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Voltage-dependent modulation of L-type calcium currents by intracellular magnesium in rat ventricular myocytes

机译：大鼠心室肌细胞中细胞内镁对L型钙电流的电压依赖性调节

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摘要

Effects of changing cytosolic free Mg2+ concentration on L-type Ca2+ (I ) and Ba2+Ca currents (IBa) were investigated in rat ventricular myocytes voltage-clamped with pipettes containing 0.2 mM or 1.8 mM [Mg2+] ([Mg2+]p) buffered with 30 mM citrate acid and 10 mM ATP. Increasing [Mg2+]p from 0.2 mM to 1.8 mM reduced current amplitude and accelerated its decay under a variety of experimental conditions. To investigate the mechanism for these effects, steady-state and instantaneous current-voltage relationships were studied with two-pulse and tail current (IT) protocols, respectively. Increasing [Mg2+]p shifted the VM for half inactivation by -20 mV but dramatically decreased ICa amplitude at all potentials tested, consistent with a change in gating kinetics that decreases channel availability. This conclusion was supported by analysis of IT amplitude, but these latter experiments also suggested that, in the millimolar concentration range, [Mg2+] might also inhibit permeation through open Ca2+p channels at positive VM.
机译：改变胞质游离Mg 2 + 浓度对L型Ca 2 + （I）和Ba 2 + Ca电流（IBa）的影响为在装有0.2 mM或1.8 mM [Mg 2 + ]（[Mg 2 + ] p）并用30 mM柠檬酸缓冲的移液器中电压钳制的大鼠心室肌细胞中进行了研究10 mM ATP。在各种实验条件下，将[Mg 2 + ] p从0.2 mM增加到1.8 mM可以减小电流幅度并加速其衰减。为了研究这些影响的机制，分别使用两脉冲和尾电流（IT）协议研究了稳态和瞬时电流-电压关系。 [Mg 2 + ] p的增加使半灭活的VM移动了-20 mV，但在所有测试电势下ICa振幅均显着降低，这与门控动力学的变化相一致，从而降低了通道的可用性。 IT幅值分析支持了这一结论，但后来的这些实验也表明，在毫摩尔浓度范围内，[Mg 2 + ]可能还通过开放的Ca 2+抑制渗透。在虚拟机正时使用sup> p通道。

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