滨蒿内酯对原代和传代培养豚鼠气道平滑肌细胞内钙的影响

目的探讨滨蒿内酯(scoparone,Scop)对原代及短期传代培养的豚鼠气道平滑肌细胞(airway smooth musclecells,ASMCs)内钙的影响,同时,比较原代与传代ASMCs在形态、生长曲线及内钙释放受Scop及caffeine影响的异同。方法细胞计数法绘制原代及传代培养ASMCs的生长曲线,应用Fluo-3/AM为细胞内Ca2+示踪剂,通过倒置荧光纤维镜观察和记录原代及短期传代培养的ASMCs的细胞形态及其细胞内钙离子浓度([Ca2+]i)的改变。结果原代和传代培养ASMCs的倍增时间分别为(31.89±1.24)h和(22.91±6.82)h,传代培养ASMCs的倍增时间明显缩短(P<0.05),传代培养的ASMCs相对原代培养ASMCs体积增大。在细胞外液无钙条件下,不同浓度的Scop(10-6、10-5、10-4mol.L-1)可降低静息状态下培养的ASMCs的[Ca2+]i,并与给药浓度有关,原代与传代培养的ASMCs比较,对不同浓度的Scop的降钙反应无明显异同(P>0.05);不同浓度咖啡因(caffeine,10-4、10-3、10-2mol.L-1)在10-4mol.L-1Scop存在下,可升高ASMCs的[Ca2+]i,传代培养的ASMCs[Ca2+]i较原代对caffeine的反应下降(P<0.01)。结论Scop可降低培养的ASMCs的[Ca2+]i,并且不受细胞传代影响。短期传代培养的ASMCs相对于原代细胞,形态及内钙释放通道特性发生了改变。     

T型钙通道在心肌肥厚大鼠心肌细胞钙内流中的作用

目的研究T型钙通道在心肌细胞钙离子内流中的作用及其对心脏兴奋收缩耦联的可能影响。方法测定选择性T型钙通道阻滞剂米贝拉地尔对培养的SD乳大鼠心室肌细胞和二肾一夹心肌肥厚大鼠心室肌细胞[Ca2+]i的影响。结果血管紧张素Ⅱ(AngⅡ)刺激使乳大鼠心室肌舒张期细胞[Ca2+]i增高,收缩期细胞[Ca2+]i降低,[Ca2+]i上升和下降的时间延长。米贝拉地尔1.25～5μmol·L-1浓度依赖性降低AngⅡ引起的细胞[Ca2+]i变化。在心肌肥厚模型大鼠,咖啡因刺激后,[Ca2+]i增幅和最高[Ca2+]i明显降低。而米贝拉地尔25mg·kg-1·d-1(灌胃给药7～9周)组加入咖啡因刺激后细胞内[Ca2+]i增幅和最高[Ca2+]i明显增高。结论T型钙通道异常开放可以引起心肌细胞内钙超载。阻断T型钙通道,可能通过改善肌浆网摄取及释放钙的功能而抑制心肌细胞钙超载。     

羊角拗苷对豚鼠心室肌细胞内游离钙离子浓度的影响

目的观察羊角拗苷(Div)对豚鼠心室肌细胞内游离钙离子([Ca2+]i)浓度的影响,以探讨Div正性肌力作用的机制。方法Fura-2/AM荧光探针标记豚鼠心室肌细胞,应用荧光离子成像系统观察Div800nmol.L-1对心室肌细胞[Ca2+]i的影响。结果在正常台氏液中,Div使心室肌细胞[Ca2+]i显著升高(243±36)%,在无钙液中对[Ca2+]i无明显影响。在无Na+、无K+台氏液中,Div使[Ca2+]i升高(96±20)%。给予L型钙通道阻滞剂CdCl2100μmol.L-1预处理后,Div仍使[Ca2+]i升高(63±10)%。给予T型钙通道阻滞剂NiCl240μmol.L-1预处理后,Div引起的[Ca2+]i升高基本被阻断。结论体外应用Div800nmol.L-1时使豚鼠心室肌细胞[Ca2+]i升高,该升高作用依赖于细胞外Ca2+的存在,可能主要由T型钙通道介导,L型钙通道和Na+-Ca2+交换蛋白亦参与其中。其正性肌力作用与心室肌细胞[Ca2+]i升高有关。     

Urocortin致心肌细胞肥大作用由细胞内游离钙离子升高诱导

目的探讨Urocortin(UCN)致心肌细胞肥大作用与细胞内游离钙离子([Ca2+]i)之间的关系。方法使用UCN0.1μmol.L-1诱导体外培养乳鼠心肌细胞肥大模型,通过计算机图像分析系统检测心肌细胞体积,荧光显微镜法测定细胞[Ca2+]i,Lowry法测定总蛋白水平,RT-PCR法测定ANP mRNA水平。结果与对照组相比UCN处理组细胞[Ca2+]i明显提高,细胞体积明显增大,所含总蛋白含量增加明显,ANP mRNA水平明显提高,且差异有统计学意义(P<0.05)。结论 UCN能引起心肌细胞肥大,其过程与其引起的[Ca2+]i提高有一定关系。     

异钩藤碱体外对家兔血小板聚集和胞浆游离钙离子浓度的影响

目的研究异钩藤碱对血小板内游离钙离子浓度([Ca2+]i)的影响,以探讨其抗血小板聚集作用的可能机制。方法比浊法测定家兔血小板聚集功能;双波长Fura-2荧光法测定血小板胞浆[Ca2+]i。结果异钩藤碱0.33~1.30mmol.L-1体外给药对ADP和凝血酶引起的血小板聚集有浓度依赖性的抑制作用。存在细胞外钙时,异钩藤碱对基础状态血小板的[Ca2+]i和ADP及凝血酶诱导的[Ca2+]i水平有浓度依赖性的降低作用,而无细胞外钙存在时,则均无明显影响,表明其可抑制血小板的外钙内流,对内钙释放无明显抑制作用。结论异钩藤碱可抑制血小板聚集,其作用机制可能与其抑制血小板胞浆[Ca2+]升高有关。     

尿皮质素诱导心肌细胞内钙离子升高与兰尼碱受体活化的关系研究

目的 探讨尿皮质素(urocortin)诱导乳大鼠心肌细胞内钙离子浓度[Ca2+]i升高与兰尼碱受体(RyR)之间的关系.方法 采用体外培养的乳大鼠心肌细胞进行指标测定.采用Till阳离子测定系统,以Fura-2/AM为荧光探针,观察心肌细胞[Ca2+]i瞬间变化.结果 urocortin使心肌细胞内钙离子浓度升高;兰尼碱受体抑制剂Ryanodine和IP3受体抑制剂Xestospongin C能够部分抑制urocortin诱导的心肌细胞内钙离子浓度升高,差别有统计学意义(P<0.01).结论 urocortin能够诱导心肌细胞内钙离子浓度[Ca2+]i升高,其作用可能与活化RyR和IP3受体使心肌细胞肌质网内钙离子释放有关.     

丹酚酸B镁抑制ATP和KCl诱导大鼠主动脉平滑肌细胞内钙的升高

目的研究丹酚酸B镁(M agnesium lithosperm ate B,MLB)对去内皮离体血管舒缩反应以及对血管平滑肌细胞内游离钙浓度[Ca2+]i的影响。方法去内皮大鼠胸主动脉血管环等张收缩实验和采用钙离子荧光指示剂F luo-3,运用F-4500阳离子测定系统动态检测胸主动脉平滑肌细胞[Ca2+]i。结果血管舒缩实验显示,无钙或常钙条件下MLB对血管基础张力均无作用。MLB 50~200μmol.L-1预给药组抑制无钙条件下苯肾上腺素(PE)1μmol.L-1诱导的血管收缩以及常钙条件下KC l 60 mmol.L-1诱导的血管收缩,并呈浓度相关性。而钙离子通道阻滞剂维拉帕米(Ver)10μmol.L-1则完全阻断KC l诱导的血管收缩。在复钙实验中观察到,MLB 50~200μmol.L-1不仅抑制PE 1μmol.L-1诱导的内钙依赖性血管收缩,而且对复钙后外钙依赖性的血管收缩也有抑制作用。细胞内钙测定实验表明,MLB预孵育的AVSMCs静息态[Ca2+]i没有变化。无钙条件下,MLB 50、100和200μmol.L-1抑制ATP20μmol.L-1诱导内钙释放引起的[Ca2+]i升高,抑制率分别为17.4%、32.4%和61.1%,显示较好的浓度相关性。AVSMCs于常钙条件下用Thapsigargin耗竭钙库后,KCl 60 mmol.L-1诱发外钙内流,引起[Ca2+]i升高,10μmol.L-1的Ver则能完全阻断这种外钙内流。在MLB预给药组,KCl诱导的[Ca2+]i升高降低,抑制率分别为20.0%、32.8%和52.6%。结论MLB能够抑制PE、高K+和复Ca2+诱导的血管收缩,并能抑制ATP和KCl诱导的血管平滑肌细胞内钙的升高,提示MLB对血管平滑肌细胞内钙的影响可能与抑制细胞内钙释放和电压依赖性钙通道有关。     

遗传性癫痫大鼠海马组织Ca~(2+)/Ca_V1.2/CaM/CaMKⅡ信号通路的异常变化

目的研究遗传性癫痫大鼠(tremor,TRM)海马组织电压门控性L型钙离子通道α1C亚单位(CaV1.2)、钙调蛋白(CaM)、钙调蛋白依赖性蛋白激酶Ⅱ(CaMKⅡ)和细胞内钙离子浓度([Ca2+]i)的变化情况。方法应用West-ern blot法与免疫荧光双标法检测TRM海马CA1、CA3和DG区CaV1.2、CaM和磷酸化CaMKⅡ(p-CaMKⅡ)的蛋白表达及分布;激光共聚焦显微镜检测TRM海马组织中[Ca2+]i。结果与正常Wistar大鼠相比,TRM海马组织中CaV1.2和CaM的蛋白表达明显升高(P<0.01),而p-CaMKⅡ的蛋白表达明显下降(P<0.01);免疫荧光双标法结果显示:CaV1.2、CaM、p-CaMKⅡ在CA1、CA3区的锥体细胞和DG区的颗粒细胞群表达丰富,同时CaV1.2与CaM、p-CaMKⅡ与CaM在海马各区域均存在共定位;激光共聚焦显微镜检测TRM海马细胞[Ca2+]i明显增强(P<0.01)。结论Ca2+/CaV1.2/CaM/CaMKⅡ通路的异常变化可能参与遗传性癫痫大鼠的癫痫发生与发展。     

哮喘豚鼠气道平滑肌细胞内钙释放通道的变化

目的检测哮喘豚鼠气道平滑肌细胞(ASMCs)内钙释放通道功能的改变,探讨与支气管哮喘的关系,同时,寻找传代培养ASMCs的方法。方法以Flou-3/AM为细胞内钙离子示踪剂,观察ASMCs在工具药作用下细胞内钙离子浓度([Ca2+]i)的改变。结果①在ASMCs外无钙情况下,不同浓度ryanodine(5×10-5,10-4,2×10-4mol·L-1)作用于原代培养正常与哮喘ASMCs,[Ca2+]i迅速升高,哮喘组明显高于正常组(P<0·01)。10-4mol·L-1的组织胺(hista-mine)作用于原代培养的正常组与哮喘组ASMCs,[Ca2+]i升高无差异(P>0·05)。②传代培养哮喘ASMCs在10-4、2×10-4mol·L-1ryanodine作用下,[Ca2+]i迅速升高,与原代细胞比较无差异(P>0·05)。在浓度为5×10-5mol·L-1时,原代明显高于传代(P<0.01)。哮喘组传代ASMCs对10-4mol·L-1的histamine反应不明显。结论哮喘豚鼠ASMCs内钙释放通道(RyRs)功能升高,特定条件下,哮喘传代细胞仍然保持原代细胞内钙释放通道的特性。     

环核苷酸调节血管平滑肌舒张的研究进展

血管张力的调控是通过调节血管收缩与舒张之间的平衡实现的,在高血压、血管痉挛等血管类疾病的病理生理过程中具有重要作用。了解血管张力调控的分子机制,是建立预防和治疗血管疾病新途径的基础[1,2]。调节血管平滑肌(VSM)细胞张力的主要因素是细胞内钙离子浓度([Ca2+]i C)的改变。[Ca2+]i C升高,VSM收缩;反之则舒张。血管收缩剂之所以能够升高[Ca2+]i C,主要有两种途径:(1)细胞外的钙离子     

Mechanism of action of volatile anesthetics: involvement of intracellular calcium signaling

There have been extensive efforts to characterize the mechanism of action of volatile anesthetics, but their molecular and cellular actions are still a matter of debate. Volatile anesthetics act primarily on synaptic transmission in the central nervous system but proof of this as the predominant mechanism of action remains elusive. Changes in neurotransmitter release may relate to direct interaction of the anesthetic molecule with an ion channel protein or synaptic protein, but can also be a consequence of alterations in intracellular signaling. Calcium is one of the most important messengers in cells and its intracellular concentration may be modified by several agents including volatile anesthetics. Neuronal excitability is in part determined by calcium availability that is controlled by several mechanisms. Because voltage-gated calcium channels (VGCC) play a key role in controlling Ca2+ entry and in initiating cellular responses to stimulation through an elevation of intracellular calcium concentration ([Ca2+](i)), they are thought to be one of the targets for volatile anesthetics. However, [Ca2+](i) can also be altered without the participation of VGCC through receptor-mediated pathways. Indeed, calcium homeostasis is also controlled by plasma membrane Ca2+ -adenosine triphosphatase, sarcoplasmic-endoplasmic reticular Ca2+ -ATPase, the Na+ -Ca2+ exchanger, and mitochondrial Ca2+ sequestration. Alteration of any of those mechanisms that control [Ca2+](i) may lead to a change in presynaptic transmission or postsynaptic excitability. Here we will review some of the recent progress in identifying putative actions of volatile anesthetics, specifically the effect on intracellular calcium homeostasis in neurons.     

Effect of anesthetics on calcium stores and membrane order of brain microsomes

The effects of anesthetic agents from different chemical classes and a nonanesthetic membrane-disordering agent, 2-[2-methoxyethoxy]ethyl-8-[cis-2-n-octylcyclopropyl]octanoate (A2C), on calcium stores of whole brain microsomes and on order of microsomal membranes were compared. Calcium release was determined by measurement of the extramicrosomal calcium concentration and membrane order by the fluorescence polarization of diphenylhexatriene (membrane core) and trimethylammonium-diphenylhexatriene (membrane "surface"). n-Alkanols (methanol, ethanol, propanol, butanol, pentanol, and hexanol), benzyl alcohol (10-100 mM), and diethyl ether (30-300 mM) released calcium from brain microsomes and decreased the surface and interior membrane order of microsomal membranes. Pentobarbital (0.05-1 mM) did not release calcium from microsomes and did not alter the order of brain microsomal membranes. Halogenated anesthetics (halothane, methoxyflurane, and enflurane), 4-phenyl-1-butanol, and A2C decreased membrane order but failed to release calcium from brain microsomes. Comparison of the effects of these agents on microsomal calcium release and order of microsomal membranes revealed that decreases in membrane order are unrelated to the calcium-mobilizing actions of anesthetic compounds. In addition, molecular size appeared to limit ability of anesthetic compounds to release calcium from microsomes. For n-alkanols, benzyl alcohol, and diethyl ether, the ability to release microsomal calcium was correlated with anesthetic potency. Our results demonstrate, for the first time, direct effects of anesthetic agents on intracellular calcium stores of brain tissue and indicate that these stores may be target sites for anesthetics.     

Effects of neurotoxicants on synaptic transmission: lessons learned from electrophysiological studies

A number of environmentally-important neurotoxicants affect chemical synaptic transmission in the peripheral and central nervous system. These include heavy metals such as lead, mercury, cadmium and tin; organophosphates; pyrethroid insecticides, and 2,5-hexanedione. Electrophysiological techniques including intracellular microelectrode recording of nerve-evoked and spontaneously occurring synaptic potentials, iontophoresis of neurotransmitter, and voltage clamp of presynaptic and postsynaptic membrane ionic current have proven to be especially useful in analyzing the cellular mechanisms by which these toxicants affect neurotransmission. The process of synaptic transmission can be broadly subdivided into those processes associated with transmitter synthesis, storage and release and sometimes termination of transmitter action (presynaptic processes), and those processes associated with binding of transmitter to its receptors on the receiving cell, activation of the receptor-associated ionic channel and degradation of chemical transmitter (postsynaptic processes). The processes associated with release of neurotransmitter are the target of a number of naturally-occurring toxins and environmentally important toxicants. General mechanisms by which these agents disrupt presynaptic processes associated with transmission include: prevention or disruption of axonal excitability (pyrethroid insecticides); disruption of calcium-dependent neurotransmitter release (heavy metals, antibiotics, certain snake and spider venom toxins, botulinum toxin); and disruption of intracellular buffering of calcium (heavy metals), Mechanisms by which these agents may disrupt postsynaptic processes include effects on transmitter degradation (organophosphates) or effects on the postsynaptic membrane receptors or associated ionic channels (organophosphates, antibiotics, and perhaps pyrethroids). Microelectrode studies have shown that cadmium, lead and mercury (organic and inorganic forms) suppress release of neurotransmitter by presynaptic mechanisms and increase spontaneous discharge of transmitter quanta from the presynaptic nerve terminal. This has led to the suggestion that a component of synaptic toxicity of these agents entails block of Ca entry into and buffering by the presynaptic nerve terminals. Conventional and patch voltage clamp studies have been used to measure effects of neurotoxicants on ionic currents carried through voltage-sensitive and receptor-operated ionic channels.(ABSTRACT TRUNCATED AT 400 WORDS)     

钙贮库调控的钙通道的药理与分子生物学特征

钙贮库调控的钙通道 (store operatedcalciumchannel,SOCC)是指位于细胞膜上的钙离子内流通道 ,当细胞内钙贮库排钙后 ,SOCC被激活开放。目前 ,虽然对SOCC机制以及分子生物学特点等的认识还非常初浅 ,但是 ,由于SOCC广泛地分布于兴奋性和非兴奋性细胞中 ,并且直接参与钙信息传递、基因表达和细胞功能调节等重要过程 ,它的生理和病理意义不容忽视。开发和研制具有高度选择性的SOCC调节药物 ,不仅可以促进实验研究的深入 ,而且可能成为新型的临床治疗药物     

Isoflurane and propofol inhibit voltage-gated sodium channels in isolated rat neurohypophysial nerve terminals

Mounting electrophysiological evidence indicates that certain general anesthetics, volatile anesthetics in particular, depress excitatory synaptic transmission by presynaptic mechanisms. We studied the effects of representative general anesthetics on voltage-gated Na+ currents (INa) in nerve terminals isolated from rat neurohypophysis using patch-clamp electrophysiological analysis. Both isoflurane and propofol inhibited INa in a dose-dependent and reversible manner. At holding potentials of -70 or -90 mV, isoflurane inhibited peak INa with IC50 values of 0.45 and 0.56 mM, and propofol inhibited peak INa with IC50 values of 4.1 and 6.0 microM, respectively. Isoflurane (0.8 mM) did not significantly alter the V1/2 of activation; propofol caused a small positive shift. Isoflurane (0.8 mM) or propofol (5 microM) produced a negative shift in the voltage dependence of inactivation. Recovery of INa from inactivation was slower from a holding potential of -70 mV than from -90 mV; isoflurane and propofol further delayed recovery from inactivation. In conclusion, the volatile anesthetic isoflurane and the intravenous anesthetic propofol inhibit voltage-gated Na+ currents in isolated neurohypophysial nerve terminals in a concentration- and voltage-dependent manner. Marked effects on the voltage dependence and kinetics of inactivation and minimal effects on activation support preferential anesthetic interactions with the fast inactivated state of the Na+ channel. These results are consistent with direct inhibition of oxytocin and vasopressin release from the neurohypophysis by isoflurane and propofol. Inhibition of voltage-gated Na+ channels may contribute to the presynaptic effects of general anesthetics on nerve terminal excitability and neurotransmitter release.     

General anesthetics selectively modulate glutamatergic and dopaminergic signaling via site-specific phosphorylation in vivo

Isoflurane, propofol and ketamine are representative general anesthetics with distinct molecular mechanisms of action that have neuroprotective properties in models of excitotoxic ischemic damage. We characterized the effects of these agents on neuronal glutamate and dopamine signaling by profiling drug-induced changes in brain intracellular protein phosphorylation in vivo to test the hypothesis that they affect common downstream effectors. Anesthetic-treated and control mice were killed instantly by focused microwave irradiation, frontal cortex and striatum were removed, and the phosphorylation profile of specific neuronal signaling proteins was analyzed by immunoblotting with a panel of phospho-specific antibodies. At anesthetic doses that produced loss of righting reflex, isoflurane, propofol, and ketamine all reduced phosphorylation of the activating residue T183 of ERK2 (but not of ERK1); S897 of the NR1 NMDA receptor subunit; and S831 (but not S845) of the GluR1 AMPA receptor subunit in cerebral cortex. At sub-anesthetic doses, these drugs only reduced phosphorylation of ERK2. Isoflurane and ketamine also reduced phosphorylation of spinophilin at S94, but oppositely regulated phosphorylation of presynaptic (tyrosine hydroxylase) and postsynaptic (DARPP-32) markers of dopaminergic neurotransmission in striatum. These data reveal both shared and agent-specific actions of CNS depressant drugs on critical intracellular protein phosphorylation signaling pathways that integrate multiple second messenger systems. Reduced phosphorylation of ionotropic glutamate receptors by all three anesthetics indicates depression of normal glutamatergic synaptic transmission and reduced potential excitotoxicity. This novel approach indicates a role for phosphorylation-mediated down-regulation of glutamatergic synaptic transmission by general anesthetics and identifies specific in vivo targets for focused evaluation of anesthetic mechanisms.     

Emerging molecular mechanisms of general anesthetic action

General anesthetics are essential to modern medicine, and yet a detailed understanding of their mechanisms of action is lacking. General anesthetics were once believed to be "drugs without receptors" but this view has been largely abandoned. During the past decade significant progress in our understanding of the mechanisms of general anesthetic action at the molecular, cellular and neural systems levels has been made. Different molecular targets in various regions of the nervous system are involved in the multiple components of anesthetic action, and these targets can vary between specific anesthetics. Neurotransmitter-gated ion channels, particularly receptors for GABA and glutamate, are modulated by most anesthetics, at both synaptic and extrasynaptic sites, and additional ion channels and receptors are also being recognized as important targets for general anesthetics. In this article, these developments, which have important implications for the development of more-selective anesthetics, are reviewed in the context of recent advances in ion channel structure and function.     

Modulators of intracellular calcium

The importance of calcium in excitation-contraction coupling in both cardiac and vascular smooth muscle has resulted in an intense research interest into the intracellular regulation of this ion. Selective foci for the modulation of intracellular calcium include the interaction of calcium with the contractile protein apparatus, sites of calcium release and sequestration, and pathways for the extrusion of calcium into the extracellular space. Research efforts directed towards elucidating these phenomena have met with varied degrees of success. The presence of different calcium regulatory systems for contractile protein function, i.e., troponin in cardiac and calmodulin-myosin light chain kinase in vascular, provides an attractive rationale for the design of selective compounds. The inherent difficulty in studying intracellular release and sequestration presently presently precludes examining the physiological implications of specific inhibition of these phenomena. However, the apparent absence of a sodium-dependent calcium extrusion pathway in vascular tissue may lead to the design of novel cardiotonics. It is anticipated that further clarification of the similarities and differences in the calcium cycle between these tissues will result in the development of tissue-selective therapeutic agents.     

Effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine by their transporters heterologously expressed in COS cells and in rat brain synaptosomes

Although the neurotransmitter uptake system is considered a possible target for the presynaptic action of anesthetic agents, observations are inconsistent concerning effects on the transporter and their clinical relevance. The present study examined the effects of volatile and intravenous anesthetics on the uptake of GABA, glutamate and dopamine in COS cells heterologously expressing the transporters for these neurotransmitters and in the rat brain synaptosomes. Halothane and isoflurane, but not thiamylal or thiopental, significantly inhibited uptake by COS cell systems of GABA, dopamine and glutamic acid in a concentration-dependent manner within clinically relevant ranges for anesthesia induced by these agents. Similarly, in synaptosomes halothane and isoflurane but not thiopental significantly suppressed the uptake of GABA and glutamic acid, respectively. These results do not support the hypothesis that volatile and intravenous anesthetics exert their action via specific inhibition of GABA uptake to enhance inhibitory GABAergic neuronal activity. Rather, they suggest that presynaptic uptake systems for various neurotransmitters including GABA may be the molecular targets for volatile anesthetic agents.