Cation‐dependent gating of the hyperpolarization‐activated cation current in the rabbit sino‐atrial node cells.
Cation‐dependent gating of the hyperpolarization‐activated cation current in the rabbit sino‐atrial node cells.
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兔窦房结细胞中超极化激活的阳离子电流的阳离子依赖性门控。
DOI：
10.1113/jphysiol.1994.sp020204
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
A. Noma
中科院分区：
文献类型：
--
作者：
F. Maruoka;Y. Nakashima;M. Takano;K. Ono;A. Noma
1.研究了兔窦房结单个起搏细胞超极化激活阳离子电流(I(F)或Ih)的门控特性。2.记录了不同阳离子存在下的全细胞i(F)。用K+取代外加Na+时，内向I(F)增大，而在Li+或Rb+溶液中内向I(F)减小。在Tris+和Cs+溶液中，向内的I(F)可以忽略不计。去极化时记录到的外向尾电流在Li+溶液中最大，在Na+、Tris+和K+溶液中较小。在Rb+和Cs+溶液中，只记录到一个很小的尾流。3.外向尾流在Na+溶液中有一个“肩”，用Li+取代Na+后，这个“肩”电流明显延迟。在K+溶液中，尾流衰减较快，未记录到明显的肩峰。尾部电流在富Li(+)和0 mM K+溶液中最慢，在0~3 mM范围内随K+浓度的增加而逐渐加快。在30 mm[K+]o处的尾流只显示了一个小肩膀。对于单价阳离子，建议了一个共同的结合部位来调节I(F)的失活。4.在Na~+和Li~+溶液中，当I(F)被更大程度地激活时，无论是延长超极化持续时间还是增加前一个超极化幅度，I(F)尾部的肩部都变得更加明显。5.先将膜超极化至-110 mV激活I(F)，然后去极化去激活I(F)。在-50 mV处，内向尾流呈单指数衰减。在更正的电位下，外向尾流的肩部变得更加明显，最终衰减率增加。6.I(F)激活的时间过程可用两个指数函数之和很好地拟合。外加阳离子(Na+、K+或Li+)对两组分的时间常数均无影响。当外加Na+被Li+取代时，准稳态活化被保守。7.在I(F)通道的顺序状态模型中假设有两个闭合状态和三个开放状态。通过假设失活速率被选择性地调制，很好地模拟了阳离子效应。计算了自发动作电位过程中的I(F)流量。I(F)的激活始于复极至最大舒张期电位，在舒张期中期达到最大值。其峰值为舒张期净内向电流的14%。
1. The gating properties of the hyperpolarization‐activated cation current (I(f) or Ih) were investigated in single pacemaker cells dissociated from the rabbit sino‐atrial node. 2. The whole‐cell I(f) was recorded in the presence of different external cations. The inward I(f) was increased when external Na+ was replaced with K+, and was decreased in Li+ or Rb+ solution. In Tris+ and Cs+ solutions, the inward I(f) was negligible. The outward tail current recorded upon depolarization was largest in Li+ solution and smaller in a sequence of Na+, Tris+ and K+ solutions. In Rb+ and Cs+ solutions, only a small tail current was recorded. 3. The outward tail current had a ‘shoulder’ in Na+ solution, which was much delayed by replacing Na+ with Li+. In K+ solution, the decay of the tail current was much faster, and no obvious shoulder was recorded. The tail current was slowest in Li(+)‐rich and 0 mM K+ solution, and was progressively accelerated by adding K+ over the range from 0 to 3 mM. The tail current at 30 mM [K+]o showed only a small shoulder. A common binding site to modulate the I(f) deactivation was suggested for monovalent cations. 4. The shoulder of the I(f) tail became more evident as I(f) was activated to a larger extent either by prolonging the duration or by increasing the amplitude of the preceding hyperpolarization in both Na+ and Li+ solutions. 5. The I(f) was first activated by hyperpolarizing the membrane to ‐110 mV, and then deactivated by depolarization. The inward tail current at ‐50 mV showed a single exponential decay. At more positive potentials, the shoulder of the outward tail currents became more evident and the rate of the final decay was increased. 6. The time course of I(f) activation was well fitted with the sum of two exponential functions. Time constants of both components were not affected by the external cation (Na+, K+ or Li+) replacement. Likewise, the quasi‐steady state activation was conserved when external Na+ was replaced with Li+. 7. Two closed and three open states were assumed in a sequential state model of the I(f) channel. The cation effects were well simulated by assuming that the deactivation rate was selectively modulated. The flow of I(f) during the spontaneous action potential was calculated. The activation of I(f) started on repolarization to the maximum diastolic potential and reached a maximum in the middle of the diastolic period. Its peak amplitude was 14% of the net inward current during the diastolic period.
窦房结细胞切除膜中心脏起搏器电流 If 的调节。
DOI：
10.1152/ajpheart.1990.258.6.h1947
发表时间：
1990
期刊：
The American journal of physiology
影响因子：
--
作者：
Yatani,A;Brown,AM
通讯作者：
Brown,AM