SENSITIVITY TO H, LI AND MG IONS OF SLOW INWARD SODIUM CURRENT IN FROG ATRIAL FIBERS
SENSITIVITY TO H, LI AND MG IONS OF SLOW INWARD SODIUM CURRENT IN FROG ATRIAL FIBERS
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DOI：
10.1016/0022-2828(75)90140-6
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发表时间：
1975-01-01
影响因子：
5
通讯作者：
VASSAS, JM
中科院分区：
文献类型：
--
作者：
CHESNAIS, JM;CORABOEUF, E;VASSAS, JM
在电压钳条件下测量了蛙心房肌纤维的膜电流（双蔗糖间隙法）;（i）增加[H]o，（ii）用Li完全取代外部Na，（iii）加入Mg对这些电流的影响进行了研究。（pH 5.6）与正常林格氏液（pH 7.8）中的值相比;在Li-Ringer中无变化，在Mg-Ringer中增加。缓慢内向钙电流（在TTX，无钠溶液中测量）在酸林格氏液和镁林格氏液中降低，在锂林格氏液中不变。影响快速钠电流和钙电流的增加或减少从未超过40%，并且通常较小。另一方面，慢内向钠电流（在TTX，无钙溶液中测得）在所研究的三种条件下均被抑制，本文讨论了钠离子对所谓正常Ringer，即无镁Ringer中慢内向电流的参与。间接证据有利于这种参与。在Ringer液中加入Mg 1.8mM后，慢内向电流仅由Ca离子携带。由于缓慢的内向钠电流显着增加，在镁无钙林格氏，它的结论是，缓慢的钠电导控制的Ca和Mg离子，除了强烈的pH值依赖性。这也表明，Na和Ca离子参与慢内向电流不一定通过同一个通道。
Membrane currents have beenmeasured in frog atrial fibres under voltage clamp conditions (double sucrose gap method); the effects on these currents of (i) an increase in [H]o, (ii) the complete substitution of external Na by Li, (iii) the addition of Mg have been studied.The TTX-sensitive rapid inward current is decreased in acid Ringer (pH 5.6) as compared to values in normal Ringer (pH 7.8); it is unchanged in Li-Ringer and increased in Mg-Ringer. The slow inward calcium current (measured in TTX, Na-free solution) is decreased in acid Ringer and in Mg-Ringer and is unchanged in Li-Ringer. Increases or decreases affecting the rapid sodium current and the calcium current never exceed 40% and are generally smaller. On the other hand the slow inward sodium current (measured in TTX, Ca-free solution) is always suppressed in the three conditions studied.The participation of Na ions to the slow inward current in so called normal Ringer, that is in Mg-free Ringer is discussed. Indirect evidences are presented in favour of such a participation. After addition of Mg 1.8 mmto Ringer the slow inward current is carried only by Ca ions. Since the slow inward sodium current increases markedly in Mg-free Ca-free Ringer, it is concluded that the slow Na conductance is controlled by both Ca and Mg ions in addition to being strongly pH-dependent. It is also suggested that Na and Ca ions participating to the slow inward current do not penetrate necessarily through the same channel.