间硝苯地平对老龄肾性高血压大鼠心肌和脑微粒体Na+,K+-ATP酶,Ca2+-ATP酶和Mg2+-ATP酶活性的影响

间硝苯地平(m-Nif,ig20mg·kg^-1·d^-1持续给药9周)可显著降低老龄肾性高血压大鼠(RVHR)血压和左室重量(P<0.01),增高心、脑微粒体Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶活性(P<0.01),降低Mg²⁺-ATP酶活性,体外量效关系研究发现,m-Nif在较高剂量(10～1000μmol·L^-1)时可增高RVHR心脑微粒体Na⁺,K⁺-ATP酶和Ca²⁺-ATP酶活性,且随剂量增加而增高。上述结果表明,m-Nif可改善老龄RVHR心脑微粒体Na⁺,K⁺泵和Ca²⁺泵功能。     

羟苯氨酮强心作用的生化机理研究

目的：研究羟苯氨酮(oxyphenamone, Oxy)强心作用的生化机理。方法：采用Na⁺,K⁺-ATP酶活性和cAMP-PDE活性、肌浆网Ca²⁺-ATP酶活性和cAMP含量以及心肌肌原纤维Ca²⁺,Mg²⁺-ATP酶活性等测定法,研究Oxy对它们的影响,并与milrinone和MCI-154作比较。 结果：Oxy对Na⁺,K⁺-ATP酶和PDE无抑制作用,也不影响心肌cAMP含量,但能显著增强心肌肌原纤维对Ca²⁺的敏感性,高浓度时轻度抑制心肌肌浆网Ca²⁺-ATP酶活性。结论：Oxy的强心作用方式不同于强心苷、β受体激动剂和PDE抑制剂等强心药,可能为一种新的钙增敏性强心药物。     

阿托伐他汀的肝毒性机制研究

目的 研究阿托伐他汀肝毒性损伤作用及机制。方法 将24只Wistar han雄鼠分为对照组和阿托伐他汀低（68.5mg/kg）、高剂量组（205.5 mg/kg）,按照10 mL/kg的药液体积给药,溶媒对照组ig等体积5% CMC-Na,连续ig 28 d。检测血清中天门冬氨酸氨基转移酶（AST）、丙氨酸氨基转移酶（ALT）、碱性磷酸酶（ALP）、尿素氮（BUN）和血肌酐（CRE）的含量,HE染色观察肝组织病理。在体外,HepG2细胞经传代培养后,给予阿托伐他汀干预24 h,检测细胞存活率,丙二醛（MDA）水平、Na⁺-K⁺-ATP酶和Ca²⁺-Mg²⁺-ATP酶活性及线粒体膜电位。结果 与对照组比较,阿托伐他汀高剂量组大鼠肝细胞弥漫性肿胀,核分裂多见,部分肝细胞极性消失,排列紊乱（P<0.05）。与对照组比较,阿托伐他汀高剂量组给药后血清中ALT和AST显著升高（P<0.05、0.01）。在体外,与对照组比较,阿托伐他汀125、250、500 μmol/L能明显抑制细胞存活率（P<0.05、0.001）。与对照组比较,阿托伐他汀500 μmol/L HepG2细胞MDA含量明显升高（P<0.01）。与对照组比较,阿托伐他汀125 μmol/L能使Na⁺-K⁺-ATP酶活性增强,500 μmol/L使Na⁺-K⁺-ATP酶活性降低（P<0.001）。与对照组比较,阿托伐他汀125、250、500 μmol/L均能使能使Ca²⁺-Mg²⁺-ATP酶活性降低（P<0.01,0.001）。与对照组比较,阿托伐他汀125、250、500 μmol/L均能降低线粒体膜电位（P<0.001）。结论 阿托伐他汀高剂量可导致肝组织损伤,其毒性作用通过破坏细胞的线粒体膜电位,抑制Na⁺-K⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶活性,细胞膜脂质过氧化,从而破坏细胞内微环境的平衡,导致细胞凋亡和坏死。     

多巴胺对大鼠纹状体突触前和突触后膜 Na+,K+-ATP 酶活性调节的差异

用蔗糖-Ficol梯度不连续离心法制备大鼠纹状体突触前膜和突触后膜,研究多巴胺(DA)受体对突触前和突触后膜Na⁺,K⁺-ATP酶活性的调节作用。结果表明,DA(10^-8～10^-5mol·L^-1)显著抑制突触后膜Na⁺,K⁺-ATP酶的活性,单独用选择性D1(SKF38393)或D2(LY171555)受体激动剂均无抑制作用,而当二者合用时则产生与DA相似的抑制效应。DA对Na⁺,K⁺-ATP酶的抑制效应可被单独用选择性D1(SCH23390)或D2(spiperone)受体拮抗剂而逆转。相反,DA却能显著激活突触前膜Na⁺,K⁺-ATP酶的活性,单用spiperone即可逆转此激活效应。结果提示,突触前和突触后DA受体对Na⁺,K⁺-ATP酶的调节存在差异,可能与它们的不同生理功能有关。     

人参二醇皂甙和三醇皂甙对兔纹状体ATP酶的影响

本文报道用体外给药法,观察了PDS和PTS对纹状体ATP酶(Na⁺、K⁺-ATP酶,Ca²⁺-ATP酶及M²⁺-ATP酶)的影响。结果发现PDS和PTS对Na⁺,K⁺-ATP酶都有明显的抑制作用,且随PDS和PTS浓度的高低,其抑制作用增强或减弱;对Ca²⁺-ATP酶,PDS在10^-5g/ml时有激活作用,当浓度增高到10^-3g/mL时则转为抑制,而PTS仅为抑制效应;对于Mg²⁺-ATP酶能被PDS所兴奋,而被PTS所抑制。此结果表明PDS和PTS对中枢神经系统的作用,可能与其影响脑内ATP酶有密切的内在联系。     

丹酚酸B预处理对心肌缺血/再灌注损伤能量代谢的影响

目的 观察丹酚酸B预处理对大鼠心肌缺血/再灌注损伤（MI/RI）能量代谢的作用。方法 通过结扎冠状动脉30min再灌注2 h建立大鼠MI/RI模型,随机分为4组：假手术组、模型组及丹酚酸B高、低（20、10 mg/kg）组,于建立模型前7 d开始ip给药,每天1次;再灌注结束后,采用比色法测定血清乳酸脱氢酶（LDH）、肌酸激酶（CK）活力,染色法测定心肌梗死面积（MIA）,定磷法测定心肌组织Na⁺-K⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶活性。结果 与模型组（42.60%）比较,丹酚酸B高、低剂量组的MIA分别缩小至35.93%和37.21%,差异显著（P<0.05）;与模型组比较,丹酚酸B高、低剂量组血清CK、LDH活力均显著降低（P<0.05、0.01）;与模型组比较,丹酚酸B高、低剂量组心肌组织Na⁺-K⁺-ATP酶、Ca²⁺-Mg²⁺-ATP酶活性均显著升高（P<0.05、0.01）。结论 丹酚酸B预处理可保护MI/RI所致心肌损伤,作用途径可能与改善心肌组织的能量代谢相关。     

清脑片对沙鼠脑缺血再灌注的保护作用及其机制研究

目的 探究清脑片对沙鼠脑缺血再灌注的保护作用及其机制。方法 采用双侧颈总动脉结扎10 min再灌注60 min,建立沙鼠脑缺血模型,观察高、中、低剂量清脑片组（1.5,0.75,0.375 g·kg^-1）对沙鼠脑组织中白介素-1β（IL-1β）、肿瘤坏死因子-α（TNF-α）、兴奋性氨基酸谷氨酸（Glu）、天门冬氨酸（Asp）、血栓烷素B₂（TXB₂）、丙二醛（MDA）含量及ATP活性和NF-кB免疫阳性表达的影响。结果 与模型组比较,高、中剂量清脑片可显著降低脑组织中IL-1β、TNF-α、Glu、Asp、TXB₂、MDA的含量及NF-κB免疫阳性表达水平（P<0.01或P<0.05）,显著提高脑组织中Na⁺-K⁺-ATP、Mg²⁺-ATP、Ca²⁺-ATP、Ca²⁺-Mg²⁺-ATP的酶活性（P<0.01或P<0.05）。结论 清脑片对沙鼠脑缺血再灌注有明显的保护作用,其作用机制可能与抑制体内炎症因子、过氧化能力及提高酶活力有关。     

α-青心酮对损伤的脑线粒体Na+,K+-ATPase活性和脑细胞耗氧的作用

目的研究α-青心酮对抗坏血酸和硫酸亚铁诱导脑线粒体Na⁺，K⁺-ATPase活性和脑细胞耗氧的作用。方法采用无机磷法测定Na⁺，K⁺-ATPase活性,分光光度法检测脑线粒体膨胀和脂质过氧化物，氧电极法测定脑细胞耗氧量。结果在抗坏血酸和硫酸亚铁的作用下，鼠脑线粒体Na⁺，K⁺-ATPase活性降低，线粒体膨胀和脑细胞脂质过氧化物升高。α-青心酮抑制其抗坏血酸和硫酸亚铁诱导脑线粒体和细胞的损伤,增加Na⁺，K⁺-ATPase活性，降低脑线粒体膨胀和脑细胞脂质过氧化物生成。α-青心酮还具有减少ADP刺激的脑细胞耗氧的作用。结论α-青心酮通过清除自由基和抗氧化作用保护脑细胞结构和功能的完整。     

D-半乳糖衰老模型观察的新指标

目的　观察D-半乳糖衰老模型与正常小鼠之间衰老指标的差别。方法　采用D 半乳糖sc造成衰老小鼠模型,测定脑组织Ca²⁺含量、Ca²⁺-ATP酶(钙泵)、Na⁺-ATP酶(钠泵)、NO和AngII胰岛素(ISN)活性。结果　D-半乳糖衰老模型小鼠与对照组比较脑组织Ca²⁺含量(P<0.01)、NO水平(P<0.05)明显增加;Ca²⁺-ATP酶、Na⁺-ATP酶活性下降(P<0.01) ,胰岛素、AngII水平明显下降(P<0.01) ,Zn²⁺/Cu²⁺比值有显著性差异。结论　D-半乳糖衰老模型小鼠与正常小鼠之间在组织Ca²⁺含量、Ca²⁺-ATP酶(钙泵)、Na⁺-ATP酶(钠泵)、NO、AngII和胰岛素活性有显著性差异,Zn²⁺/Cu²⁺比值下降,可作为抗衰老药物研究的模型。     

柴胡皂甙和甘草甜素抑制Na+,K+-ATP酶活性的构效关系

研究在离体条件下各种单体柴胡皂甙和甘草甜素抑制Na⁺,K⁺-ATP酶活性的构效关系。实验结果表明,各种柴胡皂甙抑制Na⁺,K⁺-ATP酶活性的作用强度依次为:b₁>d>b₂>b₄>a>b₃>e>c。柴胡皂甙化学结构中的C₂₃-OH,C₁₆-OH及C₁₁和C₁₃的共轭双烯可能对其抑制活性起重要作用。甘草甜素(GL),甘草次酸(GA)和生胃酮(18-β-甘草次酸半琥珀酸双钠盐,CX)抑制Na⁺,K⁺-ATP酶活性的作用强度依次为GA≥CX>GL。研究还证明,柴胡皂甙d对Na⁺,K⁺-ATP酶的抑制为非竟争性抑制。     

质子泵抑制剂引起阿尔茨海默病发病机制的研究进展

质子泵抑制剂（PPIs）是H⁺K⁺-ATP酶抑制剂,是当前应用最多的一类酸抑制药物,PPIs作用于胃黏膜上的质子泵,抑制H⁺的分泌,直接抑制胃酸产生。随着PPIs的应用越来越多,各种不良反应的报道也越来越多,且PPIs在老年人中的应用中存在疗程过长和适应症不适宜的问题。最新研究发现PPIs在老年患者中的使用可能会增加阿尔茨海默病的发生,综述了PPIs引起阿尔茨海默病发生的机制。     

Mechanism of asynchronous Ca2+ waves underlying agonist-induced contraction in the rat basilar artery

Background and purpose:

Uridine 5''-triphosphate (UTP) is a potent vasoconstrictor of cerebral arteries and induces Ca²⁺ waves in vascular smooth muscle cells (VSMCs). This study aimed to determine the mechanisms underlying UTP-induced Ca²⁺ waves in VSMCs of the rat basilar artery.

Experimental approach:

Isometric force and intracellular Ca²⁺ ([Ca²⁺]_i) were measured in endothelium-denuded rat basilar artery using wire myography and confocal microscopy respectively.

Key results:

Uridine 5''-triphosphate (0.1–1000 µmol·L⁻¹) concentration-dependently induced tonic contraction (pEC₅₀ = 4.34 ± 0.13), associated with sustained repetitive oscillations in [Ca²⁺]_i propagating along the length of the VSMCs as asynchronized Ca²⁺ waves. Inhibition of Ca²⁺ reuptake in sarcoplasmic reticulum (SR) by cyclopiazonic acid abolished the Ca²⁺ waves and resulted in a dramatic drop in tonic contraction. Nifedipine reduced the frequency of Ca²⁺ waves by 40% and tonic contraction by 52%, and the nifedipine-insensitive component was abolished by SKF-96365, an inhibitor of receptor- and store-operated channels, and KB-R7943, an inhibitor of reverse-mode Na⁺/Ca²⁺ exchange. Ongoing Ca²⁺ waves and tonic contraction were also abolished after blockade of inositol-1,4,5-triphosphate-sensitive receptors by 2-aminoethoxydiphenylborate, but not by high concentrations of ryanodine or tetracaine. However, depletion of ryanodine-sensitive SR Ca²⁺ stores prior to UTP stimulation prevented Ca²⁺ waves.

Conclusions and implications:

Uridine 5''-triphosphate-induced Ca²⁺ waves may underlie tonic contraction and appear to be produced by repetitive cycles of regenerative Ca²⁺ release from the SR through inositol-1,4,5-triphosphate-sensitive receptors. Maintenance of Ca²⁺ waves requires SR Ca²⁺ reuptake from Ca²⁺ entry across the plasma membrane via L-type Ca²⁺ channels, receptor- and store-operated channels, and reverse-mode Na⁺/Ca²⁺ exchange.     

基于网络药理学研究当归芍药散防治阿尔茨海默病的作用机制

目的 探究当归芍药散防治阿尔茨海默病的作用机制。方法 选取当归芍药散中的当归、白芍、白术、川芎、茯苓、泽泻为研究对象,应用TCMSP数据库对6味中药主要化学成分进行筛选;使用TCMSP数据库,对筛选出的化合物及阿尔茨海默病进行靶点预测,选取当归芍药散与阿茨海默病一致的6个靶点蛋白作为后续研究对象,通过生物分子功能注释系统（MAS 3.0）及KEGG通路数据库进行通路注解及分析,得到当归芍药散治疗阿茨海默病的相关靶点通路预测图及相关信号通路。结果 从当归芍药散中筛选出35个化合物,可作用于阿尔茨海默病6个潜在的蛋白靶点,找出靶点的相关通路22条。作用通路涉及阿尔茨海默病发病机制相关的钙信号途径、炎症、免疫调节、细胞与细胞之间的信号交流、肌动蛋白细胞骨架的调节等各个环节,6味中药既有共同的成分及作用靶点、通路,又各有偏重,各通路间通过共有靶点连接,显示出不同成分间的多靶点、多途径的协同作用。结论 预测出当归芍药散治疗阿尔茨海默病可能与其调节炎症、免疫系统、钙信号、细胞与细胞之间的信号交流等机制有关。     

INVOLVEMENT OF PROTEIN KINASE C IN THE REGULATION OF Na+/Ca2+ EXCHANGER IN BOVINE ADRENAL CHROMAFFIN CELLS

• 1 The Na⁺/Ca²⁺ exchanger (NCX) exchanges Na+ and Ca²⁺ bidirectionally through the forward mode (Ca²⁺ extrusion) or the reverse mode (Ca²⁺ influx). The present study was undertaken to clarify the role of protein kinase C (PKC) in the regulation of NCX in bovine adrenal chromaffin cells. The Na⁺‐loaded cells were prepared by treatment with 100 µmol/L ouabain and 50 µmol/L veratridine. Incubation of Na⁺‐loaded cells with Na⁺‐free solution in the presence of the Ca²⁺ channel blockers nicardipine (3 µmol/L) and ω‐conotoxin MVIIC (0.3 µmol/L) caused Ca²⁺ uptake and catecholamine release.
• 2 The Na⁺‐dependent Ca²⁺ uptake and catecholamine release were inhibited by 2‐[4‐[(2,5‐difluorophenyl)methoxy]phenoxy]‐5‐ethoxyaniline (SEA0400; 1 µmol/L) and 2‐[2‐[4‐(4‐nitrobenzyloxy)phenyl]isothiourea (KB‐R7943; 10 µmol/L), both NCX inhibitors. These results indicate that the Na⁺‐dependent responses are mostly due to activation of the NCX working in the reverse mode.
• 3 In addition, we examined the effects of PKC inhibitors and an activator on the NCX‐mediated Ca²⁺ uptake and catecholamine release. Bisindolylmaleimide I (0.3–10 µmol/L) and chelerythrine (3–100 µmol/L), both PKC inhibitors, inhibited NCX‐mediated responses. In contrast, phorbol 12,13‐dibutyrate (0.1–10 µmol/L), a PKC activator, enhanced the responses. Bisindolylmaleimide I and chelerythrine, at effective concentrations for inhibition of Na⁺‐dependent catecholamine release, had a little or no effect on high K⁺‐induced catecholamine release in intact cells or on Ca²⁺‐induced catecholamine release in β‐escin‐permeabilized cells.
• 4 These results suggest that PKC is involved in the activation of NCX in bovine adrenal chromaffin cells.

     

Effects of altered availability of Na+ on guinea-pig airway smooth muscle contractility

The effects of altering the availability of sodium ions (Na⁺) on contractility of the guinea-pig isolated trachealis was examined using regimens which are reported to inhibit Na⁺/K⁺ ATPase activity (ouabain), Na⁺/H⁺ exchange (amiloride, ammonium ion (NH₄⁺)) or Na⁺/Ca²⁺ exchange (reduced extracellular Na⁺). Inhibition of Na⁺/K⁺ ATPase and reversal of Na⁺/Ca²⁺ exchange resulted in increased ⁴⁵Ca uptake and contraction of the trachealis by voltage-sensitive and voltage-insensitive mechanisms respectively. When Na⁺/H⁺ exchange was inhibited by amiloride the tissues relaxed to below their baseline tension. The relaxation was not due to reduced Ca²⁺ influx. Treatment with NH₄⁺ produced a contractile response. Reduced extracellular Na⁺ caused a transient contraction as a result of reversal of the normal Na⁺/Ca²⁺exchange process leading to accumulation of Ca²⁺ within the cell. Since the effects of amiloride and reduced extracellular sodium were different, it is unlikely that amiloride is acting primarily by inhibiting Na⁺/Ca²⁺ exchange. Amiloride reduced tissue sensitivity to methacholine and KCI without affecting Ca²⁺ influx. This may involve a secondary stimulation of Na⁺/Ca²⁺ exchange following changes in [Na'];. Ouabain also reduced tissue sensitivity to methacholine and KCl.These findings suggest that Na⁺ are important in determining smooth muscle contractility. If NH₄⁺ is altering pH then, at the concentrations used, the changes in (H⁺] were not sufficient to alter responses to the spasmogens.     

Ca2+ entry through reverse Na+/Ca2+ exchanger in NCI-H716, glucagon-like peptide-1 secreting cells

Glucagon like peptide-1 (GLP-1) released from enteroendocine L-cells in the intestine has incretin effects due to its ability to amplify glucose-dependent insulin secretion. Promotion of an endogenous release of GLP-1 is one of therapeutic targets for type 2 diabetes mellitus. Although the secretion of GLP-1 in response to nutrient or neural stimuli can be triggered by cytosolic Ca²⁺ elevation, the stimulus-secretion pathway is not completely understood yet. Therefore, the aim of this study was to investigate the role of reverse Na⁺/Ca²⁺ exchanger (rNCX) in Ca²⁺ entry induced by muscarinic stimulation in NCI-H716 cells, a human enteroendocrine GLP-1 secreting cell line. Intracellular Ca²⁺ was repetitively oscillated by the perfusion of carbamylcholine (CCh), a muscarinic agonist. The oscillation of cytosolic Ca²⁺ was ceased by substituting extracellular Na⁺ with Li⁺ or NMG⁺. KB-R7943, a specific rNCX blocker, completely diminished CCh-induced cytosolic Ca²⁺ oscillation. Type 1 Na⁺/Ca²⁺ exchanger (NCX₁) proteins were expressed in NCI-H716 cells. These results suggest that rNCX might play a crucial role in Ca²⁺ entry induced by cholinergic stimulation in NCI-H716 cells, a GLP-1 secreting cell line.     

康艾注射液辅助治疗中晚期胃癌的疗效及对免疫功能影响的Meta分析

目的 评价康艾注射液辅助治疗中晚期胃癌的疗效、对免疫功能的影响及安全性。方法 检索中国学术期刊全文数据库（CNKI）、万方数据库、中国生物医学文献数据库（CBM）、维普生物医学数据库（VIP）、Cochrane Library、PubMed、Embase中关于康艾注射液辅助化疗治疗中晚期胃癌的随机对照试验（RCT）,检索时间为建库至2022年6月,采用RevMan 5.3软件进行Meta分析。结果 共纳入13项RCTs,1 205例患者。Meta分析结果显示,相较于对照组,康艾注射液辅助化疗可以提高临床总缓解率［RR=1.58,95% CI=（1.39,1.79）］,提高CD3⁺水平［SMD=3.39,95% CI=（2.09,4.69）］、CD4⁺水平［SMD=2.19,95% CI=（1.10,3.27）］、CD4⁺/CD8⁺［MD=0.34,95% CI=（0.23,0.45）］,差异均有统计学意义（P<0.01）;可减少白细胞降低发生率［RR=0.55,95% CI=（0.46,0.65）,P<0.01］、肝功能损伤发生率［RR=0.36,95% CI（0.19,0.69）,P<0.01］。结论 对比单用化疗的晚期胃癌患者,加用康艾注射液可有效提高患者的临床疗效、改善免疫功能,缓解因化疗导致的白细胞降低、肝功能损害等不良反应。     

不同生境人参茎叶总皂苷对心律失常小鼠的作用比较

目的 探讨园参茎叶总皂苷(GSLS)和林下山参茎叶总皂苷(MSLS)对心律失常小鼠的改善作用.方法 将80只SPF级BALB/c小鼠随机分为正常组、模型组、园参茎叶总皂苷低(GSLS-L)、中(GSLS-M)、高(GSLS-H)剂量组、林下山参茎叶总皂苷低(MSLS-L)、中(MSLS-M)、高(MSLS-H)剂量组....     

The therapeutic potential of small-conductance KCa2 channels in neurodegenerative and psychiatric diseases

Introduction: KCa2 or small-conductance Ca²⁺-activated K⁺ channels (SK) are expressed in many areas of the central nervous system where they participate in the regulation of neuronal afterhyperpolarization and excitability, and also serve as negative feedback regulators on the glutamate-NMDA pathway.

Areas covered: This review focuses on the role of KCa2 channels in learning and memory and their potential as therapeutic targets for Alzheimer's and Parkinson's disease, ataxia, schizophrenia and alcohol dependence.

Expert opinion: There currently exists relatively solid evidence supporting the use of KCa2 activators for ataxia. Genetic KCa2 channel suppression in deep cerebellar neurons induces ataxia, while KCa2 activators like 1-EBIO, SKA-31 and NS13001 improve motor deficits in mouse models of episodic ataxia (EA) and spinal cerebellar ataxia (SCA). Use of KCa2 activators for ataxia is further supported by a report that riluzole improves ataxia in a small clinical trial. Based on accumulating literature evidence, KCa2 activators further appear attractive for the treatment of alcohol dependence and withdrawal. Regarding Alzheimer's disease, Parkinson's disease and schizophrenia, further research, including long-term studies in disease relevant animal models, will be needed to determine whether KCa2 channels constitute valid targets and whether activators or inhibitors would be needed to positively affect disease outcomes.     

N-arachidonoyl glycine suppresses Na+/Ca2+ exchanger-mediated Ca2+ entry into endothelial cells and activates BKCa channels independently of GPCRs

Background and Purpose

N-arachidonoyl glycine (NAGly) is a lipoamino acid with vasorelaxant properties. We aimed to explore the mechanisms of NAGly''s action on unstimulated and agonist-stimulated endothelial cells.

Experimental Approach

The effects of NAGly on endothelial electrical signalling were studied in combination with vascular reactivity.

Key Results

In EA.hy926 cells, the sustained hyperpolarization to histamine was inhibited by the non-selective Na⁺/Ca²⁺ exchanger (NCX) inhibitor bepridil and by an inhibitor of reversed mode NCX, KB-R7943. In cells dialysed with Cs⁺-based Na⁺-containing solution, the outwardly rectifying current with typical characteristics of NCX was augmented following histamine exposure, further increased upon external Na⁺ withdrawal and inhibited by bepridil. NAGly (0.3–30 μM) suppressed NCX currents in a URB597- and guanosine 5′-O-(2-thiodiphosphate) (GDPβS)-insensitive manner, [Ca²⁺]_i elevation evoked by Na⁺ removal and the hyperpolarization to histamine. In rat aorta, NAGly opposed the endothelial hyperpolarization and relaxation response to ACh. In unstimulated EA.hy926 cells, NAGly potentiated the whole-cell current attributable to large-conductance Ca²⁺-activated K⁺ (BK_Ca) channels in a GDPβS-insensitive, paxilline-sensitive manner and produced a sustained hyperpolarization. In cell-free inside-out patches, NAGly stimulated single BK_Ca channel activity.

Conclusion and Implications

Our data showed that NCX is a Ca²⁺ entry pathway in endothelial cells and that NAGly is a potent G-protein-independent modulator of endothelial electrical signalling and has a dual effect on endothelial electrical responses. In agonist pre-stimulated cells, NAGly opposes hyperpolarization and relaxation via inhibition of NCX-mediated Ca²⁺ entry, while in unstimulated cells, it promotes hyperpolarization via receptor-independent activation of BK_Ca channels.