Intracellular free magnesium in hypertension

Abstract

In order to study the importance of altered intracellular ion metabolism in hypertension, we used 31P nuclear magnetic resonance (NMR) spectroscopy to measure intracellular free magnesium levels in normotensive (n = 19), essential hypertensive (n = 17) and diet-controlled diabetic (n = 6) subjects given a standard 100-g oral glucose load. The intracellular Mg level was significantly lower in hypertensives compared with normotensives (183 ± 7 versus 232 ± 10 μmol/l, P < 0.001), and for all subjects was closely linked to both systolic (r = −0.84, P < 0.001) and diastolic (r = −0.76, P < 0.001) pressure. Hypertensives also showed a significantly greater insulinaemic response to glucose loading (P < 0.001), and intracellular Mg was also closely and inversely linked to the integrated insulin response (r = −0.78, P < 0.001). Despite the absence of hyperinsulinaemia, diabetics had the lowest intracellular Mg levels (156 ± 8 μmol/l). Thus, suppressed intracellular Mg is linked to hypertension and to decreased tissue insulin sensitivity, and is not consequent to the hyperinsulinaemia itself. We suggest that intracellular Mg may provide a common pathophysiological basis for understanding the clinical association of hypertension and diabetes mellitus.