Metal-Based Drugs 
Volume 9 (2002), Issue 1-2, Pages 69-80
doi:10.1155/MBD.2002.69

Quantification and Localization of Intracellular Free Mg2+ in Bovine Chromaffin Cells

Liliana P. Montezinho,1,2 Carla P. Fonseca,1,2 Carlos F. G. C. Geraldes,1,2 and M. Margarida C. A. Castro1,2

 1Department of Biochemistry, University of Coimbra, P.O. Box 3126, Coimbra 3001-401, Portugal
2Center for Neuroscience and Cell Biology, University of Coimbra, P.O. Box 3126, Coimbra 3001-401, Portugal

Abstract

Magnesium is an essential element for all living systems. The quantification of free intracellular Mg2+ concentration (([Mg2+]i)) is of utmost importance since changes in its basal value may be an indication of different pathologies due to abnormalities of Mg2+ metabolism. In this work we used P31 NMR and fluorescence spectroscopy to determine the resting [Mg2+]i in bovine chromaffin cells, a neuron-like cellular model, as well as confocal laser scanning microscopy to study the free Mg2+ spatial distribution in these cells. P31 NMR spectroscopy did not prove to be effective for the determination of [Mg2+]i in this particular case due to some special morphological and physiological properties of this cell type. A basal [Mg2+]i value of 0.551 ± 0.008 mM was found for these cells using fluorescence spectroscopy and the Mg2+-sensitive probe furaptra; this value falls in the concentration range reported in the literature for neurons from different sources. This technique proved to be an accurate and sensitive tool to determine the [Mg2+]i.

lntraceilular free Mg2+ seems to be essentially localized in the nucleus and around it, as shown by confocal microscopy with the Mg2+-sensitive probe Magnesium Green. It was not possible to derive any conclusion about free Mg2+ localization inside the chromaffin granules and/or in the cytoplasm due to the lack of sufficient spatial resolution and to probe compartmentalization.