CAMP-INDUCED CHANGES OF INTRACELLULAR FREE MG2+ LEVELS IN HUMAN ERYTHROCYTES

To examine the role of cAMP in the regulation of intracellular free ma gnesium concentration ([Mg2+]i), we measured [Mg2+]i in human erythroc ytes by P-31-NMR spectroscopy. (-)-Isoproterenol, forskolin, Bt2cAMP a nd 8-bromo-cAMP decreased [Mg2+]i in human erythrocytes. Bt2cAMP did n ot increase the effux rate of Mg2+ from erythrocytes. HA1004, a potent inhibitor of cAMP-dependent kinases, markedly increased the [Mg2+]i i n a Mg2+-free buffer solution. Addition of 8-bromo-cGMP or 12-O-tetrad ecanoylphorbol 13-acetate (TPA) did not affect the [Mg2+]i. These resu lts suggest that beta-adrenergic stimulation and cAMP play an importan t role in the regulation of [Mg2+]i in human erythrocytes.