Natriuretic responses in labile hypertension.

To characterize humoral and renal excretory responses following provocative maneuvers in subjects with labile hypertension, we measured plasma renin activity (PRA), plasma aldosterone (PA), plasma norepinephrine (PNe), urinary norepinephrine (UNe), urinary sodium excretion (UNaV), urinary potassium excretion (UKV), and fractional excretion of sodium (FENa) following both volume expansion with a 150 mEq Na diet and intravenous administration of 2L normal saline over four hours, and volume contraction with a 10 mEq Na diet and 120 mg oral furosemide. Results from 37 labile hypertensives were compared to those from the same number of age-, race-, and sex-matched normal subjects or patients with fixed essential hypertension. PRA, PA, PNe, UNe, and UKV responses were no different in the three groups. UNaV and FENa during the saline load was greater in labile hypertensives than in the other groups. While FENa was inversely related to PRA in both normals and fixed hypertensives, no such relationship was found in subjects with labile hypertension. In labile hypertensives, FENa was correlated with PNe concentrations. Furthermore, in these subjects sodium excretion and norepinephrine excretion were associated as well. We suggest that labile hypertensives exhibit exaggerated natriuresis which may be mediated by neurogenic mechanisms.