钙离子在胃肠平滑肌收缩机制中的作用

钙离子（Ca^2 ）在胃肠平滑肌收缩机制中起重要作用。平滑肌细胞电－机械耦联主要涉及细胞膜电位改变，胞外Ca^2 内流，药物－机械耦联主要涉及胞内贮存Ca^2 的释放。Ca^2 可启动平滑肌细胞收缩蛋白之间的朴互作用，收缩张力的产生不仅与[Ca^2 ]i密切相关，而且与收缩蛋白对Ca^2 敏感性高低有关。     

胃肠平滑肌运动的细胞信号转导机制

胃肠道功能是消化系统最主要的生理功能之一,而平滑肌是维持胃肠运动的基础,近年认为胃肠道既是多脏器功能不全综合征(MODS)的动力部位,又是靶器官。所以,胃肠平滑肌运动的细胞信号转导机制的研究有一定的实际意义。本文从胃肠运动的电生理基础、钙离子和钙通道、平滑肌的收缩装置和途径、胞内信使和信息传递通路以及MODS状态下细胞因子对胃肠动力障碍的影响这五个方面对胃肠平滑肌运动的信号转导机制作一综述。     

胃肠平滑肌运动的细胞信号转导机制

胃肠道功能是消化系统最主要的生理功能之一，而平滑肌是维持胃肠运动的基础，近年认为胃肠道既是多脏器功能不全综合征(MODS)的动力部位，又是靶器官。所以，胃肠平滑肌运动的细胞信号转导机制的研究有一定的实际意义。本从胃肠运动的电生理基础、钙离子和钙通道、平滑肌的收缩装置和途径、胞内信使和信息传递通路以及MODS状态下细胞因子对胃肠动力障碍的影响这五个方面对胃肠平滑肌运动的信号转导机制作一综述。     

平滑肌细胞内钙水平对胃肠动力的调节

在胃肠平滑肌收缩与舒张的信号转导机制中，细胞内游离Ca^2 作为一种重要的第二信使广泛参与细胞的运动、分泌、代谢和分化等多种细胞功能活动的调节。高浓度Ca^2 引起平滑肌收缩，低浓度Ca^2 引起平滑肌舒张。有关胃肠动力调节机制的研究很多，并已从器官组织水平发展到细胞和分子水平，而钙水平调节是其中重要的调节机制之一。     

红霉素对兔胃肠平滑肌的收缩作用

以等长收缩的形式研究了红霉素对兔离体胃和十二指肠纵肌的收缩作用，红霉素为２Ｘ１０－１０～２ｘｌ０－７Ｍ，促使胃窦和十二指肠肌产生与浓度有关的收缩力增加，且这种作用不被阿托品，六烃季胺，心得安，酚妥拉明和纳洛酮阻断，但异搏定（１０－６Ｍ）可拮抗其作用。表明红霉素直接作用于胃肠平滑肌产生收缩效应，可作为促动力剂试用于临床治疗胃排空迟缓性疾病。     

平滑肌细胞内钙水平对胃肠动力的调节

在胃肠平滑肌收缩与舒张的信号转导机制中,细胞内游离Ca2+作为一种重要的第二信使广泛参与细胞的运动、分泌、代谢和分化等多种细胞功能活动的调节。高浓度Ca2+引起平滑肌收缩,低浓度Ca2+引起平滑肌舒张。有关胃肠动力调节机制的研究很多,并已从器官组织水平发展到细胞和分子水平,而钙水平调节是其中重要的调节机制之一。     

胆汁对兔胃肠平滑肌条运动的影响

目的:观察胆汁对兔离体小肠平滑肌的影响,并探讨其作用机制.方法:取兔十二指肠纵行肌条,安置在各恒温灌流肌槽中,并用BL-310生物技能实验系统记录十二指肠平滑肌条的收缩活动.结果:胆汁显著降低兔十二指肠肌条张力,减小其收缩波平均振幅及收缩频率,并有剂量依赖关系.结论:胆汁对十二指肠肌条收缩活动具有明显的抑制作用,这种抑制作用部分经由肾上腺素能a受体及前列腺索介导,并有壁内神经节的参与.     

钙离子在胃肠平滑肌收缩机制中的作用

钙离子(Ca~(2+))在胃肠平滑肌收缩机制中起重要作用。平滑肌细胞电-机械耦联主要涉及细胞膜电位改变,胞外Ca~(2+)内流,药物-机械耦联主要涉及胞内贮存Ca~(2+)的释放。Ca~(2+)可启动平滑肌细胞收缩蛋白之间的相互作用,收缩张力的产生不仅与[Ca~(2+)]i密切相关,而且与收缩蛋白对Ca~(2+)敏感性高低有关。     

四磨汤对大鼠胃窦平滑肌影响及其机制的研究

临床证实四磨汤可改善胃肠动力障碍疾病的症状。但机制不明。目的：研究四磨汤对大鼠离体胃窦平滑肌收缩活动的影响及其机制。方法：处死Sprague-Dawlev大鼠后收集胃窦纵行和环行平滑肌条,检测不同剂量四磨汤（1μl、5μl、25μl、50μl、100μl、150μl和200μl）对胃窦平滑肌收缩的影响,同时观察M受体阻断剂阿托品（100mol／L）、M受体激动剂乙酰胆碱（10-6mol／L）对四磨汤诱导的胃窦平滑肌收缩的影响。结果：低一中剂量（1～100μl）四磨汤剂量依赖性地诱导大鼠胃窦纵行肌和环行肌收缩增强,但两者之间的作用无明显差异。阿托品可完全阻断四磨汤对胃窦环行肌、纵行肌的促收缩作用,且对环行肌的阻断效应更明显。以乙酰胆碱预处理后,四磨汤对胃窦纵行肌和环行肌的促收缩作用进一步增强．且对环行肌的作用更明显。结论：四磨汤对大鼠胃窦纵行肌和环行肌具有明显的促收缩作用．该作用主要通过M受体介导。     

欧亚旋覆花总黄酮对血管平滑肌细胞增殖和迁移的影响

目的 探讨欧亚旋覆花总黄酮(TFIB)对培养血管平滑肌细胞(VSMC)增殖及迁移的影响.方法 采用大鼠胸腹主动脉的动脉中膜平滑肌细胞,用贴块法培养,实验用4～7代细胞,加入不同浓度的TFIB共同孵育24 h.采用噻唑蓝(MTT)法观察该药对细胞增殖的影响,倒置显微镜下观察该药对细胞迁移的影响.结果 与对照组相比,TFIB对VSMC增殖具有抑制作用,该作用呈剂量依赖性;随着TFIB浓度增加体外培养的VSMC迁移距离缩短.结论 适宜浓度的TFIB可明显抑制体外培养的大鼠VSMC的增殖、迁移.     

HEF-19-induced relaxation of colonic smooth muscles and the underlying mechanisms

AIM:To investigate the relaxant effect of chromane HEF-19 on colonic smooth muscles isolated from rabbits,and the underlying mechanisms.METHODS:The relaxant effect and action mechanisms of HEF-19 were investigated using descending colon smooth muscle of the rabbits.Preparations 1 cm long were mounted in 15-mL tissue baths containing Tyrode’s solution,maintained at 37±0.5℃and aerated with a mixture of 5%CO2in oxygen(Carbogen).The tension and amplitude of the smooth muscle strips were recorded after adding HEF-19(10-6,10-5and 10-4mol/L).After cumulative administration of four antispasmodic agents,including acetylcholine chloride(Ach)(10-4mol/L),histamine(10-4mol/L),high-K+(60 mmol/L)and BaCl2(8.2 mmol/L),HEF-19(3×10-7-3×10-4mol/L)was added to investigate the relaxant effect of HEF-19.CaCl2(10-4-2.5×10-3mol/L)was added cumulatively to the smooth muscle preparations pretreated with and without HEF-19(1×10-6or 3×10-6mol/L)and verapamil(1×10-7mol/L)to study the mechanisms involved.Finally,phasic contraction was induced with ACh(15×10-6mol/L),and CaCl2(4×10-3mol/L)was added to the smooth muscle preparations pretreated with and without HEF-19(3×10-6mol/L or 1×10-5mol/L)and verapamil(1×10-7mol/L)in calcium-free medium to further study the underlying mechanisms.RESULTS:HEF-19(1×10-6,1×10-5and 1×10-4mol/L)suppressed spontaneous contraction of rabbit colonic smooth muscles.HEF-19(3×10-7-3×10-4mol/L)relaxed in a concentration-dependent manner colonic smooth muscle preparations pre-contracted with BaCl2,high-K+solution,Ach or histamine with respective EC50values of 5.15±0.05,5.12±0.08,5.58±0.16and 5.25±0.24,thus showing a spasmolytic activity.HEF-19(1×10-6mol/L and 3×10-6mol/L)shifted the concentration-response curves of CaCl2to the right and depressed the maximum response to CaCl2.The two components contracted by Ach were attenuated with HEF-19(3×10-6mol/L or 10-5mol/L)in calcium-free medium.CONCLUSION:HEF-19 inhibited rabbit colonic smooth muscle contraction,probably through inhibiting opening of     

高浓度葡萄糖对CNP致大鼠胃窦环形肌舒张的影响

目的探讨高浓度葡萄糖（简称高糖）对C型钠尿肽（CNP）致胃窦环形肌舒张的影响及其可能机制。方法取大鼠40只制备胃窦环形肌条,肌条收缩活动稳定后,对照1、2组分别加入不同浓度CNP（1×10^-8、3×10^-8、1×10^-7mol/L）及硝普钠（SNP）（1×10^-7、3×10^-7、1×10^-6mol/L）,观察其效应,每次加药观察20 m in,冲洗3次;高糖1、2组预加葡萄糖使浴槽终浓度为30 mmol/L,其后操作同对照1、2组;甘露醇组预加甘露醇30mmol/L,其后操作同对照1组;均采用多道生理信号采集处理系统计算CNP（SNP）致平滑肌张力的抑制率。结果对照1、2组产生浓度依赖的胃窦环形肌平滑肌舒张效应,高糖1组可明显抑制CNP和硝普钠产生的平滑肌条舒张效应明显减弱;甘露醇（30 mmol/L）组CNP产生的平滑肌条舒张效应明显减弱。结论高糖抑制CNP引起的胃窦环形肌舒张效应;该效应可能与细胞内外渗透压改变有关。     

氢溴酸槟榔碱对豚鼠体外胃不同部位肌条作用及其机制

[目的]观察氢溴酸槟榔碱（Ah）对豚鼠体外胃不同部位平滑肌肌条收缩运动的影响，并初步探索其作用机制。[方法]用胃不同部位（6处）平滑肌条置于灌流浴槽，在37℃恒温、通氧和Krebs液灌注条件下，分别记录单独使用Ah和阻断剂孵育后Ah的收缩效应。[结果]①Ah可显著增高各部分体外胃平滑肌条的张力，增大收缩振幅和收缩波曲线下面积，2者均比基础值有显著增高（P〈0．05）。而且其效应强度不同部位有明显差异。纵肌效应：Ah对胃窦纵肌的作用振幅大于胃底、胃体（P〈0．01）；效应曲线下面积大于胃体（P〈0．01）。环肌效应：Ah对胃窦环肌作用振幅大于胃底（P〈0．05）；效应曲线下面积大于胃体和胃底（P〈0．05），对胃体环肌作用的曲线下面积亦大于胃底（P〈0．05）。②阿托品和维拉帕米均能部分阻断Ah的收缩作用，显著降低其振幅（P〈0．01）。[结论]Ah对豚鼠体外胃平滑肌条的收缩活动有明显兴奋作用，推测这种效应部分介导于M-胆碱能受体，L型电压依赖性Ca^2＋通道。     

黄芪总黄酮对柯萨奇B3病毒性心肌炎小鼠急性期心肌组织连接蛋白43表达的影响

目的探讨黄芪总黄酮（TFA）对柯萨奇B3病毒性心肌炎（VMC）小鼠急性期心肌组织连接蛋白43（Cx43）表达的影响。方法Balb／c小鼠腹腔注射柯萨奇B3病毒感染建立VMC小鼠模型,给予TFA40mg／L灌胃治疗,第14天无痛苦处死全部小鼠并留取心脏。免疫组织化学法检测Cx43蛋白水平表达,并进行定量分析。结果①VMC组小鼠心室肌组织炎症病灶中变性、坏死周围心肌细胞Cx43表达明显减弱,甚至阴性,分布不规则,Cx43蛋白表达明显低于对照组,差异有统计学意义（P〈0．01）。@TFA组Cx43蛋白表达明显高于模型组,差异有统计学意义（P〈0．01）。结论VMC心肌炎小鼠急性期心肌组织Cx43蛋白表达下降。TFA能明显提高CVB心肌炎小鼠急性期心肌组织Cx43蛋白表达。     

新型ATP敏感性钾通道开放剂Iptakalim对慢性缺氧大鼠肺内动脉平滑肌细胞钾电流的影响

目的探讨慢性缺氧对大鼠肺内动脉平滑肌细胞外向性钾电流的影响,及新型ATP敏感性钾(KATP)通道开放剂Iptakalim对此时钾电流的作用。方法SD雄性大鼠28只随机分成正常组、缺氧组[O2(10±0.5)%]、低剂量治疗组(每日缺氧前30min Iptakalim0.75mg·kg-1灌胃)、高剂量治疗组(每日缺氧前30min Iptakalim1.5mg·kg-1灌胃),将缺氧组和已灌胃的大鼠放入常压缺氧舱制作动物模型。4周后,急性分离大鼠动脉平滑肌细胞,用膜片钳全细胞记录技术记录细胞外向性钾电流;通过浴槽内给药,观察Iptakalim对钾电流的影响。结果Iptakalim0.1,1,10,100μmol/L呈浓度依赖性增加正常大鼠肺内动脉平滑肌外向钾电流,格列本脲30μmol/L可拮抗Iptakalim10μmol/L对钾电流的增强作用;与对照组大鼠相比,慢性缺氧大鼠肺内动脉平滑肌细胞钾电流下降,电流密度减小(690±450)pA/pFvs(420±250)pA/pF(P<0.01),膜电容增大到(4.29±1.78)pF(P<0.01),电流-电压(I-V)曲线下移;与缺血氧组相比,每日缺氧前口服Iptakalim,细胞膜电容减小为(3.09±1.71)(P<0.01),电流密度增大到(610±320)pA/pF(P<0.01)。结论慢性缺氧抑制大鼠肺内动脉平滑肌细胞钾通道,灌服Iptakalim可拮抗慢性缺氧对KATP通道的抑制作用。     

Ang-II-induced Ca influx is mediated by the 1/4/5 subgroup of the transient receptor potential proteins in cultured aortic smooth muscle cells from diabetic Goto-Kakizaki rats

Angiotensin-II (Ang-II) exerts many of its vascular effects, including the pathophysiological changes associated with type 2 diabetes, through changes in intracellular calcium concentration [Ca²⁺]_i. We sought to clarify the mechanism responsible for Ang-II-induced Ca²⁺ influx in cultured aortic VSMC using the Goto-Kakizaki (GK) rat model of type 2 diabetes. Ang-II-induced Ca²⁺ influx was blocked by neither VDCC nor c-src inhibition but was sensitive to inositol 1,4,5-trisphosphate receptor inhibition, lanthanide and the diacylglycerol analogue, oleoyl-2-acetyl-sn-glycerol. Since transient receptor potential canonical (TRPC)-3 gene expression was undetectable in both WKY and GK VSMCs and TRPC6 gene and protein expression were significantly down-regulated in GK, we believe the 1/4/5 subgroup of TRPC proteins plays a significant role. Furthermore, in GK VSMC the elevated calcium influx observed was not attributable to increased TRPC expression, but rather an alteration of TRPC activity.     

全反式维甲酸对人肺动脉平滑肌细胞表型和迁移的影响及可能机制

目的探讨全反式维甲酸(atRA)对培养的人肺动脉平滑肌细胞(PASMC)表型和迁移的影响及可能机制。方法培养的人PASMC株随机分成8组:对照组(A组)、溶媒组(B组)、10%胎牛血清干预组(C组)、atRA干预组分别加入浓度为0.001μmol/L(D组)、0.01μmol/L(E组)、0.1μmol/L(F组)、1μmol/L(G组)、10μmol/L(H)组的atRA,干预24 h后用逆转录-聚合酶链反应(RT-PCR)法检测各组细胞JWA基因mRNA表达,用改良Boyden小室法检测各组迁移细胞数,用RT-PCR法及免疫细胞化学法检测各组细胞内平滑肌细胞α肌动蛋白(SM-α-actin)mRNA及蛋白表达。结果人PASMC内JWA mRNA表达量A、B、C组分别为0.125±0.014、0.164±0.018、0.164±0.006,3组间比较差异无统计学意义(P均>0.05);而D组(0.326±0.018)、E组(0.440±0.033)、F组(0.460±0.040)、G组(0.589±0.024)、H组(0.821±0.050)分别与A、B、C组比较差异均有统计学意义(P均<0.01);迁移细胞数C组为(30.4±7.4)个/高倍视野(HP),与A组[(7.2±1.9)个/HP]、B组(6.8±2.3)个/HP]比较差异有统计学意义(P均<0.01);而D组[(21.8±2.9)个/HP]、E组[(17.2±2.3)个/HP]、F组[(14.4±3.5)个/HP]、G组[(12.6±3.4)个/HP]、H组[(8.8±2.4)个/HP]与C组比较差异有统计学意义(P均<0.01);但G、H组与A、B组比较差异无统计学意义(P均>0.05);细胞内SM-α-actin蛋白表达量C组为0.219±0.018,与A组(0.319±0.011)、B组(0.325±0.005)比较差异均有统计学意义(P均<0.01);E组(0.328±0.016)、F组(0.386±0.025)、G组(0.442±0.017)、H组(0.501±0.018)与C组比较差异均有统计学意义(P均<0.01);而F、G、H组与A、B组比较差异均有统计学意义(P均<0.01);细胞内SM--αactin mRNA表达量C组为0.144±0.009,与A组(0.299±0.023)、B组(0.296±0.041)比较差异有统计学意义(P均<0.01);而D组(0.487±0.014)、E组(0.501±0.020)、F组(0.611±0.018)、G组(0.774±0.013)、H组(0.851±0.026)与A、B、C组比较差异均有统计学意义(P均<0.01)。结论atRA能诱导人PASMCs内JWA基因表达增加,使细胞表现为收缩表型,细胞迁移受到抑制。     

Activation of natriuretic peptide receptor-C attenuates the enhanced oxidative stress in vascular smooth muscle cells from spontaneously hypertensive rats: implication of Gialpha protein

We have recently shown that vascular smooth muscle cells (VSMC) from spontaneously hypertensive rats (SHR) exhibit enhanced expression of Giα proteins, which was attributed to the enhanced oxidative stress. Since C-ANP_4-23 that specifically interacts with natriuretic peptide C (NPR-C) receptor has been shown to decrease the expression of Giα protein in VSMC, the present study was undertaken to examine if C-ANP_4-23 can also decrease the enhanced expression of Giα protein in VSMC from SHR and whether it is attributed to its ability to attenuate the enhanced oxidative stress. Aortic VSMC from 12-week-old SHR and their age-matched Wistar-Kyoto (WKY) rats were used for the present studies. VSMC from SHR exhibited enhanced expression of Giα-2 and Giα-3 proteins, different subunits of NADPH oxidase such as Nox⁴ and p^47phox proteins but not of p^22phox, enhanced production of superoxide anion as well as NADPH oxidase activity as compared to age-matched WKY rats. Treatment of VSMC from SHR with C-ANP_4-23 decreased towards control levels the enhanced expression of Giα proteins, enhanced superoxide anion production and enhanced NADPH oxidase activity as well as the enhanced expression of Nox⁴ and p^47phox. However, C-ANP_4-23-induced attenuation of the enhanced level of O₂⁻ and NADPH oxidase activity occurs at 4 h before the decrease in the enhanced expression of p^47phox that occurs at 16 h of C-ANP_4-23 treatment. The decreased expression of NADPH oxidase in SHR was also associated with further decrease in O₂⁻ and NADPH oxidase activity. Furthermore, treatment of VSMC from SHR with pertussis toxin (PT) decreased the enhanced levels of superoxide anion as well as NADPH oxidase activity; however, the enhanced levels of different subunits of NADPH oxidase were not attenuated by PT treatment. These results suggest that C-ANP_4-23 decreases the enhanced oxidative stress in SHR by attenuating the enhanced expression of Giα proteins and also the enhanced levels of NADPH oxidase.