GLUTAMATE UP-REGULATES ALPHA-1 AND ALPHA-2 SUBUNITS OF THE SODIUM-PUMP IN ASTROCYTES OF MIXED TELENCEPHALIC CULTURES BUT NOT IN PURE ASTROCYTE CULTURES

被引:11
作者
BRINES, ML
ROBBINS, RJ
机构
[1] Neuroendocrine Program, Tompkins 516, Department of Internal Medicine, Yale University School of Medicine, 333 Cedar Street, New Haven
关键词
NA+; K+-ATPASE; GLIA; SODIUM PUMP; REGULATION; GLUTAMATE; EXCITOTOXICITY; TELENCEPHALIC CULTURE;
D O I
10.1016/0006-8993(93)91180-Z
中图分类号
Q189 [神经科学];
学科分类号
071006 ;
摘要
Prior work employing an in vitro model of the cerebral cortex has shown that sodium pump activity is a critical determinant for neuronal survival of glutamate stimulation. We have hypothesized that up-regulation of total brain sodium pump activity will protect against potential excitotoxins. Increased sodium pump activity could theoretically occur by changes in the reaction rate (short-term) and/or by increased levels of sodium pump protein (long-term) and is potentially complex since the three catalytic (a) subunit isoforms of the sodium pump are distributed in a highly variable, cell-specific pattern in the brain. Short-term regulation (seconds to minutes) has been well studied: brain sodium pump exhibits a large dynamic range. In contrast, the possibility of long-term modulation of sodium pump activity has not been extensively explored. We used isoform specific antibodies and [H-3]ouabain binding to determine whether prolonged stimulation of sodium pump activity in rodent telencephalic cultures increased total sodium pump enzyme. Exposure of mixed neuronal-glial cultures to high levels of glutamate (10 mM) for 18 h, which is highly toxic to neurons, was associated with an approximate to 80% increase in alpha 1 and alpha 2 subunit expression by glia. Induction of alpha 2 subunit immunoreactivity was also associated with comparable changes in [H-3]ouabain binding, suggesting that the up-regulation corresponded to functional alpha 2 protein. Shorter (30 min) glutamate treatments, which also killed neurons, did not produce similar changes in sodium pump expression. In contrast to mixed cultures, pure astrocyte cultures had undetectable alpha 2 and alpha 3 and moderate levels of alpha 1 protein, as confirmed by low levels of [H-3]ouabain binding. Glutamate treatment using this protocol was associated with a decrease in alpha 1 sodium pump expression. We conclude that long-term regulation of the sodium pump can be demonstrated in glia which have developed in the presence of neurons. Both alpha 1 and alpha 2 isoforms of the sodium pump are involved in this response to glutamate.
引用
收藏
页码:12 / 21
页数:10
相关论文
共 54 条
[41]   BRAIN NA+,K+-ATPASE REGULATION INVIVO - REDUCTION IN ACTIVITY AND RESPONSE TO SODIUM BY INTRACEREBROVENTRICULAR TETRODOTOXIN [J].
SWANN, AC .
BRAIN RESEARCH, 1991, 543 (02) :251-255
[43]   SUBACUTE NORADRENERGIC AGONIST INFUSIONS INVIVO INCREASE NA+,K+-ATPASE AND OUABAIN BINDING IN RAT CEREBRAL-CORTEX [J].
SWANN, AC ;
STEKETEE, JD .
JOURNAL OF NEUROCHEMISTRY, 1989, 52 (05) :1598-1604
[44]   FORSKOLIN INFUSION INVIVO INCREASES OUABAIN BINDING IN BRAIN [J].
SWANN, AC ;
STEKETEE, J .
BRAIN RESEARCH, 1989, 476 (02) :351-353
[45]   ISOZYMES OF THE NA+/K+-ATPASE [J].
SWEADNER, KJ .
BIOCHIMICA ET BIOPHYSICA ACTA, 1989, 988 (02) :185-220
[46]   STABILITY OF NA+-K+-ATPASE ALPHA-SUBUNIT ISOFORMS IN EVOLUTION [J].
TAKEYASU, K ;
LEMAS, V ;
FAMBROUGH, DM .
AMERICAN JOURNAL OF PHYSIOLOGY, 1990, 259 (04) :C619-C630
[47]  
TAMKUN MM, 1986, J BIOL CHEM, V261, P1009
[48]   ELECTROGENIC PUMPS IN AXONS AND NEUROGLIA AND EXTRACELLULAR POTASSIUM HOMEOSTASIS [J].
TANG, CM ;
COHEN, MW ;
ORKAND, RK .
BRAIN RESEARCH, 1980, 194 (01) :283-286
[49]  
TAORMINO JP, 1990, J BIOL CHEM, V265, P4116
[50]   REGULATION OF PLASMINOGEN ACTIVATORS AND TYPE-1 PLASMINOGEN-ACTIVATOR INHIBITOR BY CYCLIC-AMP AND PHORBOL ESTER IN RAT ASTROCYTES [J].
TRANQUE, P ;
ROBBINS, R ;
NAFTOLIN, F ;
ANDRADEGORDON, P .
GLIA, 1992, 6 (03) :163-171