枸杞糖肽对缺氧及KCl诱导的心肌细胞钙超载的影响

目的:研究枸杞糖肽(LbGp)对低氧心肌细胞内钙浓度([Ca²⁺]_i)的影响,以及对KCl诱导的心肌细胞钙超载的影响。方法:采用SD大鼠乳鼠进行心肌细胞培养,建立心肌缺氧模型,实验分3组:正常对照组;缺氧模型组:细胞缺氧6h;枸杞糖肽预处理组:加入枸杞糖肽,再行缺氧6h。MTT法检测细胞活力。以Fluo/AM荧光指示剂负载,通过激光扫描共聚焦显微系统和Flou3/AM荧光指示剂标记技术,观察枸杞糖肽对缺氧心肌细胞游离钙含量的影响。加入终浓度60mmol·L^-1KCl溶液,动态观察KCl刺激后心肌细胞[Ca²⁺]_i的动态变化及LbGp预处理后对KCl诱导的钙超载的影响。结果:心肌细胞缺氧时间延长,损伤随之加剧,缺氧枸杞糖肽组心肌细胞荧光密度均较模型组显著降低(P<0.01),50μg·mL^-1LbGp最为明显,[Ca²⁺]_i明显减少。枸杞糖肽组加入KCl溶液后[Ca²⁺]_i荧光强度曲线升高,但与模型组比较,幅度明显减小,25,50,100μg·mL^-1LbGp且呈现量效关系。结论:低氧导致心肌细胞钙超载,而枸杞糖肽能减轻钙超载。亦能对抗KCl诱导的心肌细胞钙超载。机制之一是枸杞糖肽作用于L型钙通道。     

环维黄杨星D对心肌细胞缺氧/复氧损伤的保护作用和对心肌细胞内游离钙浓度的影响

目的:研究环维黄杨星D(CVB-D)对培养乳鼠心肌细胞缺氧/复氧损伤的保护作用和对急性分离大鼠心肌细胞内游离Ca²⁺浓度的影响。方法:采用培养的乳鼠心肌细胞建立缺氧/复氧损伤模型,测定心肌细胞搏动频率、细胞存活率、肌酸激酶(CK)的含量;应用特异性荧光指示剂Fluo-3/AM负载急性分离的大鼠心肌细胞,用激光共聚焦显微镜检测胞内游离钙的变化。结果:缺氧/复氧损伤+环维黄杨星D组(H/R+CVB-D)乳鼠心肌细胞搏动频率、细胞存活率与缺氧/复氧损伤组比较明显升高,CK含量与缺氧/复氧损伤组比较明显下降。对急性分离大鼠心肌细胞内[Ca²⁺]i逐步升高,并呈剂量依赖性;在有外钙和无外钙时,CVB-D对胞内钙的升高有显著差异(P<0.05);在无外钙并加入内罗啶孵育后,CVB-D引起的胞内[Ca²⁺]i轻度升高,但与无钙组相比无显著性差异(P>0.05)。结论:环维黄杨星D对培养乳鼠心肌细胞缺氧/复氧损伤有保护作用,对急性分离大鼠有升高心肌细胞内游离钙离子浓度的作用,[Ca²⁺]的升高既源于内钙释放又源于外钙内流。     

双参通冠方药物血清抗缺氧复氧损伤心肌细胞Ca2+超载的机制研究

目的:探讨双参通冠方药物血清对培养心肌细胞缺氧复氧损伤Ca²⁺超载的影响及其机制。方法:培养心肌细胞,建立缺氧复氧损伤模型。运用血清药理学方法研究双参通冠方药物血清对缺氧复氧损伤心肌Ca²⁺超载的影响。荧光分光光度法测定心肌细胞胞浆[Ca²⁺]i,激光扫描共聚焦显微法观察高K+及Thapsigargin诱导的细胞内Ca²⁺变化。结果:正常心肌细胞[Ca²⁺]i值较低,缺氧复氧后显著增高,高K⁺及Thapsigargin可诱导细胞内Ca²⁺的快速增多,双参通冠方药物血清能降低缺氧复氧心肌细胞Ca²⁺升高,并能抑制高K⁺及Thapsigargin所致的细胞内Ca²⁺荧光升高。结论:缺氧复氧损伤、高K⁺及Thapsigargin均可导致心肌细胞Ca²⁺增高,双参通冠方药物血清可抗心肌细胞Ca²⁺超载,其机制可能与其抑制细胞外Ca²⁺内流和促进内Ca²⁺吸收有关。     

JAK,PTPs抑制剂钙拮抗剂对As2O3引起的[Ca2+]i变化的影响

 目的　研究蛋白酪氨酸激酶 (JAK)、蛋白酪氨酸磷酸酶 (PTPs)抑制剂和Ca²⁺通道阻滞剂对As₂O₃致人脑皮层神经元和白血病细胞的胞浆 [Ca²⁺]_i变化的影响。方法　Fluo-3/AM荧光探针标记胞浆游离Ca²⁺,激光共聚焦显微镜实时测定不同浓度As₂O₃干预后胞浆[Ca²⁺]_i 的变化及JAK PTPs抑制剂和Ca²⁺通道阻滞剂对As₂O₃引起的胞浆[Ca²⁺]_i 变化的影响。结果　As₂O₃升高胞浆[Ca²⁺]_i,并被Ca²⁺通道阻滞剂不完全抑制。1μmol·L^-1的As₂O₃使NB4胞浆[Ca²⁺]_i明显增高,而对神经元胞浆[Ca²⁺]_i 影响不明显。JAK抑制剂genistein能浓度依赖性抑制As₂O₃触发的[Ca²⁺]_i 升高。给药后 280s的总抑制率均值分别为NB4:(6.7± 2.9)%,(25.6±2.5) %和(52.2±3.5)%;皮层神经元:(7.8±3.1)%,(18.1± 2.8) %和(51.3±3.3)%。结论　As₂O₃对不同细胞的胞浆[Ca²⁺]_i 升高程度不同。JAK,PTPs参与As₂O₃触发的钙池操纵性Ca²⁺内流。Ca²⁺通道阻滞剂参与了As₂O₃触发的电压门控性Ca²⁺内流。     

双苯氟嗪对大鼠脑缺血再灌注损伤后胞浆[Ca2+]i的影响

 目的研究双苯氟嗪(Dip)对大鼠局灶性脑缺血再灌注损伤后脑神经细胞胞浆Ca²⁺浓度([Ca²⁺]_i)变化的影响。方法将400pmol的内皮素-1(ET-1)灌注到大鼠大脑中动脉附近制备大鼠局灶性脑缺血再灌注模型,以Fura-2/AM作为钙荧光指示剂,双波长荧光分光光度法检测灌注ET-1后不同时间大鼠大脑皮层和纹状体神经细胞胞浆[Ca²⁺]_i的变化及Dip对灌注ET-1后4h胞浆[Ca²⁺]_i变化的影响,并采用TYC染色法观察了Dip对灌注ET-1后24h脑梗死范围的影响。结果灌注400pmolET-1诱发大鼠局灶性脑缺血再灌注损伤后,大鼠大脑皮层和纹状体神经细胞胞浆[Ca²⁺]_i明显升高,并于灌注EF-1后4h达峰值,随着再灌注时间的延长,胞浆[Ca²⁺]_i逐渐降低;Dip20,40mg·kg^-1可以明显降低灌注ET-1后4h大脑皮层和纹状体神经细胞胞浆[Ca²⁺]_i的升高(P<0.01),Dip10mg·kg^-1组虽表现出一定的降低胞浆[Ca²⁺]_i的作用,但与溶剂组比较,差异无显著性(P>0.05);对脑梗死范围的测定结果显示,Dip可以缩小脑梗死范围,其作用呈现明显的剂量依赖关系(r=0.9797,P<0.01)。结论Dip对抗脑缺血再灌注损伤后胞浆[Ca²⁺]_i升高可能是其产生神经保护作用的重要机制。     

海嘧啶体内外抗肿瘤作用研究

 目的研究海嘧啶抗胃癌作用及作用机制。方法采用MTT实验和集落形成实验观察海嘧啶的体外抗肿瘤作用;通过 海嘧啶对Fc小鼠和S₁₈₀,H₂₂荷瘤小鼠瘤重和生存时间的研究,观察海嘧啶的体内抗肿瘤作用。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[Ca²⁺]_i的影响及[Ca²⁺]_i变化时Ca²⁺的来源。结果 海嘧啶对8种人癌细胞具有一定的杀伤作用,其中以对BGC-823,Eca-109,HCT-8细胞的抑制作用最强;对 BGC-823,Eca-109,HCT-8细胞的集落形成有明显的抑制作用,并以对Eca-109细胞集落形成抑制作用最强;可明显抑制FC小鼠 和S₁₈₀小鼠瘤体的生长,明显延长H₂₂荷瘤小鼠的生存时间。海嘧啶可诱导肿瘤细胞凋亡,升高肿瘤细胞内[Ca²⁺]_i的浓度, [Ca²⁺]_i升高时Ca²⁺来源于细胞外钙内流和细胞内钙释放。结论海嘧啶有明显的抗肿瘤作用,其抗肿瘤机制为诱导肿瘤细 胞凋亡。海嘧啶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[Ca²⁺]_i,启动细胞凋亡机制,从而诱导 肿瘤细胞凋亡。     

氧化苦参碱对豚鼠单个心室肌细胞胞浆[Ca2+]i的影响

 目的 观察氧化苦参碱对急性分离的豚鼠单个心室肌细胞内游离钙离子浓度([Ca²⁺]_i)的影响。方法 采用酶解法分离豚鼠单个心肌细胞,用钙敏感的荧光指示剂Fluo-3/AM染色,以荧光强度(FI)来代表[Ca²⁺]_i,应用激光扫描共聚焦显微技术动态监测FI的变化。结果 在静息状态下,10μmol·L^-1氧化苦参碱对[Ca²⁺]_i无明显影响;但10μmol·L^-1氧化苦参碱对60mmol·L^-1KCl介导的外钙内流却有明显抑制作用(P<0.05)。结论 氧化苦参碱对电压依赖性钙通道(VDC)具有明显抑制作用,这可能是其抗心律失常作用机制之一。     

龙葵碱诱导HepG2细胞凋亡的线粒体通路研究

 目的观察龙葵碱诱导HepG₂细胞凋亡与线粒体通路的关系。方法MTT法测定龙葵碱对HepG₂细胞的细胞毒作用;AO/EB双染,激光共聚焦扫描显微镜观察龙葵碱对HepG₂细胞形态学的影响;TMRE和Fluo-3/AM双染,激光共聚焦扫描显微镜同时观察细胞线粒体膜电位和细胞内[Ca²⁺]_i的变化。结果龙葵碱对HepG₂细胞有细胞毒作用;龙葵碱诱导HepG₂细胞形态出现凋亡形态时TMRE和Fluo-3/AM双染观察表明,龙葵碱在降低线粒体膜电位的同时能够升高细胞内[Ca²⁺]_i浓度。结论龙葵碱降低膜电位,开放细胞膜PT通道,使细胞内Ca²⁺顺浓度梯度转运,从而升高细胞内Ca²⁺浓度启动细胞凋亡机制。     

小檗碱对DHF大鼠血流动力学和心肌细胞内钙离子浓度的影响

目的:观察小檗碱(Ber)对舒张性心力衰竭(diastole heart failure,DHF)大鼠血流动力学和心肌细胞内钙离子浓度[Ca²⁺]_i的影响。方法:Wistar大鼠腹主动脉缩窄法建立DHF模型;术后4周,模型大鼠随机分为DHF模型组,Ber高、中、低剂量组(63,42,21mg·kg^-1.d^-1)4组(n=10),另有假手术组10只。连续给药4周后,应用十六导生理记录仪测定血流动力学指标;用激光扫描共聚焦显微镜(LSCM)扫描用Fluo-3AM负载好的心肌细胞内的荧光强度(FI)来表示[Ca²⁺]_i。结果:模型组与假手术组比,左心室收缩压(LVSP)、左室内压最大上升速率(+dp/dt_max)无显著变化,左心室舒张末期内压(LVEDP)显著升高(P<0.01),左室内压最大下降速率(-dp/dt_max)显著降低(P<0.01),左室松弛时间常数(T)数值显著延长(P<0.01);心肌细胞内[Ca²⁺]_i明显增高(P<0.05)。与模型组比较,Ber高剂量组比中剂量组低剂量组更显著降低LVEDP,显著升高-dp/dt_max(P<0.01),显著缩短T(P<0.01),显著降低心肌细胞内[Ca²⁺]_i(P<0.01)。结论:Ber高剂量组可以明显改善DHF大鼠血流动力学和降低心肌细胞内[Ca²⁺]_i。     

蚓激酶对活化血小板[Ca2+]i、JNK1和P-选择素表达的影响

 目的 研究蚓激酶(lumbrokinase, LK对大鼠血小板内钙离子浓度（intracellular calcium concentration, [Ca²⁺]_i、c-Jun氨基末端激酶-1 (c-Jun N-terminal kinase-1, JNK1以及人血小板P-选择素(P-selection, Ps表达水平的影响,阐明LK抗血小板活化的部分机制。方法 用荧光分光光度计测定LK对大鼠血小板活化过程中胞浆[Ca²⁺]_i的影响;免疫蛋白印记方法检测LK对大鼠血小板JNK1磷酸化水平的影响;流式细胞仪测定LK对人血小板活化过程中Ps表达水平的影响。结果 LK高剂量组（100 mg·L^-1和中剂量组（50 mg·L^-1大鼠血小板[Ca²⁺]_i分别为（425.49±37.4 nmol·L^-1和（509.65±35.67 nmol·L^-1,与诱导组血小板[Ca²⁺]_i （555.59±39.71 nmol·L^-1相比显著降低（P<0.01,P<0.05;LK高剂量组（100 mg·L^-1和中剂量组（50 mg·L^-1大鼠血小板JNK1磷酸化水平分别为（0.60±0.069和（0.79±0.048,与诱导组血小板JNK1磷酸化水平（0.87±0.037相比显著降低（P<0.01,P<0.05;LK高剂量组（100 mg·L^-1和中剂量组（50 mg·L^-1人血小板Ps水平为（42.99±2.69和（44.72±2.09,与诱导组（49.99±3.81相比显著降低（P<0.01,P<0.05。结论 体外实验表明LK能够抑制大鼠血小板胞浆[Ca²⁺]_i升高和JNK1的磷酸化,同时也能抑制人血小板Ps的表达水平的升高,从而起到抗血小板活化作用。     

冬虫夏草对豚鼠心室肌细胞胞浆钙离子浓度及L-型钙电流的影响

目的　研究冬虫夏草 (Codycepssinensis,CS)水提液对豚鼠单个心室肌细胞胞浆内钙离子浓度 ([Ca2 ]i)及L 型钙电流 (ICa L)的影响。方法　酶解法分离豚鼠单个心室肌细胞 ,应用激光扫描共聚焦显微镜联合全细胞膜片钳技术测定豚鼠心室肌细胞 [Ca2 ]i以及ICa L的变化。结果　应用 0 1mg/mL (生药浓度 )冬虫夏草水提液 ,在静息状态下对 [Ca2 ]i 无影响 ;对 6 0mmol/LKCl诱导的胞浆 [Ca2 ]i升高有促进作用 ,峰值荧光强度在 12 0s时由12 0 4 3± 2 38 4增加至 185 5 2± 32 1 0 (n =6 ,P <0 0 5 )。膜片钳研究结果表明 ,冬虫夏草水提液可明显促进ICa L,使ICa L从 (- 15 1± 2 3)pA/ pF增加到 (- 19 7± 3 2 ) pA/pF (刺激电压为 10mV ,n =8,P <0 0 1)。 结论　冬虫夏草水提液促进心肌细胞钙内流 ,是该药治疗缓慢型心律失常的机制之一。     

Antiarrhythmic effects of dehydroevodiamine in isolated human myocardium and cardiomyocytes

Ethnopharmacological relevance

Dehydroevodiamine alkaloid (DeHE), a bioactive component of the Chinese herbal medicine Wu-Chu-Yu (Evodiae frutus), exerted antiarrhythmic effect in guinea-pig ventricular myocytes. We further characterize the electromechanical effects of DeHE in the human atrial and ventricular tissues obtained from hearts of patients undergoing corrective cardiac surgery or heart transplantation.

Materials and methods

The transmembrane potentials of human myocardia were recorded with a traditional microelectrode technique while sarcolemmal Na⁺ and Ca²⁺ currents in single human cardiomyocytes were measured by a whole-cell patch-clamp technique. The intracellular pH (pH_i) and Na⁺–H⁺ exchanger (NHE) activity were determined using BCECF-fluorescence in human atria.

Results

In human atria, DeHE (0.1–0.3 μM) depressed upstroke velocity, amplitude of action potential, and contractile force, both in slow and fast response action potential. Moreover, the similar depressant effects of DeHE were found in human ventricular myocardium. Both in isolated human atrial and ventricular myocytes, DeHE (0.1–1 μM) reversibly, concentration-dependently decreased the Na⁺ and Ca²⁺currents. Moreover, DeHE (0.1 and 0.3 μM) suppressed delayed afterdepolarizations and aftercontractions, induced by epinephrine and high [Ca²⁺]_o in atria. In human ventricular myocardium, the strophanthidin-induced triggered activities were attenuated by pretreating DeHE (0.3 μM). The resting pH_i and NHE activity were also significantly increased by DeHE (0.1–0.3 μM).

Conclusions

We concluded for the first time that, in the human hearts, DeHE could antagonize triggered arrhythmias induced by cardiotonic agents through a general reduction of the Na⁺ and Ca²⁺ inward currents, while increase of resting pH_i and NHE activity.     

Dual effects of lipophilic extract of Salvia miltiorrhiza (Danshen) on catecholamine secretion in cultured bovine adrenal medullary cells

Ethnopharmacological relevance

Salvia miltiorrhiza (Danshen) is a well known traditional Chinese herb, which has been used widely in China for the treatment of cardiovascular diseases in clinic.

Aim of this study

The aim of the present study is to clarify the effects of lipophilic extract of Salvia miltiorrhiza (LESM) on catecholamine (CA) secretion, a traditional Chinese medicine used widely for the treatment of cardiovascular diseases in China.

Materials and methods

LESM was evaluated for its effects on CA secretion using HPLC-ECD method. The effects of LESM on ²²Na⁺ influx and intracellular calcium ([Ca²⁺]_i) were also investigated.

Results

Our results showed that LEMS directly stimulated basal CA secretion in an extracellular Ca²⁺-dependent manner. And the stimulation was not affected by combination of hexamethonium (Hex), an inhibitor of nAChR. LESM also directly elevated [Ca²⁺]_i. In addition, using selective blockers of voltage-dependent Ca²⁺ channels, such as nitrendipine (for L-type), ω-agatoxin-IVA (for P-type) and ω-conotoxin-GVIA (for N-type), it was found that nitrendipine suppressed the elevation of [Ca²⁺]_i induced by LESM, but not ω-agatoxin-IVA or ω-conotoxin-GVIA. Compared with acetylcholine (ACh) only, however, combination of LESM with ACh inhibited the raise of CA secretion, ²²Na⁺ influx and [Ca²⁺]_i in a concentration-dependent manner. Furthermore, LESM also inhibited CA secretion induced by veratridine (Ver), and 56 mM K⁺ at concentrations similar to those for [Ca²⁺]_i rise. One of the lipophilic active compounds, cryptotanshione (Cryp), also had the same effects on CA secretion with LESM.

Conclusions

All these findings suggest that LESM exerts dual effects on CA secretion in cultured bovine adrenal medullary cells. LESM exerts antagonistic effects on nAChR, voltage-dependent Na⁺ and Ca²⁺ channels, whereas it is an agonist of L-type Ca²⁺ channel when it used alone.     

福辛普利对缺氧复氧豚鼠心室肌细胞动作电位及其离子通道的影响

 目的观察福辛普利预处理对缺氧复氧豚鼠心室肌细胞动作电位(AP)、L-型钙通道电流(ICa-L)和ATP敏感钾通道电流(I_K-ATP)的影响,探讨其抗再灌注性心律失常的电生理机制。方法采用全细胞电流钳和膜片钳技术分别记录AP和ICa-L,I_K-ATP。结果缺氧复氧使心室肌细胞AP时程(APD₅₀,APD₉₀)缩短;ICa-L峰值降低,I-V曲线上移,激活曲线右移,半数激活电压(V_1/2)增大,失活曲线左移,失活V_1/2减低;ATP敏感钾通道由正常关闭状态到完全开放。与缺氧复氧组相比,福辛普利预处理使APD₅₀,APD₉₀相对延长;ICa-L峰值增加,I-V曲线上移幅度减小,激活曲线左移,失活曲线右移,激活与失活V_1/2均接近正常,ATP敏感钾通道进一步开放,电流明显增加。结论福辛普利预处理能显著改善缺氧复氧状态下L-钙通道的抑制状态,促进动作电位参数的恢复,减少有效不应期的离散度及折返形成;通过药物预适应机制,进一步开放ATP敏感钾通道,增加ATP敏感钾电流,而发挥抗再灌注心律失常的作用。     

Effects of Total Flavones from Acanthopanax senticosus on L‐type Calcium Channels,Calcium Transient and Contractility in Rat Ventricular Myocytes

Acanthopanax senticosus (Rupr. et Maxim.) Harms (AS), a traditional herbal medicine, has been widely used to treat ischemic heart disease. However, the underlying cellular mechanisms of its benefits to cardiac function remain unclear. The present study examined the effects of total flavones from AS (TFAS) on L‐type Ca²⁺ channel currents (I_Ca‐L) using the whole cell patch‐clamp technique and on intracellular calcium ([Ca²⁺]_i) handling and cell contractility in rat ventricular myocytes with the aid of a video‐based edge‐detection system. Exposure to TFAS resulted in a concentration‐ and voltage‐dependent blockade of I_Ca‐L, with the half‐maximal inhibitory concentration (IC₅₀) of 283.12 µg/mL and the maximal inhibitory effect of 36.49 ± 1.95%. Moreover, TFAS not only increased the maximum current in the current–voltage relationship but also shifted the activation and inactivation curves of I_Ca‐L toward the hyperpolarizing direction. Meanwhile, TFAS significantly reduced amplitudes of myocyte shortening and [Ca²⁺]_i with an increase in the time to 10% of the peak (Tp) and a decrease in the time to 10% of the baseline (Tr). Thus, the cardioprotective effects of TFAS may be attributed mainly to the attenuation of [Ca²⁺]_i through the direct inhibition of I_Ca‐L in rat ventricular myocytes and consequent negative effect on myocardial contractility. Copyright © 2015 John Wiley & Sons, Ltd.     

Poncirus trifoliate fruit modulates pacemaker activity in interstitial cells of Cajal from the murine small intestine

Ethnopharmacological relevance

Poncirus fructus (PF) has been widely used as a traditional medicine in Eastern Asia, especially to ameliorate the symptoms of gastrointestinal (GI) disorders related to abnormal GI motility.

Aim of the study

Poncirus fructus (PF), also known as Poncirus trifoliata (L.) Raf. (Rutaceae), is widely used as a traditional medicine in Eastern Asia mainly to ameliorate the symptoms of gastrointestinal (GI) disorders related to abnormal GI motility. In a previous study, a methanol extract of PF was found to have particularly potent gastroprokinetic effects. Interstitial cells of Cajal (ICCs) are pacemaker cells in the gastrointestinal tract, but the action mechanisms of PF extract in mouse small intestinal ICCs have not been investigated. Therefore, in the present study, we investigated the effects of a methanol extract of PF (MPF) in mouse small intestinal ICCs. In addition, we sought to identify the receptors involved.

Materials and Methods

Enzymatic digestions were used to dissociate ICCs from small intestines. The whole-cell patch-clamp configuration was used to record potentials (current clamp) from cultured ICCs. In addition, we analyzed intracellular Ca²⁺ concentrations ([Ca²⁺]_i).

Results

MPF decreased the amplitudes of pacemaker potentials in ICCs, and depolarized resting membrane potentials in a concentration dependent manner. Y25130 (a 5-HT₃ receptor antagonist) and RS39604 (a 5-HT₄ receptor antagonist) blocked MPF-induced membrane depolarizations, whereas SB269970 (a 5-HT₇ receptor antagonist) did not. Pretreatment with Na⁺ or Ca²⁺-free solution or thapsigargin (a Ca²⁺-ATPase inhibitor in endoplasmic reticulum) abolished the generation of pacemaker potentials and suppressed MPF-induced activity. [Ca²⁺]_i analysis showed that MPF increased [Ca²⁺]_i. Furthermore, treatments with PD 98059, SB203580, or JNK II inhibitor blocked MPF-induced membrane depolarizations in ICCs.

Conclusion

These results suggest that MPF modulates pacemaker potentials through 5-HT₃ and 5-HT₄ receptor-mediated pathways via external Na⁺ and Ca²⁺ influx, and via Ca²⁺ release from internal stores in a mitogen-activated protein kinase dependent manner. The study shows MPF is a good candidate for the development of a gastroprokinetic agent. In view of the effects of MPF on ICCs, further research is required, particularly to identify the active compound(s) involved and to determine their action mechanisms.     

Relaxant effect of flavonoid naringenin on contractile activity of rat colonic smooth muscle

Ethnopharmacological relevance

Disturbed gastrointestinal (GI) motility can be associated with smooth muscle abnormalities and dysfunction. Exploring innovative approaches that can modulate the disturbed colonic motility are of great importance for clinical therapeutics. Naringenin, a flavonoid presented in many traditional Chinese herbal medicines, has been shown to have a relaxant effect on different smooth muscles. The aim of the present study was to investigate the effect of naringenin on regulation of GI motility.

Material and methods

Mechanical recording was used to investigate the effect of naringenin on isolated rat colonic smooth muscle spontaneous contractions. Whole cell patch clamp, intracellular [Ca²⁺] concentration ([Ca²⁺]_i) and membrane potential measurements were examined on primary cultures of colonic smooth muscle cells (SMCs). A neostigmine-stimulated rat model was utilized to investigate the effect of naringenin in vivo.

Results

Naringenin induced a concentration-dependent inhibition (1–1000 μM) on rat colonic spontaneous contraction, which was reversible after wash out. The external Ca²⁺ influx induced contraction and [Ca²⁺]_i increase were inhibited by naringenin (100 μM). In rat colonic SMCs, naringenin-induced membrane potential hyperpolarization was sensitive to TEA and selective large-conductance calcium-activated K⁺ (BK_Ca) channel inhibitor iberiotoxin. Under whole cell patch-clamp condition, naringenin stimulated an iberiotoxin-sensitive BK_Ca current, which was insensitive to changes in the [Ca²⁺]_i concentration. Furthermore, naringenin significantly suppressed neostigmine-enhanced rat colon transit in vivo.

Conclusion

Our results for the first time demonstrated the relaxant effect of flavonoid naringenin on colon smooth muscle both in vitro and in vivo. The relaxant effect of naringenin was attributed to direct activation of BK_Ca channels, which subsequently hyperpolarized the colonic SMCs and decreased Ca²⁺ influx through VDCC. Naringenin might be of therapeutic value in the treatment of GI motility disorders.     

滇黄芩总黄酮对豚鼠心肌细胞电压依赖性钠通道电流的影响

目的:研究滇黄芩总黄酮(totla flavonoid)对豚鼠心肌组织电压门控性钠通道的影响。方法:成年豚鼠,肝素抗凝后,腹腔麻醉,断头处死,迅速取其心脏,进行Langendorff灌流,先用无钙台式液灌流10 min,再以Ⅰ型胶原酶溶液灌流心脏,待心脏基本变软后剪取心室部分,制备单个心室肌细胞。分离出的豚鼠心肌单细胞,用全细胞电压钳技术记录电压依赖性钠电流进行研究。结果:滇黄芩总黄酮能可逆性抑制钠电流,其半数抑制浓度(IC50)为106 mg.L-1(95%的可信限是92～112 mg.L-1)。滇黄芩总黄酮并不影响钠通道激活开放的刺激电位阈值、最大激活电位值和反转电位值,但能使可激活开放的钠通道明显减少,钠离子电流明显衰减,可引出的钠电流在-40 mV处较正常组减少45.6%。细胞外给予滇黄芩总黄酮不影响钠通道激活曲线:对照组与106 mg.L-1的滇黄芩总黄酮组的半激活电压(V1/2)分别为(-50.4±1.7)mV和(-50.1±3.1)mV(n=6差异无统计学意义)。细胞外给予滇黄芩总黄酮可影响钠通道失活曲线,106 mg.L-1的滇黄芩总黄酮对电压依赖性稳态失活钠电流会引起一个大约12 mV的负向漂移,延缓失活钠通道的恢复:对照组与106 mg.L-1的滇黄芩总黄酮组的V1/2分别为(-69.4±1.6)mV和(-79.3±3.2)mV(n=7,P<0.05),两者间的差异有显著性意义,斜率分别为(-8.2±0.9)mV和(7.1±0.7)mV。细胞外给予滇黄芩总黄酮也可影响失活钠通道的恢复,使钠通道的复活时间常数显著延长:对照组和106mg.L-1的滇黄芩总黄酮组的时间常数分别为(15.6±6.3),(29.8±14.8)ms(n=6,P<0.05),差异有显著性意义。结论:滇黄芩总黄酮可阻滞豚鼠心肌细胞钠通道,是稳定的豚鼠心肌组织钠通道阻断剂。     

三氧化二砷对豚鼠心室肌细胞内游离钙离子浓度的影响

 目的 研究三氧化二砷(As₂O₃)对豚鼠心室肌细胞内游离钙离子浓度的影响。方法Fluo-3／AM荧光探针标记豚鼠心室肌细胞游离钙离子,激光共聚焦显微镜实时测定不同浓度As₂O₃干预5 min后心室肌细胞的胞浆钙的变化。不同剂量的As₂O₃对正常台氏液中的豚鼠心肌细胞体外浓度递减性干预13 h后心肌细胞DNA片断化的情况。结果 不同浓度As₂O₃对心室肌细胞的胞浆钙影响不同。在正常台氏液中,低浓度As₂O₃引起一过性钙增高,高浓度的As₂O₃引起持续钙增高,并被钙通道阻滞剂维拉帕米不完全阻断。在无钙台氏液中,低浓度As₂O₃对胞浆钙无影响,高浓度的As₂O₃引起持续钙增高。10μmol·L^-1的As₂O₃体外浓度递减性干预13 h后,豚鼠心肌细胞发生DNA的片断化。低于10μmol·L^-1的As₂O₃体外浓度递减性干预13 h后,心肌细胞无明显的DNA片断化。结论 As₂O₃影响细胞外钙内流和细胞内钙库释放,导致心肌细胞内的游离钙升高,其机制可能有电压依赖性钙通道参与。低浓度引起胞内一过性钙升高;高浓度导致胞内持续性钙升高。后者可能是As₂O₃诱导细胞凋亡的机制之一。