Reddy M M, Quinton P M
Division of Biomedical Sciences, University of California, Riverside 92521-0121.
J Membr Biol. 1991 Feb;119(3):199-210. doi: 10.1007/BF01868725.
We have measured the intracellular potassium activity, [K+]i and the mechanisms of transcellular K+ transport in reabsorptive sweat duct (RSD) using intracellular ion-sensitive microelectrodes (ISMEs). The mean value of [K+]i in RSD is 79.8 +/- 4.1 mM (n = 39). Under conditions of microperfusion, the [K+]i is above equilibrium across both the basolateral membrane, BLM (5.5 times) and the apical membrane, APM (7.8 times). The Na+/K+ pump inhibitor ouabain reduced [K+]i is insensitive to the Na+/K+/2 Cl- cotransport inhibitor bumetanide in the bath. Cl- substitution in the lumen had no effect on [K+]i. In contrast, Cl- substitution in the bath (basolateral side) depolarized BLM from -26.0 +/- 2.6 mV to -4.7* +/- 2.4 mV (n = 3; indicates significant difference) and decreased [K+]i from 76.0 +/- 15.2 mM to 57.7 +/- 12.7 mM (n = 3). Removal of K+ in the bath decreased [K+]i from 76.3 +/- 15.0 mM to 32.3 +/- 7.6 mM (n = 4) while depolarizing the BLM from -32.5 +/- 4.1 mV to -28.3* +/- 3.0 mV (n = 4). Raising the [K+] in the bath by 10-fold increased [K+]i from 81.7 +/- 9.0 mM to 95.0* +/- 13.5 mM and depolarized the BLM from -25.7 +/- 2.4 mV to -21.3* +/- 2.9 mV (n = 4). The K+ conductance inhibitor, Ba2+, in the bath also increased [K+]i from 85.8 +/- 6.7 mM to 107.0* +/- 11.5 mM (n = 4) and depolarized BLM from -25.8 +/- 2.2 mV to -17.0* +/- 3.1 mV (n = 4). Amiloride at 10(-6) M increased [K+]i from 77.5 +/- 18.8 mM to 98.8* +/- 21.6 mM (n = 4) and hyperpolarized both the BLM (from -27.5 +/- 1.4 mV to -46.0* +/- 3.5 mV, n = 4). However, amiloride at 10(-4) M decreased [K+]i from 64.5 +/- 0.9 mM to 36.0* +/- 9.9 mM and hyperpolarized both the BLM (from -24.7 +/- 1.4 mV to -43.5* +/- 4.2 mV) and APM (from -18.3 +/- 0.9 mV to -43.5* +/- 4.2 mV, n = 6). In contrast to the observations at the BLM, substitution of K+ or application of Ba2+ in the lumen had no effect on the [K+]i or the electrical properties of RSD, indicating the absence of a K+ conductance in the APM.(ABSTRACT TRUNCATED AT 400 WORDS)
我们使用细胞内离子敏感微电极（ISMEs）测量了重吸收性汗腺导管（RSD）中的细胞内钾活性、[K⁺]i以及跨细胞钾转运机制。RSD中[K⁺]i的平均值为79.8±4.1 mM（n = 39）。在微灌注条件下，[K⁺]i在基底外侧膜（BLM）两侧（5.5倍）和顶端膜（APM）两侧（7.8倍）均高于平衡值。Na⁺/K⁺泵抑制剂哇巴因降低了[K⁺]i，而浴槽中的Na⁺/K⁺/2Cl⁻共转运抑制剂布美他尼对其不敏感。管腔内的Cl⁻替代对[K⁺]i没有影响。相反，浴槽（基底外侧侧）中的Cl⁻替代使BLM从-26.0±2.6 mV去极化至-4.7*±2.4 mV（n = 3；表示显著差异），并使[K⁺]i从76.0±15.2 mM降至57.7±12.7 mM（n = 3）。浴槽中去除K⁺使[K⁺]i从76.3±15.0 mM降至32.3±7.6 mM（n = 4），同时使BLM从-32.5±4.1 mV去极化至-28.3*±3.0 mV（n = 4）。浴槽中K⁺浓度提高10倍使[K⁺]i从81.7±9.0 mM增加至95.0*±13.5 mM，并使BLM从-25.7±2.4 mV去极化至-21.3*±2.9 mV（n = 4）。浴槽中的K⁺电导抑制剂Ba²⁺也使[K⁺]i从85.8±6.7 mM增加至107.0*±11.5 mM（n = 4），并使BLM从-25.8±2.2 mV去极化至-17.0*±3.1 mV（n = 4）。10⁻⁶ M的氨氯地平使[K⁺]i从77.5±18.8 mM增加至98.8*±21.6 mM（n = 4），并使BLM超极化（从-27.5±1.4 mV至-46.0*±3.5 mV，n = 4）。然而，10⁻⁴ M的氨氯地平使[K⁺]i从64.5±0.9 mM降至36.0*±9.9 mM，并使BLM（从-24.7±1.4 mV至-43.5*±4.2 mV）和APM（从-18.3±0.9 mV至-43.5*±4.2 mV，n = 6）均超极化。与在BLM处的观察结果相反，管腔内K⁺的替代或Ba²⁺的应用对RSD的[K⁺]i或电特性没有影响，表明APM中不存在K⁺电导。（摘要截断于400字）
