Evaluation of myoca'Rdial viability and eneRgetics Regulated by intracellulae free Mg^<2+>.

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The aim of this study was to measure the concentration of intracellular free magnesium (free [Mg<@D12+@>D1] i) in isolated rat heart by analyzing<@D131@>D1P NMR spectra obtained from the linear prediction z-transform method (LPZAR), and to investigate the effect of extracellular inorganic phosphate ([Pi] o) on myocardial Mg metabolism. Free [Mg<@D12+@>D1] i of Langendorff perfused hearts was assessed by <@D131@>D1P NMR spectroscopy using LPZAR.The ionic enviroment was altered by changing [Pi] o from 1.2 to 5.0 mM in Krebs-Henseleit buffer during heart perfusion (n=6). Chenges in free [Mg<@D12+@>D1] i were calculated from the frequency difference between alpha-and beta-ATP in the<@D131@>D1P NMR spectrum. The spectra obtained using LPZAR provided peaks sharp enough for the calculation of free [Mg S12+ E1] i and distinct chemical shift of beta-peak of ATP enabled to estimate the change of free [Mg<@D12+@>D1] i. Wten [Pi] o was increased from 1.2 mM of normal concentration to 5.0 mM and then restored to 1.2 mM,free [Mg S12+ E1] i decreased significantly from 0.525(]SY.+-。[)0.048 mM to 0.407(]SY.+-。[)0.025 mM and returned to the control level of 0.601(]SY.+-。[)0.053 mM.The net movement of free Mg<@D12+@>D1 may involve Mg<@D12+@>D1-Pi exchange mechanism across the plasma membrane in rat heart, as the increase in extracellular [Pi] resulted in the decrease in free [Mg<@D12+@>D1] i.