The Gating and conductance properties of CaV3.2 low-voltage-activated T-type calcium channels
The Gating and conductance properties of CaV3.2 low-voltage-activated T-type calcium channels
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DOI：
10.2170/jjphysiol.53.165
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发表时间：
2003-06-01
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影响因子：
--
通讯作者：
Ono, K
中科院分区：
文献类型：
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作者：
Kaku, T;Lee, TS;Ono, K
钙通道对心肌细胞的兴奋-收缩耦合和起搏器电位至关重要。尽管l型Ca2+通道已被广泛研究，但t型通道在心肌细胞中的特征却很差。本文描述了在哺乳动物细胞系中表达的重组Ca(V)3.2 t型Ca2+通道的功能特性。t型Ca2+电流对去极化的响应表现为快速激活和失活阶段，在1 ~ 10 mM外Ca2+中，在-60 ~ -40 mV电压范围内呈现窗口电流。钡（Ba2+）和锶（Sr2+）以相似的活化动力学渗透通道。另一方面，一价阳离子Li+和Na+比l型Ca2+通道更容易渗透t型Ca2+通道。Ca(V)3.2 t型Ca2+通道在一价和二价阳离子间的通透顺序为Ba2+>Mn2+>Ca2+>Sr2+>Li+>Na+，通透顺序为1.39:1.25:1.00:0.95:0.55:0.29。阳离子相对于钙的离子电导顺序为Sr2+>Ba2+>Ca2+>Li+>Mn2+>Na+，电导比为1.39:1.21:1.00:0.40:0.23:0.11。锰（Mn2+）的渗透分布是复杂的。Mn2+以类似于Ca2+或Ba2+的渗透性渗透Ca2+通道，但具有更小的电流密度，导致更小的电导。Ca(V)3.2通道中与失活进展和恢复有关的性质与Ca2+或Ba2+作为电荷载体基本相同。[日本生理学杂志53:165-172,2003]。
Calcium channels are essential for excitation-contraction coupling and pacemaker potentials in cardiac muscle cells. Whereas L-type Ca2+ channels have been extensively studied, T-type channels have been poorly characterized in cardiac myocytes. We describe here the functional properties of recombinant Ca(V)3.2 T-type Ca2+ channels expressed in mammalian cell lines. The T-type Ca2+ current showed a rapid activation and an inactivation phase in response to depolarization, and it displayed a window current over the voltage range from -60 to -40 mV in 1 to 10 mM external Ca2+. Barium (Ba2+) and strontium (Sr2+) permeate the channel with similar activation kinetics. On the other hand, monovalent cations, Li+ and Na+, permeate the T-type Ca2+ channel more easily than the L-type Ca2+ channel. The permeability order of the Ca(V)3.2 T-type Ca2+ channel among monovalent and divalent cations was determined as Ba2+>Mn2+>Ca2+>Sr2+>Li+>Na+ with the permeability order of 1.39:1.25:1.00:0.95:0.55:0.29. The ionic conductance sequence for cations relative to calcium was Sr2+>Ba2+>Ca2+>Li+>Mn2+>Na+ with the conductance ratio of 1.39:1.21:1.00:0.40:0.23:0.11. The permeation profile of manganese (Mn2+) is complex. Mn2+ permeates the Ca2+ channel with a permeability similar to Ca2+ or Ba2+, but with a much smaller current density, resulting in a much smaller conductance. The properties relating to progression and recovery from inactivation in the Ca(V)3.2 channel are substantially identical with either Ca2+ or Ba2+ as the charge carrier. [The Japanese Journal of Physiology 53: 165-172, 2003].