Salt-Induced Increases in Systolic Blood Pressure Affect Renal Hemodynamics and Proteinuria

• Published in: Hypertension (Dallas, Tex. 1979) Tex. 1979), 1995-06, Vol.25 (6), p.1339-1344
• Main Authors: Weir, Matthew R, Dengel, Donald R, Behrens, Theresa M, Goldberg, Andrew P
• Format: Article
• Language: English
• Subjects: Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Blood Pressure - drug effects; Cardiology. Vascular system; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Cross-Over Studies; Female; Hemodynamics - drug effects; Humans; Kidney - drug effects; Kidney - physiology; Male; Medical sciences; Middle Aged; Proteinuria - chemically induced; Single-Blind Method; Sodium Chloride - pharmacology
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.hyp.25.6.1339

Nine white and 13 black hypertensive patients with normal serum creatinine were randomized to receive either 2 weeks of a low-salt (40 mEq Sodium) or high-salt (200 mEq Sodium) diet followed by 2 weeks of the other diet separated by a 1-week washout on their regular diet. The entire study was conducted in an outpatient setting with intensive dietary instruction and monitoring of blood pressure and 24-hour collections of urine for analysis. Urine electrolyte measurement showed that the patients were able to achieve only a modestly reduced (100 plus/minus 14 mEq Sodium h [mean plus/minus SEM]) low-salt diet as outpatients, while the higher-salt diet (236 plus/minus 22 mEq Sodium h) was more easily achieved. Eleven patients (8 black, 3 white) were classified as modestly salt sensitive on the basis of an increase or decrease in mean arterial pressure of greater or equal to 3 mm Hg going from lower- to high-or high- to lower-salt diets, respectively. In the salt-sensitive patients, the increase in dietary salt intake increased glomerular filtration rate by 29% (71.2 plus/minus 6.6 to 85.8 plus/minus 7.3 mL [centered dot] min [centered dot] 1.73 m, P = .05), with no significant change in renal plasma flow (412.7 plus/minus 36.4 to 399.6 plus/minus 27.8 mL [centered dot] min [centered dot] 1.73 m). There were no changes in these parameters in the salt-resistant patients. Increased dietary salt intake in the salt-sensitive patients was associated with a 15% increase in glomerular filtration fraction (0.18 plus/minus 0.02 to 0.22 plus/minus 0.01, P = .09), whereas in the salt-resistant group, glomerular filtration fraction did not change (0.16 plus/minus 0.01 to 0.17 plus/minus 0.02, P = .47). Greater dietary salt intake also resulted in an increase in 24-hour urine protein excretion in the salt-sensitive population (74.0 plus/minus 8.3 to 139.0 plus/minus 31.3 mg/24 h), while there was no significant change in the salt-resistant population (115.5 plus/minus 16.6 to 86.4 plus/minus 14.3 mg/24 h, P = .03 versus salt sensitive). The salt-induced increase in proteinuria was related to the increase in systolic blood pressure on the high-salt diet (r = .54, P = .04). These studies demonstrate that in the presence of modest salt sensitivity (mean arterial pressure increase greater or equal to 3 mm Hg), an increase in systolic blood pressure is predictive of potentially adverse renal hemodynamic responses to higher dietary salt in essential hypertensive patients. Conseque