Changes in Membrane Properties of Chick Embryonic Hearts during Development
Changes in Membrane Properties of Chick Embryonic Hearts during Development
复制标题
鸡胚心脏发育过程中膜特性的变化
DOI：
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发表时间：
1972
期刊：
影响因子：
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通讯作者：
K. Shigenobu
中科院分区：
文献类型：
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作者：
N. Sperelakis;K. Shigenobu
鸡胚心脏（心室）的电生理特性在发育过程中发生变化;最大的变化发生在第2天和第8天之间。静息电位（Em）和峰值过冲电位（+E max）分别从第2天的-35 mv和+11 mv增加到第12-21天的-70 mv和+28 mv。动作电位时程无明显变化。动作电位的最大上升速率（+V max）从第2-3天的约20 V/sec增加到第18-21天的150 V/sec;年轻细胞的+ V max不会因施加超极化电流脉冲而大幅增加。在静息Em与log [K+]o曲线中，年轻心脏中高K+的斜率（例如30 mv/decade）低于老年心脏中获得的50-60 mv/decade，但外推的[K+]i值（125-140 mM）几乎同样高。年轻心脏的输入电阻更高（第2天为13 MΩ，第8-21天为4.5 MΩ），表明膜电阻率（Rm）更高。渗透率的比例，P Na/P K，是高的（约0.2），在年轻的心脏，由于低P K，并在个体发育过程中下降（约0.05）。年轻心脏的低K+电导（g K）解释了超极化后电位和起搏电位的发生率较高，对[K+]o升高的敏感性较低（相对于兴奋性丧失），以及时值较高。乙酰胆碱不增加年轻或老年心室肌细胞的g K。（Na+，K+）-三磷酸腺苷酶（ATP酶）活性的增加往往补偿g K的增加。年轻和老年心脏的+Emax和+Vmax均依赖于[Na+]o。然而，在年轻的心脏（2-4天）的Na+通道是缓慢的，河豚毒素（TTX）不敏感，并在较低的Em激活-失活。相比之下，老年心脏（> 8天）细胞的Na+通道是快速和TTX敏感的，但当置于培养物中时，它们恢复为慢速通道。
The electrophysiological properties of embryonic chick hearts (ventricles) change during development; the largest changes occur between days 2 and 8. Resting potential (Em) and peak overshoot potential (+E max) increase, respectively, from -35 mv and +11 mv at day 2 to -70 mv and +28 mv at days 12–21. Action potential duration does not change significantly. Maximum rate of rise of the action potential (+V max) increases from about 20 v/sec at days 2–3 to 150 v/sec at days 18–21; + V max of young cells is not greatly increased by applied hyperpolarizing current pulses. In resting Em vs. log [K+]o curves, the slope at high K+ is lower in young hearts (e.g. 30 mv/decade) than the 50–60 mv/decade obtained in old hearts, but the extrapolated [K+]i values (125–140 mM) are almost as high. Input resistance is much higher in young hearts (13 MΩ at day 2 vs. 4.5 MΩ at days 8–21), suggesting that the membrane resistivity (Rm) is higher. The ratio of permeabilities, P Na/P K, is high (about 0.2) in young hearts, due to a low P K, and decreases during ontogeny (to about 0.05). The low K+ conductance (g K) in young hearts accounts for the greater incidence of hyperpolarizing afterpotentials and pacemaker potentials, the lower sensitivity (with respect to loss of excitability) to elevation of [K+]o, and the higher chronaxie. Acetylcholine does not increase g K of young or old ventricular cells. The increase in (Na+, K+)-adenosine triphosphatase (ATPase) activity during development tends to compensate for the increase in g K. +E max and + V max are dependent on [Na+]o in both young and old hearts. However, the Na+ channels in young hearts (2–4 days) are slow, tetrodotoxin (TTX)-insensitive, and activated-inactivated at lower Em. In contrast, the Na+ channels of cells in older hearts (> 8 days) are fast and TTX-sensitive, but they revert back to slow channels when placed in culture.