Robarts Research Institute and the Department of Physiology and Pharmacology, University of Western Ontario, London, Ontario, Canada.
Department of Neuroscience, Translational Neurobiology, University of Copenhagen, Copenhagen, Denmark.
Am J Physiol Heart Circ Physiol. 2020 Mar 1;318(3):H632-H638. doi: 10.1152/ajpheart.00628.2019. Epub 2020 Jan 31.
Arterial membrane potential () is set by an active interplay among ion channels whose principal function is to set contractility through the gating of voltage-operated Ca channels. To garner an understanding of this electrical parameter, the activity of each channel must be established under near-physiological conditions, a significant challenge given their small magnitude. The inward rectifying K (K) channel is illustrative of the problem, as its outward "physiological" component is almost undetectable. This study describes a stepwise approach to dissect small ionic currents at physiological using endothelial and smooth muscle cells freshly isolated from rat cerebral arteries. We highlight three critical steps, beginning with the voltage clamping of vascular cells bathed in physiological solutions while maintaining a giga-ohm seal. K channels are then inhibited (micromolar Ba) so that a difference current can be created, once Ba traces are corrected for the changing seal resistance and subtle instrument drift, pulling the reversal potential rightward. The latter is a new procedure and entails the alignment of whole cell current traces at a voltage where K is silent and other channels exhibit limited activity. We subsequently introduced corrected and uncorrected currents into computer models of the arterial wall to show how these subtle adjustments markedly impact the importance of K in and arterial tone regulation. We argue that this refined approach can be used on an array of vascular ion channels to build a complete picture of how they dynamically interact to set arterial tone in key organs like the brain. This work describes a stepwise approach to resolve small ionic currents involved in controlling in resistance arteries. Using this new methodology, we particularly resolved the outward component of the K current in native vascular cells, voltage clamped in near-physiological conditions. This novel approach can be applied to any other vascular currents and used to better interpret how vascular ion channels cooperate to control arterial tone.
动脉膜电位 () 是由离子通道的主动相互作用设定的，其主要功能是通过电压门控 Ca 通道的门控来设定收缩性。为了理解这个电参数，必须在接近生理的条件下建立每个通道的活动，这是一个巨大的挑战，因为它们的幅度很小。内向整流钾 (K) 通道就是一个说明问题的例子，因为其向外的“生理”成分几乎无法检测到。本研究描述了一种逐步的方法，用于在生理条件下从大鼠脑动脉中分离出的内皮和平滑肌细胞中剖析小离子电流。我们强调了三个关键步骤，首先是在生理溶液中对血管细胞进行电压钳制，同时保持千兆欧姆密封。然后抑制 K 通道（微摩尔 Ba），以便可以创建差异电流，一旦 Ba 痕迹被校正为不断变化的密封电阻和微妙的仪器漂移，就会将反转电位向右拉。后者是一个新程序，需要将整个细胞电流轨迹对齐到 K 沉默且其他通道表现出有限活动的电压处。随后，我们将校正和未校正的电流引入动脉壁的计算机模型中，以显示这些细微调整如何显著影响 K 在膜电位和动脉张力调节中的重要性。我们认为，这种改进的方法可以用于一系列血管离子通道，以构建它们如何动态相互作用以在大脑等关键器官中调节动脉张力的完整图景。这项工作描述了一种逐步的方法，用于解决控制阻力动脉中膜电位的小离子电流。使用这种新方法，我们特别在接近生理的条件下，在天然血管细胞中解析了 K 电流的外向成分。这种新方法可以应用于任何其他血管电流，并用于更好地解释血管离子通道如何合作来控制动脉张力。
