Fluid, Ionic and Hormonal Changes Induced by High Salt Intake in Salt-Sensitive and Salt-Resistant Hypertensive Patients

1. The aim of the study was to detect differences between salt-sensitive and salt-resistant hypertensive patients in the response of the renin—aldosterone axis, plasma noradrenaline and atrial natriuretic peptide to high salt intake. 2. Fifty essential hypertensive patients followed 2 weeks of a standard diet with 20 mmol of NaCl daily, supplemented by placebo tablets for the first 7 days and by NaCl tablets for the last 7 days, in a single-blind fashion. Salt sensitivity was defined as a significant rise ( P 3. Twenty-two (44%) patients fulfilled criteria of salt-sensitive hypertension, whereas the remaining 28 (56%) were considered salt-resistant. High salt intake promoted a significant decrease ( P P P not significant). Salt-sensitive patients showed an increase in plasma noradrenaline after high salt intake (from 1.15 ± 0.11 to 1.56 ± 0.14 nmol/l; P P r = 0.479; P = 0.003). 4. We conclude that the increase in blood pressure induced by high salt intake in salt-sensitive patients is associated with a stimulation of the sympathetic nervous system and a blunted decrease in plasma aldosterone. Conversely, changes in renal function, electrolyte excretion and plasma concentrations of atrial natriuretic peptide induced by high salt intake seem to be similar in both salt-sensitive and salt-resistant patients.