Control of cation transport in cultured glial cells by external Ca++: a possible signal in glial-neuronal interaction.
In cultured glial cells from chick embryonic brain, both influx and efflux of 42K+ and 22Na+ are dependent on the external Ca++ and concentration ([Ca++]0) between 2 and 0.1 mM although intracellular concentrations of K+ ([K+]i) and Na+ ([Na+]i) do not change. Only a reduction of [Ca++]0 below 0.1 mM results in both a decrease of [K+]i and an increase of [Na+]i. Ouabain significantly decreases the [Ca++]0 sensitivity of uphill cation movements (K+ influx and Na+ efflux), while the [Ca++]0 sensitivity of downhill cation movements (K+ efflux and Na+ influx) is almost not affected by the presence of ouabain. Additionally, a decrease in [Ca++]0 triggers an increase in intracellular concentration of adenosine 3':5'-cyclic monophosphoric acid (cAMP). These findings suggest that changes of [Ca++]0, which take place in vivo in the microenvironment of the glia after neuronal firing, represent a signal in the glial-neuronal interaction controlling cation transport and that this control is achieved by a co-operation between the cAMP-generating and the cation transport system.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D001921:Brain / Q000166:cytology; D002118:Calcium / Q000494:pharmacology*; D002413:Cations, Divalent; D002478:Cells, Cultured; D002642:Chick Embryo; D000242:Cyclic AMP / Q000378:metabolism; D009457:Neuroglia / Q000378:metabolism*; D009474:Neurons / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D002413:Cations, Divalent; D010042:Ouabain; D012964:Sodium; D000242:Cyclic AMP; D000254:Sodium-Potassium-Exchanging ATPase; D011188:Potassium; D002118:Calcium