钾离子和膜电位对钠依赖性谷氨酸摄取的影响。

The effects of potassium and membrane potential on sodium-dependent glutamic acid uptake.

作者信息

Burckhardt G, Kinne R, Stange G, Murer H

出版信息

Biochim Biophys Acta. 1980 Jun 20;599(1):191-201. doi: 10.1016/0005-2736(80)90067-x.

Abstract

The uptake of L-glutamic acid into brush-border membrane vesicles isolated from rat renal proximal tubules is NA+-dependent. In contrast to Na+-dependent uptake of D-glucose, pre-equilibration of the vesicles with K+ stimulates L-glutamic acid uptake. Imposition of a K+ gradient ([Ki+] > [Ko+]) further enhances Na+-dependent L-glutamic acid uptake, but leaves K+-dependent glucose transport unchanged. If K+ is present only at the outside of the vesicles, transport is inhibited. Intravesicular Rb+ and, to a lesser extent, Cs+ can replace intravesicular K+ to stimulate L-glutamic acid uptake. Changes in membrane potential incurred by the imposition of an H+-diffusion potential or anion replacement markedly affect Na+-dependent glutamic acid uptake only in the presence of K+. Experiments with a potential-sensitive cyanine dye also indicate that, in the presence of intravesicular K+ a charge movement is involved in Na+-dependent transport of L-glutamic acid. The data indicate that Na+-dependent L-glutamic acid transport can be additionally energized by a K+ gradient. Furthermore, intravesicular K+ render Na+-dependent L-glutamic acid transport sensitive to changes in the transmembrane electrical potential difference.

摘要

从大鼠肾近端小管分离的刷状缘膜囊泡对L-谷氨酸的摄取是Na⁺依赖性的。与D-葡萄糖的Na⁺依赖性摄取相反，囊泡与K⁺预平衡可刺激L-谷氨酸的摄取。施加K⁺梯度（[Ki⁺]>[Ko⁺]）可进一步增强Na⁺依赖性L-谷氨酸的摄取，但对K⁺依赖性葡萄糖转运无影响。如果K⁺仅存在于囊泡外部，则转运受到抑制。囊泡内的Rb⁺以及程度较轻的Cs⁺可替代囊泡内的K⁺以刺激L-谷氨酸的摄取。施加H⁺扩散电位或阴离子替代引起的膜电位变化仅在有K⁺存在时才会显著影响Na⁺依赖性谷氨酸的摄取。用电位敏感的花青染料进行的实验也表明，在囊泡内有K⁺存在时，电荷移动参与了L-谷氨酸的Na⁺依赖性转运。数据表明，Na⁺依赖性L-谷氨酸转运可通过K⁺梯度额外提供能量。此外，囊泡内的K⁺使Na⁺依赖性L-谷氨酸转运对跨膜电位差的变化敏感。