INCREASED ACTIVITY OF THE MG2+/NA+ EXCHANGER IN RED-BLOOD-CELLS FROM ESSENTIAL HYPERTENSIVE PATIENTS

Epidemiological, clinical, and experimental evidence suggests a relation between Mg2+ metabolism and essential hypertension. The aim of the present study was the detection of abnormalities of the erythrocyte Mg2+/Na+ exchanger in essential hypertensive patients. We studied 66 untreated essential hypertensive patients and 36 normotensive control subjects. Maximal efflux rates of total Mg2+ efflux and the Na+-dependent and Na+-independent components of Mg2+ efflux were determined in Mg2+-loaded red blood cells. Mg2+/Na+ exchanger was calculated as the Na+-dependent component of the Mg2+ efflux. Mean values of Mg2+/Na+ exchanger were clearly elevated in hypertensive subjects with respect to normotensive control subjects [184.7 +/- 15.7 versus 84.4 +/- 6 mu mol(L.cell.h)(-1); P<.001]. This elevation was due primarily to the increased total Mg2+ efflux [324.2 +/- 21.9 versus 257.9 +/- 17.3 mu mol(L.cell.h)(-1);P<.05], whereas the Na+-independent component was not significantly different between the groups [154.5 +/- 11.8 versus 173.4 +/- 15.5 mu mol(L.cell.h)(-1); P=NS]. Moreover, total erythrocyte Mg 2+ content was slightly reduced in hypertensive patients with respect to normotensive control subjects (1.84 +/- 0.04 versus 2.07 +/- 0.04 mmol/L.cell; P<.001). Using the 99% confidence limits of the normotensive population as the normal range, 30 (45.5%) hypertensive subjects showed values of Mg2+/Na+ exchanger higher than 160 mu mol(L.cell.h)(-1). The Mg2+/Na+ exchanger was inversely correlated with basal intraerythrocyte Mg2+ content (r=-.323; P=.001). From a clinical point of view, we found a positive correlation between diastolic blood pressure Values and Mg2+/Na+ exchanger (r=.246; P<.05) in the sample of essential hypertensive patients. We conclude that erythrocyte Mg2+/Na+ exchanger is altered in 45% of essential hypertensive patients. This alteration could be responsible for the low basal intraerythrocyte Mg2+ content observed in essential hypertension.