Vassilev P M, Kanazirska M V, Quinn S J, Tillotson D L, Williams G H
Department of Medicine, Brigham and Women's Hospital, Boston, Massachusetts.
Am J Physiol. 1992 Oct;263(4 Pt 1):E752-9. doi: 10.1152/ajpendo.1992.263.4.E752.
Four distinct types of K+ channels were identified in rat and bovine adrenal zona glomerulosa (ZG) cells and characterized using single-channel recording techniques. Inward rectifier channels were the most frequently observed K+ channel types in the membrane patches of both rat and bovine ZG cells. The slope conductance of the inward current was 42 pS with an extracellular K+ concentration of 150 mM. The probability of the open state of these channels increased with depolarization. With the use of inside-out membrane patches with symmetric 150 mM K+ solutions, the rectifying behavior was found to require Mg2+ on the intracellular side of the membrane. Delayed rectifier K+ channels with conductances of 27 and 48 pS were found with rat ZG cells. These channels persisted with prolonged positive voltage steps and showed long mean open times with increasing depolarization. Transient outward currents with a conductance of 28 pS were observed only in bovine ZG cells. These channels showed substantial inactivation during positive voltage steps of 250 ms duration. Ca(2+)-activated K+ channels with a large conductance (228 pS) were identified in rat and bovine ZG cells. These different classes of K+ channels may be important for the control of resting membrane potential and the generation of action potentials, thus participating in the regulation of Ca2+ influx and aldosterone secretion in ZG cells.
在大鼠和牛的肾上腺球状带（ZG）细胞中鉴定出四种不同类型的钾通道，并使用单通道记录技术对其进行了表征。内向整流通道是在大鼠和牛ZG细胞膜片上最常观察到的钾通道类型。当细胞外钾离子浓度为150 mM时，内向电流的斜率电导为42 pS。这些通道的开放状态概率随去极化而增加。在使用对称150 mM钾溶液的内向外翻膜片中，发现整流行为需要膜内侧的镁离子。在大鼠ZG细胞中发现了电导分别为27和48 pS的延迟整流钾通道。这些通道在长时间的正电压阶跃下持续存在，并且随着去极化增加显示出较长的平均开放时间。仅在牛ZG细胞中观察到电导为28 pS的瞬时外向电流。在持续250 ms的正电压阶跃期间，这些通道显示出明显的失活。在大鼠和牛ZG细胞中鉴定出大电导（228 pS）的钙激活钾通道。这些不同类型的钾通道可能对静息膜电位的控制和动作电位的产生很重要，从而参与ZG细胞中钙离子内流和醛固酮分泌的调节。
