Effect of Salt on Isoprostanes in Salt-Sensitive Essential Hypertension

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 47; no. 3; pp. 434 - 440
• Main Authors: Laffer, Cheryl L, Bolterman, Rodney J, Romero, Juan Carlos, Elijovich, Fernando
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.03.2006; Hagerstown, MD Lippincott
• Subjects: Adult; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Biomarkers - blood; Blood and lymphatic vessels; Blood Pressure - drug effects; Cardiology. Vascular system; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Dinoprost - analogs & derivatives; Dinoprost - blood; Diuretics - pharmacology; Drug Resistance; Experimental diseases; Female; Furosemide - pharmacology; Humans; Hypertension - blood; Hypertension - metabolism; Hypertension - physiopathology; Isoprostanes - blood; Male; Medical sciences; Middle Aged; Oxidative Stress - drug effects; Sodium Chloride - metabolism; Sodium Chloride - pharmacology; Sulfanilamide derivatives; Oxidative stress; Endothelin; Prognosis; Mineralocorticoid; Cardiovascular disease; sodium dependent,oxidative stress; Aldosterone; Epidemiology; Diuretic; Renin; Aspartic endopeptidases; Human; Hypertension; Prostaglandin; Enzyme; Steroid hormone; Furosemide; Morbidity; Peptidases; Phenotype; Depletion; Treatment; Sodium; Adrenal hormone; Anthranilic acid derivatives; Hydrolases; Antihypertensive agent; prostaglandins; Comparative study; essential
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.HYP.0000202480.06735.82

The controversy over beneficial versus harmful effects of salt on cardiovascular outcomes may be caused by different effects of salt on intermediate phenotypes of hypertension not characterized in epidemiological studies. Hence, we investigated acute effects of salt on oxidative stress in hypertensive subjects classified as salt sensitive (SS, n=14) or salt resistant (SR, n=13) by an inpatient protocol of salt loading (460 mmol NaCl) and salt depletion (10 mmol NaCl and furosemide). Oxidative stress was assessed by measuring the plasma isoprostane 8-iso-PGF2α. SS had lower plasma renin activity, higher aldosterone/renin ratios, and exaggerated endothelin and catecholamine responses to salt depletion compared with SR. Baseline lipid-bound isoprostanes (749±70 pmol/L) were 83% of the total and were slightly but not significantly higher in SS than SR. Baseline free isoprostanes did not differ between groups. After salt loading, lipid-bound isoprostanes were higher in SS (945±106) than SR (579±57; P<0.01). Salt depletion significantly decreased them in SS (−174±84) and increased them in SR (+129±58), equalizing their levels (771±61 versus 708±91; P value not significant). Free isoprostanes were decreased by salt depletion only if data in all of the patients were analyzed together. Total isoprostanes followed the pattern of the lipid-bound fraction. Correlations between salt depletion-induced changes in lipid-bound isoprostanes, plasma renin activity (r=0.45; P<0.02), and aldosterone/renin ratios (r=−0.41; P<0.04) suggested that the more SS the patient, the greater the reduction of oxidative stress by salt depletion. Our research is the first to show that salt affects oxidative stress acutely in humans, particularly in SS hypertension, which may explain the controversial results of epidemiological studies on salt and morbidity and may have implications for therapy.