Stockbridge N, Zhang H, Weir B
Department of Surgery, University of Alberta, Edmonton, Canada.
Pflugers Arch. 1992 May;421(1):37-42. doi: 10.1007/BF00374731.
Primary isolates of smooth muscle cells from the basilar artery of the rat were studied using whole-cell and single-channel patch-clamp techniques. Two distinct potassium currents were characterized. With low intracellular calcium, depolarization above 0 mV elicited an outward current of a few hundred pA (at +120 mV) with sigmoidal onset and little inactivation during 1.25 s steps. This current was reduced by bath application of 1 mM procaine or 1 mM strychnine, but not by 500 nM charybdotoxin. These are characteristics of the delayed rectifier potassium current in other preparations. With higher intracellular calcium, depolarization above 0 mV elicited a non-inactivating potassium current of several nA (at +120 mV). This current persisted in the presence of 1 mM procaine or strychnine but was reduced by bath application of 100 nM charybdotoxin. In whole-cell recordings in which intracellular calcium was unbuffered with EGTA, spontaneous transient outward currents were manifest and displayed voltage dependence and tail currents similar to the calcium-dependent current. The spontaneous transient current and the calcium-dependent current had similar sensitivity to charybdotoxin. Cell-free membrane patches contained one or more channels of 220 pS (in solutions symmetrical with respect to potassium) with similar voltage and calcium dependence. These are characteristics of the large conductance calcium-activated potassium current in other preparations.
采用全细胞和单通道膜片钳技术研究了从大鼠基底动脉分离的原代平滑肌细胞。鉴定出两种不同的钾电流。在细胞内钙浓度较低时，高于0 mV的去极化会引发几百皮安的外向电流（在+120 mV时），起始呈S形，在1.25 s的步长中几乎没有失活。通过浴槽施加1 mM普鲁卡因或1 mM士的宁可使该电流减小，但500 nM的蝎毒素对其无影响。这些是其他制剂中延迟整流钾电流的特征。在细胞内钙浓度较高时，高于0 mV的去极化会引发几纳安的非失活钾电流（在+120 mV时）。在存在1 mM普鲁卡因或士的宁的情况下，该电流持续存在，但通过浴槽施加100 nM的蝎毒素可使其减小。在未用乙二醇双（2-氨基乙基醚）四乙酸（EGTA）缓冲细胞内钙的全细胞记录中，出现了自发瞬时外向电流，其表现出电压依赖性和与钙依赖性电流相似的尾电流。自发瞬时电流和钙依赖性电流对蝎毒素具有相似的敏感性。无细胞的膜片包含一个或多个220 pS的通道（在钾对称的溶液中），具有相似的电压和钙依赖性。这些是其他制剂中大电导钙激活钾电流的特征。
