Increased Vmax for Na+/H+ antiporter activity in proximal tubule brush border vesicles from rabbits with metabolic acidosis.
Increased Vmax for Na+/H+ antiporter activity in proximal tubule brush border vesicles from rabbits with metabolic acidosis.
复制标题
代谢性酸中毒兔子近端小管刷状缘囊泡中 Na /H 逆向转运蛋白活性的 Vmax 增加。
DOI：
10.1152/ajprenal.1984.247.2.f339
复制
发表时间：
1984
期刊：
影响因子：
--
通讯作者：
RectorJr,FC
中科院分区：
文献类型：
--
作者：
Tsai,CJ;Ives,HE;Alpern,RJ;Yee,VJ;Warnock,DG;RectorJr,FC
使用吖啶橙法测量对照兔和用 NH4Cl 灌胃 3 天酸中毒的兔的肾刷状缘小泡中 Na+/H+ 逆向转运蛋白活性。与对照 (1.31 +/- 0.13) 相比，酸中毒的兔子表现出显着更高的反向转运蛋白活性 Vmax (2.80 +/- 0.45 荧光单位 X s-1 X mg Protein-1)，但 Na+ 的 Km 没有变化（酸中毒为 23.7 +/- 3.5，对照为 19.1 +/- 3.2 mM）。当考虑 Na+/H+ 逆向转运蛋白活性的 Vmax 与实验动物的酸中毒程度相关时，Vmax 和血浆总 CO2 浓度之间存在相关性 (r = -0.75)。阿米洛利 (100 microM) 在对照和酸中毒动物中均抑制 Na+/H+ 交换 (Na+ = 90 mM) 59 +/- 7%，表明观察到的 Na+/H+ 逆向转运蛋白活性刺激并非由于电耦合阳离子交换增加所致。这些发现表明，近端小管对慢性代谢性酸中毒的反应涉及刷状缘膜中Na+/H+逆向转运蛋白活性的Vmax的适应性增加，这与动物的酸中毒程度相关。
Na+/H+ antiporter activity in renal brush border vesicles from control rabbits and rabbits made acidotic with 3 days of NH4Cl gavage was measured using the acridine orange method. Acidotic rabbits exhibited a significantly higher Vmax for antiporter activity (2.80 +/- 0.45 fluorescence units X s-1 X mg protein-1) compared with controls (1.31 +/- 0.13) but the Km for Na+ was unchanged (23.7 +/- 3.5 for acidotic, 19.1 +/- 3.2 mM for controls). When the Vmax for Na+/H+ antiporter activity was considered in relation to the degree of acidosis achieved in the experimental animals, there was a correlation (r = -0.75) between Vmax and plasma total CO2 concentration. Amiloride (100 microM) inhibited Na+/H+ exchange (Na+ = 90 mM) by 59 +/- 7% in both control and acidotic animals, indicating that the observed stimulation in Na+/H+ antiporter activity was not due to increased electrically coupled cation exchange. These findings suggest that the response of the proximal tubule to chronic metabolic acidosis involves an adaptive increase in the Vmax for Na+/H+ antiporter activity in the brush border membrane that is correlated to the degree of acidosis in the animals.