Pacemaker current i(f) in adult canine cardiac ventricular myocytes.
Pacemaker current i(f) in adult canine cardiac ventricular myocytes.
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成年犬心室肌细胞中的起搏器电流 i(f)。
DOI：
10.1113/jphysiol.1995.sp020743
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发表时间：
1995
期刊：
影响因子：
--
通讯作者：
Cohen,IS
中科院分区：
文献类型：
--
作者：
Yu,H;Chang,F;Cohen,IS
1.采用全细胞膜片钳技术研究了从犬心室和犬浦肯野纤维酶促分离的单细胞，并比较了起搏电流i（f）的特性。2.与犬浦肯野细胞（-80至-130 mV）相比，犬心室肌细胞在负电位（-120至-170 mV）下发生稳态i（f）激活。3.在各种细胞外Na+（140、79或37 mM）和K+浓度（25、9或5.4 mM）下获得了恢复电位，以确定心室中i（f）的离子选择性。结果表明，该电流由钠离子和钾离子携带。4.犬心室肌和浦肯野肌细胞i（f）激活时间常数对电压的曲线均呈钟形。心室肌细胞的曲线向负方向移动约30 mV。在心室和浦肯野肌细胞中，完全激活的I-V关系在5.4 mM细胞外K+中表现出向外整流。5. Calyculin A（0.5 μ M）通过将其激活转移到心室肌细胞中更正的电位来增加i（f）。H-7（200 μ M）或H-8（100 μ M）对蛋白激酶的抑制逆转了i（f）激活的正电压偏移。当透化贴片用于全细胞记录时，也发生了calyculin A的这种作用。6.这些结果表明i（f）存在于心室肌细胞中。如果转换为更正的电位，i（f）可能在缺血诱导的室性心律失常中发挥作用。心室中i（f）的负移可能在区分心脏的非起搏区域与起搏区域方面发挥作用。
1. Single cells enzymatically isolated from canine ventricle and canine Purkinje fibres were studied with the whole‐cell patch clamp technique, and the properties of the pacemaker current i(f) compared. 2. Steady‐state i(f) activation occurred in canine ventricular myocytes at more negative potentials (‐120 to ‐170 mV) than in canine Purkinje cells (‐80 to ‐130 mV). 3. Reversal potentials were obtained in various extracellular Na+ (140, 79 or 37 mM) and K+ concentrations (25, 9 or 5.4 mM) to determine the ionic selectivity of i(f) in the ventricle. The results suggest that this current was carried by both sodium and potassium ions. 4. The plots of the time constants of i(f) activation against voltage were ‘bell shaped’ in both canine ventricular and Purkinje myocytes. The curve for the ventricular myocytes was shifted about 30 mV in the negative direction. In both ventricular and Purkinje myocytes, the fully activated I‐V relationship exhibited outward rectification in 5.4 mM extracellular K+. 5. Calyculin A (0.5 microM) increased i(f) by shifting its activation to more positive potentials in ventricular myocytes. Protein kinase inhibition by H‐7 (200 microM) or H‐8 (100 microM) reversed the positive voltage shift of i(f) activation. This effect of calyculin A also occurred when the permeabilized patch was used for whole‐cell recording. 6. These results indicate i(f) is present in ventricular myocytes. If shifted to more positive potentials i(f) could play a role in ischaemia‐induced ventricular arrhythmias. The negative shift of i(f) in the ventricle might play a role in differentiating non‐pacing regions of the heart from those regions that pace.
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