Differential permeabilities of rat renal brush-border and basolateral membrane vesicles.
Differential permeabilities of rat renal brush-border and basolateral membrane vesicles.
复制标题
大鼠肾刷状缘和基底外侧膜囊泡的渗透性差异。
DOI：
10.1152/ajprenal.1989.256.1.f18
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发表时间：
1989
期刊：
影响因子：
--
通讯作者：
Abramson,RG
中科院分区：
文献类型：
--
作者：
Lipkowitz,MS;Abramson,RG
采用荧光探针3,3′-二丙基硫代二碳氰碘[diS-C3-(5)]检测大鼠肾皮质刷边（BBMV）和基底外侧（BLMV）膜囊的氯化钾渗透性和相对离子电导。通过自由流动电泳同时分离囊泡。这些研究表明，尽管长时间孵育，BBMV和BLMV在100 mM KCl中都不能达到平衡。在这两种情况下，向内的KCl梯度持续了3小时。利用电致Na+依赖性[3H]谷氨酰胺运输对膜电位变化的响应，证实了BLMV的低囊内KCl浓度。BBMV和BLMV的氯离子电导明显小于钾离子电导。因此，在两层膜上都保持了内部正电位。与BBMV相比，BLMV明显更具流动性，渗透性更低，相对氯离子电导更低，并保持更大的内正电位。BBMV和BLMV的KCl通透性与内源膜铜含量呈负相关，外源铜显著降低了其通透性。通透性与膜镁含量无关，也不受外源镁的影响。这些研究表明，内源性铜以及细胞内因子可能在体内调节近端小管细胞刷缘和基底外膜的通透性。
Potassium chloride permeability and relative ionic conductances of rat renal cortical brush-border (BBMV) and basolateral (BLMV) membrane vesicles were examined using the fluorescent probe 3,3'-dipropylthiadicarbocyanine iodide [diS-C3-(5)]. Vesicles were simultaneously isolated and separated by free-flow electrophoresis. These studies demonstrated that neither BBMV nor BLMV equilibrated in 100 mM KCl despite prolonged incubation. In both, an inwardly directed KCl gradient was sustained for 3 h. The low intravesicular KCl concentration of BLMV was confirmed utilizing the response of electrogenic Na+-dependent [3H]glutamine transport to variations in the membrane potential. Chloride conductance was significantly less than potassium conductance in BBMV and BLMV. Consequently, an inside-positive potential was maintained across both membranes. BLMV were significantly more fluid, less permeable, had a lower relative chloride conductance, and maintained a greater inside-positive potential than BBMV. The KCl permeabilities of BBMV and BLMV were inversely related to endogenous membrane copper content and were significantly reduced by exogenous copper. Permeability did not correlate with membrane magnesium content, nor was it affected by exogenous magnesium. These studies suggest that endogenous copper as well as intracellular factors may regulate the permeabilities of the brush-border and basolateral membranes of proximal tubule cells in vivo.