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Voltage dependency of intracellular Na^+ activity in diseased human atrial muscles.

患病人类心房肌中细胞内Na 2 活性的电压依赖性。

基本信息

批准号：
05670639
负责人：
IMANISHI Sunao
金额：
$ 1.34万
依托单位：
Kanazawa Medical University
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (C)
财政年份：
1993
资助国家：
日本
起止时间：
1993 至 1995
项目状态：
已结题

项目摘要

Diseased human atrial fibers are characterized by low levels of resting membrane potential(Vm). As a mechanism involved in such depolarization we have investigated the possibility of an increase in Na^<<minus-plus>> permeability to the resting membrane (P_<Na>). With increased resting P_<Na>, the intracellular Na^+ activity (a_<Na>) should be expected to increase. In the present experiment both a_<Na> and Vm were recorded simultaneously using double-barreled Na^+-selective microelectrodes. The Vm averaged -44.1<plus-minus>5.0mV (mean<plus-minus>SD,n=9) as be expected and the a_<Na>,6.9<plus-minus>1.7mM under normal Tyrode solution containing 5.4mM-K^+. The a_<Na> value was within physiological levels, suggesting that the low Vm is not due to increased P_<Na>. But the partial depolarization as seen in diseased human preparations may possibly accelerate extrusion of intracellular Na^+, with consequent decreases in a_<Na>. So we tried to measure a_<Na> under the condition of membrane voltage clamp using single sucrose gap method. The a_<Na> value obtained was 7.8mM at the Vm of about-60mV and 8.6mM at about -80mV,though the voltage control was incomplete. Thus, the low Vm observed in diseased human atrial muscle may not be attributed to increased P_<Na> of the resting membrane. Further studies into mechanisms underlying the low Vm of the human specimen are necessary.

病变的人心房纤维的特点是静息膜电位(Vm)低。作为这种去极化的一种机制，我们研究了Na++对静息膜(P&lt；Na&gt；)通透性增加的可能性。随着静息P&lt；Na&gt；的增加，细胞内Na+活性(a&lt；Na&gt；)预计也会增加。在本实验中，用双管Na~+选择性微电极同时记录a&lt；Na&gt；和Vm。在含5.4mM-K^+的正常泰氏液中，Vm平均值为-44.1&lt；正负-5.0 mV(平均值正负SD，n=9)，a_&lt；Na&>，正负1.7 mm。A&lt；Na&gt；值在生理水平内，提示低Vm不是P&lt；Na&gt；升高所致。但在患病的人体制剂中看到的部分去极化可能会加速细胞内Na+的排出，从而导致a&lt；Na&gt；下降。因此，我们尝试在膜电压钳条件下，用单蔗糖间隙法来测量a&lt；Na&gt；。在-60 mV左右的Vm和-80 mV左右的电压下，a_t；Na&gt；值分别为7.8 mm和8.6 mm，但电压控制不完善。因此，在患病的人心房肌中观察到的低Vm可能不是由于静息膜P&lt；Na&Gt；增加所致。进一步研究人体标本低Vm的机制是必要的。