Absence of significant sodium-hydrogen exchange by rabbit erythrocyte sodium-lithium countertransporter.
Absence of significant sodium-hydrogen exchange by rabbit erythrocyte sodium-lithium countertransporter.
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兔红细胞钠-锂逆向转运蛋白不存在显着的钠-氢交换。
DOI：
10.1152/ajpcell.1985.249.1.c63
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Cook,KW
中科院分区：
文献类型：
--
作者：
Jennings,ML;Adams-Lackey,M;Cook,KW
几种哺乳动物物种的红细胞（例如，人、兔、牛）具有Li和Na反向转运系统。我们使用兔红细胞来确定这种反向转运蛋白的钠质子交换程度。哇巴因不敏感的22 Na流出到磷酸盐缓冲的K-乙酸介质中的不同Na浓度测定在细胞外pH 7.5和6.9。为了维持细胞内pH在约7.2，在pH 6.9的介质中的大部分乙酸盐被葡萄糖酸盐，一种非穿透性阴离子取代。细胞外钠强烈（大于10倍）刺激22钠流出在高和低pH值的介质，但这种刺激的K1/2是较高的pH值为6.9。这是一致的竞争性结合H的外向运输网站。然而，较低的pH值本身，在无钠培养基中，刺激22钠流出只有非常轻微。通过降低细胞外pH至6.9刺激的22 Na流出量小于100 mM细胞外Na产生的刺激的1%。它的结论是，虽然H似乎结合到钠锂交换器的基板网站，有没有显着的H运输在生理pH范围内。
Red blood cells of several mammalian species (e.g., human, rabbit, bovine) possess a countertransport system for Li and Na. We have used rabbit red blood cells to determine the extent of sodium-proton exchange by this countertransporter. Ouabain-insensitive 22Na efflux into phosphate-buffered K-acetate media of varying Na concentrations was determined at extracellular pH 7.5 and 6.9. To maintain the intracellular pH at approximately 7.2, most of the acetate in the pH 6.9 medium was replaced by gluconate, a nonpenetrating anion. Extracellular Na strongly (greater than 10-fold) stimulated the 22Na efflux in both high- and low-pH media, but the K1/2 for this stimulation was higher at pH 6.9. This is consistent with a competitive binding of H to the outward-facing transport site. However, the lower pH itself, in a Na-free medium, stimulated the 22Na efflux only very slightly. The 22Na efflux stimulated by lowering the extracellular pH to 6.9 was less than 1% of the stimulation produced by 100 mM extracellular Na. It is concluded that, although H appears to bind to the substrate site of the Na-Li exchanger, there is no significant H transport in the physiological pH range.