Voltage-dependent block by internal spermine of the murine inwardly rectifying K+ channel, Kir2.1, with asymmetrical K+ concentrations.
Voltage-dependent block by internal spermine of the murine inwardly rectifying K+ channel, Kir2.1, with asymmetrical K+ concentrations.
复制标题
小鼠内向整流 K 通道 Kir2.1 的内部精胺具有电压依赖性阻断，且 K 浓度不对称。
DOI：
10.1113/jphysiol.2010.194480
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
Okada M
中科院分区：
文献类型：
--
作者：
Matsuda H;Hayashi M;Okada M
在不对称K+浓度（外部K+浓度为30 mm，内部K+浓度为150 min）下，研究了内部精胺对通过强烈向内整流的K+通道（Kir2.1）向外单通道电流的影响。单通道的电流-电压（I-V）关系几乎是线性的，在−37±3 mV （VR;n= 19）时反向。通道电导为26.3±1.3 pS （n= 24）。打开时间和关闭时间直方图用单一指数函数拟合。内部精胺浓度为1-100 nm时，以浓度依赖的方式减少了向外电流的打开时间，并产生阻塞状态。在没有和存在内部精胺的情况下，向外电流的稳态打开概率随着去极化的增大而减小。不对称K+和对称K+ （150 mm外部和内部K+）浓度与驱动力（V - VR）的稳态开放概率与不存在精胺时较小的去极化和存在精胺时较大的去极化和较高的精胺浓度相吻合。在相同的驱动力下，外源K+为30 mm、150 mm时，阻滞速率常数和缓阻速率相似。外部K+为30 mm时的解离常数-膜电位关系与外部K+为150 mm时的解离常数-膜电位关系向负方向偏移了36 mV。这些结果表明，当K+的平衡势因外部K+的改变而改变时，阻滞动力学依赖于驱动力来产生驱动力依赖的内向整流，阻滞离子通过或倒伏的能垒和阱并不稳定，而是受到外部K+离子的影响。
Effects of internal spermine on outward single‐channel currents through a strongly inwardly rectifying K+channel (Kir2.1) were studied at asymmetrical K+concentrations (30 mmexternal and 150 mminternal K+). The current–voltage (I–V) relation for the single channel was almost linear and reversed at −37 ± 3 mV (VR;n= 19). The channel conductance was 26.3 ± 1.3 pS (n= 24). The open‐time and closed‐time histograms were fitted with a single exponential function. Internal spermine at a concentration of 1–100 nmreduced the open time of the outward currents in a concentration‐dependent manner and produced a blocked state. The steady‐state open probability of the outward current decreased with larger depolarizations in both the absence and presence of internal spermine. The steady‐state open probability with asymmetrical K+and symmetrical (150 mmexternal and internal K+) concentrations plotted against driving force (V−VR) coincided with smaller depolarizations in the absence of spermine and larger depolarizations and higher spermine concentrations in the presence of spermine. The blocking rate constants and unblock rates with 30 mmand 150 mmexternal K+were similar at the same driving force. The dissociation constant–membrane potential relation for 30 mmexternal K+was shifted in the negative direction from that for 150 mmexternal K+by 36 mV. These results suggested that the blocking kinetics depends on driving force to produce driving force‐dependent inward rectification when the equilibrium potential for K+is altered by changing external K+and that the energy barriers and wells for blocking ions from passing or lodging are not stable but affected by external K+ions.