Comparison of the distribution of magnesium in plasma determined by size exclusion chromatography and P-31 NMR spectroscopy

The distribution of magnesium in plasma, bound to proteins (pMg), complexed to low molecular weight anions (cMg) and ionized (iMg), was compared by si ze exclusion chromatography and an approach using a combination of atomic a bsorption spectroscopy, ion selective electrodes and P-31 nuclear magnetic resonance spectroscopy. The distribution of pMg: cMg: iMg was 28:13:59 as d etermined by chromatography and 26:14:60 as determined by the latter method ology. These results are consistent with the hypothesis that plasma protein s and weak complexing anions correspond to high and low affinity magnesium binding ligands in plasma, respectively.