FLUCTUATIONS IN MEMBRANE CURRENT DRIVEN BY INTRACELLULAR CALCIUM IN CARDIAC PURKINJE-FIBERS
FLUCTUATIONS IN MEMBRANE CURRENT DRIVEN BY INTRACELLULAR CALCIUM IN CARDIAC PURKINJE-FIBERS
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DOI：
10.1016/s0006-3495(82)84557-8
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发表时间：
1982-01-01
影响因子：
3.4
通讯作者：
TSIEN, RW
中科院分区：
文献类型：
--
作者：
KASS, RS;TSIEN, RW
在心脏细胞中经常观察到膜电位的自发振荡波动，但其基础仍然存在争议。暴露于洋地黄或无钾溶液可增强心脏浦肯野纤维的这种活性。在这些条件下，当膜电位被电压钳位时，持续存在的电流波动会产生电压噪声。电流信号的功率谱不是由单个时间常数分量组成的，正如从独立通道的门控所预期的那样，而是由0.5-2 Hz的谐振特性主导。可能的是，周期性来自细胞内游离Ca的振荡变化，其控制跨表面膜的离子运动。电流波动与收缩力的振荡波动强烈交叉相关，并通过去除细胞外Ca或暴露于D 600 [甲氧基维拉帕米]来抑制。用注射的EGTA [乙二醇双（β-氨基乙基醚）N，N“-四乙酸]也消除了电流波动。振荡机制可能涉及肌浆网和肌浆之间的钙（或锶）运动的周期，如先前所建议的皮肤心脏准备。在完整细胞中的实验表明，表面膜电位的变化可以调节细胞质钙振荡的频率，也许幅度以及。表面膜电位和细胞内钙库之间的双向相互作用可能是心脏、神经元和其他细胞类型的共同特征。
Spontaneous oscillatory fluctuations in membrane potential are often observed in heart cells, but their basis remains controversial. Such activity is enhanced in cardiac Purkinje fibers by exposure to digitalis or K-free solutions. Under these conditions, voltage noise is generated by current fluctuations that persist when membrane potential is voltage clamped. Power spectra of current signals are not made up of single time-constant components, as expected from gating of independent channels, but are dominated by resonant characteristics from 0.5-2 Hz. Possibly, the periodicity arises from oscillatory variations in intracellular free Ca that control ion movements across the surface membrane. The current fluctuations are strongly cross-correlated with oscillatory fluctuations in contractile force and are inhibited by removing extracellular Ca or exposure to D600 [methoxyverapamil]. Chelating intracellular Ca with injected EGTA [ethylene glycol bis(.beta.-aminoethyl ether) N,N''-tetraacetic acid] also abolishes the current fluctuations. The oscillatory mechanism may involve cycles of Ca (or Sr) movement between sarcoplasmic reticulum and myoplasm, as previously suggested for skinned cardiac preparations. Experiments in intact cells indicate that changes in surface membrane potential can modulate cytoplasmic Ca oscillations in frequency and perhaps amplitude as well. A 2-way interaction between surface membrane potential and intracellular Ca stores may be a common feature of heart, neuron and other cell types.