Demonstration of electrogenic Na+-dependent D-glucose transport in intestinal brush border membranes.
Demonstration of electrogenic Na+-dependent D-glucose transport in intestinal brush border membranes.
复制标题
证明肠刷状缘膜中电生 Na 依赖性 D-葡萄糖转运。
DOI：
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发表时间：
1974
影响因子：
11.1
通讯作者：
U. Hopfer
中科院分区：
文献类型：
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作者：
H. Murer;U. Hopfer
在离体肠刷状缘膜泡中研究了Na（+）-偶联D-葡萄糖转运。在囊内溶液和孵育介质之间建立SCN（-）、K（+）和H（+）的浓度梯度，并测量它们对从介质摄取D-葡萄糖的影响。NaSCN的梯度（介质>囊泡）而不是KSCN的梯度产生高于平衡水平的D-葡萄糖摄取的瞬时过冲。类似地，如果在每种情况下分别存在（囊泡>介质）K（+）-梯度或H（+）-梯度，则用缬氨霉素（K（+）-电导）或氧化磷酸化解偶联剂（H（+）-电导）增加膜电导可诱导超调D-葡萄糖摄取。瞬时过冲是D-葡萄糖逆其浓度梯度（高达10倍）被吸收的证据。SCN（-）、K（+）（在缬氨霉素存在下）和H（+）（在解偶联剂存在下）的梯度被认为通过改变囊泡膜上的电位并因此使内部更负（相对于介质）而有助于这种“主动”D-葡萄糖转运的“驱动”力。因此，这些实验提供了Na（+）-偶联的D-葡萄糖跨刷状缘膜易位是一个产电过程的证据，即，与Na（+）相关的正电荷不被经由葡萄糖“载体”的阴离子的共同运动或阳离子的反向运动所补偿。结果表明，刷状缘膜的电位可能在决定完整细胞的D-葡萄糖转运中起重要作用。
Na(+)-coupled D-glucose transport was studied in isolated membrane vesicles from intestinal brush borders. Concentration gradients of SCN(-), K(+), and H(+) were established between the intravesicular solution and the incubation medium and their influence on D-glucose uptake from the medium was measured. A gradient (medium > vesicle) of NaSCN, but not of KSCN, produced a transient overshoot of D-glucose uptake above the equilibrium level. Similarly, an increase of the membrane conductance with valinomycin (K(+)-conductance) or with uncoupling agents of oxidative phosphorylation (H(+)-conductance) induced an overshooting D-glucose uptake, provided a (vesicle > medium) K(+)-gradient or a H(+)-gradient, respectively, was present in each case. The transient overshoot is evidence that D-glucose was taken up against its concentration gradient (up to 10-fold). The gradients of SCN(-), K(+) (in the presence of valinomycin), and H(+) (in the presence of uncouplers) are thought to contribute to the "driving" force for this "active" D-glucose transport by changing the electrical potential across the vesicle membrane and thus making the inside more negative (with respect to the medium). These experiments, therefore, provide evidence that the Na(+)-coupled D-glucose translocation across the brush border membrane is an electrogenic process, i.e., the positive charge associated with Na(+) is not compensated by the co-movement of an anion or the counter-movement of a cation via the glucose "carrier". The results imply that an electrical potential across the brush border membrane may play an important role in determining the transport of D-glucose by intact cells.