Effect of salt intake on endothelium-derived factors in a group of patients with essential hypertension

The aim of the present study was to evaluate the effects of the level of sa lt intake on endothelium-derived factors in a group of patients with essent ial hypertension. A group of 50 patients with essential hypertension who ha d never been treated for the condition were placed on a low-sodium (50 mmol /day), low-nitrate (400 mu mol/day) diet, which was supplemented, in a sing le-blind fashion, with placebo tablets for the first 7 days and then with N aCl tablets (200 mmol/day) for a further 7 days (total sodium intake 250 mm ol/day). At the end of both periods, 24-h ambulatory blood pressure monitor ing was performed. In addition, plasma levels and 24-h urinary excretion of nitrites plus nitrates and cGMP were measured, along with plasma levels of endothelin. A high salt intake promoted significant decreases in plasma le vels of nitrites plus nitrates (from 41.0 +/- 2.1 to 32.8 +/- 1.8 nmol/ml; P < 0.001), 24-h urinary nitrate excretion (from 417 +/- 36 to 334 +/- 37 m u mol/24 h; P = 0.045) and plasma endothelin levels (from 5.6 +/-0.3 to 4.6 +/- 0.3 pg/ml; P = 0.007). The plasma concentration and 24-h urinary excre tion of cGMP were not altered significantly by a high salt intake. We did n ot Rnd any relationship between endothelium-derived products and 24-h mean blood pressure, at either low or high salt intakes, or between changes indu ced by the high-salt diet. A high salt intake also induced significant decr eases in plasma renin activity, angiotensin II and aldosterone, and a signi ficant increase in atrial natriuretic peptide. We conclude that a high salt intake decreases the plasma concentration and urinary excretion of nitrate s and plasma levels of endothelin in patients with essential hypertension, suggesting that the level of salt intake may affect endothelial cell functi on. However, these alterations are not correlated with changes in blood pre ssure induced by the high salt intake.