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Cultured rat astrocytes possess Na + ‐Ca 2+ exchanger
Author(s) -
Takuma Kazuhiro,
Matsuda Toshio,
Hashimoto Hitoshi,
Asano Shoichi,
Baba Akemichi
Publication year - 1994
Publication title -
glia
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.954
H-Index - 164
eISSN - 1098-1136
pISSN - 0894-1491
DOI - 10.1002/glia.440120410
Subject(s) - monensin , ouabain , astrocyte , microbiology and biotechnology , sodium calcium exchanger , biology , ion transporter , calcium , western blot , neuroglia , biophysics , intracellular , biochemistry , sodium , chemistry , endocrinology , membrane , organic chemistry , gene , central nervous system
Na + ‐Ca 2+ exchange activity in its reverse mode was demonstrated in cultured rat astrocytes. Combination of ouabain (1 mM) and monensin (20 ±M) caused a marked increase in 45 Ca 2+ uptake in astrocytes. 45 Ca 2+ uptake was also stimulated by lowering the external Na + concentration. Ouabain plus monensin‐stimulated 45 Ca 2+ uptake was blocked by 3,4‐dichlorobenzamil (IC 50 , 16 ±M), an inhibitor of Na + ‐Ca 2+ exchanger, but not by nifedipine (0.1 ±M). The stimulated‐ 45 Ca 2+ uptake was observed even in K + ‐free medium, and external K + at 5‐10 mM caused a 2.2‐fold increase in the uptake. Microspectrofluorimetry using the Ca 2+ ‐sensitive dye fura‐2 showed that ouabain plus monensin increased intracellular Ca 2+ concentration in single astrocytes. The Ca 2+ signal was dependent on external Ca 2+ (EC 50 , 1.4 mM), and blocked by 20 ±M 3,4‐dichlorobenzamil, but not by Ca 2+ channel blockers (Cd 2+ , 20 ±M; Ni 2+ , 100 ±M). Antiserum of cardiac Na + ‐Ca 2+ exchanger recognized 160 and 120‐135 kDa proteins on SDS‐polyacrylamide gel electrophoresis of astrocyte homogenate. Northern blot analysis revealed the presence of mRNA for the exchanger protein in astrocytes. These findings indicate that Na + ‐Ca 2+ exchanger which is modulated by K + is present in cultured rat astrocytes.