Chassande O, Frelin C, Farahifar D, Jean T, Lazdunski M
Centre de Biochimie, Centre National de la Recherche Scientifique, Nice, France.
Eur J Biochem. 1988 Feb 1;171(3):425-33. doi: 10.1111/j.1432-1033.1988.tb13807.x.
The role of the Na+/K+/Cl- cotransporter in the regulation of the volume of C6 astrocytoma cells was analyzed using isotopic fluxes and cell cytometry measurements of the cell volume. The system was inhibited by 'loop diuretics' with the following order of potency: benzmetanide greater than bumetanide greater than piretanide greater than furosemide. Under physiological conditions of osmolarity of the incubation media, equal rates of bumetanide-sensitive inward and outward K+ fluxes were observed. Blockade of the Na+/K+/Cl- cotransporter with bumetanide did not lead to a modification in the mean cell volume. When C6 cells were incubated in an hyperosmotic solution, a cell shrinkage was observed. It was accompanied by a twofold increase in the activity of the Na+/K+/Cl- cotransport, which then catalyzed the net influx of K+. In spite of this increased activity, no cell swelling could be measured. Incubation of the cells in an iso-osmotic medium deprived of either Na+, K+ or Cl- also produced cell shrinkage. Large activations (up to tenfold) of the Na+/K+/Cl- cotransport together with a cell swelling back to the normal volume were observed upon returning ion-deprived C6 cells to a physiological solution. This cell swelling was completely prevented in the presence of bumetanide. It is concluded that the Na+/K+/Cl- cotransport system is one of the transport systems involved in volume regulation of glial cells. The system can either be physiologically quiescent or active depending on the conditions used. A distinct volume regulating mechanism is the Na+/H+ exchange system.
利用同位素通量和细胞体积的细胞流式细胞术测量，分析了Na+/K+/Cl-共转运体在调节C6星形细胞瘤细胞体积中的作用。该系统被“袢利尿剂”抑制，其效力顺序如下：苄甲噻嗪＞布美他尼＞吡咯他尼＞呋塞米。在孵育培养基渗透压的生理条件下，观察到布美他尼敏感的内向和外向K+通量速率相等。用布美他尼阻断Na+/K+/Cl-共转运体不会导致平均细胞体积发生改变。当C6细胞在高渗溶液中孵育时，观察到细胞收缩。这伴随着Na+/K+/Cl-共转运活性增加两倍，随后催化K+的净内流。尽管活性增加，但未检测到细胞肿胀。将细胞在缺乏Na+、K+或Cl-的等渗培养基中孵育也会导致细胞收缩。当将离子缺乏的C6细胞恢复到生理溶液中时，观察到Na+/K+/Cl-共转运大幅激活（高达十倍），同时细胞肿胀恢复到正常体积。在布美他尼存在的情况下，这种细胞肿胀被完全阻止。结论是，Na+/K+/Cl-共转运系统是参与神经胶质细胞体积调节的转运系统之一。该系统根据所使用的条件可以是生理静止的或活跃的。一种独特的体积调节机制是Na+/H+交换系统。
