Farncombe Family Digestive Health Research Institute, McMaster University, Hamilton, Ontario, Canada.
Am J Physiol Gastrointest Liver Physiol. 2010 Mar;298(3):G456-66. doi: 10.1152/ajpgi.00340.2009. Epub 2010 Jan 7.
Interstitial cells of Cajal (ICC) are the pacemakers of the gut, initiating slow-wave activity. Several ion channels have been identified that contribute to the depolarization phase of the slow wave. Our aim was to contribute to knowledge about the identity and role of ICC potassium channels in pacemaking. Here we describe a transient outward potassium current in cell-attached patches of ICC. This current was activated almost instantaneously at potentials positive of the resting membrane potential and inactivated as a single exponential or biexponential with time constants that varied widely from patch to patch. Averaged traces gave a biexponential inactivation with time constants of approximately 40 and approximately 500 ms, with no clear voltage dependence. Analysis of single-channel openings and closings indicated a channel conductance of 5 pS and permeability sequence of K(+) (111) > Na(+) (1) > N-methyl-d-glucamine(+) (0.11). The current was completely blocked by 20 microM clotrimazole but was unaffected by 20 microM ketoconazole, 10 microM E4031, or 20 microM clofilium; 5 mM 4-aminopyridine slowed the activation of the current. The transient outward current may be important in moderating the upstroke of the pacemaker potential.
Cajal 间质细胞（ICC）是肠道的起搏器，引发慢波活动。已经鉴定出几种离子通道，它们有助于慢波的去极化相。我们的目的是为 ICC 钾通道在起搏中的身份和作用提供知识。在这里，我们描述了细胞贴附斑片上 ICC 中的瞬时外向钾电流。该电流在膜电位正于静息膜电位的电位处几乎瞬间激活，并以时间常数随时间呈单指数或双指数衰减而失活，时间常数在各斑片之间变化很大。平均迹线显示双指数失活的时间常数约为 40 和 500 ms，没有明显的电压依赖性。单通道开放和关闭的分析表明通道电导为 5 pS，通透性序列为 K(+)（111）> Na(+)（1）> N-甲基-d-葡萄糖胺（0.11）。电流完全被 20 μM 克霉唑阻断，但不受 20 μM 酮康唑、10 μM E4031 或 20 μM 氯非利姆阻断；5 mM 4-氨基吡啶减缓电流的激活。瞬时外向电流可能在调节起搏电位的上升中很重要。
