Castellano A, Pintado E, López-Barneo J
Departamento de Fisiología, Facultad de Medicina, Sevilla, Spain.
Cell Calcium. 1987 Oct;8(5):377-83. doi: 10.1016/0143-4160(87)90012-1.
The membrane ionic conductances of dispersed parathyroid cells kept in primary culture were studied using the "whole-cell" and "inside-out excised patch" variants of the patch-clamp technique. The major component of the total current was a voltage-dependent outward K+ current without an appreciable inward current. The amplitude of the K+ current was markedly reduced when free internal Ca2+ was buffered by addition of 10 mM EGTA. Recordings of single-channel current in excised membrane patches revealed the presence of K+ channels with large unitary conductance (200 pS in symmetrical 130 mM K+ solutions) which were also activated by depolarization when internal Ca2+ concentration was about 10(-5)-10(-6) M. At any membrane voltage these channels were closed most of the time at internal Ca2+ concentrations lower than 10(-10) M. These results demonstrate the existence of a Ca2+- and voltage-dependent K+ permeability in parathyroid cells which may participate in the unusual membrane potential changes induced by alterations of external Ca2+ and, possibly, in the regulation of parathormone secretion.
利用膜片钳技术的“全细胞”和“内面向外膜片切除”变体，研究了原代培养的分散甲状旁腺细胞的膜离子电导。总电流的主要成分是电压依赖性外向钾电流，无明显内向电流。当通过添加10 mM乙二醇双（2-氨基乙基醚）四乙酸（EGTA）缓冲游离细胞内钙离子时，钾电流的幅度显著降低。切除膜片上单通道电流的记录显示存在大单位电导（在对称的130 mM钾溶液中为200 pS）的钾通道，当细胞内钙离子浓度约为10^(-5)-10^(-6) M时，这些通道也会被去极化激活。在任何膜电压下，当细胞内钙离子浓度低于10^(-10) M时，这些通道大部分时间都是关闭的。这些结果表明甲状旁腺细胞中存在钙和电压依赖性钾通透性，这可能参与了由细胞外钙变化引起的异常膜电位变化，并可能参与甲状旁腺激素分泌的调节。
