title: Astrocytes from Na(+)-K(+)-Cl(-) cotransporter-null mice exhibit absence of swelling and decrease in EAA release.
abstract: We reported previously that inhibition of Na(+)-K(+)-Cl(-) cotransporter isoform 1 (NKCC1) by bumetanide abolishes high extracellular K(+) concentration ([K(+)](o))-induced swelling and intracellular Cl(-) accumulation in rat cortical astrocytes. In this report, we extended our study by using cortical astrocytes from NKCC1-deficient (NKCC1(-/-)) mice. NKCC1 protein and activity were absent in NKCC1(-/-) astrocytes. [K(+)](o) of 75 mM increased NKCC1 activity approximately fourfold in NKCC1(+/+) cells (P < 0.05) but had no effect in NKCC1(-/-) astrocytes. Intracellular Cl(-) was increased by 70% in NKCC1(+/+) astrocytes under 75 mM [K(+)](o) (P < 0.05) but remained unchanged in NKCC1(-/-) astrocytes. Baseline intracellular Na(+) concentration ([Na(+)](i)) in NKCC1(+/+) astrocytes was 19.0 +/- 0.5 mM, compared with 16.9 +/- 0.3 mM [Na(+)](i) in NKCC1(-/-) astrocytes (P < 0.05). Relative cell volume of NKCC1(+/+) astrocytes increased by 13 +/- 2% in 75 mM [K(+)](o), compared with a value of 1.0 +/- 0.5% in NKCC1(-/-) astrocytes (P < 0.05). Regulatory volume increase after hypertonic shrinkage was completely impaired in NKCC1(-/-) astrocytes. High-[K(+)](o)-induced (14)C-labeled D-aspartate release was reduced by approximately 30% in NKCC1(-/-) astrocytes. Our study suggests that stimulation of NKCC1 is required for high-[K(+)](o)-induced swelling, which contributes to glutamate release from astrocytes under high [K(+)](o).
authors.affiliation: Department of Neurosurgery, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA.
authors.forename: Gui
authors.initials: G
authors.lastname: Su
authors.forename: Douglas B
authors.initials: DB
authors.lastname: Kintner
authors.forename: Michael
authors.initials: M
authors.lastname: Flagella
authors.forename: Gary E
authors.initials: GE
authors.lastname: Shull
authors.forename: Dandan
authors.initials: D
authors.lastname: Sun
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000378:metabolism; D000818:Animals; D001224:Aspartic Acid / Q000378:metabolism; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D002034:Bumetanide / Q000494:pharmacology; D048429:Cell Size; D002478:Cells, Cultured; D002540:Cerebral Cortex / Q000166:cytology; D002712:Chlorides / Q000378:metabolism*; D004232:Diuretics / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism*; D051379:Mice; D018345:Mice, Knockout; D008856:Microscopy, Fluorescence; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D028021:Sodium-Potassium-Chloride Symporters / Q000235:genetics / Q000378:metabolism*
chemical_list: D002712:Chlorides; D004232:Diuretics; D028021:Sodium-Potassium-Chloride Symporters; D002034:Bumetanide; D001224:Aspartic Acid; D018698:Glutamic Acid; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D011188:Potassium