| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
(Hypertension. 2006;48:972.)
© 2006 American Heart Association, Inc.
Original Articles |
From the Department of Internal Medicine (H.M., T.T., J.K., T.I., K.K., T.E.), Circulatory and Body Fluid Regulation, and Department of Pathology (Y.A.), Faculty of Medicine, University of Miyazaki, Miyazaki, Japan; the Department of Nutrition Management (T.T.), Faculty of Health and Nutrition, Minami-Kyushu University, Miyazaki, Japan; and PharmD at Cardiovascular Research (J-P.S.), Bayer HealthCare, Wuppertal, Germany.
Correspondence to Toshihiro Tsuruda, Department of Internal Medicine, Circulatory and Body Fluid Regulation, Faculty of Medicine, University of Miyazaki, 5200 Kihara Kiyotake, Miyazaki 889-1692, Japan. E-mail ttsuruda{at}med.miyazaki-u.ac.jp
| Abstract |
|---|
|
|
|---|
Key Words: hypertension fibrosis soluble guanylate cyclase cGMP extracellular matrix
| Introduction |
|---|
|
|
|---|
Natriuretic peptidescGMP signaling has been reported to inhibit cardiac remodeling: atrial natriuretic peptide (ANP) evoked potent antihypertrophic effects on cardiac ventricles,9,10 and brain natriuretic peptide (BNP) inhibited cardiac fibrosis in vitro11,12 and in vivo through a cGMP-dependent pathway.13 Thus, cGMP signaling seems to play a critical role in attenuating cardiac remodeling. Soluble guanylate cyclase (sGC [GC]), a heterodimeric haem protein consisting of
- and ß-subunits, is an intracellular effector for NO,14 converting guanosine triphosphate to cGMP. However, it remains unknown whether pharmacological stimulation of sGC attenuates cardiac hypertrophy and fibrosis in hypertension.
BAY41-2272, developed recently as an orally active sGC stimulator,15 has been shown to have beneficial effects on hemodynamics in systemic hypertension,15 heart failure,16 and pulmonary hypertension.17 In the present study, to examine whether continuous stimulation of sGC inhibits cardiac hypertrophy and fibrosis, we administered BAY41-2272 to rats with hypertension induced by Ang II. The goal of this study was to better understand the role of sGC in cardiovascular remodeling in Ang IIinduced hypertension.
| Methods |
|---|
|
|
|---|
9 times by tail-cuff plethysmography (Softron, BP-98A) at 2:00 to 3:00 PM. The doses of BAY41-2272 used in this study were determined based on our preliminary study, where oral administration at a single dose of 1, 5, or 10 mg/kg was tested in Ang IIinfused rats (Figure I, available online at http://hyper.ahajournals.org). The blood pressurelowering effect of 1 mg/kg BAY41-2272 was minimal and insignificant, but we observed similar hypotensive actions lasting for 12 hours after the administration at 5 and 10 mg/kg. Meanwhile, the primary purpose of the present study was to test inhibitory actions of BAY41-2272 on cardiovascular remodeling, so we therefore chose the experiment period of 14 days based on our previous study, in which sufficient cardiac hypertrophy and fibrosis occurred with significant changes of LV gene expressions in this model of hypertension.18
At day 14, rats were anesthetized with pentobarbital sodium, and a 2F micromanometertipped catheter (Model SPC-721, Millar Instruments) was inserted into the LV through the right carotid artery. LV end-diastolic pressure (LVEDP) was measured using a transducer control unit (Model TCB-500, Millar Instruments) connected to a PowerLab system (ADInstruments Pty Ltd). Then the rats were euthanized by drawing blood from the abdominal aorta. After the whole heart was weighed, LV was frozen in liquid nitrogen or fixed in 4% paraformaldehyde and embedded in paraffin wax.
The present study was performed in accordance with the Animal Welfare Act and with approval of the University of Miyazaki Institutional Animal Care and Use Committee (2006-014). This investigation also conformed with the Guide for the Care and Use of Laboratory Animals published by the National Institutes of Health (NIH Publication No. 85-23, revised 1996).
Histology and Immunohistochemistry
Immunohistochemical staining was performed as described previously.18 For determining myofibroblastic differentiation, slides were stained with an anti-
-smooth muscle actin (
-SMA) monoclonal antibody (Clone 1A4, DAKO) at a dilution of 1:200 overnight at 4°C. For the detection of collagen fibers, slides were incubated with 0.1% picrosirius red (Direct Red 80, Sigma) dissolved in saturated picric acid for 10 minutes as described previously.18
Morphometric Analysis
The morphological evaluation and cell counting of myofibroblasts surrounding intramyocardial coronary arteries were performed in the middle portion of the LV by a single observer in a blinded manner as described previously.18 Each section immunostained with the antibody against
-SMA was scanned at a magnification of x400. The number of cells positive for
-SMA surrounding the intramyocardial coronary artery was counted and normalized to the coronary vessel area, encircled by the external elastic lamella. To evaluate the magnitude of perivascular fibrosis, medium-sized intramyocardial coronary arteries with a diameter of 100 to 200 µm were randomly selected from
3 different sites, and the ratio of the perivascular fibrotic area to the coronary vessel area was determined using WinROOF (Mitani Co.). Collagen volume fraction in the interstitial space of myocardial fibers was determined by calculating the ratio of the collagen area to the entire area of an individual section. To measure cardiocyte size, cross-sectional areas of
50 myocardial fibers were measured at the level of nuclei while omitting longitudinally or obliquely sectioned cells as described previously.18
Gene Expression
Gene expression for type 1 collagen and transforming growth factor (TGF)-ß1 in the LV was measured by real-time quantitative RT-PCR (ABI Prism 7700 Sequence Detector, Applied Biosystems) as described previously.18 cDNA reverse transcribed from total RNA was amplified with oligonucleotide primers, forward and reverse, and with probes labeled with 6-carboxy-fluorescencein as reporter fluorescence and 6-carboxy-tetramethyl-rhodamine as quencher fluorescence. The oligonucleotide sequences used are detailed in previous reports.18,19 The PCR products were of the expected molecular size, and the gene expression levels were normalized relative to the level of 18S ribosomal RNA.
Cell Culture
Cultured cardiac fibroblasts were isolated from ventricles of 1-day-old Wistar rats as described previously.20 The cells were treated with 1 µmol/L Ang II in the absence or presence of BAY41-2272 for 24 hours. The magnitude of their proliferation was assessed by measuring the amount of [3H]-thymidine incorporated into the cells.20
Assays for ANP, BNP, and cGMP
Blood samples were collected at day 14 with 1.5 mg/mL of di-sodium ethylenediamine tetraacetate and 500 kallikrein inactivator units per milliliter of aprotinin, centrifuged at 2000g for 15 minutes at 4°C and then stored at 80°C until use. Plasma levels of ANP were measured with a specific radioimmunoassay, as described previously,21 and those of BNP with a commercially available kit (Peninsula Laboratories Inc). To determine the effect of BAY41-2272 on cGMP levels in the LV, rats were infused with 250 ng/kg per minute of Ang II for 14 days and given orally 2 or 10 mg/kg per day of BAY41-2272 twice a day on days 13 and 14. After the animals were euthanized, the myocardial tissue was immediately collected and stored at 80°C. In the cell culture study, fibroblasts were treated with BAY41-2272 for 10 minutes and immediately collected as described previously.12 cGMP content was determined using a radioimmunoassay kit (YAMASA Cyclic GMP Assay Kit).
Statistical Analysis
Values shown are expressed as mean±SEM. Differences between groups were assessed using the 1-way ANOVA followed by Scheffes test, and statistical significance was accepted at P<0.05.
| Results |
|---|
|
|
|---|
|
Cardiac Hypertrophy and Collagen Deposition
As shown in Figure 2A and 2B, the infusion of Ang II significantly (P<0.01) increased the ratio of heart weight:body weight and cross-sectional area of myocardial fibers, compared with the control, at day 14. The low dose of BAY41-2272 had no effect on the Ang IIinduced increase in heart weight:body weight and cardiocyte size, but the high dose significantly (P<0.01) reduced both. Figure 3A shows the effect of BAY41-2272 on collagen deposition in the perivascular area of intramyocardial coronary arteries. Ang II significantly (P<0.01) increased the deposition, but the low and high doses of BAY41-2272 significantly reduced it by 20% (P<0.05) and by 30% (P<0.01), respectively. Similarly, Ang IIinduced collagen deposition in the myocardial interstitial area was reduced by both the low (21%; P<0.05) and high (38%; P<0.01) dose of BAY41-2272 (Figure 3B).
|
|
Myofibroblastic Differentiation
Figure 4 illustrates numbers of fibroblasts positive for
-SMA, a marker for myofibroblastic differentiation, in the perivascular area surrounding intramyocardial coronary arteries. Ang II increased the number of
-SMApositive cells (P<0.05) compared with controls; however, the low and high doses of BAY41-2272 similarly decreased the number by 74% and 79% (P<0.05), respectively.
|
LV Gene Expression
As shown in Figure 5A and 5B, Ang II significantly augmented the LV gene expression of type 1 collagen (P<0.01) and TGF-ß1 (P<0.05). Coadministration of BAY41-2272 significantly reduced the Ang IIinduced increases in mRNA for type 1 collagen (low dose: 41%; high dose: 49%) and TGF-ß1 (low dose: 49%; high dose: 65%). Although statistically insignificant, slight elevations of both mRNA levels were observed in the high-dose treatment group without Ang II infusion.
|
Measurements of ANP, BNP, and cGMP
The Ang II infusion significantly (P<0.01) increased the plasma level of ANP, but this was not the case for those of BNP, where both the low and high doses of BAY41-2272 had no significant effects on their plasma levels (Table 1). As shown in Table 2, tissue cGMP concentrations in the LV were significantly increased by treatment with the low and high doses of BAY41-2272 with or without the infusion of Ang II.
|
|
Cell Culture Study
Figure 6A and 6B illustrate the effects of Ang II and BAY41-2272 on proliferation and intracellular cGMP in cultured cardiac fibroblasts. As shown in Figure 6A, BAY41-2272 significantly (P<0.01) attenuated not only basal but also Ang IIstimulated [3H]-thymidine incorporation. The inhibition of fibroblast proliferation was accompanied by a significant rise in the intracellular cGMP level (Figure 6B).
|
| Discussion |
|---|
|
|
|---|
Two isotypes of GC, particulate GC and sGC, are widely distributed in various tissues and organs including the heart and kidneys.24 Although 2 isotypes of the cGMP-generating enzymes share some structural homology, their enzymatic activity is regulated differentially: natriuretic peptides stimulate particulate GC, whereas NO evokes the activity of sGC.24 Most of the actions of natriuretic peptides, including the suppression of cardiac hypertrophy and fibrosis, are assumed to be mediated by intracellular cGMP. It has been shown that the direct sGC stimulator BAY41-2272 also exerts its effects by raising intracellular cGMP levels,1517 and consistent with this, BAY41-2272 increased cGMP levels in the LV myocardium tissue and in cultured cardiac fibroblasts in the present study. Because a question may arise over activity of the natriuretic peptide particulate GC system during activation of sGC by BAY41-2272, we measured plasma ANP and BNP levels in the study groups. The subcutaneous infusion of Ang II indeed increased the plasma level of ANP, but BAY41-2272 had no effect, suggesting that natriuretic peptides were unlikely involved in the increased cGMP levels in the LV.
BAY41-2272 has been reported to be quickly oxidized after oral administration, although Straub et al25 showed that the oxidized metabolite exerted a stronger and longer pharmacological effect than BAY41-2272 itself in vivo. In contrast to nitroglycerin, which activates sGC by releasing NO, drug tolerance has been reported to hardly occur for BAY41-2272.14 In the present study, the blood pressurelowering effect of the high dose of BAY41-2272 in the Ang IIinfused rats had been significant during the first 10 days, but it became insignificant at day 14. Despite the incomplete reduction of blood pressure, BAY41-2272 substantially alleviated cardiomyocyte hypertrophy and collagen accumulation surrounding the intramyocardial coronary arteries and in the myocardial interstitium, reducing LVEDP, in the Ang IIinfused rats. The reduction in collagen deposition was accompanied by suppression of the phenotypic change of fibroblasts into myofibroblasts and by lowering of the mRNA levels of type 1 collagen and TGF-ß1. Because the phenotypic change of fibroblasts to myofibroblasts by Ang II or TGF-ß1 has been found critical in stimulating fibroblast proliferation and producing extracellular matrix,26 suppression of this process is important for attenuating cardiac fibrosis. Notably, the low dose of BAY41-2272 had no effect on blood pressure or cardiac hypertrophy but substantially suppressed fibroblastic activation, LV gene expression, and collagen deposition, raising the LV cGMP level.
Because the natriuretic peptidesparticulate GC system has been shown to suppress cardiac hypertrophy and fibrosis independently of blood pressure,9,13,27 we further investigated whether BAY41-2272 has the direct effects in vitro on the cultured cardiac fibroblasts. In the cell culture study, BAY41-2272 inhibited the proliferation of cardiac fibroblasts, elevating the intracellular cGMP level, supporting a direct inhibitory action of this compound on cardiac fibrosis observed in vivo. On the other hand, alleviation of the cardiomyocyte hypertrophy was observed in the high-dose group but not in the low-dose group in the present study, and we found that BAY41-2272 had little effect on hypertrophy in the cultured cardiomyocytes (data not shown). Thus, we speculate that the improvement of cardiomyocyte hypertrophy observed in this study is largely dependent on mechanical load rather than a direct effect of BAY41-2272.
In conclusion, this study demonstrated that the continuous stimulation of sGC with BAY41-2272 for 2 weeks ameliorated Ang IIinduced cardiac remodeling in rats, and the effects on the extracellular matrix may have been exerted partially via cGMP, independently of blood pressure. Thus, sGC generating cGMP would be a therapeutic target for reducing the adverse cardiovascular remodeling associated with hypertension.
Perspectives
Given the significance of myocardial fibrosis and hypertrophy in the process of cardiac remodeling in hypertensive subjects, the present findings may have important implications with regard to pharmacological stimulation of sGC for attenuating the remodeling process of the LV. In this study, we have shown that the orally available compound BAY41-2272, a direct sGC stimulator, would be useful not only in reducing blood pressure but also in attenuating cardiac remodeling. In addition, no adverse effects of BAY41-2272 on the liver or kidneys were detected at least in data of the serum aminotransferases and creatinine levels (Table I, available online at http://hyper.ahajournals.org). Because of the limited clinical use of human recombinant ANP and BNP because of their short half-lives, the present study suggests a potential usefulness for this compound in the treatment of hypertension, warranting further studies, such as administration to other models of hypertension or treatment for longer time periods.
| Acknowledgments |
|---|
Sources of Funding
This study was supported by Grants-in-Aid for Scientific Research on Priority Areas; by the 21st Century Centers of Excellence Program (Life Science) from the Ministry of Education, Culture, Sports, Science, and Technology, Japan; and by a grant from Bayer HealthCare.
Disclosures
H.M. and T.T. have received a research grant from Bayer HealthCare, and J-P.S. is an employee of that company. BAY41-2272 was synthesized at Bayer HealthCare as a research tool but not for use in humans.
| Footnotes |
|---|
Received May 18, 2006; first decision June 6, 2006; accepted August 8, 2006.
| References |
|---|
|
|
|---|
2. Nicoletti A, Michel JB. Cardiac fibrosis and inflammation: interaction with hemodynamic and hormonal factors. Cardiovasc Res. 1999; 41: 532543.
3. Mandinov L, Eberli FR, Seiler C, Hess OM. Diastolic heart failure. Cardiovasc Res. 1999; 45: 813825.
4. Koren MJ, Devereux RB, Casale PN, Savage DD, Laragh JH. Relation of left ventricular mass and geometry to morbidity and mortality in uncomplicated essential hypertension. Ann Intern Med. 1991; 114: 345352.
5. Levy D, Garrison RJ, Savage DD, Kannel WB, Castelli WP. Prognostic implications of echocardiographically determined left ventricular mass in the Framingham Heart Study. N Engl J Med. 1990; 322: 15611566.[Abstract]
6. Weber KT. Fibrosis in hypertensive heart disease: focus on cardiac fibroblasts. J Hypertens. 2004; 22: 4750.[CrossRef][Medline] [Order article via Infotrieve]
7. Olsen MH, Wachtell K, Hermann KL, Frandsen E, Dige-Petersen H, Rokkedal J, Devereux RB, Ibsen H. Is cardiovascular remodeling in patients with essential hypertension related to more than high blood pressure? A LIFE substudy. Am Heart J. 2002; 144: 530537.[CrossRef][Medline] [Order article via Infotrieve]
8. Rosenkranz S. TGF-ß1 and angiotensin networking in cardiac remodeling. Cardiovasc Res. 2004; 63: 423432.
9. Calderone A, Thaik CM, Takahashi N, Chang DL, Colucci WS. Nitric oxide, atrial natriuretic peptide, and cyclic GMP inhibit the growthpromoting effects of norepinephrine in cardiac myocytes and fibroblast. J Clin Invest. 1998; 101: 812818.[Medline] [Order article via Infotrieve]
10. Mori T, Chen YF, Feng JA, Hayashi T, Oparil S, Perry GJ. Volume overload results in exaggerated cardiac hypertrophy in the atrial natriuretic peptide knockout mouse. Cardiovasc Res. 2004; 61: 771779.
11. Cao L, Gardner DG. Natriuretic peptides inhibit DNA synthesis in cardiac fibroblasts. Hypertension. 1995; 25: 227234.
12. Tsuruda T, Boerrigter G, Huntley BK, Noser JA, Cataliotti A, Costello-Boerrigter LC, Chen HH, Burnett JC Jr. Brain natriuretic peptide is produced in cardiac fibroblasts and induces matrix metalloproteinases. Circ Res. 2002; 91: 11271134.
13. Tamura N, Ogawa Y, Chusho H, Nakamura K, Nakao K, Suda M, Kasahara M, Hashimoto R, Katsuura G, Mukoyama M, Itoh H, Saito Y, Tanaka I, Otani H, Katsuki M. Cardiac fibrosis in mice lacking brain natriuretic peptide. Proc Natl Acad Sci. 2000; 97: 42394244.
14. Stasch JP, Schmidt P, Alonso-Alija C, Apeler H, Dembowsky K, Haerter M, Heil M, Minuth T, Perzborn E, Pleiss U, Schramm M, Schroeder W, Schröder H, Stahl E, Steinke W, Wunder F. NO- and haem-independent activation of soluble guanylyl cyclase: molecular basis and cardiovascular implications of a new pharmacological principle. Br J Pharmacol. 2002; 136: 773783.[CrossRef][Medline] [Order article via Infotrieve]
15. Stasch JP, Becker EM, Alonso-Alija C, Apeler H, Denbowsky K, Feurer A, Gerzer R, Minuth T, Perzborn E, Pleiß U, Schröder H, Schroeder W, Stahl E, Steinke W, Straub A, Schramm M. NO-independent regulatory site on soluble guanylate cyclase. Nature (Lond). 2001; 410: 212215.[CrossRef][Medline] [Order article via Infotrieve]
16. Boerrigter G, Costello-Boerrigter LC, Cataliotti A, Tsuruda T, Harty GJ, Lapp H, Stasch JP, Burnett JC Jr. Cardiorenal and humoral properties of a novel direct soluble guanylate cyclase stimulator BAY41-2272 in experimental congestive heart failure. Circulation. 2003; 107: 686689.
17. Evgenov OV, Ichinose F, Evgenov NV, Gnoth MJ, Falkowski GE, Chang Y, Bloch KD, Zapol WM. Soluble guanylate cyclase activator reverses acute pulmonary hypertension and augments the pulmonary vasodilator response to inhaled nitric oxide in awake lambs. Circulation. 2004; 110: 22532259.
18. Tsuruda T, Kato J, Hatakeyama K, Masuyama H, Cao YN, Imamura T, Kitamura K, Asada Y, Eto T. Antifibrotic effect of adrenomedullin on coronary adventitia in angiotensin IIinduced hypertensive rats. Cardiovasc Res. 2005; 65: 921929.
19. Naito Y, Tsujino T, Fujioka Y, Ohyanagi M, Iwasaki T. Augmented diurnal variations of the cardiac renin-angiotensin system in hypertensive rats. Hypertension. 2002; 40: 827833.
20. Tsuruda T, Kato J, Kitamura K, Kawamoto M, Kuwasako K, Imamura T, Koiwaya Y, Tsuji T, Kangawa K, Eto T. An autocrine or a paracrine role of adrenomedullin in modulating cardiac fibroblast growth. Cardiovasc Res. 1999; 43: 958967.
21. Hirano S, Imamura T, Matsuo T, Ishiyama Y, Kato J, Kitamura K, Koiwaya Y, Eto T. Differential responses of circulating and tissue adrenomedullin and gene expression to volume overload. J Card Fail. 2000; 6: 120129.[Medline] [Order article via Infotrieve]
22. Weber KT. Cardioreparation in hypertensive heart disease. Hypertension. 2001; 38: 588591.
23. Tokuda K, Kai H, Kuwahara F, Yasukawa H, Tahara N, Kudo H, Takemiya K, Koga M, Yamamoto T, Imaizumi T. Pressure-independent effects of Angiotensin II on hypertensive myocardial fibrosis. Hypertension. 2004; 43: 499503.
24. Andreopoulos S, Papapetropoulos A. Molecular aspects of soluble guanylyl cyclase regulation. Gen Pharmacol. 2000; 34: 147157.[CrossRef][Medline] [Order article via Infotrieve]
25. Straub A, Benet-Buckholz J, Fröde R, Kern A, Kohlsdorfer C, Schmitt P, Schwarz T, Siefert HM, Stasch JP. Metabolites of orally active NO-independent pyrazolopyridine stimulators of soluble guanylate cyclase. Bioorg Med Chem. 2002; 10: 17111717.[CrossRef][Medline] [Order article via Infotrieve]
26. Campbell SE, Katwa LC. Angiotensin II stimulated expression of transforming growth factor-ß1 in cardiac fibroblasts and myofibroblasts. J Mol Cell Cardiol. 1997; 29: 19471958.[CrossRef][Medline] [Order article via Infotrieve]
27. Rosenkranz AC, Woods RL, Dusting GJ, Ritchie RH. Antihypertrophic actions of the natriuretic peptides in adult rat cardiomyocytes: Importance of cyclic GMP. Cardiovasc Res. 2003; 57: 515522.
Related Article:
Hypertension 2006 48: 822-823.
This article has been cited by other articles:
![]() |
T. Tsuruda, K. Hatakeyama, H. Masuyama, Y. Sekita, T. Imamura, Y. Asada, and K. Kitamura Pharmacological stimulation of soluble guanylate cyclase modulates hypoxia-inducible factor-1{alpha} in rat heart Am J Physiol Heart Circ Physiol, October 1, 2009; 297(4): H1274 - H1280. [Abstract] [Full Text] [PDF] |
||||
![]() |
M. P. Ruiz-Torres, M. Griera, A. Chamorro, M. L. Diez-Marques, D. Rodriguez-Puyol, and M. Rodriguez-Puyol Tirofiban increases soluble guanylate cyclase in rat vascular walls: pharmacological and pathophysiological consequences Cardiovasc Res, April 1, 2009; 82(1): 125 - 132. [Abstract] [Full Text] [PDF] |
||||
![]() |
T. Nagayama, M. Zhang, S. Hsu, E. Takimoto, and D. A. Kass Sustained Soluble Guanylate Cyclase Stimulation Offsets Nitric-Oxide Synthase Inhibition to Restore Acute Cardiac Modulation by Sildenafil J. Pharmacol. Exp. Ther., August 1, 2008; 326(2): 380 - 387. [Abstract] [Full Text] [PDF] |
||||
![]() |
B. Williams The Year in Hypertension J. Am. Coll. Cardiol., May 6, 2008; 51(18): 1803 - 1817. [Full Text] [PDF] |
||||
![]() |
B. Kemp-Harper and R. Feil Meeting Report: cGMP Matters Sci. Signal., March 4, 2008; 1(9): pe12 - pe12. [Abstract] [Full Text] [PDF] |
||||
![]() |
D. A. Heaton, D. Li, S. C. Almond, T. A. Dawson, L. Wang, K. M. Channon, and D. J. Paterson Gene Transfer of Neuronal Nitric Oxide Synthase into Intracardiac Ganglia Reverses Vagal Impairment in Hypertensive Rats Hypertension, February 1, 2007; 49(2): 380 - 388. [Abstract] [Full Text] [PDF] |
||||
![]() |
V. Franco and S. Oparil Is There a New Treatment for Hypertensive Disease in the Horizon?: Role of Soluble Guanylate Cyclase Hypertension, November 1, 2006; 48(5): 822 - 823. [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hypertension Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 2006 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |