Kimelberg H K, Biddlecome S, Bourke R S
Brain Res. 1979 Sep 7;173(1):111-24.
The uptake and efflux of Cl- were measured in primary astroglial cultures from neonatal rat brain using 36Cl- as a tracer. Both uptake and efflux were found to be inhibited by the specific anion inhibitor SITS. The rate of Cl- efflux showed a broad optimum at pH values greater than 7.5, and both this pH dependence and the effect of SITS suggests that these cells contain a Cl- in equilibrium Cl- or Cl- in equilibrium HCO3- exchange carrier similar to that described in erythrocytes. In addition, the cells rapidly lost Cl- when placed in media of decreasing Cl- concentrations, and ploting the initial rate of uptake of 36Cl- as a function of external Cl- concen-ration gave an apparent Km for Cl- uptake of 56 mM. Pretreatment of these cultures with DBcAMP is known to cause the cells to form numerous processes, resulting in their morphology more closely resembling that of astroglia in brain. Treatment with DBcAMP resulted in decreased equilibrium levels of 36Cl- and a small decrease in the initial rate of uptake of 36Cl-, but did not affect inhibition by SITS. Addition of Na+ to the cells suspended in Na+-free media specifically increased the rate of acidification of the medium. These observations suggest that these cells have both Cl- in equilibrium HCO3- and Na+ in equilibrium H+ exchange processes which, if these cultures can be considered to be representative of cells in vivo, may also occur in astroglial cells in the central nervous system. Based on these results and other work, a model is proposed by which these processes would lead to the astroglial swelling which is often observed in vivo in pathological conditions.
利用³⁶Cl⁻作为示踪剂，在新生大鼠脑原代星形胶质细胞培养物中测量了Cl⁻的摄取和流出。发现摄取和流出均受到特异性阴离子抑制剂SITS的抑制。Cl⁻流出速率在pH值大于7.5时呈现出较宽的最佳值，这种pH依赖性以及SITS的作用表明，这些细胞含有一种与红细胞中描述的类似的Cl⁻/Cl⁻或Cl⁻/HCO₃⁻平衡交换载体。此外，当将细胞置于Cl⁻浓度降低的培养基中时，细胞会迅速失去Cl⁻，将³⁶Cl⁻的初始摄取速率绘制为外部Cl⁻浓度的函数，得到Cl⁻摄取的表观Km为56 mM。已知用二丁酰环磷腺苷（DBcAMP）预处理这些培养物会使细胞形成许多突起，导致其形态更类似于脑中的星形胶质细胞。用DBcAMP处理导致³⁶Cl⁻的平衡水平降低，³⁶Cl⁻的初始摄取速率略有下降，但不影响SITS的抑制作用。向悬浮在无钠培养基中的细胞中添加Na⁺会特异性地增加培养基的酸化速率。这些观察结果表明，这些细胞具有Cl⁻/HCO₃⁻和Na⁺/H⁺平衡交换过程，如果这些培养物可被视为体内细胞的代表，那么中枢神经系统中的星形胶质细胞中也可能发生这些过程。基于这些结果和其他研究，提出了一个模型，通过该模型这些过程将导致在病理条件下体内经常观察到的星形胶质细胞肿胀。
