张力升高。其作用机制可能与内外钙、氯通道、Na＋/H＋交换有关。     

阿魏硝胺的血管舒张作用与机制

 目的观察阿魏酸硝酸酯类药物阿魏硝胺(FLNT)的血管舒张作用并探讨其可能机制。方法测定大鼠外周血管环(腔静脉、胸主动脉)张力,比较FLNT、硝酸甘油(NG)和硝酸异山梨酯(ISDN)对胸主动脉的舒张作用;观察鸟苷酸环化酶阻断剂亚甲蓝对FLNT血管舒张作用的影响以及FLNT对钾通道阻断剂(氯化钡、四乙胺、4-氨基吡啶和格列苯脲)血管张力的影响,研究FLNT对鸟苷酸环化酶和钾通道的作用。结果在大鼠内皮完整腔静脉,FLNT有浓度依赖性(1×10^-7～1×10^-4mol·L^-1)舒张作用。在内皮完整及去内皮胸主动脉血管上,FLNT均浓度依赖性地降低去甲肾上腺素(NE)或高钾预收缩血管的张力,对内皮没有依赖性;FLNT使NE或高钾收缩曲线非平行右移,且使最大张力减小;FLNT对胸主动脉的舒张程度类似于ISDN。FLNT可以显著地对抗无钙环境下由NE引起的血管收缩。亚甲蓝能显著减弱FLNT的胸主动脉血管舒张作用,FLNT可显著地降低氯化钡和四乙胺的血管张力。结论FLNT对大鼠胸主动脉和腔静脉产生浓度依赖性舒张,其中胸主动脉产生舒张作用类似于硝酸异山梨酯,且为非内皮依赖性的。FLNT作用机制可能其与激活鸟苷酸环化酶,开放钾通道,抑制钙通道有关。     

Vasodilatory effects of ethanol extract of Radix Paeoniae Rubra and its mechanism of action in the rat aorta

Ethnopharmacological relevance

Radix Paeoniae Rubra (RPR) is an important traditional Chinese medicine (TCM) commonly used in clinic for a long history in China. RPR is the radix of either Paeonia lactiflora Pall. or Paeonia veitchii Lynch. RPR has a wide variety of pharmacological actions such as anti-thrombus, anti-coagulation, and anti-atherosclerotic properties, protecting heart and liver. However, the mechanisms involved are to be defined.

Aim of the study

The aim of the present study was to define the effect of Paeonia lactiflora Pall. extracts on vascular tension and responsible mechanisms in rat thoracic aortic rings.

Materials and methods

Ethanol extract of Paeonia lactiflora Pall. (EPL) was examined for their vascular relaxant effects in isolated phenylephrine-precontracted rat thoracic aorta.

Results

EPL induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Vascular relaxation induced by EPL was significantly inhibited by removal of the endothelium or pretreatment of the rings with N^G-nitro-l-arginine methylester (l-NAME) or 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ). Extracellular Ca²⁺ depletion or diltiazem significantly attenuated EPL-induced vasorelaxation. Modulators of the store-operated Ca²⁺ entry (SOCE), thapsigargin, 2-aminoethyl diphenylborinate and Gd³⁺, and an inhibitor of Akt, wortmannin, markedly attenuated the EPL-induced vasorelaxation. Further, the EPL-induced vasorelaxation was significantly attenuated by pretreatment with tetraethylammonium, a non-selective K_Ca channels blocker, or glibenclamide, an ATP-sensitive K⁺ channels inhibitor, respectively. Inhibition of cyclooxygenases with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the EPL-induced vasorelaxation.

Conclusions

The present study suggests that EPL relaxes vascular smooth muscle via endothelium-dependent and Akt- and SOCE-eNOS-cGMP-mediated pathways through activation of both K_Ca and K_ATP channels and inhibition of L-type Ca²⁺ channels.     

Mechanisms of the dilator action of the Erigerontis Herba on rat aorta

Ethnopharmacological relevance

Erigerontis Herba is widely used as a traditional Chinese medicine and is commonly used for neuroprotection and vascular protection.

Aim of study

In this study, the vasodilator effects of Erigerontis Herba (DZXX) were investigated using rat isolated aorta rings.

Material and method

The involvement of endothelium in the vasorelaxation was studied by comparing response of endothelium-intact and endothelium-denuded aorta rings which precontracted with U46619. The involvement of K⁺ channels was studied by pretreatment of the aorta rings with various K⁺ channel inhibitors. The involvement of Ca²⁺ channel was studied by incubating aorta rings with Ca²⁺-free solution, primed with U46619 prior to elicit contraction by addition of Ca²⁺ solution.

Results

DZXX (0.2–2 mg/ml) induced a concentration-dependent relaxation on U44619-precontracted aorta rings with EC₅₀ of 0.354±0.036 mg/ml. Removal of endothelium or pretreatment with a BK_Ca inhibitor iberiotoxin, K_IR inhibitor barium chloride or K_v inhibitor 4-aminopyridine produced no effect on the DZXX-induced vasorelaxation. However, pretreatment with a K_ATP inhibitor glibenclamide or a non-selective K⁺ channel inhibitor tetraethylammonium produced significant inhibition on the DZXX-induced vasorelaxation by 29.9% and 21.3%, respectively. Pretreatment with DZXX (0.4, 1.2 and 2 mg/ml) produced a concentration-dependent inhibition on Ca²⁺-induced vasoconstriction.

Conclusions

These results suggest that the vasodilator effect of DZXX was endothelium-independent, mediated by decreasing the influx of Ca²⁺ by calcium channel inhibition and increasing the influx of K⁺ by opening of a K_ATP channel.     

Vascular relaxation by ethanol extract of Xanthoceras sorbifolia via Akt- and SOCE-eNOS-cGMP pathways

Aim of the study

The aim of the present study was to define the effect of Xanthoceras sorbifolia extracts (XS) on vascular tension and responsible mechanisms in rat thoracic aortic rings.

Materials and methods

Ethanol extract of the leaves of XS (EXS) was examined for their vascular relaxant effects in isolated phenylephrine-precontracted rat thoracic aorta.

Results

EXS (0.1-100 μg/ml) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished EXS-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N^G-nitro-l-arginine methylester (l-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ) inhibited EXS-induced vasorelaxation. Inhibition of Ca²⁺ entry via l-type Ca²⁺ channels failed to block the EXS-induced vasorelaxation. Extracellular Ca²⁺ depletion significantly attenuated EXS-induced vasorelaxation. Modulators of the store-operated Ca²⁺ entry (SOCE), thapsigargin, 2-aminoethyl diphenylborinate (2-APB) and Gd³⁺, and an inhibitor of Akt, wortmannin, markedly attenuated the EXS-induced vasorelaxation. EXS increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by l-NAME, ODQ, thapsigargin, Gd³⁺, 2-APB, and wortmannin. Further, EXS-induced vasorelaxation was significantly attenuated by tetraethylammonium, a non-selective K_ca channels blocker, but not by glibenclamide, an ATP-sensitive K⁺ channels inhibitor. Inhibition of cyclooxygenase with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on EXS-induced vasorelaxation.

Conclusions

The present study suggests that EXS relaxes vascular smooth muscle via endothelium-dependent NO-cGMP signaling through activation of the Akt- and SOCE-eNOS-sGC pathways, which may, at least in part, be related to the function of K⁺ channels.     

前胡对兔离体肺动脉的作用

以兔离体肺动脉环为研究对象，观察到前胡水煎剂及其石油醚提取物具有舒张肺动脉及降低肺动脉环对去甲肾上腺素和氯化钾所致收缩的反应性；其中石油醚提取物还能使去甲肾上腺素收缩肺动脉的量效曲线呈非平行右移，且最大反应降低，PD’2＝4．73±0．43。     

Vasorelaxant effects of Cerebralcare Granule are mediated by NO/cGMP pathway,potassium channel opening and calcium channel blockade in isolated rat thoracic aorta

Ethnopharmacological relevance

Cerebralcare Granule (CG), one of the famous classical recipes in traditional Chinese medicine, is developed from the “Decoction of Four Drugs”. It has been used for treatment of cerebrovascular related diseases, such as hypertension. It is well known that vasodilatation plays a very important role in hypertensive. Despite the popular medicinal use of CG, little data was available to its activity and mechanism involved in vasodilatation. Therefore, we aimed to investigate the vasorelaxant effects of CG on isolated rat thoracic aorta so as to assess some of the possible mechanisms. The present study was performed to examine the vasodilative activity of CG and its mechanisms in isolated rat thoracic aorta.

Materials and methods

CG was studied on isolated rat thoracic aorta in vitro, including endothelium-intact and endothelium-denuded aortic rings. In present study, specific inhibitors including NO synthase inhibitor N^G-nitro-l-arginine methyl ester (l-NAME), cyclooxygenase (COX) inhibitor indomethacin (INDO), non-selective K⁺ channel inhibitor tetraethylammonium chloride (TEA), K_ir channel inhibitor BaCl₂, K_ATP channel inhibitor Glibenclamide (Gli) and cholinergic receptor antagonist atropine were used, they were added 20 min before NE contraction and then added CG-induced vasodilation.

Results

Removal of endothelium or pretreatment of aortic rings (intact endothelium) with l-NAME (0.1 mM) or INDO (0.01 mM) significantly blocked the CG induced relaxation. Pretreatment with the non-selective K⁺ channel inhibitor TEA (1 mM), or the K_ir channel inhibitor BaCl₂ (0.1 mM), neither of them had no influence on the CG-induced response (p>0.05). However, pretreatment with the K_ATP channel inhibitor Gli (0.01 mM) produced significant inhibition on the CG-induced response (p<0.01). Besides, CG also inhibited the contraction triggered by NE in endothelium-denuded rings in Ca²⁺-free medium. CG (0.4, 0.8 and 3.2 mg/mL) produced rightward parallel displacement of CaCl₂ curves and reduced the maximum contraction induced by 30 mM CaCl₂ to 31.1±9.3%, 18.8±6.9% and 9.4±4.5%, respectively. The relaxation, induced by CG on endothelium-intact rat aortic rings pre-contracted with NE, was significantly attenuated in the presence of atropine (EC₅₀=3.7 mg/mL, p<0.01).

Conclusions

Our results suggest that CG induces relaxation in rat aortic rings through an endothelium-dependent pathway mediated by NO/cGMP pathway and an endothelium-independent pathway involving blockade of Ca²⁺ channels, inhibition of Ca²⁺ mobilization from intracellular stores, opening of K_ATP channel. In addition, the muscarinic receptor stimulation is also one of the vasorelaxant mechanisms.     

Water extract of Zanthoxylum piperitum induces vascular relaxation via endothelium-dependent NO-cGMP signaling

Aim of the study

The aim of the present study was to define the effects of extracts of leaves of Zanthoxylum piperitum (ZP) on the vascular tension and its mechanisms responsible in rat thoracic aortic rings.

Materials and methods

Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) were examined for their vascular relaxant effects in isolated phenylephrine-precontracted aortic rings.

Results

Methanol extract of ZP and aqueous fraction of the methanol extract (AZP) induced relaxation of the phenylephrine-precontracted aortic rings in a concentration-dependent manner. Endothelium-denudation abolished the AZP-induced vasorelaxation. Pretreatment of the endothelium-intact aortic rings with N^G-nitro-l-arginine methylester (L-NAME) and 1H-[1,2,4]-oxadiazolo-[4,3-α]-quinoxalin-1-one (ODQ) inhibited the AZP-induced vasorelaxation. Inhibition of Ca²⁺ entry via L-type Ca²⁺ channels failed to block the AZP-induced vasorelaxation. Extracellular Ca²⁺ depletion slightly but significantly attenuated the AZP-induced vasorelaxation. Thapsigargin significantly attenuated the AZP-induced vasorelaxation. Further, Gd³⁺ and 2-aminoethyl diphenylborinate (2-APB), inhibitors of store-operated Ca²⁺ entry (SOCE), markedly attenuated the AZP-induced vasorelaxation. Also, wortmannin, an inhibitor of Akt, an upstream signaling molecule of eNOS, attenuated the AZP-induced vasorelaxation. AZP increased cGMP levels of the aortic rings in a concentration-dependent manner and the effect was blocked by L-NAME, ODQ, thapsigargin, Gd³⁺, 2-APB, and wortmannin. K⁺ channel inhibition with glibenclamide and tetraethylammonium, cyclooxygenase inhibition with indomethacin, and adrenergic and muscarinic receptors blockade had no effects on the AZP-induced vasorelaxation.

Conclusion

Taken together, the present study suggests that AZP relaxes vascular smooth muscle via endothelium-dependent activation of NO-cGMP signaling through the Akt- and SOCE-eNOS pathways.     

白藜芦醇对大鼠离体胸主动脉环的舒张作用

目的:观察白藜芦醇(resveratrol,RVL)对大鼠离体胸主动脉血管的舒张作用并探讨其机制。方法:采用离体血管环灌流方法,观察RVL在含Ca²⁺或无Ca²⁺ Krebs液孵育条件下对去甲肾上腺素(NA)引起的血管平滑肌收缩的影响;同法观察RVL对30,80mmol·L^-1的KCl引起的血管平滑肌收缩的影响;RVL对NA引起的依赖于细胞内钙和细胞外钙收缩反应的影响,以及加入N-G-硝基-L-精氨酸(L-NNA)和优降糖后RVL舒张大鼠离体主动脉环效应的变化。结果:RVL呈浓度依赖性舒张NA引起的血管收缩;无Ca²⁺ 组RVL抑制NA所致血管平滑肌收缩效应大于含Ca²⁺ 组;RVL能够拮抗NA诱发的依内钙的收缩反应,而对外钙收缩无抑制。RVL对80,30mmol·L^-1 的KCl引起的血管平滑肌收缩均有抑制作用,且前者量效曲线明显上移。L-NNA使RVL舒血管效应降低(26.0±4.6)%;优降糖组的血管舒张受抑程度与对照组无显著差别(P>0.05)。结论:RVL可呈内皮依赖性舒张血管平滑肌,其作用机制可能与该药促进NO合成释放,开放钙激活的钾通道以及抑制血管平滑肌细胞外钙内流和内钙释放有关。     

Mechanisms of the relaxant effect of a Danshen and Gegen formulation on rat isolated cerebral basilar artery

Aim of the study

Danshen (root of Salvia miltiorrhiza) and Gegen (root of Pueraria lobata) are two herbs used in traditional Chinese medicine, most commonly for their putative cardioprotective and anti-atherosclerotic effects. In this study, the actions of a Danshen and Gegen formulation (DG; ratio 7:3) were investigated on rat-isolated cerebral basilar artery.

Materials and methods

Rat basilar artery rings were precontracted with 100 nM U46619. Involvement of endothelium-dependent mechanisms was investigated by mechanical removal of the endothelium; K⁺ channels were investigated by pretreatment of the artery rings with various K⁺ channel inhibitors, and Ca²⁺ channels were investigated in artery rings incubated with Ca²⁺-free buffer and primed with 100 nM U46619 for 5 min prior to adding CaCl₂ to elicit contraction.

Results

DG produced concentration-dependent relaxation of the artery rings with an IC₅₀ of 895 ± 121 μg/ml. Mechanical removal of the endothelium or pretreatment with the BK_Ca channel inhibitor iberiotoxin (100 nM), the K_V channel inhibitor 4-aminopyridine (1 mM), or the K_IR channel inhibitor barium chloride (100 μM), all had no effect on the DG-induced response (P > 0.05 for all). However, pretreatment with the K_ATP channel inhibitor glibenclamide (1 μM), the non-selective K⁺ channel inhibitor tetraethylammonium (TEA, 100 mM), or a combination of all the K⁺ channel inhibitors (iberiotoxin + 4-aminopyrindine + barium chloride + glibenclamide + TEA) produced significant inhibition on the DG-induced response (P < 0.01 for all); its maximum vasorelaxant effect (Imax) was reduced by 37, 24, and 30%, respectively. Preincubation of the artery rings with DG for 10 min produced concentration-dependent (1, 3 and 7 mg/ml) and total inhibition on the CaCl₂-induced vasoconstriction.

Conclusions

These findings suggest the vasorelaxant effect of DG on rat basilar artery is independent of endothelium-derived mediators, whereas, inhibition of Ca²⁺ influx in the vascular smooth muscle cells is important, and a minor component is mediated by the opening of K_ATP channels. DG could be a useful cerebroprotective agent in some patients with occlusive cerebrovascular disease.