ACTIVATION OF A POTASSIUM CURRENT BY RAPID PHOTOCHEMICALLY GENERATED STEP INCREASES OF INTRACELLULAR CALCIUM IN RAT SYMPATHETIC NEURONS
ACTIVATION OF A POTASSIUM CURRENT BY RAPID PHOTOCHEMICALLY GENERATED STEP INCREASES OF INTRACELLULAR CALCIUM IN RAT SYMPATHETIC NEURONS
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DOI：
10.1073/pnas.84.10.3496
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发表时间：
1987-05-01
影响因子：
11.1
通讯作者：
LESTER, HA
中科院分区：
文献类型：
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作者：
GURNEY, AM;TSIEN, RY;LESTER, HA
虽然Ca 2+是一个公认的细胞内信使，有很多问题的动力学和空间定位的影响。这些问题现在可以用光敏Ca 2+螯合剂nitr-5来解决。该分子的Ca 2+亲和力在吸收近UV光后降低40倍; Ca 2+以时间常数apeq释放。300 μ s。用膜片钳电极以全细胞电压钳模式透析大鼠交感神经节细胞，将与Ca ~（2+）复合的Nitr-5或相关化合物Nitr-2和Nitr-7导入交感神经节细胞。闪光释放Ca 2+并激活K+电流。闪光诱导的电流弛豫遵循一个简单的指数时间过程，时间常数为5毫秒。螯合剂，以不同的速率光解之间的动力学比较表明，从nitr-5释放Ca 2+太快，限制放松。因此，我们直接证实，Ca 2+可以在进入细胞后的几毫秒内调节膜特性。给出了大鼠交感神经元中Ca 2+激活K+电流的初步动力学描述; Ca 2+似乎以至少2倍的速率常数与通道结合。107 M-1. s-1条件下
Although Ca2+ is a well-established intracellular messenger, there are many questions concerning the kinetics and spatial localization of its effects. Such problems may now be approached with the photosensitive Ca2+ chelator nitr-5. The Ca2+ affinity of this molecule decreases by a factor of 40 after absorption of near-UV light; Ca2+ is liberated with a time constant of .apprxeq. 300 .mu.s. Nitr-5 or the related compounds nitr-2 and nitr-7, complexed with Ca2+, were introduced into rat sympathetic ganglion cells by dialysis from a patch pipette electrode operating in the whole-cell, voltage-clamp mode. Light flashes released Ca2+ and activated a K+ current. Flash-induced current relaxations followed a simple exponential time course with time constants as brief as 5 ms. Comparison of the kinetics among the chelators, which photolyze at different rates, suggests that release of Ca2+ from nitr-5 is too fast to limit the relaxation. Thus we confirm directly that Ca2+ can modulate membrane properties within a few milliseconds after entering a cell. A preliminary kinetic description of K+ current activation by Ca2+ in rat sympathetic neurons is presented; Ca2+ appears to bind to the channel with a rate constant of at least 2 .times. 107 M-1 .cntdot. s-1.