Role of Na/K/Cl cotransport in astrocytes.
The kinetic characterization of the Na/K/Cl cotransport of cultured astrocytes and evidence for its involvement in volume regulation and K+ net uptake during K+ clearance are reviewed. Emphasis is put on experimental evidence for a proposed sodium cycle in astrocytes; this cycle involves a Na(+)-K+ ATPase that is stimulated by both a high external K+ and intracellular Na+. Elevated external K+ also stimulates the Na/K/Cl carrier, transporting these ions inward. As a result Na+ is cycled across the membrane, carried inward by the Na/K/Cl carrier, and returned by the Na(+)-K+ ATPase. Both functionally coupled mechanisms lead to intracellular KCl accumulation and inward movements of water to compensate for increased osmolarity. The combined cycle is expected to play a major role in the regulation of physiological K+ levels in the brain.
Walz
W
W
Department of Physiology, College of Medicine, University of Saskatchewan, Saskatoon, Canada.
D000818:Animals; D001253:Astrocytes / Q000378:metabolism*; D002352:Carrier Proteins / Q000378:metabolism*; D002712:Chlorides / Q000378:metabolism*; D006801:Humans; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D002712:Chlorides; D028021:Sodium-Potassium-Chloride Symporters; D012964:Sodium; D011188:Potassium