Regulation of sodium balance in hypertension.

SUMMARY Pressure natriuresis, defined as the relationship between sodium excretion and mean arterial pressure (MAP), was assessed during graded reduction of arterial pressure with nltroprusside in 12 uncomplicated essential hypertensives. In all patients, sodium excretion fell linearly with reductions in arterial pressure (r > 0.71; p < 0.05). The percent change of sodium excretion from control per mm Hg change in MAP (AU N V/AMAP) was less in patients with resting MAP above 120 mm Hg than in those with lower BP (1.4% ± 0.1% versus 3.2% ± 0.3%; p < 0.001), but the pressure at which urine flow extrapolated to zero (77 ± 4 mm Hg) was not significantly different in the two groups. Further, there was a significant correlation between AU N V/AMAP and resting MAP (r = − 0.65, p < 0.05), suggesting that the sensitivity of pressure natriuresis was, in part, determined by the level of resting arterial pressure. This attenuation of pressure natriuresis might reduce sodium loss and thereby preserve body fluid volume in the face of persistent hypertension.