Olson J E, Li G Z
Department of Emergency Medicine, Wright State University School of Medicine, Dayton, Ohio 45429, USA.
Glia. 1997 Jul;20(3):254-61. doi: 10.1002/(sici)1098-1136(199707)20:3<254::aid-glia9>3.0.co;2-7.
Membrane conductances during hypoosmotic swelling were characterized in rat astrocytes in primary tissue culture. Using whole cell patch clamp techniques, mean +/- SEM cell conductance in isoosmotic phosphate-buffered saline (PBS) was 55.6 +/- 5.8 pS/pF. Cell conductance (mean +/- SEM) increased from this initial value to 187 +/- 46%, 561 +/- 188%, and 1216 +/- 376% within 9 min of exposure to 220 mOsm, 190 mOsm, and 145 mOsm PBS, respectively. With each of these hypoosmotic exposures, no change occurred in membrane capacitance. When CsCl replaced KCl in the microelectrode solution, a similar conductance increase was obtained at each osmolality. However, when gluconate salts were used in place of chloride salts in the electrode solution, no significant conductance increase was observed with 190 mOsm PBS. With a KCl microelectrode solution, all conductance increase which occurred in 190 mOsm PBS was inhibited by 200 microM niflumic acid, but not by 5 mM BaCl(2). Both niflumic acid and BaCl(2) inhibited 60-80% of the conductance increase of cells in 145 mOsm PBS. Using a microelectrode solution containing taurine as the major anion, membrane conductance increased 5-fold when cells were placed in 250 mOsm medium. This conductance increase was completely inhibited by 200 microM niflumic acid. Thus, independent chloride and potassium conductances are activated by hypoosmotic swelling of cultured astrocytes while plasma membrane area is unaltered. The chloride conductance pathway is activated at a significantly lower degree of hypoosmotic exposure than that which activates the potassium pathway and may be permeable to anionic taurine. These conductance pathways may mediate diffusive loss of potassium, chloride, and taurine from these cells during volume regulation following hypoosmotic swelling.
在原代组织培养的大鼠星形胶质细胞中，对低渗肿胀期间的膜电导进行了表征。使用全细胞膜片钳技术，等渗磷酸盐缓冲盐水（PBS）中的平均±标准误细胞电导为55.6±5.8 pS/pF。在分别暴露于220 mOsm、190 mOsm和145 mOsm PBS的9分钟内，细胞电导（平均±标准误）从该初始值分别增加到187±46%、561±188%和1216±376%。在每次这些低渗暴露中，膜电容没有变化。当氯化铯替代微电极溶液中的氯化钾时，在每个渗透压下都获得了类似的电导增加。然而，当在电极溶液中使用葡萄糖酸盐代替氯化物盐时，用190 mOsm PBS未观察到明显的电导增加。使用氯化钾微电极溶液时，在190 mOsm PBS中发生的所有电导增加都被200 μM氟尼辛抑制，但不被5 mM氯化钡抑制。氟尼辛和氯化钡都抑制了145 mOsm PBS中细胞电导增加的60 - 80%。使用含有牛磺酸作为主要阴离子的微电极溶液，当细胞置于250 mOsm培养基中时，膜电导增加了5倍。这种电导增加被200 μM氟尼辛完全抑制。因此，培养的星形胶质细胞的低渗肿胀激活了独立的氯和钾电导，而质膜面积未改变。氯电导途径在比激活钾途径显著更低程度的低渗暴露下被激活，并且可能对阴离子牛磺酸具有通透性。这些电导途径可能在低渗肿胀后的体积调节过程中介导这些细胞中钾、氯和牛磺酸的扩散性丢失。
