cAMP-induced changes of intracellular free Mg2+ levels in human erythrocytes

To examine the role of cAMP in the regulation of intracellular free magnesium concentration ([Mg2+]i), we measured [Mg2+]i in human erythrocytes by 31P-NMR spectroscopy. (-)-Isoproterenol, forskolin, Bt2cAMP and 8-bromo-cAMP decreased [Mg2+]i in human erythrocytes. Bt2cAMP did not increase the efflux rate of Mg2+ from erythrocytes. HA1004, a potent inhibitor of cAMP-dependent kinases, markedly increased the [Mg2+]i in a Mg(2+)-free buffer solution. Addition of 8-bromo-cGMP or 12-O-tetradecanoylphorbol 13-acetate (TPA) did not affect the [Mg2+]i. These results suggest that beta-adrenergic stimulation and cAMP play an important role in the regulation of [Mg2+]i in human erythrocytes.