EFFECTS OF THE EXTERNAL PH ON CA CHANNELS - EXPERIMENTAL STUDIES AND THEORETICAL CONSIDERATIONS USING A 2-SITE, 2-ION MODEL
EFFECTS OF THE EXTERNAL PH ON CA CHANNELS - EXPERIMENTAL STUDIES AND THEORETICAL CONSIDERATIONS USING A 2-SITE, 2-ION MODEL
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DOI：
10.1073/pnas.83.3.654
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发表时间：
1986-02-01
影响因子：
11.1
通讯作者：
HAGIWARA, S
中科院分区：
文献类型：
--
作者：
IIJIMA, T;CIANI, S;HAGIWARA, S
用全细胞膜片钳技术研究了pH对杂交瘤细胞株（mAb-7 B）钙通道的影响。随着pH值的降低，激活和失活曲线都向负膜电位方向移动，表明pH值诱导的外部负表面电位降低，由门控机制检测。半激活电位V1/2和半失活电位Vh与斜率为1的直线相关。内向电流随V1/2呈指数变化，如果通道内的场和入口处的Ca 2+浓度对表面电位敏感，则会如所预期的那样。然而，反转电位和外向电流不受pH值变化的影响。在通道感知表面电位的假设下，所有这些结果，以及在以前的研究中观察到的反转电位相对于Ca 2+的能斯特行为，都是由通道的三势垒，两离子模型解释的，假设沟道中的电势几乎完全跨过与外部溶液相邻的势垒而下降。
Some effects of the external pH on Ca channels were studied in a hybridoma cell line (mAb-7B), by using the whole-cell configuration of the patch-clamp technique. As the pH was lowered, both the activation and the inactivation curves shifted toward less negative membrane potentials, suggesting a pH-induced decrease of an external negative surface potential, sensed by the mechanism of gating. The potential for half-activation, V1/2, and that for half-inactivation, Vh, were related by a straight line with a slope of one. The inward current varied exponentially with V1/2, as would be expected if the field inside the channel and the Ca2+ concentration at the entrance were sensitive to the surface potential. However, the reversal potential and the outward current were unaltered by changes in the pH. Under the hypothesis that the channel senses the surface potential, all these results, as well as the nernstian behaviour of the reversal potential with respect to Ca2+, observed in previous studies, are accounted for by a three-barrier, two-ion model for a channel, provided it is assumed that the potential in the channel drops almost entirely across the barrier adjacent to the external solution.