Ca2+-activated K+ channels contribute to the resting potential of vascular myocytes. Ca2+-sensitivity is increased by intracellular Mg2+-ions
Ca2+-activated K+ channels contribute to the resting potential of vascular myocytes. Ca2+-sensitivity is increased by intracellular Mg2+-ions
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Ca2 激活的 K 通道有助于血管肌细胞的静息电位。
DOI：
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发表时间：
2004
期刊：
影响因子：
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通讯作者：
G. Isenberg
中科院分区：
文献类型：
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作者：
U. Trieschmann;G. Isenberg
结果和讨论在这些“生理条件”下，静息电位（Vm）自发地在-55 mV和-70 mV之间波动（图1A）。在电压钳条件下，全细胞电流（-55 mV）显示约50 ms短暂的外向电流，幅度范围在1和2 pA之间。在其振幅和时间过程中，电流类似于通过单个Ca 2+激活的最大通道（iKCa）的电流，如从具有缓冲[Ca 2 +]c的无细胞贴片记录的（例如Magleby和Palotta 1983）。钾通道阻断剂四乙铵（TEA）可逆地抑制电流和波动的Vm。尽管图1中提出了iKC a对Vm有贡献的假设，但尚未通过单通道分析得到证实。通常，iKCa已在正电位和微摩尔的钙离子浓度[Ca 2 +] c下进行了分析（两种干预均增加了开放概率Po），并且将数据外推至静息电位仅表明Po“几乎为零”。在这里，我们试图量化这些非常低的Po值在负Vm和亚微摩尔[Ca 2 +] c。此外，我们将表明，PO是显着较大时，胞浆镁离子的存在。从面向对称的150 mM KCl溶液（10 mM Tris/HEPES，pH 7.4）的由内而外的贴片记录单通道电流，其中Ca 2+激活的maxi-K+通道具有172 ± 6.8 pS的单通道电导（n=6）。用10 mM Ca-EGTA补充面向膜的胞质位点的溶液，将其调节至所需的[Ca 2 +] c值。在Vm=-40 mV和100 nM [Ca ~（2+）] c时，N. PO低至
Results and discussion In these "physiological conditions", the resting potential (Vm) spontaneously fluctuates between -55 and -70 mV (Fig. 1A). Under voltage-clamp conditions the whole-cell current (-55 mV) shows about 50 ms brief shots of outward current, the amplitudes ranging between 1 and 2 pA. In its ampitude and time course, the current resembles the current through single Ca2+-activated maxi-channels (iKCa), as recorded from cell-free patches with buffered [Ca2+]c (e.g. Magleby and Palotta 1983). The K+ channel blocker tetraethylammonium (TEA) reversibly inhibits currents and fluctuations of Vm. Although suggested by Fig. 1, the hypothesis of iKC a contributing to Vm has not yet been proven by single channel analysis. Usually iKCa has been analysed at positive potentials and micromolar cystolic calcium concentrations [Ca2+] c (both interventions increase the open probability, Po), and extrapolation of data to the resting potential only suggests that Po is "almost zero". Here we are trying to quantify these very low Po values at negative Vm and submicromolar [Ca2+] c. In addition, we will show that Po is significantly larger when cytosolic Mg2+-ions are present. Single channel currents were recorded from inside out patches facing symmetrical 150 mM KC1 solutions (10 mM Tris/HEPES, pH 7.4), where the Ca2+-activated maxi-K+ channel has a single channel conductance of 172 +_6.8 pS (n=6). The solution facing the cytosolic site of the membrane was complemented with 10 mM Ca-EGTA which was adjusted to the desired [Ca2+]c-values. At Vm=-40 mV and 100 nM [Ca2+] c, N.P o was as low as
Mg2 对哺乳动物骨骼肌 Ca2 激活 K 通道门控的变构作用。
DOI：
10.1242/jeb.124.1.5
发表时间：
1986
期刊：
The Journal of experimental biology
影响因子：
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作者：
Golowasch,J;Kirkwood,A;Miller,C
通讯作者：
Miller,C