Swelling and potassium uptake in cultured astrocytes.
The intracellular water content of astrocytes in primary cultures shows a biphasic swelling pattern on exposure to various increased external K+ concentrations over the range of 1.5-100 mM. The two phases (physiological, 1.5-12 mM K+; pathological, 25-100 mM K+) are based on two different mechanisms. Both can be blocked by low Cl- solutions and involve intensive net uptake of K+. However, the physiological phase consists of the activation of a KCl + NaCl carrier, while the Na+ in turn is pumped out by Na+-K+ ATPase, with a resultant net accumulation of KCl. At pathological K+ concentrations the KCl + NaCl carrier is less active because the Na+ driving force, its energy source, is reduced (owing to depolarization by K+). However, the Donnan equilibrium across the cell membrane is heavily disturbed, which leads to passive KCl accumulation. The results suggest that volume changes in cultured glial cells during exposure to high K+ should be taken into consideration since they disguise K+ accumulation when only ion activity is measured.
D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001834:Body Water / Q000378:metabolism*; D002478:Cells, Cultured; D005110:Extracellular Space / Q000378:metabolism; D005665:Furosemide / Q000494:pharmacology; D007424:Intracellular Fluid / Q000378:metabolism; D008564:Membrane Potentials; D051379:Mice
D005665:Furosemide