The effect of dietary sodium loading on the kinetics of sodium excretion and blood pressure regulation in essential hypertensive men

Abstract

The kinetics of urinary sodium excretion defined as the rate of urinary sodium excretion during five-days oral sodium loading was investigated in 12 male patients with essential hypertension. The change in blood pressure under oral 200 mmol/24 h NaCl intake correlated inversely with the rate of urinary sodium excretion (r = -0.60, p less than 0.05), but did not significantly depend on the change in the absolute amount of excreted sodium. The rate of sodium excretion correlated directly with preload glomerular filtration rate (GFR) (r = 0.63, p less than 0.05), effective renal plasma flow (ERPF) (r = 0.78, p less than 0.01) and inversely with renal vascular resistance (RVR) (r = 0.67, p less than 0.01). The fall of renal plasma flow at moderate increment in the filtration fraction under sodium loading correlated directly with the rate of urinary sodium excretion (r = 0.73, p less than 0.01). The results suggest that: 1) the rate of sodium excretion is a more important factor in blood pressure regulation than the ability of the kidney to excrete the entire sodium load; 2) renal haemodynamics plays an indirect role in blood pressure regulation.