ELECTROGENIC SODIUM-BICARBONATE COTRANSPORT IN RABBIT RENAL CORTICAL BASOLATERAL MEMBRANE-VESICLES
ELECTROGENIC SODIUM-BICARBONATE COTRANSPORT IN RABBIT RENAL CORTICAL BASOLATERAL MEMBRANE-VESICLES
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DOI：
10.1172/jci112738
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发表时间：
1986-12-01
影响因子：
15.9
通讯作者：
WARNOCK, DG
中科院分区：
文献类型：
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作者：
AKIBA, T;ALPERN, RJ;WARNOCK, DG
本研究探讨了碳酸氢盐跨过兔肾皮质制备的基底外侧膜囊泡的转运机制。与葡萄糖酸盐相比，碳酸氢盐刺激了同位素钠的吸收（每 5 秒 2.5 nmol/mg 蛋白质，每 5 秒 1.4 nmol/mg 蛋白质），并且该过程被二磺酸二苯乙烯抑制。施加内部正钾扩散电位进一步刺激同位素钠摄取量达到每 5 秒 3.4 nmol/mg 蛋白质，这种效应仅在存在碳酸氢盐的情况下发生，并被二磺酸二苯乙烯阻断。作为钠浓度函数的碳酸氢盐依赖性钠吸收速率的动力学分析表明，饱和刺激的 Vmax 为每 2 秒 27 nmol/mg 蛋白质，Km 为 10.4 mM。碳酸氢盐浓度对碳酸氢盐依赖性钠吸收的影响更为复杂。目前的结果表明，兔肾皮质基底外侧膜囊泡中存在产电（带负电）钠/碳酸氢盐协同转运蛋白。生电性意味着每个钠离子至少有两个碳酸氢根离子的化学计量。
The present studies examined the mechanism of bicarbonate transport across basolateral membrane vesicles prepared from rabbit renal cortex. Isotopic sodium uptake was stimulated by bicarbonate when compared with gluconate (2.5 nmol/mg protein per 5 s versus 1.4 nmol/mg protein per 5 s), and this process was inhibited by disulfonic stilbenes. Imposition of an interior-positive potassium diffusion potential further stimulated isotopic sodium uptake to 3.4 nmol/mg protein per 5 s, an effect that occurred only in the presence of bicarbonate and was blocked by disulfonic stilbenes. Kinetic analysis of the rate of bicarbonate-dependent sodium uptake as a function of sodium concentration revealed saturable stimulation with a Vmax of 27 nmol/mg protein per 2 s and a Km of 10.4 mM. The effect of bicarbonate concentration on bicarbonate-dependent sodium uptake was more complex. The present results demonstrate an electrogenic (negatively charged) sodium/bicarbonate cotransporter in basolateral membrane vesicles from the rabbit renal cortex. The electrogenicity implies a stoichiometry of at least two bicarbonate ions for each sodium ion.