Sodium sensitivity in human subjects: Hemodynamic and hormonal correlates

Abstract

To investigate factors associated with sodium sensitivity, 157 subjects were studied while receiving 10 and 200 mEq sodium diets. Measurements included blood pressure (BP), forearm vascular resistance, plasma renin activity (PRA), and plasma aldosterone. Sodium repletion was associated with a greater than 5% increase in mean BP in 16% of the normotensive subjects and 29% of the borderline hypertensive subjects. Sodium-sensitive subjects were compared with sodiumresistant subjects in both the normotensive (n=92) and borderline hypertensive (n=65) groups. Forearm vascular resistance was significantly higher (p < 0.05) during sodium loading in the sodiumsensitive subgroups of both the normotensive and borderline hypertensive groups (35.8 ± 29 vs 23.8 ± 20 [SD] and 37.5 ± 29 vs 22.5 ± 14 mm Hg/ml/min/100 g, respectively. Venous capacitance was lower in the sodium-sensitive than in the sodium-resistant borderline hypertensive subjects (0.8 ± 0.21 vs 1.69 ± 0.24 ml/100 g). During sodium restriction, PRA was significantly lower (p < 0.01) in the sodium-sensitive subsets (2.56 ± 1.6 vs 4.04 ± 2.6; 2.65 ± 2.1 vs 3.88 ± 2.6 ng angiotensin I/ml/hr). Aldosterone was lower (p < 0.01) during sodium depletion in the sodium-sensitive subsets (17.3 ± 12 vs 26.3 ± 16; 18.5 ± 18 vs 27.9 ± 17 ng/ml). A significant inverse correlation existed between change in BP with sodium repletion and change in PRA or level of PRA during sodium depletion (p < 0.003). We conclude that both normotensive and borderline hypertensive sodiumsensitive subjects are characterized by an increase in forearm vascular resistance during high sodium intake and that this characteristic is associated with decreased responsiveness of the renin-aldosterone system during sodium depletion. © Williams and Wilkins 1988. All Rights Reserved.