Rosenthal M, Sick T J
Department of Neurology, University of Miami School of Medicine, FL 33101.
Can J Physiol Pharmacol. 1992;70 Suppl:S165-9. doi: 10.1139/y92-258.
Putative roles of glycolytic and oxidative metabolism in the removal of potassium ion from the extracellular space were examined in rat cerebral cortex. In response to direct electrical stimulation of the cerebral surface, the activity of extracellular potassium ion (Ko+) transiently increased. Inhibition of glycolysis with iodoacetate prolonged the time required for dissipation of the elevated Ko+. This slowing was most evident in the early period after stimulation, when Ko+ was relatively high. Levels of high-energy intermediates were unchanged by iodoacetate. In contrast, severe hypoxemia was without effect during the early phase of K+ removal but hypoxemia slowed the later restoration of the Ko+ baseline. These data demonstrate that the rapid removal of potassium ion from the extracellular space following intense neuronal activity is aided by the Embden-Myerhoff metabolic pathways and perhaps by direct coupling of ATP produced by glycolysis. We suggest that removal of potassium ion from the brain extracellular space depends on two ATP pools, one derived from oxidative phosphorylation, the other from glycolysis. The glycolytic ATP pool may be most involved in the early and rapid phase of potassium clearance; the oxidative ATP pool may be more associated with the second and slower phase of Ko+ clearance, and with the maintenance of the Ko+ baseline under 'resting' conditions.
在大鼠大脑皮层中研究了糖酵解和氧化代谢在从细胞外空间清除钾离子方面的假定作用。响应于对脑表面的直接电刺激，细胞外钾离子（Ko +）的活性短暂增加。用碘乙酸抑制糖酵解延长了升高的Ko +消散所需的时间。这种减慢在刺激后的早期最为明显，此时Ko +相对较高。高能中间体的水平不受碘乙酸影响。相反，严重低氧血症在K +清除的早期阶段没有影响，但低氧血症减缓了Ko +基线的后期恢复。这些数据表明，强烈神经元活动后从细胞外空间快速清除钾离子得益于Embden-Myerhoff代谢途径，也许还得益于糖酵解产生的ATP的直接偶联。我们认为，从脑细胞外空间清除钾离子依赖于两个ATP池，一个来自氧化磷酸化，另一个来自糖酵解。糖酵解ATP池可能最参与钾清除的早期和快速阶段；氧化ATP池可能更多地与Ko +清除的第二个较慢阶段相关，并与“静息”条件下Ko +基线的维持相关。
