Intracellular levels of free Mg2+ in human erythrocytes were determined by 31P NMR spectroscopy in 26 fasted subjects and were correlated with blood pressures and serum levels of total magnesium (bound and free Mg2+) and ionized calcium from the same subjects in a seated position.
Untreated hypertensive individuals consistently demonstrated lower levels of intracellular free magnesium (192 ± 8 µ M, n = 11) than either normotensive (261 ± 9.8 µ M, n = 7, P < 0.001 vs. untreated hypertensive subjects) or hypertensive subjects whose blood pressure had been normalized on therapy (237 ± 7.8 µ M, n = 8, P < 0.005 vs. untreated hypertensives). For all subjects, strong relationships existed between intracellular free magnesium and diastolic blood pressure (r = -0.85, P < 0.001) and systolic blood pressure (r = -0.71, P < 0.001). Significant relationships also were observed between intracellular free magnesium levels and extracellular serum levels of calcium ion (r = -0.77, P < 0.001) as well as serum concentrations of total magnesium (r = 0.62, P < 0.001).
We conclude that significant depletion of intracellular free magnesium levels are apparent in erythrocytes of subjects with essential hypertension. Furthermore, the close, inverse relationship of free magnesium levels with the height of the blood pressure suggests that abnormalities of intracellular magnesium metabolism may contribute to the pathophysiology of human essential hypertension.