Competition between Li+ and Mg2+ in neuroblastoma SH-SY5Y cells: A fluorescence and 31P NMR study

Louis Amari, Brian Layden, Joyce Nikolakopoulos, Qinfen Rong, Duarte Mota De Freitas*, Graça Baltazar, M. Margarida C A Castro, Carlos F G C Geraldes

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

26 Scopus citations

Abstract

Because Mg2+ and Li+ ions have similar chemical properties, we have hypothesized that Li+/Mg2+ competition for Mg2+ binding sites is the molecular basis for the therapeutic action of lithium in manic-depressive illness. By fluorescence spectroscopy with furaptra-loaded cells, the free intracellular Mg2+ concentration within the intact neuroblastoma cells was found to increase from 0.39 ± 0.04 mM to 0.60 ± 0.04 mM during a 40-min Li+ incubation in which the total intracellular Li+ concentration increased from 0 to 5.5 mM. Our fluorescence microscopy observations of Li+-free and Li+-loaded cells also indicate an increase in free Mg2+ concentration upon Li+ incubation. By 31P NMR, the free intracellular Mg2+ concentrations for Li+-free cells was 0.35 ± 0.03 mM and 0.80 ± 0.04 mM for Li+-loaded cells (final total intracellular Li+ concentration of 16 mM). If a Li+/Mg2+ competition mechanism is present in neuroblastoma cells, an increase in the total intracellular Li+ concentration is expected to result in an increase in the free intracellular Mg2+ concentration, because Li+ displaces Mg2+ from its binding sites within the nerve cell. The fluorescence spectroscopy, fluorescence microscopy, and 31P NMR spectroscopy studies presented here have shown this to be the case.

Original languageEnglish (US)
Pages (from-to)2934-2942
Number of pages9
JournalBiophysical Journal
Volume76
Issue number6
DOIs
StatePublished - Jun 1999

ASJC Scopus subject areas

  • Biophysics

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