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Regulation of Na + ,K + ‐ATPase by persistent sodium accumulation in adult rat thalamic neurones
Author(s) -
Senatorov Vladimir V.,
Stys Peter K.,
Hu Bin
Publication year - 2000
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2000.00343.x
Subject(s) - veratridine , monensin , ionophore , ouabain , biophysics , chemistry , membrane potential , sodium , diaphragm pump , microbiology and biotechnology , biochemistry , sodium channel , membrane , biology , materials science , organic chemistry , micropump , nanotechnology
1 The present study investigated the regulatory mechanism of the Na + ,K + ‐ATPase and the level of internal Na + and Ca 2+ in response to persistent Na + influx in acutely dissociated rat thalamic neurones. 2 Whole‐cell patch‐clamp recordings and Na + imaging revealed a stable [Na + ] i and low background pump activity. Exposure to veratridine (50 μ m ) for 1 h resulted in a progressive rise in [Na + ] i (Δ F Na = 64 ± 22 %) and [Ca 2+ ] i (Δ F Ca = 44 ± 14%) over 3 h. Increases in [Na + ] i and [Ca 2+ ] i were also observed during neuronal exposure to the Na + ionophore monensin (50 μ m ). 3 Subcellular confocal immunofluorescence quantification of α3 catalytic Na + ‐K + pump subunits showed that a veratridine‐induced rise in [Na + ] i was accompanied by a significant increase in pump density in both membrane and cytoplasmic compartments, by 39 and 54%, respectively. Similar results were also obtained in experiments when neurones were treated with monensin. 4 A fluorescent 9‐anthroylouabain binding assay detected a 60 and 110% increase in phosphorylated (active) pumps after veratridine and monensin exposure, respectively. 5 During the entire experiment, application of ouabain or veratridine alone induced little cell swelling and death, but pump inhibition in cells pre‐loaded with Na + led to rapid cell swelling and necrosis. 6 The above results indicate that a persistent influx of Na + may trigger rapid enhancement of pump synthesis, membrane redistribution and functional activity. However, these compensatory mechanisms failed to prevent persistent Na + accumulation.