Olson J E, Evers J A
Wright State University School of Medicine, Department of Emergency Medicine, Dayton, OH 45429.
Can J Physiol Pharmacol. 1992;70 Suppl:S350-5. doi: 10.1139/y92-282.
Energy metabolism, ion transport, and water content are interrelated in mechanisms of homeostasis of the brain intracellular and extracellular environment. The simplest model of cell homeostasis, the pump-leak hypothesis, incorporates basic relationships between these variables. Although this model accurately calculates steady-state cell volumes, ion concentrations, and metabolic rates, it fails to predict dynamic changes in these properties during elevated extracellular potassium, metabolic inhibition, and osmotic swelling. We have investigated relationships between ions, energy metabolism, and water content in cerebral astrocytes cultured from the neonatal rat. These cells swell more in hypoosmotic phosphate-buffered saline (PBS) containing NaCl than in hypoosmotic PBS with all NaCl replaced equiosmotically by sucrose. Unidirectional Na+ influx also is greater in cells suspended in hypoosmotic, compared with isoosmotic PBS. These data suggest that astrocytes possess a cell volume dependent mechanism of Na+ accumulation. The influx of Na+ during swelling may be coupled to metabolism via Na-K ATPase and may contribute to the sustained swelling of astrocytes observed in hypoosmotic swelling of the brain in situ.
能量代谢、离子转运和水分含量在脑内细胞内和细胞外环境的稳态机制中相互关联。细胞稳态的最简单模型，即泵-漏假说，纳入了这些变量之间的基本关系。尽管该模型能准确计算稳态细胞体积、离子浓度和代谢率，但它无法预测细胞外钾升高、代谢抑制和渗透性肿胀期间这些特性的动态变化。我们研究了新生大鼠培养的脑星形胶质细胞中离子、能量代谢和水分含量之间的关系。与等渗磷酸盐缓冲盐水（PBS）相比，这些细胞在含有NaCl的低渗PBS中比在所有NaCl被等渗蔗糖替代的低渗PBS中肿胀得更厉害。与等渗PBS悬浮的细胞相比，低渗PBS悬浮的细胞中单向Na+内流也更大。这些数据表明星形胶质细胞具有一种依赖细胞体积的Na+积累机制。肿胀期间Na+的内流可能通过Na-K ATP酶与代谢偶联，并可能导致原位脑低渗肿胀中观察到的星形胶质细胞持续肿胀。
