MICROGLIA GENERATE EXTERNAL H+ & K+ ION GRADIENTS UTILIZING H & K ATPASE FAMILY

从新生大鼠脑内分离小胶质细胞培养7天 天，积极地挤压质子以换取钾离子的产生 过剩质子的梯度和钾离子的亏缺 靠近细胞膜外表面的。这些 用离子选择性测定仪测量浓度梯度 自参考电极，在10 mm的距离内消散 从细胞中释放，并被高浓度的 胞外钾离子或质子。药理和 免疫组织化学研究表明，H+/K+-ATPase是 这些渐变的主要来源。无论是Na+/K+-ATPase还是 内向整流钾通道对 这些梯度的产生。在5 mM的胞外钾 浓度，记录到的梯度为-9.43±4.2 mm(n=48 在距细胞膜10 mm的距离内消散。而当 转运蛋白活性可被奥美拉唑(10 MM)和 特异性H+/K+-ATP酶阻断剂SCH28080(1 MM)，对 哇巴因和司多芬替丁。神经胶质细胞K转运蛋白的解离常数 离子的数量比(3.7毫米)高一个数量级 上皮性H+/K+-ATPase。这是一种H+/K+的首次报道 川崎病生理范围内小胶质细胞的转运蛋白 [K+]完毕。H~+/K~+-ATPase在钾稳态中的意义 高细胞外钾和低pH下的小胶质细胞，如在 并对脑损伤的部位进行了讨论。

Microglia isolated from newborn rat brains and cultured for 7 days, actively extrude protons in exchange for potassium ions creating a gradient of excess protons and a deficit of potassium ions in close proximity to the outer surface of the cell membrane. These concentration gradients, measured with an ion selective self-referencing electrode, dissipate over a distance of 10mm away from the cell and are activated by high concentrations of extracellular potassium ions or protons. Pharmacological and immunohisto-chemical studies revealed that an H+/K+-ATPase is the major generator of these gradients. Neither the Na+/K+-ATPase nor the inward rectifier potassium channel make significant contributions to the generation of these gradients. At 5mM extracellular potassium concentration, a gradient of -9.43+ 4.2 mM (n=48) was recorded dissipating over a distance of 10mm from the cell membrane. While the transporter activity could be blocked by Omeprazole (10mM) and by the specific H+/K+-ATP ase blocker SCH28080 (1mM), it was insensitive to ouabain and strophantidine. The Kd of the glial transporter for K ions is an order of magnitude higher (3.7 mM) than that of the epithelial H+/K+-ATPase. This is a first report of an H+/K+ transporter in microglial cells with Kd in the physio-logical range of [K+]out. Implications of the H+/K+-ATPase on potassium homeostasis in microglia under high extracellular potassium and low pH, as found at the site of brain injury, are discussed.