A linked active transport system for Na+ and K+ in a glial cell line

Ouabain (5 X 10(-4) M) induced a 6-fold increase in intracellular Na+ and a 65% loss of cellular K+ in C6 glial cells which was accompanied by a 12 mV decrease in the resting membrane potential. Following ouabain washout intracellular ion concentrations and the membrane potential returned to control levels suggesting that C6 is capable of active Na+ transport which is linked to uptake of K+. A portion of K+ uptake under steady-state conditions is also active since K+ influx was reduced 32% by ouabain. Five mM cyanide significantly increased cell Na+ and significantly decreased cell K+ and the membrane potential. The similarity in the ratio of Na+ gained/K+ lost (ouabain 1.24, cyanide 1.41) suggests that the two agents inhibit the same ion transport system. Decreased temperature had the paradoxical effect of increasing intracellular K+ while significantly decreasing both membrane potential and K+ influx. Part of this effect may be due to the marked reduction in K+ efflux at low temperature. At 6 degrees C cell loss of K+ was much less than loss of K+ with ouabain at 37 degrees C. The observation of a linked Na+-K+ transport system in C6 cell confirms the hypothesis that coupled active Na+-K+ exchange occurs in glial cells and suggests that ionic transport may regulate certain aspects of glial metabolism.