Pasantes-Morales H, Schousboe A
Instituto de Fisiologia Celular, Universidad Nacional Autónoma de México, México City.
Glia. 1989;2(1):45-50. doi: 10.1002/glia.440020105.
Cultured astrocytes superfused with isosmotic solutions containing high concentrations of potassium, i.e., 25, 56, 75, and 100 mM, showed a proportional increase in cell volume corresponding to 25, 36, 57, and 75% greater than the cell volume in physiological solutions. This volume increase was abolished in low chloride or hypertonic solutions. The release of 3H-taurine previously accumulated by astrocytes was stimulated by potassium at all concentrations examined. During 4-minute exposure to 25, 56, 75, or 100 mM of potassium, cells released 13.5, 15.6, 20.2, or 36.2%, respectively, of the total labeled taurine accumulated during the preloading period. The potassium-stimulated release of 3H-taurine was calcium-independent and insensitive to BaCl2 and bumetanide. Substitution of chloride by gluconate to concentrations necessary to maintain the K+ X Cl- product constant abolished the potassium-stimulated release of 3H-taurine. Superfusion with solutions made hypertonic with sucrose also decreased the potassium-elicited efflux of 3H-taurine. In both conditions, the depolarizing effect of potassium measured with 3H-TPP+ was unchanged. High potassium concentrations and hyposmotic solutions released 3H-taurine by a nonadditive mechanism. These results indicate that in cultured astrocytes high concentrations of potassium produce both swelling and depolarization, but only swelling elicits the release of taurine. These observations suggest an involvement of taurine in cell-volume regulation in astrocytes.
用含有高浓度钾（即25、56、75和100 mM）的等渗溶液对培养的星形胶质细胞进行灌流，结果显示细胞体积呈比例增加，分别比生理溶液中的细胞体积大25%、36%、57%和75%。在低氯或高渗溶液中，这种体积增加被消除。在所有检测浓度下，钾离子均能刺激星形胶质细胞先前积累的3H-牛磺酸的释放。在暴露于25、56、75或100 mM钾离子的4分钟内，细胞分别释放了预加载期积累的总标记牛磺酸的13.5%、15.6%、20.2%或36.2%。钾离子刺激的3H-牛磺酸释放不依赖于钙，且对氯化钡和布美他尼不敏感。用葡萄糖酸盐替代氯化物至维持K+XCl-乘积恒定所需的浓度，可消除钾离子刺激的3H-牛磺酸释放。用蔗糖使溶液变为高渗状态进行灌流，也可减少钾离子引起的3H-牛磺酸外流。在这两种情况下，用3H-TPP+测量的钾离子去极化作用均未改变。高钾浓度和低渗溶液通过非加和机制释放3H-牛磺酸。这些结果表明，在培养的星形胶质细胞中，高浓度钾离子会导致细胞肿胀和去极化，但只有肿胀会引发牛磺酸的释放。这些观察结果提示牛磺酸参与了星形胶质细胞的细胞体积调节。
