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

Quabain (5 × 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 m M cyanide significantly increased cell Na s+ 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 due to the marked reduction in K + efflux at low temperature. At 6 °C cell loss of K + was much less than loss of K + with ouabain at 37 °C. The observation of a linked Na + K + transport system in C6 cells 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.