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首页> 外文期刊>Journal of Neurophysiology >Spermine mediates inward rectification in potassium channels of turtle retinal Muller cells.
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Spermine mediates inward rectification in potassium channels of turtle retinal Muller cells.

机译：精胺介导乌龟视网膜穆勒细胞钾通道的内向整流。

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摘要

Retinal Muller cells are highly permeable to potassium as a consequence of their intrinsic membrane properties. Therefore these cells are able to play an important role in maintaining potassium homeostasis in the vertebrate retina during light-induced neuronal activity. Polyamines and other factors present in Muller cells have the potential to modulate the rectifying properties of potassium channels and alter the Muller cells capacity to siphon potassium from the extracellular space. In this study, the properties of potassium currents in turtle Muller cells were investigated using whole cell voltage-clamp recordings from isolated cells. Overall, the currents were inwardly rectifying. Depolarization elicited an outward current characterized by a fast transient that slowly recovered to a steady level along a double exponential time course. On hyperpolarization the evoked inward current was characterized by an instantaneous onset (or step) followed by a slowly developing sustained inward current. The kinetics of the time-dependent components (block of the transient outward current and slowly developing inward current) were dependent on holding potential and changes in the intracellular levels of magnesium ions and polyamines. In contrast, the instantaneous inward and the sustained outward currents were ohmic in character and remained relatively unaltered with changes in holding potential and concentration of applied spermine (0.5--2 mM). Our data suggest that cellular regulation in vivo of polyamine levels can differentially alter specific aspects of potassium siphoning by Muller cells in the turtle retina by modulating potassium channel function.
机译：由于其固有的膜特性，视网膜穆勒细胞对钾具有很高的渗透性。因此，这些细胞能够在光诱导的神经元活动期间在维持脊椎动物视网膜的钾稳态中起重要作用。穆勒细胞中存在的多胺和其他因子具有调节钾通道的整流特性并改变穆勒细胞从细胞外空间虹吸钾的能力。在这项研究中，使用分离细胞的全细胞电压钳记录来研究乌龟穆勒细胞中钾电流的性质。总体而言，潮流正在向内纠正。去极化引起向外的电流，其特征在于快速的瞬态，该瞬态沿双指数时间过程缓慢恢复到稳定水平。在超极化时，诱发的内向电流的特征是瞬时发作（或阶跃），然后是缓慢发展的持续内向电流。时间依赖性成分的动力学（瞬态向外电流的阻断和缓慢发展的向内电流的阻断）取决于保持电位以及镁离子和多胺的细胞内水平的变化。相反，瞬时的内向和持续的外向电流是欧姆性的，并且保持力和所施加的精胺浓度（0.5--2 mM）的变化相对不变。我们的数据表明，体内多胺水平的细胞调节可以通过调节钾通道功能，差异改变乌龟视网膜中穆勒细胞虹吸钾的特定方面。

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