在地昔帕明诱导胶质瘤C6细胞凋亡过程中caspase 3基因表达和[Ca~(2 )]_i稳态(英文)

目的:研究抗抑郁药地昔帕明(Des)对胶质瘤C6细胞的凋亡诱导作用以及对凋亡关键效应分子caspase3和凋亡早期信号[Ca~(2 )]_i的调控作用.方法:采用流式细胞术(FCM)和凝胶电泳观察Des对C6细胞凋亡的DNA裂解作用,RT-PCR分析。caspase 3基因的表达以及激光扫描共聚焦显微镜测量单个活细胞[Ca~(2 )]_i浓度.结果:Des(10,20,40μmol/L)处理C6细胞24 h后,FCM图的G_1峰左侧出现凋亡特征性亚二倍体细胞峰,凋亡细胞百分率分别为5.2％,21.9％和 41.9％.同时,凝胶电泳显示典型的DNA“梯带”.DeS 20 μmol/L处理C6细胞24 h可明显增强caspase 3基因的表达,而未经Des处理的C6细胞则检测不到caspase 3基因的表达.此外,Des 40 μmol/L可使 C6细胞[Ca~(2 )]_i迅速升高并维持超过28 min,而钙螯合剂依他酸可显著降低C6细胞[Ca~(2 )]_i增高幅度,提示Des致C6细胞[Ca~(2 )]_i增高主要与细胞外钙内流有关.结论:Des诱导C6胶质瘤细胞凋亡可能与caspase 3基因表达的上调以及细胞内钙稳态的失衡有关.     

粉防己碱对培养乳牛基底动脉平滑肌细胞内游离钙浓度的影响

目的：研究粉防己碱对培养乳牛基底动脉平滑肌细胞游离钙浓度（[Ca^2 ]i)的影响。方法：利用AR－CM－MIC阳离子测定系统,采用Fura 2-AM为指示剂,测量单个细胞内[Ca^2 ]i。结果：粉防己碱10－100μmol/L对培养乳牛基底动脉平滑肌细胞静息[Ca^2 ]i无明显影响。在细胞外钙为1．3mmol/L,粉防己碱可浓度依赖性地抑制KC1引起[Ca^2 ]i的升高。咖啡因10mmol/L可诱导一次[Ca^2 ]i瞬间快速升高,随后自发回复到静息水平,粉防己碱10和30μmol/L对咖啡因诱导的[Ca^2 ]i瞬间升高没有作用,但高浓度（100μmol/L）粉防己碱抑制了[Ca^2 ]i瞬间升高。在细胞外钙为1.3mmol/L,苯肾上腺素10μmol/L可引起双相[Ca^2 ]i变化,包括快速升高相和持续升高相。在细胞外钙为零,苯肾上腺素仅引起[Ca^2 ]i的快速升高相。粉防己碱可浓度依赖性地抑制苯肾上腺素引起[Ca^2 ]i快速升高相。结论：在培养乳牛基底动脉平滑肌细胞,粉防己碱可能通过影响电压依赖性和苯肾上腺素受体介导的钙通道而抑制钙内流。高浓度粉防己碱也可能影响肌浆网钙释放或钙摄取。     

海嘧啶注射剂对SGC-7901人胃癌细胞凋亡的实验研究

目的：揭示海嘧啶的抗肿瘤作用机理。方法：采用流式细胞仪测定海嘧啶对人胃癌细胞凋亡及细胞周期的影响，采用激光扫描共聚焦技术观测海嘧啶对人胃癌细胞内[Ca^2 ]i的影响及[Ca^2 ]i变化时Ca^2 的来源，结果：海嘧啶可诱导肿瘤细胞凋亡，升高肿瘤细胞内[Ca^2 ]i浓度，[Ca^2 ]i升高来源于细胞外钙内流和细胞内钙释放，结论：海嘧啶的抗肿瘤作用机理为诱导肿瘤细胞凋亡,通过开放细胞膜钙通道和引起细胞内钙释放两条途径升高肿瘤细胞内[Ca^2 ]i，启动细胞凋亡机制，从而诱导肿瘤细胞凋亡。     

MG132诱导人血管平滑肌细胞凋亡及对caspase3表达的影响

目的观察蛋白酶体抑制剂MG132对人脐静脉血管平滑肌细胞(VSMC)的致凋亡作用及其对凋亡相关的天冬氨酸特异的半胱氨酸蛋白酶3(caspase3)表达的影响。方法采用多个浓度(2.5,5,10μmol/L)的蛋白酶体抑制剂MG132处理人脐静脉VSMC48h;DNA琼脂糖凝胶电泳检测细胞凋亡;流式细胞术分析细胞周期和细胞凋亡率;反转录-聚合酶链反应(RT-PCR)检测caspase3基因转录水平;免疫细胞化学检测细胞caspase3蛋白表达。结果蛋白酶体抑制剂MG132处理48h后细胞凋亡率增加;RT-PCR检测发现细胞内凋亡相关基因caspase3mRNA表达上调;免疫细胞化学检测细胞caspase3蛋白表达水平升高。结论蛋白酶体抑制剂MG132能够诱导人脐静脉VSMC凋亡,其作用呈量-效关系;MG132诱导VSMC凋亡的机制可能与MG132抑制泛素-蛋白酶体途径(UPP)活性,促进caspase3基因转录,使细胞内caspase3增加而促进细胞凋亡。     

毒胡萝卜素诱导大鼠皮层神经元内质网应激及丹红注射液的干预作用

目的：探讨毒胡萝卜紊诱导大鼠皮层神经元内质网应激凋亡的机制及丹红注射液的干预作用。方法：体外培养SD乳鼠皮层神经元，免疫组织化学、免疫荧光染色鉴定神经元纯度。流式细胞术Annexin V、PI双标检测凋亡率及活性caspase-3、caspase-8、caspase-7、caspase-9表达，Western Noting免疫印迹分析caspase-12、GRP78、Bcl-2、细胞色素C蛋白表达，Fura-2／AM法荧光分光光度计检测细胞内钙浓度（[Ca^2＋]i）。结果：SD乳鼠皮层神经元可纯化体外培养。2μmol／L毒胡萝卜素作用神经元24、48h细胞凋亡率分别是17.88％、21.38％，丹红治疗组分别是6．30％、6．11％，两组比较差异有统计学意义（P〈0．05）。毒胡萝卜素诱导神经元GRP78表达上调，剪切活化caspase-3、caspase-8、caspase-9、caspase-12，使细胞色素C表达增加，Bcl-2表达减少。丹红注射液促进细胞Bcl-2表达，抑制细胞色素C释放，减少活化的caspase-3、caspase-8、caspase-9含量，稳定游离钙浓度。结论：毒胡萝卜素诱导神经元内质网应激反应性凋亡。丹红注射液能抑制体外培养神经元内质网应激所致凋亡。     

TNF-α抑制胶质瘤细胞增殖和诱导凋亡的研究

目的　探讨TNF α对胶质瘤细胞生物学活性的影响。方法　应用MTT法研究经TNF α处理的大鼠C 6胶质瘤细胞的生长和增殖活性 ,采用透射电镜的方法和DNA琼脂糖凝胶电泳的方法观察TNF α诱导胶质瘤细胞的凋亡以及应用免疫细胞化学方法检测抑凋亡蛋白bcl 2的表达。结果　TNF α对体外培养C 6胶质瘤细胞的生长和增殖具有抑制作用 ;并诱导胶质瘤细胞凋亡 ,但抑凋亡蛋白bcl 2的表达无明显变化。结论　TNF α对恶性胶质瘤细胞具有抑制生长和诱导凋亡作用 ,而bcl 2蛋白表达水平不受影响。     

眼睛蛇毒心脏毒素对大鼠心肌细胞收缩及细胞内钙离子的作用

目的 研究眼睛蛇毒心脏毒素（Cardiotoxin，CTX）对心肌细胞的形态、收缩幅度和细胞内钙离子（[Ca^2＋]i）的作用。方法 应用荧光计量法（以Fura-2／AM为荧光染料）及光学成像系统来测定单个心肌细胞[Ca^2＋]i和收缩幅度。结果 0．001～1μmol／L的CTX使心肌细胞由杆状变成圆形，药物的作用从第1分钟时开始，到第20分钟时趋于稳定。在电刺激存在的情况下，1μmol／L的CTX最初导致电诱导的[Ca^2＋]i和收缩幅度瞬间增加，接下来[Ca^2＋]i时程延长，最终细胞对电刺激不敏感、突然收缩、[Ca^2＋]i持续增高。在缺乏电刺激的情况下，1μmol／L的CTX可诱导Ca^2＋震荡波、持续性[Ca^2＋]i增高，这种作用与40mmol／L的KCl和10mmol／L咖啡因所引起的[Ca^2＋]i瞬间增加不同。结论 CTX作用初期使[Ca^2＋]i增高，使细胞[Ca^2＋]。超载，同时伴随细胞形状的改变。     

替莫唑胺对胶质瘤细胞U251凋亡的影响

目的探究替莫唑胺对胶质瘤细胞U251凋亡的影响及其作用机制。方法 40、80、120μmol/L替莫唑胺培养U251细胞系48 h,观察形态变化,流式细胞术检测细胞凋亡率,实时荧光定量PCR(q RT-PCR)法检测caspase 3表达,用caspase3试剂盒检测caspase 3的活性,蛋白免疫印迹(Western blotting)法检测热休克蛋白90(HSP90)、p-HSP90、丝氨酸苏氨酸蛋白激酶(AKT)和p-AKT表达。结果替莫唑胺80、120μmol/L组细胞数目减少,细胞核体积明显缩小,染色质固缩。替莫唑胺80、120μmol/L组细胞凋亡率、caspase 3的表达水平和活性明显高于对照组,p-HSP90、p-AKT的表达水平明显低于对照组(P0.05),呈剂量相关性。结论替莫唑胺能够促进胶质瘤细胞U251凋亡,可能是通过抑制HSP90和AKT表达来实现的。     

蛋白酶体抑制剂MG132诱导人血管平滑肌细胞凋亡及其机制研究

目的：观察蛋白酶体抑制剂MG132对人脐静脉血管平滑肌细胞（vascular smooth musele cells,VSMC）的致凋亡作用及其对凋亡相关的天冬氨酸特异的半胱氨酸蛋白酶3（caspase 3）表达的影响。方法：采用多个浓度（2．5、5、10μmol／L）的蛋白酶体抑制剂MG132处理人脐静脉VSMC 24h和48h;流式细胞术分析细胞凋亡率;RT-PCR检测泛素-蛋白酶体途径（ubiquitin-proteasome pathway,UPP）相关基因泛素、泛素活化酶（E1）、泛素缀合酶（E2）、泛素连接酶（E3）、26S蛋白酶体和caspase 3基因转录水平;免疫细胞化学检测细胞caspase 3蛋白表达。结果：蛋白酶体抑制剂MG132处理48h后细胞凋亡率增加：细胞内UPP相关的基因rnRNA表达降低,而caspase 3 mRNA表达增高;免疫细胞化学检测细胞caspase 3蛋白表达水平升高。结论：蛋白酶体抑制剂MG132能够诱导人脐静脉VSMC凋亡,其作用呈量-效关系;MG132诱导vSMC凋亡与下调UPP相关基因和上调caspase 3基因及蛋白的表达有关。     

尼莫地平对人结肠癌细胞系HCT增殖的影响及机制探讨

目的：研究钙拮抗剂尼莫地平对人结肠癌细胞系HCT生长的影响及探讨其相应的机制。方法：MTT法检测不同剂量尼莫地平对HCT细胞生长的影响。探讨经尼莫地平作用的HCT细胞是否发生凋亡；用流式细胞术检测凋亡细胞亚二倍体峰；DNA凝胶电泳检测HCT细胞DNA的梯度条带；瑞士－姬姆萨染色观察HCT细胞的形态学变化，激光共聚焦扫描显微镜检测在尼莫地平作用下HCT细胞内钙离子的浓度及分布状态的变化。结果：MTT法示尼莫地平可抑制人结肠癌细胞系HCT的生长。流式细胞术检测显示，尼莫地平作用后，HCT细胞亚二倍体峰面积增大，且凋亡细胞数呈剂量依赖性，高剂量尼莫地平组可见典型的DNA的梯度条带；细胞形态呈现细胞的胞膜泡化，胞质浓缩，染色质断裂等变化。Fluo-3荧光标记显示尼莫地平作用于HCT细胞后，细胞内Ca^2 浓度[Ca^2 ]i升高，PI荧光标记的细胞核型发生变化。结论：尼莫地平作为钙拮抗剂对结肠癌HCT细胞系的生长有抑制作用；其机制可能是通过细胞凋亡作用的。     

维拉帕米、噻庚啶和山莨菪碱拮抗TNFα诱导单个内皮细胞胞内游离Ca^2＋浓度的增高

目的：研究肿瘤坏死因子（TNFα）对单个内皮细胞胞内游离Ca^2 浓度（[Ca^2 ]i)的影响及维拉帕米（Ver)、噻庚啶（Cyp)和山莨菪碱（Ani)对TNFα介导休克和Cyp、Ani的抗休克的机制。方法：人脐静脉内皮细胞株（ECV304）接种于35mm含有2mL DMEM培养基的组织培养盘中培养,Fluo-3/AM负载细胞,激光扫描共聚集显微技术测定单个内皮细胞[Ca^2 ]i。结果：TNFα使单个内皮细胞[Ca^2 ]i呈剂量依赖性升高,在60s内达到峰值,然后下降并保持在基础水平之上。共聚焦扫描图像显示细胞核区[Ca^2 ]i升高比胞浆区明显,下降比胞浆区慢。维拉帕米1和2,噻庚啶30和60或山莨菪碱20和40μmol/L均能显著抑制由TNFα 1.2nmol/L诱导的单个内皮细胞[Ca^2 ]i升高。结论：TNFα介导休克的重要机制;维拉帕米、噻庚啶和山莨菪碱对TNFα诱导的[Ca^2 ]i升高有拮抗作用,可能是噻庚啶和山莨菪碱抗休克作用的机制之一。     

Effects of econazole on Ca2+ levels in and the growth of human prostate cancer PC3 cells

1. Econazole is used clinically as an antifungal drug with many different in vitro effects. However, the effects of econazole on prostate cancer cells are unknown. The effects of econazole on intracellular Ca2+ concentrations ([Ca2+]i) in and the proliferation of human PC3 prostate cancer cells was explored in the present study using fura-2 and tetrazolium as fluorescent dyes. 2. At a concentration of 0.1 micromol/L, econazole started to increase [Ca2+]i in a concentration-dependent manner. The econazole-induced increase in [Ca2+]i was reduced by 48% by removal of extracellular Ca2+, suggesting that the econazole-induced increase in [Ca2+]i was composed of extracellular Ca2+ influx and intracellular Ca2+. 3. This econazole-induced Ca2+ influx was via an L-type Ca2+ channel-like pathway. In Ca2+-free medium, 1 micromol/L thapsigargin, an inhibitor of the endoplasmic reticulum Ca2+-ATPase, caused a monophasic increase in [Ca2+]i, after which the effect of econazole to increase [Ca2+]i was substantially inhibited. Conversely, pretreatment with 5 micromol/L econazole to deplete intracellular Ca2+ stores totally prevented thapsigargin from releasing more Ca2+. 4. The phospholipase C (PLC) inhibitor U73122 (2 micromol/L) abolished the increase in [Ca2+]i induced by 10 micromol/L ATP (a Ca2+ mobilizer that needs inositol 1,4,5-trisphosphate). 5. Overnight incubation with 1-30 micromol/L econazole inhibited proliferation of PC3 cells in a concentration-dependent manner. 6. These findings suggest that, in PC3 cells, econazole increases [Ca2+]i by stimulating Ca2+ influx into cells and Ca2+ release from the endoplasmic reticulum via a PLC-independent mechanism. Econazole is cytotoxic at submicromolar concentrations.     

Effect of the antidepressant maprotiline on Ca2+ movement and proliferation in human prostate cancer cells

1. The effect of maprotiline, an antidepressant, on human prostate cells is unclear. In the present study, the effect of maprotiline on [Ca2+]i and growth in PC3 human prostate cancer cells was measured using the fluorescent dyes fura-2 and tetrazolium, respectively. 2. Maprotiline caused a rapid, concentration-dependent increase in [Ca2+]i (EC50 = 200 micromol/L). The maprotiline-induced [Ca2+]i increase was reduced by removal of extracellular Ca2+ or pretreatment with nicardipine. 3. The maprotiline-induced Mn2+ influx-associated fura-2 fluorescence quench directly suggests that maprotiline caused Ca2+ influx. 4. In Ca(2+)-free medium, thapsigargin, an inhibitor of the endoplasmic reticulum Ca(2+)-ATPase, caused a monophasic [Ca2+]i increase, after which the effects of maprotiline of increasing [Ca2+]i were abolished. In addition, pretreatment with maprotiline reduced a major portion of the thapsigargin-induced increase in [Ca2+]i. 5. U73122, an inhibitor of phospholipase C, abolished the ATP (but not maprotiline)-induced increase in [Ca2+]i. 6. Overnight incubation with 1-10 micromol/L maprotiline did not alter cell proliferation, although incubation with 30-50 micromol/L maprotiline decreased cell proliferation. 7, These findings suggest that maprotiline rapidly increases [Ca2+]i in human prostate cancer cells by stimulating both extracellular Ca2+ influx and intracellular Ca2+ release and that it may modulate cell proliferation in a concentration-dependent manner.     

BAY 41-2272, a potent activator of soluble guanylyl cyclase, stimulates calcium elevation and calcium-activated potassium current in pituitary GH cells

The effects of BAY 41-2272, a nitric oxide-independent activator of soluble guanylyl cyclase, on Ca2+ signalling and ion currents were investigated in pituitary GH3 cells. Intracellular Ca2+ concentrations ([Ca2+]i) in these cells were increased by BAY 41-2272. Removing extracellular Ca2+ abolished the BAY 41-2272-induced increase in [Ca2+]i. After [Ca2+]i was elevated by BAY 41-2272 (300 nmol/L), subsequent application of 1-benzyl-3-(5'-hydroxymethyl-2'-furyl) indazole (YC-1; 1 micromol/L) did not increase [Ca2+]i further. In whole-cell recordings, BAY 41-2272 reversibly stimulated Ca2+-activated K+ current (I(K(Ca))) with an EC50 of 225 +/- 8 nmol/L. At 3 micromol/L, BAY 41-2272 slightly and significantly decreased L-type Ca2+ current.In the cell-attached configuration, BAY 41-2272 (300 nmol/L) enhanced the activity of large-conductance Ca2+-activated K+ (BK(Ca)) channels. After BK(Ca) channel activity was stimulated by spermine NONOate (30 micromol/L) or YC-1 (10 micromol/L) in cell-attached patches, subsequent application of BAY 41-2272 (300 nmol/L) further increased the channel open probability. In the inside-out configuration, BAY 41-2272 applied to the intracellular surface of excised patches enhanced BK(Ca) channel activity. Unlike 1 micromol/L paxilline, 1H-[1,2,4]oxadiazolol-[4,3a] quinoxalin-1-one (ODQ; 10 micromol/L) or heme (10 micromol/L) had no effect on BAY 41-2272-stimulated channel activity. BAY 41-2272 caused no shift in the activation curve of BK(Ca) channels; however, it did increase the Ca2+ sensitivity of these channels. At 300 nmol/L, BAY 41-2272 reduced the firing rate of spontaneous action potentials stimulated by thyrotropin-releasing hormone (10 micromol/L). The BK(Ca) channel activity was also enhanced by 300 nmol/L BAY 41-2272 in neuroblastoma IMR-32 cells. Therefore, the BAY 41-2272-induced increase in [Ca2+]i is primarily explained by an increase in Ca2+ influx. The BAY 41-2272-mediated simulation of IK(Ca) may result from direct activation of BKCa channels and indirectly as a result of elevated [Ca2+]i.     

利用体外诱导的钙振荡估测在体内源性物质的生理浓度．肝脏中的情况

AIM: To identify the physiological concentration ranges of norepinephrine (NE), vasopressin (VP), and ATP in the rat liver. METHODS: Rat hepatocytes were isolated by collagenase perfusion. Isolated cells were loaded with the fluorescent calcium indicator Fura-2 acetoxymethyl ester (Fura-2 AM). The effects of different concentrations of norepinephrine, vasopressin, and ATP on intracellular calcium concentration ([Ca2+]i) increases in the freshly isolated rat hepatocytes were investigated. [Ca2+]i was measured by microfluorometry and recorded as fluorescence ratios (F340/F380). RESULTS: NE, VP, and ATP induced increases in [Ca2+]i in a concentration-dependent manner. At lower concentrations, [Ca2+]i tended to show an oscillatory increase; with increasing concentrations, [Ca2+]i in more cells tended to show phasic or plateau increases. NE, VP, and ATP concentrations likely to induce an oscillatory [Ca2+]i response were 100 - 500 nmol/L, 50 - 100 pmol/L, and < 1 micromol/L respectively. CONCLUSION: Physiological concentrations of NE, VP, and ATP are 100 - 500 nmol/L, 50 - 100 pmol/L, and < 1 micromol/L respectively in the rat liver.     

细胞保护作用是抗抑郁剂作用的共同通路之一

目的：探讨抗抑郁剂可能的共同作用机制。方法：以MTT比色法检测细胞活性状态;以Fura 2-AM荧光标记法测定胞内Ca^2 浓度：以RT-PCR法检测神经生长因子(NGF)mRNA水平。结果：以高浓度皮质酮0．2mmol/L处理PC12细胞48h以模拟抑郁症脑神经细胞损伤状态,发现目前三类经典抗抑郁剂,包括三环抗抑郁剂地昔帕明(DIM)0．625—10μmol／L,5-HT重摄取抑制剂氟西丁(FLU)0．625—10μmol／L,单胺氧化酶A抑制剂马氯贝胺(MOC)2．5—40μmol／L对皮质酮损伤的PC12细胞具有显著的保护作用,而抗精神病药氯丙嗪和抗焦虑药地西泮无此作用、DIM1,5μmol/L或FLU1,5μmol/L几显著减弱皮质酮0．1mmol／L处理PC12细胞48h诱导的胞内Ca^2 超载,进一步研究发现,DIM或FLU 10μmol／L处理PC12细胞48h显著提高NGF mRNA的表达水平。结论：尽管各类抗抑郁剂结构迥异,但细胞保护作用可能是其共同作用通路,而减弱胞内Ca^2 超载和提高NGF等神经营养因子的表达是抗抑郁药的细胞保护作用机制之一。     

埃他卡林对大鼠尾动脉平滑肌细胞［Ca2+］i， PKA和PKC活性的影响埃他卡林对大鼠尾动脉平滑肌细胞［Ca2+］i， PKA和PKC活性的影响

细胞内钙参与了对几乎所有类型细胞的各种生理活动的调节[1],并通过影响PKA和PKC等大分子蛋白,进一步调控细胞的分裂和增殖。以ATP敏感型钾通道(KATP)为靶点的钾通道开放剂(KCO)是一类新型的抗高血压药物[2,3]。KCO激活血管平滑肌KATP,间接抑制钙通道的开放,从而使[Ca2 ]i降低,     

GDP对柴胡皂甙（I）促大鼠胰腺腺泡酶分泌和升高[Ca^2＋]i的影响

目的：研究鸟苷二磷酸（GDP）对柴胡皂甙（I）[SA(I)]刺激大鼠胰腺腺泡酶分泌和胞内钙离子升高的影响。方法：分离大鼠胰腺腺泡细胞,用链球菌溶血素－O（SLO）通透细胞膜,检测腺泡分泌蛋白量标志腺泡酶分泌功能。用钙离子荧光指示剂Fluo-3和荧光光谱测定胞内钙离子浓度。结果：GDP可凶制SA（I）促胰腺腺泡的酶分泌作用,抑制作用随剂量增加而加强;SA（I）10μmol/L以双峰值为特征使[Ca^2 ]i显著上升;GDP 5mmol/L,导致[Ca^2 ]i逐步升高且两个峰值消失。细胞通透以后,与正常细胞相比,SA（I）刺激的30min酶分泌的累积量下降了57％;GDP5mmol/L使SA（I）刺激的早期酶分泌速率进一步降低。结论：GDP通过抑制细胞[Ca^2 ]i的升高抑制了SA（I）刺激的胰腺腺泡酶分泌作用。     

Effect of tetramethylpyrazine on potassium channels to lower calcium concentration in cultured aortic smooth muscle cells

1. Tetramethylpyrazine (TMP) is one of the active principles contained in Ligusticum chuanxiong Hort. (Umbelliferae), a herb that has been used widely in China to treat vascular disorders. 2. In an attempt to elucidate the possible mechanisms of action of TMP, the effect of TMP on intracellular calcium concentrations ([Ca2+]i) was investigated in cultured vascular smooth muscle (A7r5) cells using the Ca(2+)-sensitive dye Fura-2 as an indicator. 3. The increase in [Ca2+]i in A7r5 cells produced by vasopressin (1 micromol/L) or phenylephrine (1 micromol/L) was attenuated by TMP in a concentration-dependent manner. Only inhibitors specific to ATP-sensitive potassium (KATP) channels or small conductance calcium-activated potassium (SKCa) channels attenuated the action of TMP (10 micromol/L) on [Ca2+]i. However, blockers of other K+ channels failed to modify the inhibitory action of TMP (10 micromol/L) on [Ca2+]i. 4. The action of TMP on membrane potential in A7r5 cells was monitored by the fluorescence of bisoxonol. Tetramethylpyrazine caused a concentration-dependent inhibition of changes in membrane potential elicited by KCl (20 mmol/L) or phenylephrine (1 micro mol/L), an effect that was totally reversed by glibenclamide (100 micromol/L) and apamin (100 nmol/L) in combination. 5. The results obtained indicate that the decrease in [Ca2+]i in A7r5 cells produced by TMP is mediated mainly by opening of KATP and/or SKCa channels.