Published online before print August 7, 2006, doi: 10.1161/01.HYP.0000237572.64079.80
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(Hypertension. 2006;48:E13.)
© 2006 American Heart Association, Inc.
Letters to the Editor |
Response to Surgical Menopause, Salt Sensitivity, and NO Bioavailability in Women
Nephrology and Hypertension Section, Veterans Affairs Medical Center and, Division of Nephrology and Hypertension and Vascular Biology Institute, University of Miami Miller School of Medicine, Miami, FL
Hypertension and Vascular Risk Unit, University General Hospital, Malaga, Spain
Nephrology and Hypertension Section, Veterans Affairs Medical Center and, Division of Nephrology and Hypertension and Vascular Biology Institute, University of Miami Miller School of Medicine, Miami, FL
Department of Internal Medicine, University of Bologna, Bologna, Italy
Hypertension and Vascular Risk Unit, University General Hospital, Malaga, Spain
We appreciate the letter by Tsuda.1 Experimental and clinical studies have demonstrated that 17ß-estradiol, via genomic and nongenomic mechanisms, increases the bioavailability of endothelium-derived NO. NO plays an important role in renal hemodynamics, sodium homeostasis, and pressure natriuresis, inducing renal vasodilatation and natriuresis.2 Gender differences exist in NO production in the kidney. Experimental animal studies have demonstrated that endothelial NO synthase (eNOS) protein and mRNA expression were higher in the female kidney compared with male subjects.3,4 We have shown that ovariectomized salt-sensitive rats, despite normal dietary salt, developed hypertension accompanied by a significant decline in renal medullary eNOS activity.2,5 However, ovariectomy did not significantly affect blood pressure or renal eNOS activity in salt-resistant rats.2,5 These findings imply that, in the presence of salt sensitivity, a loss of estrogen may impair the bioavailability of NO, thereby contributing, at least in part, to the development of hypertension.
Recent clinical studies have demonstrated that 17ß-estradiol therapy lowered plasma concentrations of asymmetrical dimethylarginine ([ADMA] an endogenous NO synthase inhibitor) in healthy, normotensive postmenopausal women.6,7 These studies did not assess whether there is a relationship among estrogen status, ADMA levels, and salt sensitivity of blood pressure. Although we did not measure plasma NO metabolites or ADMA concentrations in our cohort of women before and after surgical menopause, we agree with Tsuda1 that it is important for future studies to elucidate the role of NO bioavailability in the development of salt sensitivity and hypertension after menopause.
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Disclosures
None.
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 Top References |
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1. Tsuda K. Surgical menopause, salt sensitivity and nitric oxide bioavailability in women. Hypertension. 2006; 48: e12.[Medline] [Order article via Infotrieve]
2. Hernandez Schulman I, Raij L. Salt Sensitivity and hypertension after menopause: role of nitric oxide and angiotensin II. Am J Nephrol. 2006; 26: 170–180.[CrossRef][Medline] [Order article via Infotrieve]
3. Reckelhoff JF, Hennington BS, Moore AG, Blanchard EJ, Cameron J. Gender differences in the renal nitric oxide (NO) system: dissociation between expression of endothelial NO synthase and renal hemodynamic response to NO synthase inhibition. Am J Hypertens. 1998; 11: 97–104.[CrossRef][Medline] [Order article via Infotrieve]
4. Ji H, Pesce C, Zheng W, Kim J, Zhang Y, Menini S, Haywood JR, Sandberg K. Sex differences in renal injury and nitric oxide production in renal wrap hypertension. Am J Physiol Heart Circ Physiol. 2005; 288: H43–H47.
5. Harrison-Bernard LM, Schulman IH, Raij L. Postovariectomy hypertension is linked to increased renal AT1 receptor and salt sensitivity. Hypertension. 2003; 42: 1157–1163.
6. Holden DP, Cartwright JE, Nussey SS, Whitley GS. Estrogen stimulates dimethylarginine dimethylaminohydrolase activity and the metabolism of asymmetric dimethylarginine. Circulation. 2003; 108: 1575–1580.
7. Verhoeven MO, Hemelaar M, van der Mooren MJ, Kenemans P, Teerlink T. Oral, more than transdermal, oestrogen therapy lowers asymmetric dimethylarginine in healthy postmenopausal women: a randomized, placebo-controlled study. J Intern Med. 2006; 259: 199–208.[CrossRef][Medline] [Order article via Infotrieve]
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