부산대학교 도서관

We reported previously that inhibition of [Na.sup.+]-[K.sup.+]-[Cl.sup.-] cotransporter isoform 1 (NKCC1) by bumetanide abolishes high extracellular [K.sup.+] concentration ([[[K.sup.+]].sub.o])-induced swelling and intracellular [Cl.sup.-] accumulation in rat cortical astrocytes. In this report, we extended our study by using cortical astrocytes from NKCC1-deficient (NKCC[1.sup.-/-]) mice. NKCC1 protein and activity were absent in NKCC[1.sup.-/-] astrocytes. [[[K.sup.+]].sub.o] of 75 mM increased NKCC1 activity approximately fourfold in NKCC[1.sup.+/+] cells (P < 0.05) but had no effect in NKCC[1.sup.-1-] astrocytes. Intracellular [Cl.sup.-] was increased by 70% in NKCC[1.sup.+/+] astrocytes under 75 mM [[[K.sup.+]].sub.o] (P < 0.05) but remained unchanged in NKCC[1.sup.-/-] astrocytes. Baseline intracellular [Na.sup.+] concentration ([[[Na.sup.+]].sub.i]) in NKCC[1.sup.+/+] astrocytes was 19.0 [+ or -] 0.5 mM, compared with 16.9 [+ or -] 0.3 mM [[[Na.sup.+]].sub.i] in NKCC[1.sup.-/-] astrocytes (P < 0.05). Relative cell volume of NKCC[1.sup.+/+] astrocytes increased by 13 [+ or -] 2% in 75 mM [[[K.sup.+]].sub.o], compared with a value of 1.0 [+ or -] 0.5% in NKCC[1.sup.-/-] astrocytes (P < 0.05). Regulatory volume increase after hypertonic shrinkage was completely impaired in NKCC[1.sup.-/-] astrocytes. High-[[[K.sup.+]].sub.o]-induced [sup.14]C-labeled D-aspartate release was reduced by ~30% in NKCC[1/sup.-/-] astrocytes. Our study suggests that stimulation of NKCC1 is required for high-[[[K.sup.+]].sub.o]-induced swelling, which contributes to glutamate release from astrocytes under high [[[K.sup.+]].sub.o]. cell swelling; high potassium ion concentration; cultured astrocytes; glutamate release; bumetanide; intracellular chloride; excitatory amino acid