钙稳态失衡在致结肠平滑肌收缩性改变中的作用

目的:应激可影响胃肠运动,是肠易激综合征(IBS)的重要发病因素之一。钙离子(Ca2+)在平滑肌收缩运动中起重要作用,肌细胞收缩时,胞浆内游离Ca2+浓度([Ca2+]i)增加来源于细胞外Ca2+内流或肌浆网贮存钙释放;Ca2+可通过肌浆网再摄取或通过细胞膜排出胞外,导致[Ca2+]i降低,平滑肌舒     

慢性低氧后钙转运的变化(英文)

目的 :本文研究大鼠慢性低氧后心肌钙转运的变化。方法 :将大鼠放置于 10 %氧环境下 4周 ,分离正常及慢性缺氧大鼠的右心室肌细胞 ,用光谱荧光法测定电刺激和咖啡因引起的细胞内 [Ca2 + ]i瞬变 ,并测定肌浆网膜上的Ca2 + ATP酶 （SERCA）和ryanodine受体 （RyR）蛋白的水平。结果 :低氧后电刺激和咖啡因引起的细胞内 [Ca2 + ]i瞬变的幅度降低且时程延长 ,RyR水平无明显改变但SERCA已显著减少。结论 :Ca2 + ATP酶活性和蛋白水平的降低是低氧钙转运异常的主要原因。     

枳实含药血清对大鼠胃窦平滑肌细胞收缩效应及细胞内钙离子浓度、钙调蛋白表达的影响

目的:观察单味中药枳实含药血清对大鼠胃窦平滑肌细胞收缩效应及细胞内Ca2+、钙调蛋白表达的影响.方法:按照血清药理学通法制备大鼠枳实含药血清,将血清分为枳实组(10%、20%、50%枳实含药血清)、空白血清对照组,酶解法提取胃窦平滑肌细胞并进行培养,倒置显微镜下观察各组对胃窦平滑肌细胞收缩效应,激光共聚焦显微镜技术检测各组加药前后胃窦平滑肌细胞内Ca2+浓度变化,免疫组织化学方法观察各组对胃窦平滑肌细胞内钙调蛋白的表达.结果:10%、20%、50%枳实含药血清对胃窦平滑肌细胞收缩及细胞内Ca2+荧光强度的影响呈药物剂量依赖关系,细胞收缩、细胞内Ca2+荧光强度随药物浓度的增高而增强(P<0.05),20%、50%枳实含药血清与空白血清对照组对胃窦平滑肌细胞收缩、细胞内Ca2+荧光强度差异有统计学意义(P<0.05),50%枳实组与空白血清对照组对胃窦平滑肌细胞内钙调蛋白表达差异有统计学意义(P<0.05).结论:枳实含药血清可以促进胃窦平滑肌细胞收缩,其机制可能与增加细胞内Ca2+浓度、调节钙调蛋白的表达有关.     

钙调神经磷酸酶对钙化细胞Ⅰ型三磷酸肌醇受体表达的影响

目的探讨大鼠血管平滑肌细胞钙化过程中钙调神经磷酸酶对Ⅰ型三磷酸肌醇受体蛋白和mRNA表达的影响。方法大鼠胸主动脉血管平滑肌细胞经传代培养后随机分为对照组、钙化组和环孢素A组,采用磷酸二氢钠诱导大鼠动脉血管平滑肌细胞钙化。应用免疫印迹法及实时荧光定量RT-PCR法测定钙调神经磷酸酶B亚基、Ⅰ型三磷酸肌醇受体的表达变化,同时测定Ca2+浓度及碱性磷酸酶、钙调神经磷酸酶活性。结果与对照组比较,钙化组钙调神经磷酸酶B亚基、Ⅰ型三磷酸肌醇受体蛋白和mRNA表达显著增加(P<0.01);与钙化组比较,环孢素A组钙调神经磷酸酶B亚基、Ⅰ型三磷酸肌醇受体蛋白和mRNA表达显著降低(P<0.01)。钙化组Ca2+浓度、钙调神经磷酸酶活性、碱性磷酸酶活性较对照组显著增高(P<0.01);环孢素A组碱性磷酸酶活性、Ca2+浓度较钙化组显著增加(P<0.05或P<0.01),钙调神经磷酸酶活性较钙化组显著降低(P<0.01)。结论钙调神经磷酸酶能够增强钙化细胞中Ⅰ型三磷酸肌醇受体mRNA和蛋白的表达。     

敦煌石室大宝胶囊对衰老大鼠脑组织钙稳态的影响

目的 探讨敦煌石室大宝胶囊对衰老模型大鼠脑组织钙稳态的影响.方法 采用D-半乳糖建立大鼠衰老模型,测定大脑组织内Na+-K+-ATPase、Ca2+-ATPase、Ca2+-Mg2+-ATPase活性和Ca2+含量.结果 模型组大鼠脑组织内Na+-K+-ATPase、Ca2+-ATPase、Ca2+-Mg2+-ATPase活性显著降低,Ca2+含量显著升高(P<0.01,P<0.05);应用敦煌石室大宝胶囊治疗后,治疗组大鼠脑组织内Na+-K+-ATPase、Ca2+-ATPase、Ca2+-Mg2+-ATPase活性增高,Ca2+含量显著降低(P<0.01,P<0.05).结论 敦煌石室大宝胶囊具有调节衰老大鼠脑组织钙稳态的作用.     

血管钙化对血管组织内皮素表达的影响

通过观察血管钙化大鼠血管组织和钙化血管平滑肌细胞内皮素含量的变化 ,探讨血管钙化对血管组织内皮素表达的影响。用维生素D3加尼古丁诱导大鼠血管钙化模型 ,β 磷酸甘油制备钙化血管平滑肌细胞 ,采用VonKossa染色、钙含量测定、4 5Ca聚集及碱性磷酸酶活性测定判断钙化程度 ,放射免疫分析法测定血浆、血管和血管平滑肌细胞培养基中内皮素含量 ,用竞争性定量逆转录聚合酶链反应方法测定血管和血管平滑肌细胞中内皮素mRNA水平。结果发现 :钙化血管平滑肌细胞VonKossa染色见有大量黑色颗粒沉积 ,钙化细胞的钙含量、4 5Ca2 + 摄入及碱性磷酸酶活性分别较正常平滑肌细胞增加 1 1 8%、1 74 %和 7倍 (P均 <0 .0 1 ) ;钙化细胞培养基中内皮素含量较对照组增加 35 % (P <0 .0 5 ) ,内皮素mRNA水平较对照组高 1 2 0 % (P <0 .0 5 ) ;钙化组大鼠血管组织VonKossa染色见血管中层有大量黑色颗粒沉积 ,主动脉钙含量、4 5Ca2 + 沉积及碱性磷酸酶活性分别较对照组高 5 .0倍、1 .4倍和1 .4倍 (P均 <0 .0 1 ) ;钙化大鼠血浆和血管内皮素含量分别较对照组增加 1 0 2 %和 1 0 3% (P均 <0 .0 1 ) ;钙化血管内皮素mRNA水平较正常对照组高 2 2 % (P <0 .0 1 ) ;波生坦处理的大鼠血管钙含量、4 5Ca2 + 聚集及碱性磷酸酶活性较单     

阿托伐他汀对高血压大鼠动脉血压和血管平滑肌细胞离子泵活性的影响

目的探讨阿托伐他汀对自发性高血压大鼠的动脉血压及血管平滑肌细胞离子泵活性的影响。方法选用12周龄自发性高血压大鼠12只,随机分为阿托伐他汀治疗组(简称阿托伐他汀组,n=6)和蒸馏水组(n=6),并以正常血压大鼠作为对照组。阿托伐他汀组大鼠给以阿托伐他汀[50mg(kg·d)]加适量蒸馏水灌胃12周。观察给药前后大鼠尾动脉血压的变化,测定大鼠血清总胆固醇、甘油三酯和低密度脂蛋白胆固醇浓度,以及胸主动脉平滑肌细胞Na K ATP酶和Ca2 Mg2 ATP酶活性。结果阿托伐他汀组动脉血压显著低于蒸馏水组(161.8±9.9比192.9±10.4,P<0.05);阿托伐他汀组大鼠胸主动脉平滑肌细胞Na K ATP酶和Ca2 Mg2 ATP酶活性明显高于蒸馏水组(5.20±0.54比3.06±0.42,P<0.01;4.62±0.35比2.98±0.17,P<0.05),略低于对照组,而蒸馏水组则显著低于对照组(3.06±0.42比5.92±0.31,P<0.01;2.98±0.17比4.86±0.26,P<0.01)。Na K ATP酶活性、Ca2 Mg2 ATP酶活性与血压呈显著负相关(r=-0.426、r=-0.359,P<0.01)。结论长期应用阿托伐他汀可以显著降低自发性高血压大鼠血压。阿托伐他汀可能通过增高血管平滑肌细胞离子泵活性而影响血压形成的过程。     

钠钙交换体在支气管哮喘发病中的作用

支气管哮喘(简称哮喘)是一种常见的慢性呼吸系统疾病,特征性表现为气道高反应性和气道重塑,其中气道平滑肌细胞作为主要的效应细胞,发挥了非常重要的作用.尽管相关调控机制尚不清楚,但大量研究表明平滑肌细胞胞浆钙稳态失衡能够导致细胞收缩及舒张功能紊乱,与哮喘发病关系密切.钠钙交换体是一种存在于细胞膜上的Na+-Ca2+转运蛋白,通过调控细胞内钙离子浓度对维持平滑肌细胞钙稳态以及细胞结构与功能具有重要作用.本文就钠钙交换体的结构、功能及其在哮喘发病中的病理生理学意义作一综述.     

内脏脂肪素在大鼠结肠平滑肌收缩障碍中的作用及其机制研究

背景:肥胖与多种功能性胃肠病相关,肥胖者常存在胃肠动力障碍,且血清脂肪细胞因子内脏脂肪素(VF)水平明显升高。既往研究显示VF可抑制子宫、血管平滑肌收缩。目的:探讨VF对大鼠结肠平滑肌收缩的影响及其可能机制。方法:取正常Sprague-Dawley(SD)大鼠远端结肠制备成0. 3 cm×0. 8 cm的肌条,使用生物信号分析系统记录VF对肌条收缩活动的影响。体外培养SD乳大鼠结肠平滑肌细胞,予VF干预,以蛋白质印迹法检测肌球蛋白轻链(MLC)磷酸化水平和钙通道Cav1. 2(α1亚基)表达;以激光共聚焦显微镜观察细胞外有或无Ca~(2+)的情况下乙酰胆碱刺激引起的细胞内Ca~(2+)浓度变化。结果:在肌条收缩实验中,VF(200 ng/mL)可显著减弱正常大鼠结肠平滑肌肌条的收缩张力(P 0. 05)。在结肠平滑肌细胞实验中,VF(200 ng/mL)可下调Cav1. 2通道表达,降低细胞内Ca~(2+)浓度和MLC磷酸化水平(P 0. 05)。结论:VF可能通过下调结肠平滑肌细胞膜Cav1. 2通道表达降低细胞内Ca~(2+)浓度,引起结肠平滑肌收缩障碍,从而参与结肠动力障碍的发生。     

钙网蛋白介导缺氧预处理对心脏保护机制的研究

目的探讨缺氧预处理(HPC)对于心肌钙网蛋白表达与肌浆网钙稳态的影响及其信号转导机制。方法选择SD大鼠22只,随机分为假手术组6只,模型组8只,HPC组8只。复制SD大鼠HPC和心肌梗死模型,检测左心室压力最大上升速率和最大下降速率(±dp/dtmax)、TTC法测定心肌梗死面积,差速离心法制备心肌肌浆网并鉴定其纯度,以Millipore滤过法测定肌浆网Ca2+摄取活性和肌浆网Ca2+释放速率,Western blot检测钙网蛋白、p38丝裂原活化蛋白激酶和磷酸化p38丝裂原活化蛋白激酶水平。结果与假手术组比较,模型组+dp/dtmax和-dp/dtmax分别下降39%和46%(P<0.05);与模型组比较,HPC组分别升高43%和59%(P<0.05),肌浆网Ca2+摄取升高[(60.38±5.76)nmol Ca2+/(mg·min)vs(31.10±3.13)nmol Ca2+/(mg·min)],肌浆网Ca2+释放降低[(32.12±1.18)nmol Ca2+/(mg·15s)vs(39.61±1.16)nmol Ca2+/(mg·15s),P<0.05],钙网蛋白表达和p38丝裂原活化蛋白激酶水平明显升高(P<0.05)。结论 HPC通过p38丝裂原活化蛋白激酶途径上调钙网蛋白表达,改善心肌肌浆网Ca2+摄取和肌浆网Ca2+释放功能、减轻细胞内钙超载而保护缺血心肌。     

Effect of pinaverium bromide on stress-induced colonic smooth muscle contractility disorder in rats

AIM: To investigate the effect of pinaverium bromide, a L-type calcium channel blocker with selectivity for the gastrointestinal tract on contractile activity of colonic circular smooth muscle in normal or cold-restraint stressed rats and its possible mechanism. METHODS: Cold-restraint stress was conducted on rats to increase fecal pellets output. Each isolated colonic circular muscle strip was suspended in a tissue chamber containing warm oxygenated Tyrode-Ringer solution. The contractile response to ACh or KCl was measured isometrically on ink-writing recorder. Incubated muscle in different concentrations of pinaverium and the effects of pinaverium were investigated on ACh or KCl-induced contraction. Colon smooth muscle cells were cultured from rats and (Ca(2+))(i) was measured in cell suspension using the Ca(2+) fluorescent dye fura-2/AM. RESULTS: During stress, rats fecal pellet output increased 61 % (P<0.01). Stimulated with ACh or KCl, the muscle contractility was higher in stress than that in control. Pinaverium inhibited the increment of (Ca(2+))(i) and the muscle contraction in response to ACh or KCl in a dose dependent manner. A significant inhibition of pinaverium to ACh or KCl induced (Ca(2+))(i) increment was observed at 10(-6) mol/L. The IC(50) values for inhibition of ACh induced contraction for the stress and control group were 1.66X10(-6) mol/L and 0.91X10(-6) mol/L, respectively. The IC(50) values for inhibition of KCl induced contraction for the stress and control group were 8.13X10(-7) mol/L and 3.80X10(-7) mol/L, respectively. CONCLUSION: Increase in (Ca(2+))(i) of smooth muscle cells is directly related to the generation of contraction force in colon. L-type Ca(2+) channels represent the main route of Ca(2+) entry. Pinaverium inhibits the calcium influx through L-type channels; decreases the contractile response to many kinds of agonists and regulates the stress-induced colon hypermotility.     

钙离子在大鼠结肠平滑肌运动中作用机制的研究

目的 应用束缚应激大鼠实验模型,研究离体结肠平滑肌的收缩运动及其影响因素,探讨鸟苷素在结肠运动中的作用。方法 建立束缚应激大鼠动物模型,制备离体结肠平滑肌环行肌及纵行肌肌条,应用张力换能器,测定其肌张力。应用放射配基法测定结肠组织及血浆中鸟苷素含量。结果 束缚应激刺激可诱发大鼠排便增加,该动物模型是较好的模拟人ＩＢＳ的实验动物模型。束缚应激大鼠离体结肠平滑肌的张力升高,对Ｋ＾＋、Ｃａ＾２＋、乙酰胆     

Role of Ca2+, membrane excitability, and Ca2+ stores in failing muscle contraction with aging

Excitation-contraction (EC) coupling in a population of skeletal muscle fibers of aged mice becomes dependent on the presence of external Ca(2+) ions (Payne, A.M., Zheng, Z., Gonzalez, E., Wang, Z.M., Messi, M.L., Delbono, O., 2004b. External Ca(2+)-dependent excitation - contraction coupling in a population of aging mouse skeletal muscle fibers. J. Physiol. 560, 137-155.). However, the mechanism(s) underlying this process remain unknown. In this work, we examined the role of (1) extracellular Ca(2+); (2) voltage-induced influx of external Ca(2+) ions; (3) sarcoplasmic reticulum (SR) Ca(2+) depletion during repeated contractions; (4) store-operated Ca(2+) entry (SOCE); (5) SR ultrastructure; (6) SR subdomain localization of the ryanodine receptor; and (7) sarcolemmal excitability in muscle force decline with aging. These experiments show that external Ca(2+), but not Ca(2+) influx, is needed to maintain force upon repetitive fiber electrical stimulation. Decline in fiber force is associated with depressed SR Ca(2+) release. SR Ca(2+) depletion, SOCE, and the putative segregated Ca(2+) release store do not play a significant role in external Ca(2+)-dependent contraction. More importantly, a significant number of action potentials fail in senescent mouse muscle fibers subjected to a stimulation frequency. These results indicate that failure to generate action potentials accounts for decreased intracellular Ca(2+) mobilization and tetanic force in aging muscle exposed to a Ca(2+)-free medium.     

Morphological and functional characterization of vascular muscle cells enzymatically dispersed from dog mesenteric arteries.

The objective of this study was to compare the properties of single smooth muscle cells enzymatically dispersed from the dog mesenteric arteries to the properties of similar cells functioning in tissue strips. The isolated cells remained relaxed in nominally Ca(2+)-free medium for about 1-2 h after exposure to 1 mM Ca2+ and like intact mesenteric artery rings did not contract spontaneously. Enzymatically dispersed cells maintained all the characteristic morphological features observed in strips of muscle prior to isolation except that the amorphous materials covering the smooth muscle cell surfaces (basal lamina) were absent after enzymatic dispersion. Addition of 100 mM KCl to these vascular muscle cells elicited maximal shortening in the presence but not in the absence of extracellular Ca2+ and KCl-induced cell shortening was prevented by 10(-7) M nifedipine indicating the presence of functional voltage-operated Ca2+ channels. However, in contrast to the vascular muscle strips, in which graded contractile responses were observed with increasing KCl concentrations, isolated vascular muscle cells underwent nearly maximal contraction at concentrations as low as 15 mM KCl. Both intact tissue and isolated cell preparations responded similarly to phenylephrine in a concentration-dependent manner and the responses were blocked by prazosin. In contrast to muscle strips, the isolated cells did not shorten in response to phenylephrine in Ca(2+)-free medium. Isolated muscle shortened in the presence of sarcoplasmic reticulum selective Ca2+ transport ATPase inhibitors, cyclopiazonic acid or thapsigargin. Ryanodine also caused contraction. We conclude that enzymatically dispersed smooth muscle cells from dog mesenteric arteries are potentially useful for studies of the regulation of smooth muscle contractility, but have significantly increased sensitivity to external K+, implying an altered membrane potential or voltage dependence of ion channels. Their impaired ability to contract to phenylephrine in Ca(2+)-free medium implies some alteration in intracellular Ca2+ stores of their coupling to cellular activation. These differences will affect how the data obtained from freshly isolated enzymatically dispersed vascular muscle cells may be extrapolated to cell studies in intact tissues.     

Ca2+-recruitment in tachykinin-induced contractions of gut smooth muscle from African clawed frog,Xenopus laevis and rainbow trout,Oncorhynchus mykiss

Changes in intracellular Ca(2+) concentration control many essential cellular functions like the contraction of smooth muscle cells. The aim of this study was to investigate if the tachykinin substance P (SP) engages external Ca(2+)-sources, internal Ca(2+)-sources, or both in the contraction of the gastrointestinal smooth muscle of rainbow trout (Oncorhynchus mykiss) and the African clawed frog (Xenopus laevis). Strip preparations made of either longitudinal smooth muscle of proximal intestine or circular smooth muscle of cardiac stomach were mounted in organ baths and the tension was recorded via force transducers. Ca(2+)-free Ringer's solution containing the Ca(2+) chelating agent EGTA (2mM) abolished all spontaneous contractions. Exposure to SP in Ca(2+)-free solution decreased the response. Preparations were also treated with the Ca(2+)-ATPase inhibitor thapsigargin (10 microM) during 30 min. Thapsigargin reduced the effect of SP on intestinal longitudinal smooth muscle in rainbow trout and on stomach circular smooth muscle in the African clawed frog and to a less extent in the intestinal longitudinal smooth muscle. The results show that external Ca(2+) is of great importance, but is not the only source of Ca(2+) recruitment in SP-activation of gastrointestinal smooth muscle in rainbow trout and the African clawed frog.     

Effects of magnolol and honokiol derived from traditional Chinese herbal remedies on gastrointestinal movement

AIM: To study the effects of magnolol and honokiol on isolated smooth muscle of gastrointestinal tract and their relationship with Ca2+, and on the gastric emptying and the intestinal propulsive activity in mice. METHODS: Routine experimental methods using isolated gastric fundus strips of rats and isolated ileum segments of guinea pigs were adopted to measure the smooth muscle tension. The effects of magnolol 10-3,10-4,10-5 mol/L, and honokiol 10-4, 10-5,10-6 mol/L on the contractility of gastric fundus strips of rats and ileum of guinea pigs induced by acetylcholine (Ach) and 5-hydroxvtryptamine (5-HT) was assessed respectively. The method using nuclein and pigment methylene blue was adopted to measure the gastric retention rate of nuclein and the intestinal propulsive ratio of a nutritional semi-solid meal for assessing the effect of magnolol and honokiol (0.5, 2, 20 mg/kg) on gastric emptying and intestinal propulsion. RESULTS: Magnolol and honokiol significantly inhibited the contractility of isolated gastric fundus strips of rats treated with Ach or 5-HT and isolated ileum guinea pigs treated with Ach or CaCI2, and both of them behaved as non-competitive muscarinic antagonists. Magnolol and honokiol inhibited the contraction induced by Ach in Ca2+-free medium and extracellular Ca2+-dependent contraction induced by Ach. Each group of magnolol and honokiol experiments significantly decreased the residual rate of nuclein in the stomach and increased the intestinal propulsive ratio in mice. CONCLUSION: The inhibitory effect of magnolol and honokiol on contractility of the smooth muscles of isolated gastric fundus strips of rats and isolated ileum of guinea pigs is associated with a calcium-antagonistic effect. Magnolol and honokiol can improve the gastric emptying of a semi-solid meal and intestinal propulsive activity in mice.     

Thyroid hormone regulates Ca(2+)-ATPase mRNA levels of sarcoplasmic reticulum during neonatal development of fast skeletal muscle.

In gastrocnemius muscle from newborn rats the mRNA for the fast sarcoplasmic reticulum (SR) Ca(2+)-ATPase isoform (SERCA1) comprised over 90% of total SR Ca(2+)-ATPase mRNA content and increased 5-fold between day 5 and 20 after birth, whereas in hypothyroid muscle the SERCA1 message level remained constant. Triiodothyronine (T3) treatment of 2-day-old euthyroid rats induced a precocious stimulation of SERCA1 mRNA levels, indicating that T3 is the determining factor in the stimulation of SERCA1 message levels and that this stimulation underlies the previously reported effect of the thyroid status on the neonatal development of SR Ca(2+)-ATPase activity. The low mRNA level for the slow SR Ca(2+)-ATPase isoform (SERCA2) was constant in both euthyroid and hypothyroid muscle development. Nevertheless, T3 treatment of hypothyroid neonates induced a transient stimulation of SERCA2 message levels, indicating that SERCA2 is responsive to higher levels of T3.     

Sources of calcium in neurokinin A–induced contractions of human colonic smooth muscle in vitro

OBJECTIVES: Tachykinins have been implicated in the pathogenesis of colonic dysmotility. The sources of activator calcium for neurokinin A (NKA)-induced contraction of human colonic smooth muscle have not been assessed. We evaluated the contribution of extracellular and intracellular Ca2+ to NKA-induced contractions. METHODS: Circular smooth muscle strips of human colon were suspended under 1 g of tension in organ baths containing Krebs solution at 37 degrees C gased with 95% O2/5% CO2. Contractile activity was recorded isometrically. RESULTS: Cumulatively applied NKA (0.1 nmol/L-0.3 micromol/L), produced concentration-dependent contractions of human colonic smooth muscle strips that were not affected by tetrodotoxin (1 micromol/L). The contractile response to NKA was abolished in a Ca2+-free medium containing ethylenediaminetetraacetate (EDTA) (1 mmol/L). Pretreatment of muscle strips with nifedipine (1 micromol/L), an L-type voltage-operated Ca2+ channel antagonist, abolished the contractile responses to NKA. Pretreatment with SK&F 96365 (10 micromol/L and 30 micromol/L), a putative receptor-activated and voltage-operated Ca2+ channel antagonist, attenuated the contractile responses. Depletion of intracellular Ca2+ stores with thapsigargin (1 micromol/L), an inhibitor of the sarcoplasmic reticulum Ca2+ ATP-ase, had no effect on NKA-induced contractions. CONCLUSIONS: NKA-mediated contraction of human colonic smooth muscle is dependent on an influx of extracellular Ca2+ through L-type voltage-operated Ca2+ channels. Intracellular Ca2+ release seems to have little role to play in NKA-mediated contractions.     

Down-regulation of L-type calcium channels in inflamed circular smooth muscle cells of the canine colon

BACKGROUND & AIMS: Circular smooth muscle phasic contractions and tone are suppressed during colonic inflammation, but the contributing factors are poorly understood. This study investigated if the expression level of voltage-gated long-lasting (L-type) Ca(2+) channel protein and functional Ca(2+) channel current are down-regulated in the circular muscle cells of the inflamed canine colon. METHODS: L-type Ca(2+) channel expression was compared between normal and inflamed smooth muscle cells by Western immunoblots using an antibody directed against the pore-forming alpha 1C-subunit, and patch-clamp methods were used to evaluate Ca(2+) channel current density. RESULTS: The expression of the L-type Ca(2+) channel protein was significantly reduced in inflamed compared with normal circular smooth muscle cell membranes, and this finding was associated with suppressed levels of Ca(2+) channel current in patch-clamped cells. The L-type Ca(2+) channel current in normal and inflamed cells increased proportionately in response to Bay K 8644, but the maximal current density was still lower in the inflamed cells. Acetylcholine increased the L-type Ca(2+) channel current in normal but not in inflamed cells. CONCLUSIONS: The expression level of L-type Ca(2+) channels is down-regulated in the circular smooth muscle cell membranes of the inflamed colon, which may result in reduced Ca(2+) influx. The functional and pharmacologic properties of the channels seem normal. Although some Ca(2+) channels are still present in the inflamed cells, acetylcholine does not activate these channels, which may be caused by additional upstream defects in the receptor signaling cascade. The down-regulation of L-type Ca(2+) channel expression may suppress circular smooth muscle contractions in the inflamed colon and contribute to the abnormalities in motility and digestion observed during inflammatory disorders.     

Increased norepinephrine sensitive intracellular Ca2+ pool in the caudal artery of spontaneously hypertensive rats

The contractions evoked by norepinephrine (NE) and caffeine in Ca2+-free solution were determined using denervated caudal artery rings from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR). The magnitude of contractions produced by different concentrations of NE was significantly greater (P less than 0.05) in SHR caudal artery rings compared to WKY. The contractions evoked by NE in Ca2+-free solution were mediated primarily through the activation of postsynaptic alpha 1-adrenoceptors. In addition to alpha 1-adrenoceptor stimulation, caffeine also evoked significantly greater (P less than 0.05) contractions in Ca2+-free solution in SHR caudal arteries compared to WKY. From these observations it is concluded that intracellular Ca2+ pool (presumably sarcoplasmic reticulum, SR) is increased in SHR caudal arteries which, at least in part, may account for the increased contraction observed in response to NE and caffeine stimulation in the absence of extracellular Ca2+.