Intracellular free magnesium in erythrocytes of essential hypertension: relation to blood pressure and serum divalent cations.

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 microM, n = 11) than either normotensive (261 +/- 9.8 microM, n = 7, P less than 0.001 vs. untreated hypertensive subjects) or hypertensive subjects whose blood pressure had been normalized on therapy (237 +/- 7.8 microM, n = 8, P less than 0.005 vs. untreated hypertensives). For all subjects, strong relationships existed between intracellular free magnesium and diastolic blood pressure (r = -0.85, P less than 0.001) and systolic blood pressure (r = -0.71, P less than 0.001). Significant relationships also were observed between intracellular free magnesium levels and extracellular serum levels of calcium ion (r = -0.77, P less than 0.001) as well as serum concentrations of total magnesium (r = 0.62, P less than 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.