Carrier-mediated Cl- transport in cultured mouse oligodendrocytes.
We studied the steady state and the regulation of intracellular Cl- activity (aCl-i) and the mechanisms of KCl uptake in cultured oligodendrocytes from mouse spinal cord using Cl(-)-selective microelectrodes. The majority of oligodendrocytes actively accumulated Cl- above passive distribution (2-3 mM), few cells showed a passive Cl- distribution. To identify the carriers mediating Cl- uptake, oligodendrocytes were maintained in a solution with low extracellular Cl- concentration ([Cl-]o) which resulted in a rapid decrease in aCl-i. The recovery of aCl-i above its passive distribution in normal [Cl-]o was blocked in the absence of Na+ or in the presence of furosemide and of bumetanide, which has been reported to inhibit Na+/K+/Cl- cotransport. We therefore conclude that Cl- uptake is primarily due to the activity of a Na+K+/Cl- transport system. Cl- uptake above passive distribution was not affected in HCO3(-)-free solution or in the presence of SITS and DIDS, indicating that Cl-/HCO3- exchange is not involved in Cl- uptake by oligodendrocytes. Elevation of [K+]o induced an increase in aCl-i and, as shown earlier, intracellular K+ activity. This K+-induced Cl- uptake was not blocked by bumetanide, furosemide, SITS, or DIDS, suggesting that under conditions of raised [K+]o the combined uptake of K+ and Cl- is not mediated by a carrier, but can be explained by the entry through channels driven by Donnan forces.
Department of Neurobiology, University of Heidelberg, Federal Republic of Germany.
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Kettenmann
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D002478:Cells, Cultured; D002712:Chlorides / Q000493:pharmacokinetics / Q000502:physiology*; D004563:Electrochemistry; D005665:Furosemide / Q000494:pharmacology; D051379:Mice; D009457:Neuroglia / Q000502:physiology*; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011189:Potassium Chloride / Q000493:pharmacokinetics*; D012964:Sodium / Q000494:pharmacology; D013116:Spinal Cord / Q000166:cytology / Q000378:metabolism / Q000502:physiology*
D002712:Chlorides; D002034:Bumetanide; D011189:Potassium Chloride; D005665:Furosemide; D012964:Sodium