Heppner T J, Bonev A D, Nelson M T
Department of Pharmacology, University of Vermont College of Medicine, University of Vermont Medical Research Facility, Colchester 05446, USA.
Am J Physiol. 1997 Jul;273(1 Pt 1):C110-7. doi: 10.1152/ajpcell.1997.273.1.C110.
The goal of this study was to examine the role of large conductance Ca(2+)-activated K+ channels in the regulation of cell excitability in urinary bladder smooth muscle from the guinea pig. Ca(2+)-activated K+ channels were studied with single-channel recording techniques and found to be intracellular Ca2+ and voltage dependent and sensitive to external tetraethylammonium and blocked by nanomolar concentrations of iberiotoxin (apparent dissociation constant of 4 nM). Spontaneous action potentials recorded from intact tissue strips depended on external Ca2+ and were inhibited by Ca2+ channel blockers. Iberiotoxin (100 nM) significantly altered the configuration of the action potential by increasing the duration and peak amplitude of the action potential and decreasing the rate of decay. Iberiotoxin also increased the action potential frequency from 0.11 to 0.29 Hz. This study suggests that Ca(2+)-activated K+ channels play a significant role in the repolarization of the action potential and in the maintenance of the resting membrane potential of the urinary bladder smooth muscle.
本研究的目的是探讨大电导钙激活钾通道在豚鼠膀胱平滑肌细胞兴奋性调节中的作用。采用单通道记录技术对钙激活钾通道进行研究，发现其依赖于细胞内钙和电压，对细胞外四乙铵敏感，且可被纳摩尔浓度的iberiotoxin阻断（表观解离常数为4 nM）。从完整组织条带记录到的自发动作电位依赖于细胞外钙，并被钙通道阻滞剂抑制。Iberiotoxin（100 nM）通过增加动作电位的持续时间和峰值幅度以及降低衰减速率，显著改变了动作电位的形态。Iberiotoxin还将动作电位频率从0.11 Hz提高到0.29 Hz。本研究表明，钙激活钾通道在动作电位复极化和膀胱平滑肌静息膜电位的维持中起重要作用。
