黄连素对结肠平滑肌细胞膜钙激活钾通道和延迟整流钾通道的影响

目的　研究黄连素对结肠平滑肌细胞膜钙离子激活钾通道 (IK(Ca) )和延迟整流钾通道 (IK(V) )的影响以初步探讨其治疗运动性腹泻的机制。方法　酶解法急性分离单个豚鼠结肠平滑肌细胞 ,运用膜片钳方法检测 10、5 0、10 0 μmol·L-1的黄连素对结肠平滑肌细胞膜IK(Ca) 和IK(V) 的影响。结果　 10、5 0、10 0 μmol·L-1的黄连素可抑制豚鼠单个结肠平滑肌细胞膜IK(Ca) (P <0 0 1) ,当阶跃刺激为 +80mV时 ,其IK(Ca) 分别为生理盐水对照组的 (6 8 2 0± 5 17) % ,(5 5 89± 1 6 1) % ,(4 8 0 8± 2 4 5 ) % (P <0 0 1) ;10、5 0、10 0 μmol·L-1的黄连素可抑制豚鼠单个结肠平滑肌细胞膜IK(V) (P <0 0 1) ,当阶跃刺激为 +80mV时 ,其IK(V) 分别为生理盐水对照组的 (77 0 6± 6 4 2 ) % ,(6 8 6 7± 6 79) % ,(6 1 0 7±7 72 ) % (P <0 0 1)。结论　Ber能抑制豚鼠结肠平滑肌钙离子激活钾通道和延迟整流钾通道的开放 ,这可能是其治疗运动性腹泻的机制之一。     

大黄素对豚鼠结肠带平滑肌细胞钾通道活性的影响

用检测平滑肌细胞电活动和张力技术,研究了大黄素对豚鼠结肠带平滑肌细胞电和收缩活动的影响并与 cromakalim, glybenclamide,四乙胺及BaCl₂的作用进行比较。结果表明,大黄素加强平滑肌细胞电和收缩活动,作用效果与剂量有关;大黄素与cromakalim的作用相互抑制。其促进平滑肌细胞电和收缩活动的作用与glybenclamide相似,而与四乙胺和BaCl₂有明显区别。提示大黄素的作用机制与抑制细胞膜K_ATP等钾通道的活性相关。     

内皮素对大鼠肺动脉平滑肌细胞膜钾通道的影响

目的观察内皮素(ET-1)对大鼠肺动脉平滑肌细胞(PASMCs)膜电压门控钾通道(K_V)的作用。方法用全细胞膜片钳记录方法研究ET-1对膜电位(E_m)、膜电容(C_m)、电压门控钾电流(IK_V)的影响。结果ET-1可引起PASMCs去极化,并抑制IK_V,抑制IK_V时间明显早于其对E_m变化的影响,ET-1对IK_V的影响呈可逆性和浓度依赖性,在有钙的环境中,ET-1对IK_V峰电流的抑制率明显高于无钙时。结论ET-1可浓度依赖性的抑制IK_V,使常氧大鼠PASMCs去极化,且ET-1对IK_V的抑制作用早于对E_m的影响,这些作用不完全依赖于钙的参与,但钙可加强ET-1对IK_V的抑制作用。     

大黄素增强平滑肌细胞钙离子依赖的氯离子电流

本文利用全细胞膜片钳技术观察大黄素对大鼠近端结肠ClCa电流的直接作用,并探讨该作用的信号传导途径.     

羟苯氨酮激活家兔血管平滑肌细胞钙敏感钾通道

目的研究羟苯氨酮(oxyphenamone,Oxy)扩张血管作用机理。方法用全细胞膜片钳技术,监测家兔肠系膜阻力血管平滑肌细胞钙敏感钾通道电流变化以及Oxy对其的影响。结果0.1 μmol·L^-1 Oxy明显增加钙敏感钾通道电流,冲洗后恢复至给药前水平;0.01～10 μmol·L^-1 Oxy明显增加钙敏感钾通道电流,且呈现浓度依赖性。结论 Oxy呈浓度依赖性和可逆性的增大血管平滑肌细胞钙敏感钾通道电流。     

异丙酚对大鼠肺动脉平滑肌细胞钾通道电流的影响

目的：评价异丙酚对正常血压及肺动脉高压大鼠肺动脉平滑肌K^＋通道的影响。方法：用SD大鼠建立肺动脉高压大鼠模型。急性分离正常血压和肺动脉高压大鼠肺内动脉平滑肌细胞，用膜片钳全细胞记录技术记录细胞K^＋通道电流。通过浴槽内给药。结果：在50、100μmol／L浓度下，异丙酚可明显引起正常血压和肺动脉高压大鼠肺动脉平滑肌细胞外向K^＋通道电流I-V曲线上移。与对照组比较，异丙酚作用后5min内细胞外向K^＋通道电流强度分别增强为初始电流强度的（121±11）％、（113±5）％（P〈0．01）和（126±5）％、（122±8）％（P〈0.01）。结论：异丙酚可增强正常血压及肺动脉高压大鼠动脉平滑肌细胞的外向K^＋通道电流，这可能是其降低肺血管张力、舒张肺血管的机制之一。     

碘化N-正丁基氟哌啶醇对大鼠心室肌细胞膜钾通道的影响

目的研究碘化N-正丁基氟哌啶醇(F2)对大鼠心室肌细胞膜瞬时外向钾通道的影响。方法采用酶急性消化法分离得到单个大鼠心室肌细胞,应用膜片钳全细胞记录技术观察F2对大鼠心室肌细胞膜瞬时外向钾电流(Ito)的影响。结果F2可剂量依赖地抑制Ito,IC50为0.28mmol·L-1。F2可使Ito的稳态失活曲线左移,半量膜电位Vmid变负,斜率因子S变大;但对激活曲线几乎无影响;对Ito灭活后再复活时程无影响。结论F2对心室肌膜Ito具有抑制作用。     

内皮素对慢性低氧大鼠肺动脉平滑肌细胞膜钾通道活性的影响

目的观察内皮素(ET-1)对慢性低氧大鼠肺动脉平滑肌细胞(PASMCs)膜电压门控钾通道(K_V)活性的影响。方法将12只Wistar大鼠随机分为对照组和慢性低氧组，每组6只。用全细胞膜片钳记录方法研究ET-1对两组大鼠PASMCs膜电位(E_m)、膜电容(C_m)及电压门控钾电流(IK_V)的影响。结果ET-1可引起两组大鼠PASMCs去极化，且对两组大鼠IK_V均有明显的浓度依赖性抑制作用。在慢性低氧组，高浓度ET-1对IK_V的抑制作用强于对照组。结论低氧并未改变ET-1引起PASMCs去极化及浓度依赖性抑制IK_V的特性，且慢性低氧可能改变了PASMCs对ET-1的敏感性，内皮素和低氧对PASMCs IK_V的抑制作用有协同性。     

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。     

大黄素对豚鼠结肠收缩性的影响及其机制的研究

目的研究大黄素对豚鼠离体远端结肠平滑肌收缩活动的影响及其可能机制。方法急性分离豚鼠远端结肠平滑肌,采用生理记录仪记录不同浓度大黄素对远端结肠收缩的影响;木瓜蛋白酶消化分离豚鼠近端结肠平滑肌细胞,采用全细胞膜片钳技术记录钾电流。结果不同浓度的大黄素（1～50μmol.L-1）对豚鼠远端结肠具有双向调节作用,且其效应呈剂量依赖的趋势1～10μmol.L-1大黄素可浓度依赖性地增强豚鼠远端结肠平滑肌的收缩10μmol.L-1浓度时,大黄素的作用达到平台期。当大黄素的浓度大于10μmol.L-1时,逐渐呈现明显的抑制作用,且其抑制作用与浓度正相关10μmol.L-1硝苯地平孵育肌条后,大黄素不能增强肌条的收缩。大黄素（1～30μmol.L-1）浓度依赖性地抑制豚鼠近端结肠平滑肌细胞钾电流。结论大黄素增强豚鼠结肠的收缩作用可能与L-型钙通道及钾通道有关。     

Pharmacological properties of Ca2+-activated K+ currents of ramified murine brain macrophages

Using the whole-cell configuration of the patch clamp technique, calcium-activated potassium currents (I_K,Ca) were investigated in ramified murine brain macrophages. In order to induce I_K,Ca the intracellular concentration of nominal free Ca²⁺ was adjusted to 1μM. The Ca²⁺-activated K⁺ current of brain macrophages did not show any voltage dependence at test potentials between –120 and +30mV. A tenfold change in extracellular K⁺ concentration shifted the reversal potential of I_K,Ca by 51mV. The bee venom toxin apamin applied at concentrations of up to 1μM did not affect I_K,Ca. Ca²⁺-activated K⁺ currents of ramified brain macrophages were highly sensitive to extracellularly applied charybdotoxin (CTX). The half-maximal effective concentration of CTX was calculated to be 4.3nM. In contrast to CTX, the scorpion toxin kaliotoxin did not inhibit I_K,Ca at concentrations between 1 and 50nM. Tetraethylammonium (TEA) blocked 8.0% of I_K,Ca at a concentration of 1mM, whereas 31.4% of current was blocked by 10mM TEA. Several inorganic polyvalent cations were tested at a concentration of 2mM for their ability to block I_K,Ca. La³⁺ reduced I_K,Ca by 72.8%, whereas Cd²⁺ decreased I_K,Ca by 17.4%; in contrast, Ni²⁺ did not have any effect on I_K,Ca. Ba²⁺ applied at a concentration of 1mM reduced I_K,Ca voltage-dependently at hyperpolarizing potentials. Received: 17 January / Accepted: 5 May 1997     

Distribution of Ca2+-activated K+ channel (SK2 and SK3) immunoreactivity in intestinal smooth muscles of the guinea-pig

1. The tissue distribution of small conductance Ca(2+)-activated K(+) channels (SK2 and SK3) was examined in three preparations of the guinea-pig intestine: the taneia caeci and the circular muscle layer of the stomach and proximal colon. 2. The SK3 immunoreactive (SK3-IR) cells were bi- or multipolar in appearance with numerous short processes, which formed an interconnecting network at the myenteric and submucous borders of the stomach and proximal colon. The SK3-IR cells were also present within the circular muscle layer of these preparations and throughout the taenia caeci. 3. Although SK3-IR cells had a similar distribution as cells immunoreactive for c-Kit (c-Kit-IR), the marker for interstitial cells of Cajal (ICC), only 5-10% of c-Kit-IR ICC were also SK3-IR. 4. The SK3-IR cells were clearly ICC when examined with the electron microscope. Close associations of SK3-IR ICC (ICC-SK3) and nerves were often observed, as were gap junctions with SK3-negative ICC and smooth muscle cells. 5. Punctate SK2 and SK3 channel immunoreactivity was present on the plasmalemmal surface of all smooth muscle cells examined. 6. We conclude that ICC-SK3 are a subpopulation of ICC that are directly innervated by enteric inhibitory motor nerves.     

Activation of large‐conductance Ca2+‐activated K+ channels by pinacidil in human umbilical vascular endothelial cells

The effect of pinacidil, an opener of ATP‐sensitive K⁺ (K_ATP) channels, on large‐conductance Ca²⁺‐activated K+ (BK_Ca) channels was investigated in cultured endothelial cells of human umbilical veins. In whole cell configuration, pinacidil (30 μM) increased the amplitude of K⁺ outward currents (I_K). Charybdotoxin (100 nM), but not glibenclamide (10 μM), suppressed pinacidil‐induced increase in I_K. Neither carbonyl cyanide m‐chlorophenyl hydrazone (CCCP; 10 μM), an inhibitor of mitochondrial Ca²⁺‐uniporter, nor cyclosporin A (200 nM), an inhibitor of the mitochondrial permeability transition pore, affected pinacidil‐induced increase in I_K. In inside‐out patch configuration, bath application of pinacidil (30 μM) did not change single channel conductance but increased the activity of BK_Ca channels. Pinacidil (30 μM) shifted the activation curve of BK_Ca channels to less positive membrane potential by approximately 15 mV. Pinacidil stimulated the activity of these channels in a concentration‐dependent manner. The EC₅₀ value for pinacidil‐induced channel activity was 20 μM. After BK_Ca channels had been enhanced by Evans blue (100 μM), subsequent application of pinacidil (100 μM) did not further increase the channel activity. These results clearly indicate that in addition to the activation of K_ATP channels, pinacidil can also stimulate BK_Ca channels in endothelial cells. These effects could contribute to the regulation of vascular tone if similar results were found in endothelial cells in vivo. Drug Dev. Res. 48:6–16, 1999. © 1999 Wiley‐Liss, Inc.     

Inhibitory effects of large Ca2+-activated K+-channel blockers on β-adrenergic- and NO-donor-mediated relaxations of human and guinea-pig airway smooth muscles

In human bronchi, relaxations to salbutamol and sodium nitroprusside were performed in the presence or absence of blockers of the large Ca²⁺-activated K⁺-channels (BK_Ca): charybdotoxin (Chtx), iberiotoxin (Ibtx) or tetraethylammonium (TEA). In bronchi under basal tone in presence of indomethacin (1 μM) or precontracted with acetylcholine (in presence or absence of indomethacin), the relaxations to salbutamol or sodium nitroprusside were unaffected or weakly inhibited by pretreatment with the BK_Ca blockers (Chtx (100 nM), Ibtx (100 and 300 nM) and TEA (1 mM)). Significant inhibitions were mainly observed with TEA (1 mM) and iberiotoxin at high concentration (300 nM). These results contrasts with the potent inhibitory effects exerted by Chtx (100 nM) or Ibtx (100 nM) in guinea-pig trachea precontracted with acetylcholine in absence or presence of indomethacin indicating that human airways are less susceptible to BK_Ca blockade than guinea-pig airways. In addition, the BK_Ca blockers induced slowly developing contractions of human bronchi at basal tone. The contraction induced by TEA (1 mM) was abolished by verapamil (10 μM) suggesting that BK_Ca blockade promotes an increase in membrane Ca²⁺-conductance through activation of voltage-gated Ca²⁺-channels. Verapamil also reversed the effects of TEA on salbutamol-induced relaxations in human bronchi as well as the effects of Ibtx on salbutamol- or sodium nitroprusside-induced relaxations in guinea-pig trachea. These data suggest that BK_Ca blockers induce activation of voltage-gated Ca²⁺-channels and therefore influx of Ca²⁺ which in turn cause a functional antagonism of β₂-adrenoceptor-agonist- and NO-donor-induced relaxations. Moreover, the BK_Ca opener, NS-1619, induced weak relaxations in human bronchi and guinea-pig trachea which were not blocked by TEA or Ibtx suggesting that BK_Ca opening is of minor significance for the relaxation of human airway smooth muscles. In conclusion, although a wealth of studies have demonstrated that β-adrenoceptor agonists or NO-donors activate BK_Ca, the present study provides evidence that in human bronchi, as recently suggested in guinea-pig trachea, opening of BK_Ca does not appear to functionally participate in the relaxation to these relaxant agents. Received: 25 April 1997 / Accepted: 15 September 1997     

豚鼠气管平滑肌细胞钾离子通道动力学特性及对拮抗剂的敏感性

钾离子通道功能与细胞的兴奋性有关，在豚鼠支气管平滑肌细胞膜上，用膜片钳技术证实了一类电压依赖性钾通道的存在，该通道电导为７５±５ｐＳ，翻转电位为－７３±８ｍＶ．动力学特性显示，通道开放时程分布直方图符合双指数拟合．其中τ０２随去极化程度增大而增大．通道开放概率有明显的电压依赖性．该类通道可被四乙胺从膜的内，外侧面阻断，对４－氨基吡啶不敏感．可被铯离子阻断，通道活动与细胞内钙水平降低无关．提示钾离子通道特性在不同组织细胞上有差异．     

赛庚啶对豚鼠心室肌细胞钙电流的影响

应用全细胞记录式膜片钳技术研究了赛庚啶(Cyp)对豚鼠心室肌细胞慢钙电流(I_(Ca))的影响,Cyp 3和8μmol·L~1对I_(Ca)的电流-电压关系曲线(I-V曲线)之各电流均有降低作用,使I-V曲线上抬;在指令电位0 mV时,I_(Ca)为次最大值,Cyp 0.3～10μmol·L~1使该I_(Ca)呈浓度依赖性降低,IC_(50)值为1.98μmol·L~1,还观察到Cyp 1μmol·L~1明显增加外向电流(I_(out)),且四乙基铵(TEA)1 mmol·L~1对其有显著的拮抗作用,但对控制电位从80 mV跃升至-40 mV时所出现的瞬时快内向电流,无明显影响.以上结果直接证明了Cyp对心室肌细胞钙跨膜转运有明显降低作用,还可能增加钾外流。     

Characterization of the outer pore region of the apamin-sensitive Ca2+-activated K+ channel rSK2.

We have studied the interaction between the SK2 channel and different scorpion toxins in order to find similarity and differences to other K⁺ channels. Beside apamin, ScTX is a high affinity blocker of the SK2 channel, whereas CTX is unable to block current through SK2. In order to prove that the ScTX affinity can be explained by the character of the different residues in the outer pore of the SK channels we introduced point mutations that render SK2 K⁺ channel SK1 and SK3 like. Directed by the results of the toxin receptor on the ShakerK⁺ channel, we changed single amino acids of the SK2 K⁺ channel that should render it sensitive to other peptide toxins like CTX a blocker of the IK channel, or KTX a blocker of the voltage-dependent channel Kv1.1 and Kv1.3. Amino acids V342G, S344E, and G384D of SK2 were changed to amino acids known from ShakerK⁺ channel to improve Shaker K⁺ channel CTX sensitivity. Interestingly SK2 V342G became CTX sensitive with a K_d of 19 nM and was also KTX sensitive K_d=97 nM. SK2 S344E (K_dCTX=105 nM,K_dKTX=144 nM) and G348D (K_dCTX=31 nM,Kd KTX=89 nM) became also CTX and KTX sensitive with a lower affinity. The mutant channels SK V342G, SK2 S344E and SK2 G348D showed reduced ScTX sensitivity (K_d=6 nM,K_d=48 nM, and K_d=12 nM). Because the exchange of a single residue could create a new high affinity binding site for CTX and KTX we concluded that the outer vestibule around position V342, S344, and G348 of the SK2 K⁺ channel pore is very similar to those of voltage-gated K⁺ channels such as the Shaker K⁺ channel, Kv1.1 and Kv1.3 channels and also to the prokaryotic KcsA channel. From mutant cycle analysis of KTX position H34 and SK2 position V342G, S344E, and G348D we could deduce that KTX binds in a similar way to SK2 channel mutant pore than to the Kv1.1 pore.     

Effects of nitric oxide on large‐conductance Ca2+‐activated K+ currents in human cardiac fibroblasts through PKA and PKG‐related pathways

The human cardiac fibroblast (HCF) is the most abundant cell type in the myocardium, and HCFs play critical roles in maintaining normal cardiac function. However, unlike cardiomyocytes, the electrophysiology of HCFs is not well established. In the cardiovascular system, Ca²⁺‐activated K⁺ (KCa) channels have distinct physiological and pathological functions, and nitric oxide (NO) plays a key role. In this study, we investigated the potential effects of NO on KCa channels in HCFs. We recorded strong oscillating, well‐maintained outward K⁺ currents without marked inactivation throughout the test pulse period and detected outward rectification in the I‐V curve; these are all characteristics that are typical of KCa currents. These currents were blocked with iberiotoxin (IBTX, a BKCa blocker) but not with TRAM‐34 (an IKCa blocker). The amplitudes of the currents were increased with SNAP (an NO donor), and these increases were inhibited with IBTX. The SNAP‐stimulating effect on the BKCa currents was blocked by pretreatment with KT5823 (a protein kinase G [PKG] inhibitor) or 1 H‐[1,‐2, ‐4] oxadiazolo‐[4,‐3‐a] quinoxalin‐1‐one (ODQ; a soluble guanylate cyclase inhibitor). Additionally, 8‐bromo‐cyclic guanosine 3’,5’‐monophosphate (8‐Br‐cGMP) stimulated the BKCa currents, and pretreatment with KT5720 (a protein kinase A [PKA] inhibitor) and SQ22536 (an adenylyl cyclase inhibitor) blocked the NO‐stimulating effect on the BKCa currents. Furthermore, 8‐bromo‐cyclic adenosine 3’,5’‐monophosphate (8‐Br‐cAMP) activated the BKCa currents. These data suggest that BKCa current is the main subtype of the KCa current in HCFs and that NO enhances these currents through the PKG and PKA pathways.     

Blocking effect of tanshinone Ⅱ－Aon L－type Ca~（2＋） curent of single ventricular myocyte from guinea pig

本实验采用全细胞膜片钳技术，观察了丹参酮Ⅱ－Ａ对分离的豚鼠单个心室肌细胞Ｌ－型钙电流及跨膜电位的影响．使用Ｌａｎｇｅｎｄｏｒｆ装置和蛋白酶循环消化（０．２ｇ·Ｌ－１）的方法，获取了７０％～８０％的横纹清晰，呈杆状的耐钙心肌细胞．并使用ｐＣＬＡＭＰ５．５１微机程序和ＥＬＰ－７膜片钳放大器记录心肌细胞膜电流和跨膜电位的变化．丹参酮采用累积加药法，所有的观察指标均在同一细胞完成．数据分析采用配对ｔ检验．当使心肌细胞的保持电压为－４０ｍＶ，除极到０ｍＶ，刺激电压的时程为２５０ｍｓ，频率为０．５Ｈｚ时，１０，２０和４０μｍｏｌ·Ｌ－１的丹参酮Ⅱ－Ａ可使维拉帕米敏感的钙内向电流分别减少３５．２％，５７．７％和７４．７％（Ｐ＜０．０５），并能使动作电位时程亦呈剂量依赖性缩短，冲洗后两指标均部分恢复．该药的三种不同浓度，对不同电压最大激活的钙电流的电压依赖曲线均无影响．结果表明，丹参酮Ⅱ－Ａ具有类似维拉帕米样Ｌ－型钙通道阻断剂作用，其阻断作用呈非电压依赖性．