In vivo estimation of cardiac transmembrane current.
In vivo estimation of cardiac transmembrane current.
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心脏跨膜电流的体内估计。
DOI：
10.1161/01.res.72.2.424
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发表时间：
1993
影响因子：
20.1
通讯作者：
Plonsey,R
中科院分区：
文献类型：
--
作者：
Witkowski,FX;Kavanagh,KM;Penkoske,PA;Plonsey,R
心脏激活期间穿过心肌膜的离子电流在细胞外空间中具有相应的返回路径。原位激活心肌细胞期间的跨膜电流（Im）以前仅在数学模型中设想过。我们开发了一种非常简单的体内技术，该技术结合了具有细胞尺寸的电极阵列，可以连续估计心脏 Ims 的细胞外对应物。对均匀平面波传播进行数学建模，以阐明该方法固有的生物物理基础和基本假设。实验验证了包含中心距为 210 微米的 75 微米直径银电极的五元件电极阵列，可为心肌激活的电压梯度测定提供空间上足够的样本。使用中心间距为 65 微米、直径为 25 微米的电极也获得了类似的结果。 Im 的估计值是从测量的间隙电位的电压梯度幅度的导数获得的。在体内测量到 37 摄氏度下正常 Na+ 通道激活产生的 Im 的内向分量持续时间小于 1 毫秒，与先前已知的电压钳和模拟结果一致。静脉内KCl推注用于证明体内Na(+)介导的Im电压依赖性抑制，最终导致Na(+)介导或Ca(2+)介导的激活严重抑制。使用这种技术可以在体内记录正常的Na(+)-、抑制的Na(+)-和可能的Ca(2+)介导的电流。
The ionic currents that cross the myocardial membrane during cardiac activation have a corresponding return path in the extracellular space. The transmembrane current (Im) during activation of cardiac cells in situ has previously been envisioned only in mathematical models. We have developed a remarkably simple in vivo technique that incorporates an electrode array with cellular dimensions to continuously estimate the extracellular counterparts of cardiac Ims. Mathematical modeling was performed for uniform plane wave propagation to clarify the biophysical basis and underlying assumptions inherent in this approach. Five-element electrode arrays incorporating 75-microns-diameter silver electrodes with center-to-center distances of 210 microns were experimentally verified to provide spatially sufficient samples for voltage gradient determinations of myocardial activation. Similar results were obtained with 25-microns-diameter electrodes at a center-to-center spacing of 65 microns. An estimate of Im was obtained from the derivative of the magnitude of the voltage gradient of the measured interstitial potentials. The inward component of Im generated by normal Na+ channel activation at 37 degrees C was measured in vivo to be less than 1 msec in duration, consistent with previously known voltage-clamp and simulation results. Intravenous KCl bolus injection was used to demonstrate the voltage-dependent depression of Na(+)-mediated Im in vivo, culminating in either severely depressed Na(+)-mediated or Ca(2+)-mediated activations. Normal Na(+)-, depressed Na(+)-, and possibly Ca(2+)-mediated currents can be recorded in vivo using this technique.