Urinary excretion rate of endothelin-1 in patients with essential hypertension and salt sensitivity

To assess the possible role of ET-1 in the pathogenesis of hypertension and salt sensitivity levels of immunoreactive endothelin-1 (irET-1) were measured in plasma and urine of 17 patients with essential hypertension and in 19 normotensive control subjects. Effects of alterations in dietary sodium content on urinary irET-1 levels also were assessed. Plasma levels of irET-1 did not differ between the hypertensives and normotensive groups (1.1 +/- 0.3 and 1.3 +/- 0.1 pg/ml). Urine samples of both groups contained high concentrations of irET-1. However, the mean daily urinary excretion of irET-1 in the hypertensives was less than one-third that in controls (29 +/- 3 vs. 109 +/- 21 ng/day, respectively, P < 0.01). Changing dietary sodium content in the hypertensives had no effect on mean irET-1 excretion. However, on either low, intermediate, or high salt diet, "salt sensitive" hypertensives had lower levels of the peptide than "salt resistant" patients (23 +/- 3 vs. 36 +/- 5 ng/day, respectively, P < 0.05). The data demonstrate a marked reduction in irET-1 excretion in patients with essential hypertension, despite normal plasma levels of the peptide. Since ET-1 has diuretic and natriuretic properties, the decreased renal excretion of ET-1 may be of relevance to the pathophysiology of hypertension and salt sensitivity.