钠泵离子结合位点之间的联系。

The connexion between the ion-binding sites of the sodium pump.

Chipperfield A R, Whittam R

J Physiol. 1976 Sep;260(2):371-85. doi: 10.1113/jphysiol.1976.sp011520.

Abstract

A study has been made of K influx into human red blood cells in order to determine the influence of internal Na on the affinity of the Na pump for external K. Cells were prepared to contain minimal K and two Na concentrations (about 10 and 30 mueqiv/ml. cells) and incubated in solutions with a range of K concentrations. 2. In choline (Na-free) Ringer, activation of K influx by external K was hyperbolic. The Km for external K increased as the internal Na concentration was raised. The increase was greater than the increase in K influx with saturating external K. The Km for external K increased towards a limiting value as the internal Na concentration was raised. 3. In contrast, in Na-Ringer, the activation by external K was sigmoidal and the affinity for external K was independent of the internal Na concentration. 4. K influx was measured at two submaximal levels of external K with a range of internal Na. The affinity for internal Na fell as external K was raised. 5. The results suggest that in the absence of competition between Na and K on the same side of the membrane, there is a connexion between the ion-binding sites of the Na pump.

摘要

为了确定细胞内钠离子对钠泵与细胞外钾离子亲和力的影响，对钾离子流入人体红细胞的情况进行了一项研究。制备的细胞含有最低限度的钾离子以及两种钠离子浓度（约10和30微当量/毫升细胞），并在含有一系列钾离子浓度的溶液中孵育。2. 在胆碱（无钠）林格液中，细胞外钾离子对钾离子流入的激活呈双曲线型。随着细胞内钠离子浓度升高，细胞外钾离子的米氏常数（Km）增加。这种增加大于饱和细胞外钾离子时钾离子流入的增加。随着细胞内钠离子浓度升高，细胞外钾离子的Km朝着一个极限值增加。3. 相比之下，在含钠林格液中，细胞外钾离子的激活呈S型，且对细胞外钾离子的亲和力与细胞内钠离子浓度无关。4. 在一系列细胞内钠离子浓度下，在两个低于最大水平的细胞外钾离子浓度下测量钾离子流入。随着细胞外钾离子浓度升高，对细胞内钠离子的亲和力下降。5. 结果表明，在膜同一侧不存在钠离子和钾离子竞争的情况下，钠泵的离子结合位点之间存在联系。