七鳃鳗红细胞膜的钾通道对K⁺的选择性高于Rb⁺：⁸⁶Rb和⁴¹K转运的比较研究。

Potassium channels of the lamprey erythrocyte membrane exhibit a high selectivity to K+ over Rb+: a comparative study of 86Rb and 41K transport.

作者信息

Gusev G P, Fleishman D G, Nikiforov V A, Sherstobitov A O

机构信息

Sechenov Institute of Evolutionary Physiology and Biochemistry, Russian Academy of Sciences, St. Petersburg.

出版信息

Gen Physiol Biophys. 1997 Sep;16(3):273-84.

PMID:9452948

Abstract

In order to assess the specificity of potassium channels, we examined the K+ transport pathways in the lamprey red blood cells using 86Rb and stable isotope 41K as tracers measured by the mass spectrometric method. Upon replacing 4 mmol/l K+ with 4 mmol/l Rb+ in the incubation medium, the rate coefficient for unidirectional 86Rb influx (Kin) was significantly reduced from 1.48 +/- 0.10 h-1 to 0.82 +/- 0.05 h-1 (P < 0.001). Addition of 1 mmol/l Ba2+ to the incubation medium significantly decreased 86Rb influx in K(+)- (by 53%) and Rb(+)-media (by 26%). Thus, the reduction in the rate coefficient for 86Rb influx in Rb(+)-medium as compared to K(+)-medium was mainly due to the Ba(2+)-sensitive component (0.23 +/- 0.04 vs. 0.78 +/- 0.10 h-1, P < 0.001). The ouabain-sensitive component of 86Rb influx was also higher in K(+)-(Kin = 0.62 +/- 0.05 h-1) than in Rb(+)-medium (Kin = 0.54 +/- 0.05 h-1, P < 0.05). In the presence of 4 mmol/l 41KCl, the average value of the rate coefficient for the total 41K influx was 8.1 +/- 0.5 h-1. The rate coefficient for 41K influx was reduced to 0.82 +/- 0.13 h-1 in the presence of 1 mmol/l Ba2+. Under the conditions of our assays, the rate of 86Rb uptake via potassium channels of the lamprey red cells was only about 11% in K(+)-medium and only about 3% in Rb(+)-medium compared to 41K influx. These data clearly demonstrate a high selectivity of potassium channels for K+ over Rb+, as already reported for some potassium channels in a variety of cells and tissues.

摘要

为了评估钾通道的特异性，我们使用⁸⁶Rb和稳定同位素⁴¹K作为示踪剂，通过质谱法测量，研究了七鳃鳗红细胞中的钾转运途径。在孵育培养基中用4 mmol/L Rb⁺替代4 mmol/L K⁺后，单向⁸⁶Rb内流的速率系数（Kin）从1.48±0.10 h⁻¹显著降低至0.82±0.05 h⁻¹（P<0.001）。向孵育培养基中添加1 mmol/L Ba²⁺可显著降低K⁺培养基（降低53%）和Rb⁺培养基（降低26%）中的⁸⁶Rb内流。因此，与K⁺培养基相比，Rb⁺培养基中⁸⁶Rb内流速率系数的降低主要归因于Ba²⁺敏感成分（0.23±0.04对0.78±0.10 h⁻¹，P<0.001）。⁸⁶Rb内流的哇巴因敏感成分在K⁺培养基（Kin = 0.62±0.05 h⁻¹）中也高于Rb⁺培养基（Kin = 0.54±0.05 h⁻¹，P<0.05）。在存在4 mmol/L ⁴¹KCl的情况下，总⁴¹K内流速率系数的平均值为8.1±0.5 h⁻¹。在存在1 mmol/L Ba²⁺的情况下，⁴¹K内流的速率系数降至0.82±0.13 h⁻¹。在我们的实验条件下，与⁴¹K内流相比，七鳃鳗红细胞通过钾通道摄取⁸⁶Rb的速率在K⁺培养基中仅约为11%，在Rb⁺培养基中仅约为3%。这些数据清楚地表明钾通道对K⁺的选择性高于Rb⁺，正如先前在各种细胞和组织中的一些钾通道中所报道的那样。