Modes of operation and variable stoichiometry of the furosemide- sensitive Na and K fluxes in human red cells.
Modes of operation and variable stoichiometry of the furosemide- sensitive Na and K fluxes in human red cells.
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DOI：
10.1085/jgp.87.1.113
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发表时间：
1986-01
影响因子：
3.8
通讯作者：
Tosteson, D C
中科院分区：
文献类型：
--
作者：
Canessa, M;Brugnara, C;Cusi, D;Tosteson, D C
我们在这篇论文中报道了不同的Na和K在人红细胞中的运输模式，在沃巴因存在的情况下，可以被速尿抑制。实验提供了Na和K向内和向外耦合输运、Ki/Ko和Nai/Nao交换以及Na或K非耦合流出的证据。Na和K的向外共输被定义为Na和K向胆碱介质流出的速尿敏感（FS）成分，以及耐瓦巴因（or） Na和K流出的cl依赖或顺式刺激成分。Na和K的向内共输定义为外部Na （Nao）对K内流的刺激和外部K （Ko）对存在钾巴因的Na内流的刺激。这两种效应都依赖于FS和Cl。通过(a)外部K对FS K内流和外排的刺激，以及(b)在没有外部Na的情况下，内部Na或K对FS K内流的刺激，为Na/K共转运的FS Ki/Ko交换途径提供了实验证据。无k介质（130 mM NaCl）内部Na刺激FS Na内流，为FS Nai/Nao交换途径提供了证据。这个途径比Ki/Ko交换小4到6倍。在仅含Na或K的细胞中，分别在仅含Na或K的培养基中孵育，阳离子的FS外排没有同时向内运输（FS不耦合的Na和K外排）。Na和K向胆碱介质外输FS的化学计量比随Nai/Ki浓度的比值而变化，当Nai/Ki接近1时，FS向外输Na与K通量的比值也为1。在胆碱介质中，外源K（非竞争性）抑制了FS Na的流出，而FS K的流出则受到刺激。对FS - K外排的刺激是由于Ko对Ki/Ko交换途径的刺激。因此，在外部K存在的情况下，FS Na和K外排的化学计量也发生了变化。FS Na和K转运反应方案的最小模型考虑了顺式刺激、反式抑制和反式刺激，以及FS阳离子通量的可变化学计量。
We report in this paper different modes of Na and K transport in human red cells, which can be inhibited by furosemide in the presence of ouabain. Experimental evidence is provided for inward and outward coupled transport of Na and K, Ki/Ko and Nai/Nao exchange, and uncoupled Na or K efflux. The outward cotransport of Na and K was defined as the furosemide-sensitive (FS) component of Na and K effluxes into choline medium and as the Cl-dependent or cis-stimulated component of the ouabain-resistant (OR) Na and K effluxes. Inward cotransport of Na and K was defined by the stimulation by external Na (Nao) of the K influx and the stimulation by external K (Ko) of the Na influx in the presence of ouabain. Both effects were FS and Cl dependent. Experimental evidence for an FS Ki/Ko exchange pathway of the Na/K cotransport was provided by (a) the stimulation by external K of FS K influx and efflux, and (b) the stimulation by internal Na or K of FS K influx in the absence of external Na. Evidence for an FS Nai/Nao exchange pathway was provided by the stimulation of FS Na influx by internal Na from a K-free medium (130 mM NaCl). This pathway was four to six times smaller than the Ki/Ko exchange. In cells containing only Na or K, incubated in media containing only Na or K, respectively, there was FS efflux of the cation without simultaneous inward transport (FS uncoupled Na and K efflux). The stoichiometric ratio of FS outward cotransport of Na and K into choline medium varied with the ratio of Nai-to-Ki concentrations, and when Nai/Ki was close to 1, the ratio of FS outward Na to K flux was also 1. In choline media, FS Na efflux was inhibited by external K (noncompetitively), whereas FS k efflux was stimulated. The stimulation of FS K efflux was due to the stimulation by Ko of the Ki/Ko exchange pathway. Thus, the stoichiometry of FS Na and K effluxes also varied in the presence of external K. A minimal model for a reaction scheme of FS Na and K transport accounts for cis stimulation, trans inhibition, and trans stimulation, and for variable stoichiometry of the FS cation fluxes.