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cotransporter to high-[K+]o- induced
swelling and EAA release in astrocytes
Departments of 1 Neurological Surgery and 2 Physiology, University of Wisconsin Medical School, Madison, Wisconsin 53792
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 µM, 1.0 ± 3.1%; P < 0.05). Intracellular
36Cl accumulation was increased from a
control value of 0.39 ± 0.06 to 0.68 ± 0.05 µmol/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 14C-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.
cell swelling; high potassium ion concentration, cultured astrocytes; glutamate release; bumetanide; intracellular chloride
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