Role of endogenous endothelin in renal function during altered sodium balance

This study was conducted to determine the involvement of endogenous endothelin-1 (ET-1), a potent vasoconstricting peptide, in systemic and renal hemodynamics and in the renin-angiotensin system, by inhibiting ET-1 action with an infusion of specific ET-1 antiserum during altered sodium balance. Infusion of 1:50 diluted ET-1 antiserum, which completely inhibited renal vasoconstriction caused by exogenously administered ET-3 (0.25 to 1.0 nmol/kg), increased urinary sodium excretion (UNaV) and fractional excretion of sodium (FENa), and decreased the plasma renin concentration (PRC) without significant changes in blood pressure, heart rate, GFR, RPF, or urine volume (UV) in conscious rats fed a low-salt diet, but not those on a high-salt diet. A time-control study showed no significant changes in any of these parameters. These results suggest that during low salt intake, in comparison to high salt intake, endogenous ET is more potent. Endogenous ET may thus contribute to the adaptive modulation of sodium excretion by a renal tubular action, and of renin release in association with a change in sodium balance.