Increased Sodium Influx into Erythrocytes in Diabetes Mellitus and Hypertension

Abstract

A variety of abnormality has been reported in the cation transport systems in erythrocytes in essential hypertension. To determine the existence of similar abnormality in diabetics with hypertension, sodium (Na+) influx into erythrocytes in the presence of ouabain (measured by using 22Na+), and the Na+ and potassium (K+) content in intact erythrocytes were examined. Subjects, all of whom were Japanese, were divided into 4 groups; 23 nondiabetic, normotensive control subjects without family history of hypertension (control group), 20 patients with essential hypertension (group 1), 21 normotensive diabetics without family history of hypertension (group 2) and 15 hypertensive diabetics (group 3). Na+-K+ pump activity (measured by using 86Rb+) was studied in some of them, too. Na+ influx in group 1 was 0.451±0.111 m mol/Kg erythrocytes/h, significantly more elevated than that in the control group (0.345±0.080, p < 0.001). Na+ influx in group 2(0.435±0.094) was significantly greater than that in the control group(p < 0.005), but no significant difference was found between groups 1 and 2. Na+ influx in group 3 (0.551±0.128) was significantly higher than that in the control group (p < 0.001), in group 1(p < 0.02), or in group 2(p < 0.005). There were no significant differences in Na+-K+ pump activity, or Na+ and K+ content among the 4 groups. These findings suggested that: 1) Na+ influx into ouabain-treated erythrocytes was higher in patients with essential hypertension than in control subjects in Japanese, 2) diabetes mellitus per se might increase Na+ influx, and 3) the elevation of blood pressure in hypertensive diabetics as well as in essential hypertensives might be related to the increased Na+ influx.