CIRCADIAN-RHYTHM OF URINARY ENDOTHELIN-1 EXCRETION IN MILD HYPERTENSIVE PATIENTS

Endothelin-1 (ET-1) is a potent vasoconstrictive peptide with diverse physiologic actions and has been considered to be involved in the path ogenesis of hypertension. We sought to investigate the role of renal s ynthesis of ET-1 in the regulation of daily sodium homeostasis and the possible contribution of renal synthesized ET-1 in the pathogenesis o f essential hypertension (EHT), Urinary ET-1-like immunoreactivity (ET -1-Ll) was measured by a radioimmunoassay after extraction in 23 ENT p atients without detectable target organ damage, and in 11 normotensive controls, All study subjects received a controlled diet during an 8-d ay study period. Urinary and blood samples were collected by four samp ling periods/day from the 4th to 6th days, and on the 7th day, study s ubjects were given an intravenous infusion of 1250 mt normal saline ov er 2 h, In the basal state, the urinary sodium and ET-1-Ll excretions showed diurnal patterns in both the normal and hypertensive groups, an d urinary ET-1-Ll excretion rate correlated well with urinary sodium e xcretion rate. There were no differences found in plasma ET-1 levels, urinary ET-1-Ll, and sodium excretion rates between the control and hy pertensive groups. After saline infusion, ten hypertensive patients sh owed nonexaggerated natriuresis, and the 24-h urinary ET-1-Ll excretio n (47.0 +/- 4.0 pmol/day), collected during the day of saline infusion , was significantly lower than that of the control group (86.3 +/- 10. 0 pmol/day) or the exaggeratedly natriuretic hypertensive patients (91 .7 +/- 8.4 pmol/day), Our results suggest that renal ET-1 may be respo nsible for the renal handling of sodium homeostasis, and alteration of renal ET-1 synthesis may be a contributory factor in the pathogenesis of essential hypertension and salt sensitivity. (C) 1998 American Jou rnal of Hypertension, Ltd.