Contribution of Na(+)-K(+)-Cl(-) cotransporter to high-[K(+)](o)- induced swelling and EAA release in astrocytes |
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Authors: | Su Gui Kintner Douglas B Sun Dandan |
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Affiliation: | Department of Neurological Surgery, University of Wisconsin Medical School, Madison, Wisconsin 53792, USA. |
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Abstract: | We hypothesized that highextracellular K+ concentration([K+]o)-mediated stimulation ofNa+-K+-Cl cotransporter isoform 1 (NKCC1) may result in a net gain of K+ and Cland thus lead to high-[K+]o-induced swellingand glutamate release. In the current study, relative cell volumechanges were determined in astrocytes. Under 75 mM[K+]o, astrocytes swelled by 20.2 ± 4.9%. This high-[K+]o-mediated swelling wasabolished by the NKCC1 inhibitor bumetanide (10 µM, 1.0 ± 3.1%; P < 0.05). Intracellular36Cl accumulation was increased from acontrol value of 0.39 ± 0.06 to 0.68 ± 0.05 µmol/mgprotein in response to 75 mM [K+]o. Thisincrease was significantly reduced by bumetanide (P < 0.05). Basal intracellular Na+ concentration([Na+]i) was reduced from 19.1 ± 0.8 to16.8 ± 1.9 mM by bumetanide (P < 0.05).[Na+]i decreased to 8.4 ± 1.0 mM under75 mM [K+]o and was further reduced to5.2 ± 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 presenceof bumetanide (P < 0.05). Bumetanide inhibitedhigh-[K+]o-induced 14C-labeledD-aspartate release by ~50% (P < 0.05).These results suggest that NKCC1 contributes tohigh-[K+]o-induced astrocyte swelling andglutamate release. |
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