Contribution of Na(+)-K(+)-Cl(-) cotransporter to high-[K(+)](o)- induced swelling and EAA release in astrocytes.
We hypothesized that high extracellular K(+) concentration ([K(+)](o))-mediated stimulation of Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) may result in a net gain of K(+) and Cl(-) and thus lead to high-[K(+)](o)-induced swelling and glutamate release. In the current study, relative cell volume changes were determined in astrocytes. Under 75 mM [K(+)](o,) astrocytes swelled by 20.2 +/- 4.9%. This high-[K(+)](o)-mediated swelling was abolished by the NKCC1 inhibitor bumetanide (10 microM, 1.0 +/- 3.1%; P < 0.05). Intracellular (36)Cl(-) accumulation was increased from a control value of 0.39 +/- 0.06 to 0.68 +/- 0.05 micromol/mg protein in response to 75 mM [K(+)](o). This increase was significantly reduced by bumetanide (P < 0.05). Basal intracellular Na(+) concentration ([Na(+)](i)) was reduced from 19.1 +/- 0.8 to 16.8 +/- 1.9 mM by bumetanide (P < 0.05). [Na(+)](i) decreased to 8.4 +/- 1.0 mM under 75 mM [K(+)](o) and was further reduced to 5.2 +/- 1.7 mM by bumetanide. In addition, the recovery rate of [Na(+)](i) on return to 5.8 mM [K(+)](o) was decreased by 40% in the presence of bumetanide (P < 0.05). Bumetanide inhibited high-[K(+)](o)-induced (14)C-labeled D-aspartate release by ~50% (P < 0.05). These results suggest that NKCC1 contributes to high-[K(+)](o)-induced astrocyte swelling and glutamate release.
Su
Gui
G
Department of Neurological Surgery, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA.
Kintner
Douglas B
DB
Sun
Dandan
D
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D002034:Bumetanide / Q000494:pharmacology; D048429:Cell Size; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism*; D004232:Diuretics / Q000494:pharmacology; D009994:Osmolar Concentration; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism*; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters / Q000378:metabolism*
D002712:Chlorides; D004232:Diuretics; D049994:Sodium Potassium Chloride Symporter Inhibitors; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D001224:Aspartic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium