ERYTHROCYTE NA-K-CL COTRANSPORT ACTIVITY IN LOW RENIN ESSENTIAL HYPERTENSIVE PATIENTS - A NA-23 NUCLEAR-MAGNETIC-RESONANCE STUDY

The Na-K-Cl cotransport activity in red blood cells from essential hypertensive men with low (n = 8, mean age 42 +/- 4 years) or normal renin activity (n = 4, mean age 43 +/- 3 years), and in normotensive men with normal renin activity (n = 7, mean age 38 +/- 4 years) has been evaluated by means of a recently developed Na-23 nuclear magnetic resonance (NMR) method. Sodium efflux was determined by relating the resonating frequency of the NMR signal from extracellular sodium to sodium concentration in the presence of the shift reagent Dy(PPP)(2)(7-). The maximum Na+ efflux driven by cotransport (V-max) was measured in Na+-loaded erythrocytes in the presence of ouabain to block the Na-K-Cl pump activity. A significant difference (P < 0.05) was found in V-max values of low renin patients (0.70 mmol/h/L cells, range 0.40 to 0.90 mmol/h/L cells) as compared with normotensive controls (0.39 +/- 0.08 mmol/h/L cells) and normal renin hypertensives (mean 0.49 +/- 0.04 mmol/h/L cells). In conclusion, this study showed an increased activity of the Na-K-CI cotransport in red blood cells from low renin hypertensive men as compared with normal renin hypertensives and normotensives.