Sánchez-Olea R, Morán J, Pasantes-Morales H
Department of Neurosciences, National University of Mexico, Mexico City.
J Neurosci Res. 1992 May;32(1):86-92. doi: 10.1002/jnr.490320111.
Cultured astrocytes grown chronically (1-3 days) in medium made hyperosmotic (450 mOsm) with NaCl or sucrose showed an increase in taurine concentration from 294 to 501 nmol/mg protein in NaCl and to 382 nmol/mg protein in sucrose. The effect of hyperosmolarity on taurine uptake and release was examined to investigate whether or not changes in these processes may account for the increase observed in cell taurine content. Hyperosmolarity significantly affected the two components of taurine uptake (i.e., the Na(+)-dependent and the diffusional component). The Vmax of the Na(+)-dependent, active transport increased 50%, whereas no change was observed in the Km. The diffusion coefficient was markedly decreased by hyperosmolarity, being 2.2 x 10(-4) and 6.6 x 10(-6) ml/min/mg protein in isosmotic and hyperosmotic conditions, respectively, indicating a blockade of the leak pathway. These changes in the active and passive components of taurine transport were opposite to those induced by hyperosmolarity. The effect of hyperosmolarity increasing cell taurine content was insensitive to cycloheximide and colchicine. The basal efflux of taurine from astrocytes also decreased in cells exposed to hyperosmotic medium, indicating that alterations in both influx and efflux of taurine are involved in the mechanism responsible for the increase in taurine levels induced by hyperosmolarity in astrocytes.
在添加氯化钠或蔗糖使其渗透压升高（450毫渗量）的培养基中培养1 - 3天的星形胶质细胞，其牛磺酸浓度从294纳摩尔/毫克蛋白质增加到氯化钠处理组的501纳摩尔/毫克蛋白质以及蔗糖处理组的382纳摩尔/毫克蛋白质。研究了高渗对牛磺酸摄取和释放的影响，以探究这些过程的变化是否可以解释细胞牛磺酸含量的增加。高渗显著影响牛磺酸摄取的两个组成部分（即钠依赖型和扩散型）。钠依赖型主动转运的Vmax增加了50%，而Km没有变化。高渗使扩散系数显著降低，在等渗和高渗条件下分别为2.2×10⁻⁴和6.6×10⁻⁶毫升/分钟/毫克蛋白质，表明渗漏途径被阻断。牛磺酸转运的主动和被动组成部分的这些变化与高渗诱导的变化相反。高渗增加细胞牛磺酸含量的作用对环己酰亚胺和秋水仙碱不敏感。暴露于高渗培养基中的星形胶质细胞中牛磺酸的基础外流也减少，这表明牛磺酸流入和流出的改变都参与了星形胶质细胞中高渗诱导的牛磺酸水平升高的机制。
