海马神经干细胞体外诱导分化过程中延迟整流钾通道的电生理特性

目的 研究大鼠海马源神经干细胞(NSC)分化前及其体外诱导分化的神经元样细胞在不同发育阶段延迟整流钾电流(IDR)的电生理特性.方法 利用无血清培养、单细胞克隆技术,体外培养SD大鼠海马组织源NSC.应用膜片钳技术全细胞模式记录IDR的电生理特性.结果 IDR的电流密度在NSC分化前和体外分化(DIV)0～6 d分别为45 pA/pF±4 pA/pF和56 pA/pF±10 pA/pF(+50 mV,标本数=9),而在DIV＞6 d的发育过程中保持稳定;IDR的半数最大激活膜电位(V1/2)在NSC分化前和DIV 0～6 d分别为9 mV±3 mV和12 mV±3 mV(标本数=9,P＜0.05),激活曲线右移,斜率参数K值无明显改变,但IDR激活特性在DIV＞6 d的发育过程中无明显改变;IDR的失活特性NSC分化前后及不同发育阶段的神经元样细胞中均无改变.结论 NSC分化/发育过程中,IDR的特性改变均发生在DIV 0～6 d,提示IDR通道在神经发育过程中发挥作用,且发育初始阶段对于细胞功能的成熟尤为重要.     

钙激活钾通道电流在膀胱逼尿肌不稳定中的表达变化研究

目的观察膀胱逼尿肌不稳定(DI)中钙激活钾通道(BKCa)电流变化,探讨BKCa在DI发生机制中的作用。方法通过膀胱出口部位梗阻法建立大鼠DI模型,取其膀胱平滑肌,酶消化分离单个平滑肌细胞,采用全细胞膜片钳技术记录BKCa宏观电流,比较其电流密度在DI和正常大鼠中的变化。结果大鼠膀胱平滑肌细胞表达较为丰富的BKCa电流,具有其他平滑肌细胞BKCa相似的电生理特性,即外向整流特性,能够被BKCa通道特异性阻断剂IbTX(300 nM)阻断。DI大鼠膀胱平滑肌BKCa在多个膜电位时电流密度明显下降,在膜电位为+60时电流密度由(32.42±7.97)pA/pF(n=21)下降到(20.56±4.63)pA/pF(n=18),两组相比,P<0.01。结论 BKCa可能参与了大鼠膀胱DI的发生,调控DI时BKCa通道活性可能作为治疗DI的靶点之一。     

川芎嗪对正常人体肠系膜血管平滑肌细胞大电导钙激活钾通道的作用

目的：研究川芎嗪（（tetramethylpyrazine,TMP））对正常人体肠系膜血管平滑肌细胞大电导钙激活钾通道宏观电流（large-conductance Ca^2＋-activated potassium channels,BKCa）的作用,探讨TMP对BKCa的作用机制。方法：用急性酶分离法分离人体肠系膜动脉平滑肌细胞,采用全细胞穿孔膜片钳技术记录该细胞上的大电导钙激活钾通道宏观电流,并测试TMP对该电流的作用。结果：TMP在0.73、3.67mmol/L时可明显地可逆性地激活正常人体肠系膜血管平滑肌细胞上的BKCa,在0.73mmol/L浓度时,测试电压从-50～＋60mV时差异都有统计学意义,其中测试电压在-50mV时,电流密度从0.25±0.03pA/pF增加到0.34±0.039pA/pF（P〈0.01,n=12）,测试电压在＋60mV时,电流密度从8.37±1.75pA/pF增加到14.12±2.66pA/pF（P〈0.01,n=12）;TMP在3.67mmol/L时可明显地可逆性地激活正常人体肠系膜血管平滑肌细胞上的BKCa,测试电压从0～＋60mV时差异都有统计学意义,其中测试电压在0mV时,电流密度从1.25±0.23pA/pF增加到1.90±0.31pA/pF（P〈0.05,n=7）,测试电压在＋60mV时,电流密度从10.57±3.61pA/pF增加到20.32±4.68pA/pF（P〈0.05,n=7）。但TMP在8.07mmol/L时可明显地可逆性地抑制正常人体肠系膜血管平滑肌细胞上的BKCa,测试电压从-60～＋60mV时差异都有统计学意义,其中测试电压在-60mV时,电流密度从0.28±0.02pA/pF降低到0.15±0.04pA/pF（P〈0.01,n=6）,测试电压在＋60mV时,电流密度从10.49±0.44pA/pF降低到1.83±0.68pA/pF（P〈0.01,n=6）。结论：TMP在0.73、3.67mmol/L下,可激活正常人体肠系膜血管平滑肌细胞大电导钙激活钾通道,而在8.07mmol/L时可明显地可逆性地抑制正常人体肠系膜血管平滑肌细胞上的BKCa。在低浓度和较高浓度下TMP对正常人体肠系膜血管平滑肌细胞上的BKCa有不同效应的实验结果,为TMP应用于临床提供了实验依据     

KCNE2对Kv4.3通道功能的调节作用

目的研究KCNE2对人类心肌细胞瞬间外向钾电流的主要α亚基-Kv4.3功能的调节。方法通过基因转染技术将Kv4.3或Kv4.3与KCNE2cDNA转入COS-7细胞株,采用膜片钳全细胞记录方式记录通道电流。结果KCNE2对Kv4.3功能有明显调控作用:减小Kv4.3通道电流密度;Kv4.3单独表达组通道电流密度为375.13±112.87pA/pF(n=11),KCNE2与Kv4.3共表达组电流密度为152.96±33.71pA/pF(n=16);减慢Kv4.3通道激活和衰减,在 60mV电压刺激下通道激活达峰值的时间由4.82±0.32ms(n=11)延长至20.41±2.13ms(n=16),P<0.05;通道电压依赖性失活发生正向移位,半数失活电压由-53.62±1.24mV(n=8)移至-46.58±1.6mV(n=10);通道从失活中恢复的速度加快,恢复时间常数由193.43±17.98ms缩短137.71±18.29ms,(n=7,P<0.05)。结论KCNE2可能作为人类心肌细胞膜Kv4.3钾离子通道一个重要的辅助亚基-β亚基参与Ito通道功能的调节。     

良性家族性婴儿惊厥KCNQ2基因G271V突变体钾通道的功能研究

目的 观察良性家族性婴儿惊厥相关基因KCNQ2突变体G271V的钾通道的功能,进一步探讨KCNQ2基因G271V突变的致病机理。方法 将前期成功构建的突变体G271V或和Kv7.2及Kv7.3的真核表达载体转染进真核表达细胞（HEK293细胞）,利用全细胞膜片钳技术检测G271V突变体的钾通道功能。结果 转染HEK293细胞后,G271V突变体无电流产生,与野生型相比,激活电流明显下降,诱导电压门控去极化改变。G271V的最大激活电流密度为(2.47±0.41) pA/pF（n=12）,Kv7.2的最大激活电流密度为(20.53±2.51) pA/pF（n=10）,差异有统计学意义（Pn=15）,Kv7.2/G271V/Kv7.3的最大激活电流密度为(42.71±6.27) pA/pF（n=10）,而G271V/Kv7.3的最大激活电流密度为(3.74±0.76) pA/pF（n=10）,差异有统计学意义（P<0.05）,突变体引起Kv7.2/G271V/Kv7.3异源通道电流减少约50%。结论 G271V突变体不能使钾通道开放去极化钾电流,突变体引起钾通道功能缺陷。     

大鼠背根神经节神经元瞬时外向钾电流与非洲爪蟾卵母细胞上表达的Kv4.2通道电流特性的比较

目的为最终揭示大鼠背根神经节神经元上天然瞬时外向钾通道的结构与功能调节提供依据。方法采用双极电压钳技术记录非洲爪蟾卵母细胞上表达的Kv4.2电流,用全细胞膜片钳技术记录大鼠背根神经节神经元上瞬间外向钾电流(IA),并对二者进行动力学特征的比较。结果背根神经节神经元上IA和Kv4.2通道电流①均具有明显的A型电流特征;②半数最大激活电位分别为(-29.5±3.1)mV和(-3.9±1.0)mV;③半数最大失活电位分别为(-78.5±3.4)mV和(-48.5±0.6)mV;④失活后再激活恢复时间常数(τ)分别为(32.0±4.8)ms和(71.4±13.2)ms。结论Kv4.2通道电流可能是背根神经节神经元上IA电流的主要成分,但不是唯一成分。     

BRL-37344对豚鼠心肌细胞ICa-L、Ito的影响

目的 为研究β3肾上腺素能受体介导的心脏生物学效应--β3肾上腺素能受体激活后心肌细胞电生理活动的变化.方法 以原代培养的豚鼠心肌细胞为对象, 采用全细胞膜片钳技术记录心肌细胞孵育β3肾上腺素能受体激动剂4-[-[2-hydroxy-(3-chlorophenyl)ethyl-amino]propyl]phenoxyacetate(BRL-37344; BRL)5~10 min前后ICa-L,Ito(L型钙离子通道和瞬时外向钾通道)的变化.结果 显示10-6 mol/L的BRL显著增强豚鼠心肌细胞的Ito,上移I-V曲线;去极化刺激到+80 mV时,电流密度从(6.11±1.03) pA/pF上升到(8.46±2.07) pA/pF(n=6,P=0.013064).10-6 mol/L的BRL显著增强豚鼠心肌细胞的ICa-L,为对照组的(2.30±0.75)倍(n=5,P=0.0063);去极化刺激到+10 mV时,电流幅度从(89.25±17.83) pA上升到(205.00±72.24) pA.结论 BRL-37344可增强豚鼠心肌瞬时外向钾电流和L型钙电流,进而调控心脏的活动.     

蛋白激酶C对慢性吸烟大鼠支气管平滑肌细胞膜电压门控钾通道的作用

目的 探讨蛋白激酶C对慢性吸烟大鼠支气管平滑肌细胞（bronchial smooth muscle cells, BMSCs）膜电压门控钾通道（Kv通道）的作用,为慢性阻塞性肺疾病的防治提供理论依据。方法 建立大鼠的慢性吸烟模型。大鼠随机分为吸烟组（A组）和对照组（B组）。采用急性酶分离法获得单个大鼠的支气管平滑肌细胞。用全细胞膜片钳技术测定其膜电位和Kv通道电流。比较用蛋白激酶C激动剂12-佛波醇脂（PMA）和抑制剂GFX前后两组细胞Kv通道电流的不同变化。结果 慢性吸烟大鼠BSMC的静息膜电位和Kv通道电流明显低于对照组。PKC可抑制正常大鼠BSMC+50 mV刺激时的峰值Kv通道电流（从78.3±10.5 pA/pF 下降到50.4±8.6 pA/pF, n=10 cells, P<0.05）。该抑制作用可被GFX抵消（77.9±7.8 pA/pF vs 70.4±9.6 pA/pF, n=10 cells, P>0.05）。但是PKC对慢性吸烟大鼠的BSMC的Kv通道电流无抑制作用（58.3±7.6 pA/pF vs 56.4±6.3 pA/pF, n=10 cells, P>0.05）。结论 慢性吸烟可抑制大鼠BMSC膜电压门控钾通道（Kv通道）的电流。PKC活化后对正常大鼠的BSMC有抑制作用,但对慢性吸烟大鼠的BSMC则无抑制作用。 【关键词】吸烟 支气管 钾通道     

急性冠状动脉综合征患者淋巴细胞电压依赖性钾通道的变化

[郭丽芬,张存泰,吴杰等.中华心血管病杂志,2007,35(9):818～821]用全细胞膜片钳技术和Western印迹法,探讨急性冠状动脉综合征(ACS)患者外周血淋巴细胞电压依赖性钾通道(Kv)电流及Kv1.3蛋白表达的变化。收集12例ACS患者和10例健康志愿者外周血淋巴细胞,采用膜片钳全细胞电流记录方法,记录淋巴细胞膜Kv的电流密度。用Western印迹法检测外周血淋巴细胞Kv1.3蛋白的表达。发现ACS患者淋巴细胞Kv的电流密度为(269±94)pA/pF,明显高于正常人[(191±64)pA/pF,P<0.01]。ACS组淋巴细胞膜电容为(2.3±0.7)pF,对照组为(2.2±0.5)pF,两组间差…     

大鼠海马锥体神经元延迟整流钾电流的发育变化

目的 研究大鼠海马锥体细胞延迟整流钾电流(Ik)在出生后不同发育阶段的变化.方法 采用膜片钳全细胞记录模式比较3个不同年龄组,即出生后7～10天(P7-10组)、25～30天(P25-30组)和56～60天(P56-60组)Wistar大鼠急性分离的海马锥体神经元Ik的变化及通道动力学和药理学特征.结果 随着动物的发育,Ik的电流密度上调,由p-10的(32±13)pA/pF逐渐增加到P25-30的(54±20)pA/pF和P56-60的(70±18)pA/pF.随年龄增大,Ik的激活曲线左移,其半数最大激活电位(V1/2)由-12.2mV逐渐增加到-17.8 mv,而斜率因子无明显变化.四乙铵(TEA)可剂量依赖性地抑制Ik,其中P7-10组的Ik对低浓度的TEA(2和5mmol/L)较P25-30及P56-60组更敏感.结论 在大鼠海马锥体神经元的发育过程中Ik逐渐增加,并伴有通道激活动力学和药理学特性的改变.上述变化可能与海马锥体神经元的成熟以及认知功能的日益完善有关.     

Electrophysiological properties of delayed rectifier outward K+ currents in the differentiation and development of hippocampal neural stem cells

OBJECTIVE: To study the developmental electrophysiological properties of delayed rectifier outward K+ currents (IDR) in undifferentiated NSC and NSC-derived neurons at various time points of adult SD rat hippocampus in vitro. METHODS: Neural stem cells were isolated from the hippocampus of adult SD rats with serum-free incubation and single-cell cloning technique. Electrophysiological recordings of IDR were performed using whole-cell patch clamp. RESULTS: The current density of IDR increased in NSC-derived neurons DIV 0-6 d whereas remained constant in DIV > 6 d. The current density of IDR at +50 mV was 45 pA/pF +/- 4 pA/pF and 56 pA/pF +/- 10 pA/pF in undifferentiated NSCs and NSC-derived neurons DIV 0-6 d respectively (n = 9). The activation process of IDR was also altered in DIV 0-6 d whereas remained constant in DIV > 6 d. The positive shift in steady-state activation curve of IDR revealed an increase of V1/2, however the slope factors K remained unchanged. V1/2 was 9 mV +/- 3 mV and 12 mV +/- 3 mV in undifferentiated NSCs and NSC-derived neurons DIV 0-6 d respectively (n = 9, P < 0.05). The inactivation properties of IDR were not altered before and after differentiation. CONCLUSION: Electrophysiological characteristics of IDR were all altered in DIV 0-6 d, suggesting the essential role of IDR in neurogenesis and early stage of differentiation/development process is very important for the functional mature of neuron.     

Cardioprotective effects of simvastatin on reversing electrical remodeling induced by myocardial ischemia-reperfusion in normocholesterolemic rabbits

Background Recent studies have revealed that pretreatment with statin is effective in preventing arrhythmia, but its electrophysiological mechanism is unclear. This study was conducted to investigate the cardioprotective effects of simvastatin on reversing electrical remodeling in left ventricular myocytes of rabbit heart undergoing ischemia-reperfusion, so as to explore the ionic mechanism responsible for the anti-arrhythmic effect of statin. Methods Forty-five rabbits were randomly divided into three groups： ischemic-reperfusion group （I-R）, simvastatin intervention group （Statin） and sham-operated control group （CON）. Anesthetized rabbits were subjected to 30-minute ischemia by ligation of the left anterior descending coronary artery and a 60-minute reperfusion after a 3-day administration of oral simvastatin of 5 mg-kg^-1.d^-1 in the Statin group or a placebo in the I-R group. Single ventricular myocytes were isolated enzymatically from the epicardial zone of the infracted region dedved from the hearts in the I-R and Statin group and the same anatomical region in the CON animals. The whole cell patch-clamp technique was used to record membrane ionic currents, including sodium current （IRa）, L-type calcium current （Ica-L） and transient outward potassium current （Ito）. Simultaneously, the level of serum cholesterol was examined. Results There was no significant difference in the serum cholesterol concentration among the three groups. The peak IRa current density （at -30 mV） was significantly decreased in I-R （（22.46±5.32） pA/pF, n=12） compared with CON （（42.78±5.48） pA/pF, n=16, P〈0.01） and Statin （（40.66±5.89） pA/pF, n=15, P〈0.01）, while the peak IRa current density in the Statin group was not different from CON （P〉0.05）. The peak ICa-L current density （at 0 mV） was significantly increased in I-R （（4.34±0.92） pA/pF, n=15） compared with CON （（3.13±1.22） pA/pF, n=13, P〈0.05） and Statin （（3.46±0.85） pNpF, n=16, P〈0     

Na+/Ca2+ exchanger current and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle]

OBJECTIVE: To investigate the characteristics of Na+/Ca2+ exchanger current (INa+ /Ca2+) and K+ current remodeling in midmyocardial cells of hypertrophic left ventricle for understanding the ionic basis of arrhythmia of the hypertrophic heart. METHODS: Twenty New Zealand rabbits were divided equally into normal control group and operation group, and in the latter, left ventricular hypertrophy was induced in the rabbits by partial ligation of the abdominal aorta. Action potentials, INa+/Ca2+, slowly activating delayed rectifier K+ current (IKs) and rapidly activating delayed rectifier K+ current (IKr) were recorded in the two groups by using whole-cell patch-clamp technique. RESULTS: At the basic cycle length of 2 s, 90% action potential duration (APD90) in control and operation groups was 522.0+/-19.5 ms (n=6) and 664.7+/-32.7 ms (n=7) respectively; at the testing potential of +40 mV, outward INa+/Ca2+ density in the two groups was 0.94+/-0.11 pA/pF (n=9) and 1.30+/-0.11 pA/pF (n=8) respectively; the testing potential of -100 mV elicited inward INa+/Ca2+ density of 0.40+/-0.05 pA/pF (n=9) and 0.56+/-0.02 pA/pF (n=8) respectively. The testing potential of +50 mV induced IKs tail current density of 0.26+/-0.03 pA/pF (n=8) and 0.17+/-0.01 pA/pF (n=9), and IKr tail current density of 0.34+/-0.02 pA/pF (n=8) and 0.23+/-0.02 pA/pF (n=9) respectively. Statistically significant differences were identified between the control and operation groups in all the above indices measured. CONCLUSION: The characteristics of electrical remodeling changes in midmyocardial cells of hypertrophic left ventricle, exhibited by prolonged action potential, up-regulated INa+/Ca2+ and down-regulated IKs and IKr.     

老年SD大鼠前列腺上皮细胞膜钾离子通道变化及意义

目的探讨雄性SD大鼠前列腺上皮细胞膜钾离子通道电流的变化和对钾通道阻断剂的反应。方法分别取3个月龄成年和12个月龄的老年SD大鼠的背外侧叶前列腺组织,剪成1—2mm^3大小,经消化、培养、免疫组鉴别,将形态正常、贴壁良好的腺上皮细胞用全细胞膜片钳模式记录钾通道电流。结果成年和老年SD大鼠的前列腺上皮细胞膜＋80mV钾电流密度分别为（10．84±1．54）pA／pF vs（18．48±1．7）pA／pF（n=20,P〈0．01）;钙激活型钾通道抑制剂（KCa通道）四乙胺（TEA）对老年大鼠峰电流阻断从19．1±2．9到7．2±3．2,KCa电流被抑制约63％;成年大鼠为9．5±1．8到5．4±3．1,KCa通道电流被抑制约44％。电压依赖型钾通道抑制剂4-AP（四氨基吡啶）对大鼠前列腺上皮细胞膜钾电流有显著阻断效应。结论老年大鼠的前列腺上皮细胞膜钾通道电流比成年大鼠显著增强,同时老年大鼠KCa通道电流对TEA更敏感。由此结果可推论老年大鼠的前列腺上皮细胞分泌功能是降低的。     

小鼠心室肌细胞钾电流及动作电位特征

目的比较小鼠左心室、右心室及室间隔心肌细胞的钾电流、动作电位的特征.方法采用全细胞膜片钳技术.结果左、右心室肌细胞的动作电位特征和Ito, Ik1钾电流密度无差异;与左心室比较,室间隔细胞存在两种特征的Ito,Ikslow (5.9pA/pF±1.35pA/pF,+50mV) 电流密度低型和Itof(3.47pA/pF±1.1pA/pF) and Ikslow (4.75pA/pF±1.5pA/pF)电流密度均低型;室间隔细胞亦存在两种特征的动作电位,一种与左、右心室无差异,另一种明显延长.结论小鼠心脏细胞存在不同的电生理特征分布,这种分布是由于编码通道的基因分布不同造成的.     

The effect of protein kinase C on voltage-gated potassium channel in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia

Background Chronic hypoxia can cause pulmonary hypertension and pulmonary heart disease with high mortality.The signal transduction pathway of protein kinase C (PKC) plays an important role in chronic pulmonary hypertension. So it is necessary to investigate the effect of PKC on voltage-gated potassium (K+) channels in pulmonary artery smooth muscle cells of rats exposed to chronic hypoxia.Methods Male Wistar rats were randomly divided into a control group (group A) and a chronic hypoxia group (group B). Group B received hypoxia ［oxygen concentration （10±1）%］ eight hours per day for four consecutive weeks. Single pulmonary artery smooth muscle cells were obtained using an acute enzyme separation method. Conventional whole cell patch clamp technique was used to record resting membrane potential, membrane capacitance and voltage-gated K+ currents. The changes in voltage-gated K+ currents before and after applying paramethoxyamphetamine (PMA) (500 nmol/L), an agonist of PKC, and PMA plus carbohydrate mixture of glucose, fructose and xylitol (GFX) (30 nmol/L), an inhibitor of PKC, were compared between the two groups.Results The resting membrane potential in group B was significantly lower than that of group A: －(29.0±4.8) mV (n=18) vs －(42.5±4.6) mV (n=35) (P&lt;0.01). But there was no change in membrane capacitance between the two groups: (17.9±4.6) pF (n=40) vs (19.7±5.8) pF (n=31) (P&gt;0.05). The voltage-gated K+ currents were significantly inhibited by PMA in group A, and this effect was reversed by GFX. However, the voltage-gated K+ currents in group B were not affected by PMA.Conclusions The resting membrane potential and voltage-gated K+ currents in pulmonary artery smooth muscle cells from rats exposed to chronic hypoxia decreased significantly. It seems that PKC has different effects on the voltage-gated K+ currents of pulmonary artery smooth muscle cells under different conditions.     

Effects of Chinese herbs on multiple ion channels in isolated ventricular myocytes

Background Shensong Yangxin (SSYX) is one of the compound recipe of Chinese materia medica. This study was conducted to investigate the effects of SSYX on sodium current (I(Na)), L-type calcium current (I(Ca,L)), transient outward potassium current (I(to)), delayed rectifier current (I(K)), and inward rectifier potassium currents (I(K1)) in isolated ventricular myocytes. Methods Whole cell patch-clamp technique was used to study ion channel currents in enzymatically isolated guinea pig or rat ventricular myocytes. Results SSYX decreased peak I(Na) by (44.84±7.65)% from 27.21±5.35 to 14.88±2.75 pA/pF (n=5, P&lt;0.05). The medicine significantly inhibited the I(Ca,L). At concentrations of 0.25, 0.50, and 1.00 g/100 ml, the peak I(Ca,L) was reduced by (19.22±1.10)%, (44.82±6.50)% and (50.69±5.64)%, respectively (n=5, all P&lt;0.05). SSYX lifted the I-V curve of both I(Na) and I(Ca,L) without changing the threshold, peak and reversal potentials. At the concentration of 0.5%, the drug blocked the transient component of I(to) by 50.60% at membrane voltage of 60 mV and negatively shifted the inactive curve and delayed the recovery from channel inactivation. The tail current density of I(K) was decreased by (30.77±1.11)% (n=5, P&lt;0.05) at membrane voltage of 50 mV after exposure to the medicine and the time-dependent activity of I(K) was also inhibited. Similar to the effect on I(K), the SSYX inhibited I(K1) by 33.10% at the test potential of –100 mV with little effect on reversal potential and the rectification property. Conclusions The experiments revealed that SSYX could block multiple ion channels such as I(Na) I(Ca,L), I(k), I(to) and I(K1), which may change the action potential duration and contribute to some of its antiarrhythmic effects.     

K~+ Channels and Their Effects on Membrane Potential in Rat Bronchial Smooth Muscle Cells

In order to investigate the K~+ channels and their effects on resting membrane potential(Em) and excitability in rat bronchial smooth muscle cells (BSMCs), the components of outward K~+channel currents and the effects of K~+ channels on Em and tension in rat bronchial smooth musclewere observed by using standard whole-cell recording of patch clamp and isometric tension recordingtechniques. The results showed that under resting conditions, total outward K~+ channel currents infreshly isolated BSMCs were unaffected by ATP-sensitive K~+ channel blocker. There were two typesof K~+ currents: voltage-dependent delayed rectifier K~+ channel (Kv) and large conductance calcium-activated K~+ channel (BK_(Ca)) currents. 1 mmol/L 4-aminopyridine (4-AP, an inhibitor of Kv)caused a significant depolarization (from — 8.7±5.9mV to —25.4±3.1mV, n=18, P<0.001).In contrast, 1 mmol/L tetraethylammonium (TEA, an inhibitor of BK_(Ca)) had no significant effect onEm (from —37.6±4.8 mV to —36.8±4.1 mV, n=12, P>0.05). 4