Greger R, Weidtke C, Schlatter E, Wittner M, Gebler B
Pflugers Arch. 1984 May;401(1):52-7. doi: 10.1007/BF00581532.
The Na+2Cl-K+ cotransporter in the apical membrane of the cortical thick ascending limb of the Henle's loop (cTAL) of rabbit nephron utilizes the electrochemical gradient for Na+ to transport K+ and Cl- against an unfavorable electrochemical gradient from lumen to cell interior. In the present study attempts are made to measure intracellular K+ activity (a cell K+) under control conditions and after inhibition of the cotransport system by furosemide (50 X 10(-6) mol X l-1). 70 cTAL segments of 55 rabbits were perfused in vitro. Conventional Ling-Gerard and K+-selective microelectrodes were used to measure the PD across the basolateral membrane (PDbl) as well as the PD sensed by the single barrelled K+-selective electrode (PDK+). PDbl was -64 +/- 1 (n = 65) mV and PDK+ + 15 +/- 1 (n = 32) mV under control conditions. The positive PDK+ value, significantly different from zero, indicates that a cell K+ is higher than predicted for passive distribution. The estimate for a cell K+ obtained from PDbl and PDK+ was 113 +/- 8 mmol X l-1. Furosemide lead to the previously reported hyperpolarization of PDbl by 17 +/- 4 (n = 13) mV and to a reduction of PDK+ from 15 +/- 1 to 5 +/- 1 (n = 20) mV. The a cell K+, obtained from this set of data, was 117 +/- 9 mmol X l-1, and was not different from the control value. The present data indicate that a cell K+ is significantly above Nernst equilibrium under control conditions.(ABSTRACT TRUNCATED AT 250 WORDS)
兔肾单位髓袢升支粗段（cTAL）顶端膜中的Na⁺-2Cl⁻-K⁺协同转运体利用Na⁺的电化学梯度，逆着从管腔到细胞内的不利电化学梯度转运K⁺和Cl⁻。在本研究中，尝试在对照条件下以及用呋塞米（50×10⁻⁶ mol·L⁻¹）抑制协同转运系统后测量细胞内K⁺活性（细胞K⁺）。对55只兔子的70个cTAL节段进行体外灌注。使用传统的凌-杰勒德电极和K⁺选择性微电极测量跨基底外侧膜的电位差（PDbl）以及单管K⁺选择性电极检测到的电位差（PDK⁺）。在对照条件下，PDbl为-64±1（n = 65）mV，PDK⁺为+15±1（n = 32）mV。PDK⁺的正值显著不同于零，表明细胞K⁺高于被动分布预测值。从PDbl和PDK⁺获得的细胞K⁺估计值为113±8 mmol·L⁻¹。呋塞米导致先前报道的PDbl超极化17±4（n = 13）mV，PDK⁺从15±1降低到5±1（n = 20）mV。从这组数据获得的细胞K⁺为117±9 mmol·L⁻¹，与对照值无差异。目前的数据表明，在对照条件下细胞K⁺显著高于能斯特平衡。（摘要截短至250字）
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