Hagenbuch B, Murer H
Pflugers Arch. 1986;407 Suppl 2:S149-55. doi: 10.1007/BF00584944.
Basolateral membrane vesicles were isolated from rat renal proximal tubules by a Percoll-centrifugation method. Transport of phosphate could be stimulated by a sodium gradient but transport of D-glucose was not or only slightly affected by sodium. The Percoll-basolateral membrane fraction showed sodium-independent trans-stimulation of phosphate by itself. To test whether sodium stimulation of phosphate transport is influenced by the crosscontamination of basolateral with brush border membranes, the basolateral membrane fraction obtained by the Percoll-method was applied to free-flow electrophoresis for further purification. Thereby a separation of basolateral from brush border marker enzymes was obtained. It was possible to correlate net sodium-dependent phosphate transport with the brush border marker enzyme activity. ATP-dependent calcium uptake and cytochalasin B sensitive, sodium-independent D-glucose uptake followed basolateral, whereas phlorizin sensitive, sodium-dependent D-glucose followed brush border marker enzymes. Sodium dependent phosphate uptake was inhibited by D-glucose, this inhibition was released by phlorizin. It is concluded that the sodium-dependent phosphate uptake present in the Percoll-basolateral membrane fraction is due to crosscontamination with brush border membranes and that phosphate translocation across the basolateral membrane is carrier-mediated and sodium-independent.
采用Percoll离心法从大鼠肾近端小管分离出基底外侧膜囊泡。磷酸盐的转运可被钠梯度刺激，但D-葡萄糖的转运不受钠的影响或仅受到轻微影响。Percoll基底外侧膜部分自身显示出对磷酸盐的钠非依赖性反式刺激。为了测试钠对磷酸盐转运的刺激是否受基底外侧膜与刷状缘膜交叉污染的影响，将通过Percoll法获得的基底外侧膜部分应用于自由流动电泳以进一步纯化。由此实现了基底外侧膜与刷状缘标记酶的分离。可以将净钠依赖性磷酸盐转运与刷状缘标记酶活性相关联。ATP依赖性钙摄取以及细胞松弛素B敏感的、钠非依赖性D-葡萄糖摄取遵循基底外侧膜的情况，而根皮苷敏感的、钠依赖性D-葡萄糖摄取遵循刷状缘标记酶的情况。D-葡萄糖抑制钠依赖性磷酸盐摄取，根皮苷可解除这种抑制。得出的结论是，Percoll基底外侧膜部分中存在的钠依赖性磷酸盐摄取是由于与刷状缘膜的交叉污染，并且磷酸盐跨基底外侧膜的转运是由载体介导的且不依赖于钠。
