Competition between Li+ and Mg2+ for ATP in human erythrocytes A 31P NMR and optical spectroscopy study

Abstract
We have investigated the influence of Li+ on free intracellular Mg2+ concentration in human erythrocytes by 31P NMR and optical absorbance spectroscopies. In red cells loaded with 3 mM intracellular Li+, the chemical shift separation between the α- and β-phosphate resonances of MgATP2− was approx. 0.9 ppm larger than that observed in Li+-free red cells. By analyzing the interaction of each red cell component with Mg2+ and Li+, we found that Mg2+ is displaced in part from MgATP2− upon addition of Li+ and that the released Mg2+ is bound to the red cell membrane causing an overall decrease in free intracellular Mg2+ concentration.