Molecular pharmacologycal investigations on K channel openers-New

应用微电极、电压钳和膜片钳技术研究了新合成的钾通道开放剂尼可地尔、色满卡林和吡那地尔对兔和大鼠门静脉、肠系膜动、静脉平滑肌细胞的作用。家兔肠系膜动脉平滑肌细胞膜电位为-70mV，门静脉平滑肌细胞膜电位为-55mV。上述三种药物均使膜超极化，并增加膜的离子电导。比较用药前后的电流-电压关系，所有药物均使膜电阻增加，两条关系曲线在-80mV左右相交。这意味着尼可地尔、吡那地尔和色满卡林诱导的超极化是由于膜的K渗透性增加。用电压钳方法，尼可地尔、色满卡林和吡那地尔在-40mV的保持电位下，在浓度为2.0mV时产生的外向电流均为2.0mV，而在浓度为2.0mV时产生的外向电流均为2.0mV。 ...更多信息 独立的方式。这种外向电流可被四乙基铵（TEA）轻微抑制，而被4-氨基吡啶（4-AP）显著抑制。这些潜在的变化是非常敏感的细胞内（细胞硅）钙。当施加矩形去极化脉冲或斜坡电流（-120V ~+140mV）时，K电流持续增大。这三种药物诱发的外向电流可被预先应用格列本脲阻断。当用膜片钳方法记录到细胞内钙敏感性钾通道时，即大电导（280 pS）和小电导（30 pS）的钙依赖性钾电流。前者对TEA比4-AP敏感，后者对4-AP比TEA敏感。ATP（1 mM以上）抑制3 OpS K通道的产生，10 mM ATP阻断该通道。尼可地尔、吡那地尔和克罗马卡林加速了30 pS K通道的产生，并且钙通道开放剂的这些作用被预先应用格列本脲所阻断。这些钾通道开放的概率和延长开放时间的ATP敏感的钙依赖性钾通道。因此，我们认为钾通道开放剂作用于30 pS钙依赖性ATP敏感性钾通道。尼可地尔具有硝酸甘油样作用，吡那地尔具有二氢吡啶敏感的钙拮抗作用，吡那地尔具有三磷酸肌醇合成抑制剂的作用。这种K通道开放的作用可能值得作为抗心绞痛和抗高血压药物。少

Effects of newly synthesized K channel openers, nicorandil, cromakalim and pinacidil on smooth muscle cells of the rabbit and rat portal vein, mesenteric artery and vein were investigated using the microelectrode, voltage clamp and patch clamp methods. The membrane potential of smooth muscle cells of the rabbit mesenteric artery was -7OmV and that of the portal vein was -55mV. Above three agents consistently hyperpolarized the membrane and increased the ionic conductance of the membrane. When the current-voltage relation-ships were compared before and after application of these agents, all agents increased the membrane resistance and both relation curves cross at about -8OmV. This means that the hyperpolarization induced by nicorandil, pinacidil and cromakalim was due to increase in the K permeability of the membrane. Using the voltage clamp method, when nicorandil, cromakalim or pinacidil was applied at the holding potantial of -40mV, the outward current generated in a concentration d … More ependent manner. This outward current was slightly inhibited by application of tetraethyl-ammonium (TEA) and markedly inhibited by 4-aminopyridine (4-AP). These potential changes were very sensitive to intracellular (cytosilic) Ca. When rectangular depolarization pulse or ramp current (-120V - +140mV) was applied, the K current was consistently enlarged. These outward current evoked by these three agents were blocked by preapplication of glibencalmide. When the patch clamp method was applied on fragmented membranes (inside out patch), the cytosolic Ca sensitive K channels were recorded, i.e. large conductance (280pS) and small conductance (30pS) of the Ca dependent K current. The former was more sensitive to TEA that 4-AP and the latter was more sensitive to 4-AP than TEA. ATP (over 1mM) inhibited the generation of the 3OpS K channel and blocked this channel with of 1OmM ATP. Nicorandil, pinacidil and cromakalim accelerated the generation of the 30pS K channel and these actions of Ca channel openers were blocked by pre- application of glibenclamide. These K channel openers the open probability and prolonged the open time of the ATP-sensitive Ca dependent K channel. Therefore, we concluded that K channel openers acts on the 30pS Ca dependent ATP sensitive K channel. Nicorandil possessed aproperty of nitroglycerine-like action, pinacidil a property of dihydropyridine sensitive Ca antagonistic action and pinacidil a property of synthesis inhibitor of inositol 1,4,5-trisphosphate. Such actions with the K channel opening may merit as anti-anginal and anti-hypertensive agents. Less