新型小鼠肠道平滑肌细胞制剂中外向整流钾通道的特性分析。

Characterization of the outward rectifying potassium channel in a novel mouse intestinal smooth muscle cell preparation.

作者信息

Molleman A, Thuneberg L, Huizinga J D

机构信息

Department of Biomedical Sciences, McMaster University, Hamilton, Ontario, Canada.

出版信息

J Physiol. 1993 Oct;470:211-29. doi: 10.1113/jphysiol.1993.sp019855.

DOI:10.1113/jphysiol.1993.sp019855

PMID:8308726

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1143914/

Abstract

The outward rectifying K+ conductance and underlying single channel behaviour in mouse small intestine (MSI) smooth muscle cells was studied using microelectrode impalement and the patch clamp technique. 2. At 37 degrees C, smooth muscle cells in MSI explants had a resting membrane potential around -65 mV and showed spontaneous electrical and mechanical activity. 3. Under whole-cell voltage clamp, depolarization of smooth muscle cells in the explants evoked a methoxyverapamil (D600)-sensitive, partially inactivating inward current and a non-inactivating outward current. The outward current was also observed in enzymatically dispersed cells from neonatal mouse small intestine. 4. The reversal potential of the outward current as established in tail current experiments was -70.2 mV. Tail currents could be fitted with a single exponential, suggesting the participation of only one population of channels. 5. The outward current was sensitive to 4-aminopyridine (10(-4) M), Ba2+ (1 mM) and to the presence of Cs+ in the pipette, but not to D600 (10(-6) M), or the presence of ATP (1 mM) in the pipette. 6. In the cell-attached patch configuration, a unitary outward current was observed that showed increased activity upon depolarization of the patch. The current-voltage relationship was close to linear with a slope conductance of 186 pS. 7. With normal K+ (6 mM) in the pipette, the extrapolated reversal potential for the unitary current was around -75 mV, while with high K+ (120 mM) the reversal potential was close to 0 mV. 8. Averaging single channel traces recorded under a depolarizing pulse protocol resulted in a trace with similar time characteristics as the outward current observed in the whole-cell configuration. 9. The burst behaviour of the channel was described by a simple model consisting of two closed states, Cf (intraburst closed state) and Cs (interburst closed state) and an open state (O). The rate constants in the model showed differential sensitivity to potential changes, channel blockade by Ba2+ and equimolar K+ conditions. 10. It was concluded that the outward rectifying potassium current in MSI smooth muscle cells is mediated by a 186 pS bursting channel. Voltage dependency and Ba2+ blockade are mainly reflected by changes in the transition rate from the open channel state to the interburst closed state.

摘要

运用微电极刺入法和膜片钳技术研究了小鼠小肠（MSI）平滑肌细胞外向整流钾离子电导及相关单通道行为。2. 在37℃时，MSI外植体中的平滑肌细胞静息膜电位约为 -65 mV，并呈现出自发性电活动和机械活动。3. 在全细胞电压钳制下，外植体中平滑肌细胞的去极化引发了一种对甲氧基维拉帕米（D600）敏感、部分失活的内向电流以及一种非失活的外向电流。在新生小鼠小肠经酶分散的细胞中也观察到了这种外向电流。4. 尾电流实验所确定的外向电流反转电位为 -70.2 mV。尾电流可用单一指数函数拟合，表明仅有一种通道群体参与其中。5. 外向电流对4-氨基吡啶（10⁻⁴ M）、Ba²⁺（1 mM）以及移液管中Cs⁺的存在敏感，但对D600（10⁻⁶ M）或移液管中ATP（1 mM）的存在不敏感。6. 在细胞贴附膜片配置中，观察到一种单一外向电流，其在膜片去极化时活性增加。电流-电压关系接近线性，斜率电导为186 pS。7. 当移液管中为正常钾离子浓度（6 mM）时，单一电流的外推反转电位约为 -75 mV，而当钾离子浓度较高（120 mM）时，反转电位接近0 mV。8. 对去极化脉冲协议下记录的单通道轨迹进行平均，得到的轨迹与全细胞配置中观察到的外向电流具有相似的时间特征。9. 通道的爆发行为由一个简单模型描述，该模型包含两个关闭状态，即Cf（爆发内关闭状态）和Cs（爆发间关闭状态）以及一个开放状态（O）。模型中的速率常数对电位变化、Ba²⁺引起的通道阻断以及等摩尔钾离子条件表现出不同的敏感性。10. 得出结论，MSI平滑肌细胞中的外向整流钾电流由一个186 pS的爆发通道介导。电压依赖性和Ba²⁺阻断主要通过从开放通道状态到爆发间关闭状态的转变速率变化来体现。