Glial cell function: active control of extracellular K + concentration

To investigate the ability of the glial cell to control the extracellular K+ ion concentration in the CNS 3 kinds of experiment were carried out. (1) The ability of isolated cell fractions enriched in glia or neurons to reaccumulate K+ was measured. (2) The activation of the Na+single bondK+-ATPase by K+ was measured on these isolated cell suspensions. (3) Plasma membrane fractions were prepared from neurons and glia and the Na+single bondK+-ATPase activity was studied as a function of K+ ion concentration. The glial cell Na+single bondK+-ATPase was always more active, approximately 2.5- to 4-fold, and markedly more sensitive to variations in the K+ ion concentration than the neuronal ATPase. These results support the idea that control of the extracellular K+ ion concentration in the CNS is at least in part dependent on the metabolically coupled sodium-potassium pump of the glial cell