Effect of chronic Li+ treatment on free intracellular Mg2+ in human neuroblastoma SH-SY5Y cells


Corresponding author: Duarte Mota de Freitas, Department of Chemistry, Loyola University Chicago, 6525 N. Sheridan Road, Chicago, IL 60626, USA. Fax: (773) 508 3086; e-mail: dfreita@luc.edu


Objectives:  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.

Methods:  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.

Results:  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).

Conclusions:  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.