Voltage and beat dependence of Ca2+ transient in feline ventricular myocytes.
Voltage and beat dependence of Ca2+ transient in feline ventricular myocytes.
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猫心室肌细胞中 Ca2 瞬变的电压和搏动依赖性。
DOI：
10.1152/ajpheart.1989.257.3.h746
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Houser,SR
中科院分区：
文献类型：
--
作者：
duBell,WH;Houser,SR
休息一段时间后的正收缩阶梯可归因于钙瞬变幅度的正阶梯。本研究采用电压钳技术和钙离子荧光指示剂INDO-1，研究了膜电位、去极化时间和慢内向钙电流(ISI)对钙稳态瞬变幅度和稳态发展的调节作用。稳态时，钙瞬变在+10 mV处最大，ISI也在+10 mV处最大。然而，ISI-电压关系比Ca~(2+)暂态电压关系更接近钟形。稳态钙瞬变的幅度和持续时间不受短至25ms的脉冲持续时间的影响。然而，延长的电压脉冲对于维持稳定状态是必不可少的。正向阶梯的发展非常依赖于电压。静止期后，电压钳驱动至+30 mV时出现正阶梯，而电压钳驱动至-10 mV时则未见正阶梯，该电位可引起同等大小的ISI。这些结果支持了ISI早期峰值可触发肌浆网钙离子释放的观点。然而，肌浆网钙负荷依赖于长时间的去极化，可能通过Na+-Ca~(2+)交换调节。
The positive contractile staircase after a period of rest is attributable to a positive staircase in the magnitude of the Ca2+ transient. The present study used voltage-clamp techniques and the fluorescent Ca2+ indicator, indo-1, to examine the effects of membrane potential, the duration of depolarization, and the slow inward Ca2+ current (Isi) in the regulation of the magnitude of the steady-state Ca2+ transient and the development of the steady state during the positive staircase. In the steady state, the Ca2+ transient was greatest at +10 mV, the potential at which Isi was also the greatest. However, the Isi-voltage relationship was much more bell-shaped than the Ca2+ transient-voltage relationship. The magnitude and duration of the steady-state Ca2+ transient was not affected by pulse durations as short as 25 ms. However, prolonged voltage pulses were essential to maintain the steady state. The development of the positive staircase was very voltage dependent. After a rest period, a positive staircase was seen when voltage-clamp drives were done to +30 mV but not when done to -10 mV, potentials that elicit Isi of comparable magnitude. These results support the idea that the early peak of Isi can act as a trigger for release of Ca2+ from the sarcoplasmic reticulum. However, sarcoplasmic reticulum Ca2+ loading is dependent on prolonged depolarization and may be mediated through Na+-Ca2+ exchange.