Permeation of divalent cations through the Ca2+ channel of rabbit portal vein myocytes.
Permeation of divalent cations through the Ca2+ channel of rabbit portal vein myocytes.
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二价阳离子通过兔门静脉肌细胞 Ca2 通道的渗透。
DOI：
10.1152/ajpheart.1992.262.2.h326
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Morad,M
中科院分区：
文献类型：
--
作者：
Katzka,DA;Cox,R;Davidoff,AJ;Morad,M
采用全细胞钳法检测兔门静脉肌细胞Ca2+通道的二价选择性。发现二价离子渗透具有浓度依赖性选择性，当 Ca2+ 被 Ba2+ 或 Sr2+ 取代时，最大电流的顺序为 Ca2+ = Ba2+ 在 2 mM 时大于 Sr2+，Ba2+ 在 5-10 mM 时大于 Sr2+ 大于或等于 Ca2+。检查了微摩尔浓度的“污染物”Ca2+ 阻断Ca2+通道的可能性，作为二价选择性顺序变化的决定因素。乙二醇-双(β-氨基乙基醚)-N,N,N',N'-四乙酸 (500 µM) 显着增加含有 5 mM Ba2+ 或 Sr2+ 的溶液中的最大 Ba2+ 电流 (IBa) 或 ISr。此外，在细胞外 Ba2+ 浓度为 5 mM 时，添加 10、20、50 和 100 microM Ca2+ 分别导致 IBa 降低 6%、14%、22% 和 33%。这些结果表明，门静脉Ca2+通道对Ca2+的选择性比Ba2+和Sr2+高三个数量级，因此微摩尔Ca2+可以阻止其他二价物通过通道的渗透。
The divalent selectivity of the Ca2+ channel in the rabbit portal vein myocyte was examined by the whole cell clamp method. A concentration-dependent selectivity of divalent ion permeation was found such that when Ca2+ was replaced by Ba2+ or Sr2+, the order of maximum current was Ca2+ = Ba2+ greater than Sr2+ at 2 mM and Ba2+ greater than Sr2+ greater than or equal to Ca2+ at 5-10 mM. The possibility of block of the Ca2+ channel by micromolar concentrations of "contaminant" Ca2+ as a determinant of change in the order of selectivity of divalents was examined. Ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (500 microM) significantly increased maximum Ba2+ current (IBa) or ISr in solution containing 5 mM Ba2+ or Sr2+. Furthermore, at 5 mM extracellular Ba2+ concentration, addition of 10, 20, 50, and 100 microM Ca2+ caused a 6, 14, 22, and 33% decrease in IBa, respectively. These results suggest that the portal vein Ca2+ channel has three orders of magnitude higher selectivity for Ca2+ over Ba2+ and Sr2+ such that micromolar Ca2+ may block permeation of other divalents through the channel.