Abukhdeir Abde M, Layden Brian T, Minadeo Nicole, Bryant Fred B, Stubbs Evan B, Mota de Freitas Duarte
Department of Chemistry, Loyola University Chicago, Illinois 60626, USA.
Bipolar Disord. 2003 Feb;5(1):6-13. doi: 10.1034/j.1399-5618.2003.02238.x.
Previous findings have demonstrated Li+/Mg2+ competition at therapeutic intracellular Li+ levels after acute Li+ treatment in human neuroblastoma SH-SY5Y cells. In the current study, we examined whether Li+/Mg2+ competition exists at therapeutically relevant extra- and intracellular [Li+] after chronic Li+ loading times.
In human neuroblastoma cells, intracellular free Mg2+ was determined by fluorescence spectroscopy with the fluorophore furaptra. Intracellular Li+ and Mg2+ were measured by atomic absorption spectrophotometry.
After loading of the neuroblastoma cells with 1-2 mM extracellular Li+ for 24-72 h, the observed, increased intracellular free [Mg2+] levels were significantly higher (p < 0.03) than those in matched Li+ free cells, and intracellular [Li+] was found to be at therapeutic intracellular levels (0.7-1.5 mM).
The results demonstrate that Li+/Mg2+ competition exists after chronic treatment with Li+ at therapeutically relevant intracellular Li+ levels in neuroblastoma cells. We found differences between acute and chronic Li+ treatment effects on the extent of Li+/Mg2+ competition. Possible reasons for these differences are discussed.
