Properties of the Na+/K+ pump current in small neurons from adult rat dorsal root ganglia
Properties of the Na+/K+ pump current in small neurons from adult rat dorsal root ganglia
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DOI：
10.1038/sj.bjp.0705170
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发表时间：
2003-04-01
影响因子：
7.3
通讯作者：
Yasuda, H
中科院分区：
文献类型：
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作者：
Hamada, L;Matsuura, H;Yasuda, H
1 本研究旨在表征从成年大鼠腰椎 L4-6 节段分离的小型背根神经节 (DRG) 神经元（体细胞直径小于或等于 25 µm）的 Na+/K+ 泵电流。2 使用全细胞膜片钳技术，在膜电位在 + 40 和 - 120 mV 之间的平方电压阶跃期间，Na+/K+ 泵电流被确定为哇巴因敏感电流，其中Ca2+ 和 K+ 通道电流以及 Na+/Ca2+ 交换电流被最小化。 Na+/K+ 泵浦电流在整个检测电压范围内几乎与时间无关，并表现出电压依赖性；其电流 - 电压 (I-V) 关系在 - 120 和 0 mV 之间显示出正斜率，但在正膜电位时接近平台水平。3 哇巴因在 0.1 mum 和 5 mM 浓度之间对 Na+/K+ 泵电流（由 30 mM 移液管 Na+ 激活）的浓度依赖性阻断是双相的，并且使用具有高和解离常数的双结合位点模型得到了很好的描述。低亲和力结合位点分别为 0.20 和 140.1 muM。在移液器溶液中存在 30 mM Na+ 的情况下，低亲和力位点和高亲和力位点（分别可能是 alpha1beta1 和 alpha3beta1 同工酶）产生的 Na+/K+ 泵电流的相对振幅估计为 13:1。4 此外，在浓度范围为 5 至 100 mM 的浓度范围内，移液器 Na+ 激活的 Na+/K+ 泵电流也表现出双相浓度依赖性，可以很好地拟合假设存在两种对 Na+ 具有高亲和力和低亲和力的同工酶（分别为 6.7 和 67.6 mM）。5 因此，本研究提供了功能证据，表明 Na+/K+ ATP 酶包含两种功能不同的同工酶，正如大鼠小 DRG 神经元中 α1β1 和 α3β1 所预期的那样。
1 The present investigation was undertaken to characterize the Na+/K+ pump current in small (less than or equal to 25 mum in soma diameter) dorsal root ganglion (DRG) neurons isolated from lumbar L4-6 segments of adult rats.2 The Na+/K+ pump current was identified as an ouabain-sensitive current during square voltage steps to membrane potentials between + 40 and - 120 mV, using the whole-cell patch-clamp technique in which Ca2+ and K+ channel currents and Na+/Ca2+ exchange currents were minimized. The Na+/K+ pump current was practically time-independent over the entire voltage range examined and exhibited a voltage-dependence; its current - voltage (I-V) relationship displayed a positive slope at potentials between - 120 and 0 mV but nearly plateau levels at positive membrane potentials.3 The concentration-dependent block of Na+/K+ pump current (activated by 30 mM pipette Na+) by ouabain at concentrations between 0.1 mum and 5 mM was biphasic and was well described using a two-binding site model with dissociation constants for high- and low-affinity binding sites of 0.20 and 140.1 muM, respectively. The relative amplitude of the Na+/K+ pump current produced by low- and high-affinity sites (probably alpha1beta1 and alpha3beta1 isozymes, respectively) was estimated to be 13: 1 in the presence of 30 mM Na+ in the pipette solution.4 Additionally, the activation of Na+/K+ pump current by pipette Na+ at concentrations ranging from 5 to 100 mM also exhibited a biphasic concentration dependence which can be reasonably well fitted by assuming the existence of two isozymes having high and low affinities for Na+ (6.7 and 67.6 mM, respectively).5 Thus, the present investigation provides functional evidence to suggest that the Na+/K+ ATPase comprises two functionally distinct isozymes as expected for a alpha1beta1 and alpha3beta1 in rat small DRG neurons.