Grichtchenko I I, Chesler M
Department of Neurosurgery, N.Y.U. Medical Center, NY 10016.
Neuroscience. 1994 Oct;62(4):1071-8. doi: 10.1016/0306-4522(94)90344-1.
Depolarization-induced, intracellular alkaline shifts were studied in reactive astrocytes within slices of gliotic hippocampus. Slices were prepared 10-28 days after sterotaxic injection of kainic acid into the hippocampus of anesthetized rats. Astrocytes in gliotic CA3 were impaled with double-barreled pH sensitive microelectrodes and depolarized by iontophoresis of K+ from an adjacent micropipette. Elevation of extracellular K+ produced an intracellular alkalinization that grew with increasing membrane depolarization, ranging from approximately 0.10 to 0.30 pH units. Exposure to Ba2+ depolarized the cells and produced a similar alkalinization. In the presence of Ba2+, the K(+)-induced depolarization and the associated alkaline shift were abolished. The depolarization-induced alkaline shifts were partially inhibited (40 +/- 8.9%) in Na(+)-free media and were enhanced in bicarbonate versus HEPES-buffered saline. The alkalinizations were unaffected by incubation in chloride-free media, or by the stilbene 4,4'-dinitrostilbene-2,2'-disulfonic acid. It is concluded that the depolarization-induced alkaline shift of reactive astrocytes is mediated in part by a Na+ and HCO3(-)-dependent mechanism that is insensitive to stilbenes. These characteristics correspond well with the properties of depolarization-induced acid secretion in the gliotic tissue. In addition, a separate, Na(+)-independent mechanism contributes to the depolarization-induced alkalinization. In view of the absolute Na+ dependence of acid secretion in the gliotic slices, we propose that the latter mechanism does not extrude acid across the plasma membrane.
在胶质化海马切片中的反应性星形胶质细胞中研究了去极化诱导的细胞内碱化。切片是在向麻醉大鼠海马体立体定位注射海藻酸10 - 28天后制备的。用双管pH敏感微电极刺入胶质化CA3区的星形胶质细胞，并通过相邻微吸管离子电泳施加K +使其去极化。细胞外K +升高导致细胞内碱化，随着膜去极化程度增加而增强，范围约为0.10至0.30个pH单位。暴露于Ba2 +使细胞去极化并产生类似的碱化。在存在Ba2 +的情况下，K +诱导的去极化和相关的碱化转变被消除。在无Na +培养基中，去极化诱导的碱化转变受到部分抑制（40±8.9％），并且在碳酸氢盐缓冲液与HEPES缓冲盐溶液相比时增强。在无氯培养基中孵育或使用二苯乙烯4,4'-二硝基二苯乙烯-2,2'-二磺酸处理后，碱化不受影响。得出的结论是，反应性星形胶质细胞的去极化诱导的碱化转变部分由对二苯乙烯不敏感的Na +和HCO3（ - ）依赖性机制介导。这些特性与胶质化组织中去极化诱导的酸分泌特性非常吻合。此外，一种独立于Na +的机制促成了去极化诱导的碱化。鉴于胶质化切片中酸分泌对Na +的绝对依赖性，我们提出后一种机制不会通过质膜排出酸。
