Renal endothelin-1 is linked to changes in urinary salt and volume in essential hypertension

Methods: We investigated the influence of salt intake on urinary and plasma endothelin-1 (ET-1) in 55 patients who entered a two-week double-blind, ra ndomised, crossover study comparing a 50 mMol/day salt intake and 150 mMol/ day. Twenty-four-hour ET-1 excretion and plasma ET-1 were measured by RIA o n pre-extracted samples. Results: In the whole cohort (n=55), changes in urinary ET-1 were related t o salt excretion (r=0.28, P=0.04) and urinary volume (r=0.47, P=0.0001). In a multivariable model, changes in PRA, plasma aldosterone, blood pressure and heart rate did not add any predictive power to salt excretion with rega rd to urinary ET-1 variations, The relationship bet cr een urinary volume a nd urinary ET-1 was stronger than that of urinary sodium with ET-1 excretio n because sodium was excluded from the multivariable model when urinary vol ume was introduced. Changes iu urinary ET-1 were unrelated to mean blood pr essure changes (P=0.66). Changes in plasma ET-1 were unaffected by changes in salt intake (P=0.58) but were strongly related to those in PRA (r= - 0.4 5, P=0.01) and plasma aldosterone (r= - 0.53, P=0.002). Conclusions: The renal excretion of ET-1 is influenced by changes in salt i ntake and appears largely independent of the blood pressure response to sal t, Changes in urinary volume which accompany variations in salt excretion p lay an important role in this response, Since urinary ET-1 reflects its ren al synthesis, our data support the notion that renal ET-1 plays a role in t he regulation of sodium balance in patients with mild hypertension.