(Hypertension. 2000;35:694.)
© 2000 American Heart Association, Inc.
Scientific Contributions |
From the Department of Medicine and Experimental Oncology (P.M., D.S., F.R., L.C., F.V.), Hypertension Unit, University of Torino, Torino, Italy; Department of Medical and Surgical Sciences (F.F., C.P.), Division of Endocrinology, University of Padova, Padova, Italy; and Fondation Jean Dausset CEPH (L.P.), Paris, France.
Correspondence to Dr Paolo Mulatero, University of Torino, Department of Medicine and Experimental Oncology, Hypertension Unit, San Vito Hospital, S San Vito 34, 10133 Torino, Italy. E-mail mulatero{at}tin.it
| Abstract |
|---|
|
|
|---|
Key Words: aldosterone hypertension, essential hyperaldosteronism genetics polymorphism
| Introduction |
|---|
|
|
|---|
1% to 2%
of hypertensive patients, but it is usually considered in the
differential diagnosis of hypertension, because some forms are curable
with surgical intervention. A solitary adrenocortical
aldosterone-producing adenoma (APA) is the most common
cause of PA, occurring in
60% of cases. Idiopathic
hyperaldosteronism (IHA), which can be associated with bilateral
micronodular or macronodular adrenal hyperplasia, accounts for
40%
of cases and is sometimes considered a variant of essential
hypertension (EHT).1 Very rarely, PA can be caused by the
inheritance of a hybrid gene originating from a previous recombination
between the CYP11B1 and CYP11B2
genes.2 The activity of the aldosterone synthase enzyme (CYP11B2) is necessary for normal aldosterone secretion. This enzyme has the steroid 11ß-hydroxylase, 18-hydroxylase, and 18-oxidase activities that are required to catalyze the synthesis of aldosterone from 11-deoxycorticosterone.3 4 The expression of CYP11B2 is normally limited to the zona glomerulosa of the human adrenal cortex, the normal site of aldosterone synthesis, where it is controlled principally by serum potassium and angiotensin II concentrations. The enzyme is encoded by the CYP11B2 gene located on chromosome 8q24.5 6 We hypothesized that polymorphic variants of the CYP11B2 gene could contribute to susceptibility to PA and, in particular, to IHA.
In a sample of 128 patients with PA (38 APA and 90 IHA), in 72 patients with EHT, and in 102 normotensive volunteers, we studied 3 polymorphisms in the CYP11B2 gene that may influence either its expression or the activity of the encoded enzyme. The first polymorphism was a frequent singlebase pair substitution (C to T) at position -344 in the promoter of the gene, occurring in a sequence that binds to the steroidogenic factor-1 transcription factor.7 The second polymorphism was a common gene conversion of CYP11B2 in which most of intron 2 is replaced by that of the homologous CYP11B1 gene,7 and the third was a point mutation (R173K), previously reported to be at increased frequency in patients with low-renin EHT.8 Genetic analysis of our samples revealed strong linkage disequilibrium between these markers, with 2 frequent haplotypes, of which 1, C2R (-344C, CYP11B2 intron2 sequence, and 173R), had an increased frequency in the IHA group. No differences in haplotype frequencies were found among the normotensive individuals, patients with APA, and patients with EHT. The association of the C2R haplotype with IHA is the first genetic polymorphism shown to be at an increased frequency in such patients.
| Methods |
|---|
|
|
|---|
|
Hormonal Measurements
Plasma aldosterone and plasma renin activity (PRA)
were determined with radioimmunoassay kits purchased from Sorin
Biomedical Diagnostics. The intra-assay and interassay
coefficients of variation for aldosterone were 7.9% and
9.6%, respectively, with a normal range of 55.5 to 333 pmol/L supine
and 139 to 832 pmol/L upright. The intra-assay and interassay
coefficients of variations for PRA were 5.4% and 9.1%, respectively,
with a normal range of 0.11 to 0.83 ng ·
L-1 · s-1 supine
and 0.42 to 1.67 ng · L-1 ·
s-1 upright. Patients were left in a recumbent
position for 1 hour before supine samples were collected and for 2
hours in an upright position before upright samples were collected.
PCR Amplification and Genotyping of CYP11B2
Fragments
Genomic DNA was prepared from peripheral blood
leukocytes with microspin columns (QIAamp Blood Kit; Qiagen).
Analysis of the R173K substitution and the intron 2 gene
conversion was performed by first amplifying this region with PCR with
gene-specific primers 1S and 1A (Table 2). The 50-µL reaction was subjected to
35 cycles at 94°C for 1 minute, 65°C for 1 minute, and 72°C for 2
minutes with an additional 5 seconds each cycle, followed by a final
extension at 72°C for 7 minutes. This reaction allows the
amplification of a 2.8-kb fragment that includes exons 1 to 3 of
CYP11B2.
|
The promoter region containing the -344C/T polymorphism was
amplified with the oligonucleotide primers 2S and 2A
(Table 2). This PCR was subjected to 35 cycles at 94°C for 30
seconds, 52°C for 30 seconds, and 72°C for 30 seconds, followed by
a final extension at 72°C for 10 minutes, producing a 160-bp fragment
from the CYP11B2 promoter region. The amplified DNA samples
were subjected to electrophoresis in a 1% agarose gel and transferred
to nylon membranes (GENE Screen Plus; DuPont-New England Nuclear) that
were subsequently hybridized with oligonucleotides that
had been radioactively labeled with
-32P-ATP
and T4 polynucleotide kinase. The membranes were incubated
with the appropriate radiolabeled allele-specific
oligonucleotides (Table 2) in a solution
containing 0.9 mol/L NaCl, 0.09 mol/L Na citrate, 1% SDS, and 1x
Denhardts solution (1% Ficoll, 1% polyvinyl pyrrolidone, and 1%
BSA fraction V) for 4 hours at 42°C. The final stringent washes
before autoradiography were conducted in 0.9 mol/L
NaCl, 0.09 mol/L Na citrate, and 0.5% SDS at 56°C, 63°C, and
56°C for R173K, the intron 2 conversion, and -344C/T
polymorphisms, respectively.
Statistical Analysis
Haplotype frequencies were estimated according to the method of
maximum likelihood with the program EH,12 with assumption
of independence of the markers and separate allowance for linkage
disequilibrium. Haplotype frequencies were estimated in each group
individually and in the total data, and the statistical significance of
comparisons was assessed by comparing twice the difference in logarithm
of the likelihood (-2Ln L) with the
2
distribution with appropriate degrees of freedom.
| Results |
|---|
|
|
|---|
24=861.4,
P<0.001) and in each subgroup
(
24=232.6,
P<0.001,
24=125.8,
P<0.001,
24=201.0,
P<0.001, and
24=305.8, P<0.001
for the IHA, APA, EHT, and control groups, respectively), as is
expected for such tightly linked polymorphisms. The occurrence of
the same haplotypes in each group is consistent with the fact
that they were all drawn from the same population. No deviations of
genotype frequencies from H-W equilibrium were observed for the
alleles tested individually in each group.
|
|
There is significant heterogeneity between the
haplotype frequencies in the IHA and control groups
(het
27=19.06,
P<0.01) but none between any of the other patient groups
and the controls. The haplotype frequencies in these latter groups are
remarkably uniform, whereas those in the IHA group are clearly
different from them (Table 4). In particular, the frequency of
the C2R haplotype is higher in the IHA group (47%) than in the other
groups (36%), in large part at the expense of the T1K haplotype, which
is decreased (38% versus 53%). A separate analysis of the
intron 2 genotypes alone, which are not in complete linkage
disequilibrium with the other 2 markers, revealed essentially identical
results.
Because of the significant linkage disequilibrium in the region, the allele frequencies at each of the polymorphic sites are highly correlated, and similar differences in allele frequencies are seen for each marker (Table 4). We also reexamined our EHT group, classifying them into 27 patients characterized by low PRA (<0.0833 ng · L-1 · s-1) and 45 patients with normal to high PRA. The haplotype and allele frequencies in the normal- to high-renin group were essentially identical to the control and APA values. The values for the low-renin group were intermediate between those of the controls and the IHA group (Table 4), although the difference from the control values was not statistically significant. The intron 2 polymorphism is not in complete linkage disequilibrium with the other polymorphisms.
| Discussion |
|---|
|
|
|---|
Aldosterone secretion is influenced by many factors, but all of these factors must eventually act through the aldosterone synthase enzyme, the only enzyme capable of synthesis of aldosterone, or through limitation of its substrates. Genetic polymorphisms in the aldosterone synthase gene that could render it insensitive to the normal transcriptional control or directly affect its activity are natural candidates to contribute to IHA. In contrast, APAs seem more likely to be caused by mutations in the genes that control growth and proliferation of adrenal cortical cells.
We studied the association of 3 different polymorphisms of CYP11B2 with IHA, using as controls patients with APA or EHT and normotensive volunteers. Alleles of the -344T/C polymorphism were previously found to be associated with EHT5 or with aldosterone levels14 in French populations. This polymorphism is located in a site capable of binding to steroidogenic factor-1 transcription factor.7 The R173K polymorphism has been associated with low-renin EHT in a Chilean population8 but apparently does not influence the rate of production of aldosterone from the precursor deoxycorticosterone by CYP11B2 in vitro.15 The third polymorphism is a common gene conversion in intron 2 of CYP11B2, in which most of the intron is replaced by that of CYP11B1.7 It has been suggested that this intron may contain regulatory elements of the CYP11B genes.16
The 3 polymorphisms were in strong linkage disequilibrium, which is consistent with previous studies that found disequilibrium in this region in other populations.7 17 18 19 The C2R haplotype was increased in frequency in the patients with IHA whom we studied. Due to the strong linkage disequilibrium in the region, it is not possible to determine whether this difference is due to 1 of the 3 markers studied or to another polymorphism that controls aldosterone synthesis that is in linkage disequilibrium with the 3 that were studied. Many genes could theoretically be involved, together with the CYP11B2 gene, in the genetic predisposition to IHA, such as those involved in stimulation (angiotensin II, serotonin, endothelin, and so on) or inhibition (dopamine, adrenomedullin) of aldosterone synthesis. Mutations or regulatory polymorphisms in these genes could cause the altered aldosterone secretion seen in patients with IHA. For example, a recent study demonstrated the overexpression of CYP11B2 mRNA in the lymphocytes of patients with IHA, suggesting an increase in stimulatory factors or variants in the promoter region causing the overproduction of aldosterone in this disease.20 The present study provides the first demonstration of an association between a specific haplotype of a candidate gene and the risk of the development of IHA and indicates that CYP11B2 gene polymorphisms may contribute to its pathogenesis.
In contrast, there was no association among the 3 CYP11B2 polymorphisms that were studied and the occurrence of APAs in our study population. This observation suggests that the genes involved in adrenal tumorigenesis or hyperplasia are more important in the pathogenesis of PA due to APA than the genes involved in steroid biosynthesis. The mechanisms of adrenocortical tumorigenesis are still poorly understood.21 The fact that the majority of these tumors are monoclonal in origin22 23 suggests an accumulation of specific genetic aberrations, such as the activation of proto-oncogenes, overexpression of growth-promoting factors,24 or inactivation of tumor suppressor genes,25 26 27 28 leading to abnormal cell proliferation.29 In this case, the excess aldosterone production would be secondary to proliferation of aldosterone-producing cells rather than dysregulation of its synthesis.
There also was no association between the CYP11B2 polymorphisms and EHT in our study, although the number of patients studied was small. When the patients were reclassified into groups with either low PRA or normal to high PRA, we found that haplotype frequencies in the low-renin group were intermediate between the control values and those observed in the patients with IHA, although the difference in frequency was not statistically significant. It is possible that a subset of the low-renin hypertension group carrying the C2R haplotype may be susceptible to the development of IHA. Previous studies have found an association between the -344T allele and EHT in French and Scottish populations5 18 and between the -344C allele and hypertension in a Japanese population. Furthermore, the R173 allele was associated with low-renin EHT in a Chilean population.8 The association of different alleles with hypertension in different populations could be due to linkage disequilibrium of the alleles studied with a functional polymorphism that may have a different phase in each of the populations showing association with different alleles.
Associations of specific haplotypes with a disease may also arise from unsuspected population subdivision. For example, the presence of a genetically distinct subgroup that is susceptible to IHA could cause spurious associations of any genetic polymorphisms differing between the 2 groups and IHA, regardless of whether the variants had some causative role. However, our patients were all recruited from the same region in northern Italy, and we have no reason to suspect genetic heterogeneity. On the contrary, the uniformity of the haplotype frequencies in the 3 control groups suggests a genetically homogeneous population. In conclusion, we tentatively suggest that variants of the CYP11B2 gene may be associated with an increased risk of the development of IHA.
| Acknowledgments |
|---|
Received August 11, 1999; first decision September 27, 1999; accepted October 28, 1999.
| References |
|---|
|
|
|---|
2. Lifton RP, Dluhy RG, Powers M, Rich GM, Cook S, Ulick S, Lalouel JM. A chimaeric 11 beta-hydroxylase/aldosterone synthase gene causes glucocorticoid-remediable aldosteronism and human hypertension. Nature. 1992;355:262265.[Medline] [Order article via Infotrieve]
3.
Kawamoto T, Mitsuuchi Y, Toda K, Yokoyama Y, Miyahara
K, Miura S, Ohnishi T, Ichikawa Y, Nakao K, Imura H, Ulick S, Shizuta
Y. Role of steroid 11beta-hydroxylase and steroid 18-hydroxylase in the
biosynthesis of glucocorticoids and mineralocorticoids in humans.
Proc Natl Acad Sci U S A. 1992;89:14581462.
4.
Curnow KM, Tusie-Luna MT, Pascoe L, Natarajan R, Gu
JL, Nadler JL, White PC. The product of the CYP11B2 gene
is required for aldosterone biosynthesis in the human
adrenal cortex. Mol Endocrinol. 1991;5:15131522.
5.
Brand E, Chatelain N, Mulatero P, Fery I, Curnow KM,
Jeunemaitre X, Corvol P, Pascoe L, Soubrier F. Structural
analysis and evaluation of the aldosterone synthase
gene in hypertension. Hypertension. 1998;32:198204.
6.
Taymans SE, Pack S, Pak E, Torpy DJ, Zhuang Z,
Stratakis CA. Human CYP11B2 (aldosterone synthase) maps to
chromosome 8q24.3. J Clin Endocrinol Metab. 1998;83:10331036.
7. White PC, Slutsker L. Haplotype analysis of CYP11B2. Endocr Res. 1995;21:437442.[Medline] [Order article via Infotrieve]
8. Fardella CE, Rodriguez H, Montero J, Zhang G, Vignolo P, Rojas A, Villarroel L, Miller W. Genetic variation in p450c11AS in Chilean patients with low renin hypertension. J Clin Endocrinol Metab. 1996;81:43474351.[Abstract]
9.
Mulatero P, Veglio F, Pilon C, Rabbia F, Zocchi C,
Limone P, Boscaro M, Sonino N, Fallo F. Diagnosis of
glucocorticoid-remediable aldosteronism in primary aldosteronism:
aldosterone response to dexamethasone and long
polymerase chain reaction for chimeric gene. J Clin
Endocrinol Metab. 1998;83:25732575.
10. Veglio F, Rabbia F, Mengozzi G, Mulatero P, Zocchi C, Martini G, Morra di Cella S, Chiandussi L. Assessment of a threshold value of the aldosterone/plasma renin activity ratio in the screening of primary aldosteronism. Intern Med. 1999;7:18.
11. Vallotton MB. Primary aldosteronism, I: diagnosis of primary aldosteronism. Clin Endocrinol (Oxf). 1996;45:4752.[Medline] [Order article via Infotrieve]
12. Terwilliger J, Ott J. Handbook of Human Genetic Linkage. Baltimore, Md: Johns Hopkins University Press; 1994.
13. Gordon RD. Primary aldosteronism: a new understanding. Clin Exp Hypertens. 1997;19:857870.
14. Pojoga L, Gautier S, Blanc H, Guyene TT, Poirier O, Cambien F, Benetos A. Genetic determination of plasma aldosterone levels in essential hypertension. Am J Hypertens. 1998;11:856860.[Medline] [Order article via Infotrieve]
15.
Portrat-Doyen S, Tourniaire J, Richard O, Mulatero P,
Aupetit-Faisant B, Curnow KM, Pascoe L, Morel Y. Isolated
aldosterone synthase deficiency caused by
simultaneous E198D and V386A mutations in the CYP11B2 gene.
J Clin Endocrinol Metab. 1998;83:41564161.
16. Pascoe L, Curnow KM. Genetic recombination as a cause of inherited disorders of aldosterone and cortisol biosynthesis and a contributor to genetic variation in blood pressure. Steroids. 1995;60:8190.[Medline] [Order article via Infotrieve]
17. Tamaki S, Iwai N, Tsujita Y, Kinoshita M. Genetic polymorphism of CYP11B2 gene and hypertension in Japanese. Hypertension. 1999;33(suppl II):II-266II-270.
18.
Davies E, Holloway CD, Ingram MC, Inglis GC, Friel EC,
Morrison C, Anderson NH, Fraser R, Connell JM. Aldosterone
secretion rate and blood pressure in essential hypertension are related
to polymorphic differences in the aldosterone synthase
gene CYP11B2. Hypertension. 1999;33:703707.
19.
Kupari M, Hautanen A, Lankinen L, Koskinen P,
Virolainen J, Nikkila H, White PC. Associations between human
aldosterone synthase (CYP11B2) gene
polymorphisms and left ventricular size, mass, and
function. Circulation. 1998;97:569575.
20.
Takeda Y, Furukawa K, Inaba S, Miyamori I, Mabuchi H.
Genetic analysis of aldosterone synthase in
patients with idiopathic hyperaldosteronism. J Clin
Endocrinol Metab. 1999;84:16331637.
21.
Gicquel C, Bertagna X, Le Bouc Y. Recent advances in
the pathogenesis of adrenocortical tumors. Eur J Endocrinol. 1995;133:133144.
22.
Beuschlein F, Reincke M, Karl M, Travis WD,
Jaursch-Hancke C, Abdelhamid S, Chousos GP, Allolio B. Clonal
composition of human adrenocortical neoplasm. Cancer Res. 1994;54:49274932.
23. Gicquel C, Leblond-Francillard M, Bertagna X, Louvel A, Chapuis Y, Luton JP, Girard F, Le Bouc Y. Clonal analysis of human adrenocortical carcinomas and secreting adenomas. Clin Endocrinol (Oxf). 1994;40:465477.[Medline] [Order article via Infotrieve]
24. Gicquel C, Xavier B, Schneid H, Leblond-Francillard M, Luton JP, Girard F, Le Bouc Y. Rearrangements at the 11p15 locus and overexpression of insulin-like growth factor-II gene in sporadic adrenocortical tumors. J Clin Endocrinol Metab. 1994;78:14441453.[Abstract]
25. Lin SR, Lee YJ, Tsai JH. Mutations of the p53 gene in human functional adrenal neoplasm. J Clin Endocrinol Metab. 1994;78:483491.[Abstract]
26. Reincke M, Karl M, Travis WH, Mastorakos G, Allolio B, Lineham HM, Chrousos GP. p53 mutations in human adrenocortical neoplasms: immunohistochemical and molecular studies. J Clin Endocrinol Metab. 1994;78:790794.[Abstract]
27. Perrett CW, Pistorello M, Boscaro M, Fallo F, Clayton RN. Molecular genetic studies on adrenal tumors: where phenotype does not match genotype. In: New MI, ed. Frontiers in Endocrinology. Rome, Italy: Ares-Serono Symposia Publications; 1996:139143.
28.
Pilon C, Pistorello M, Moscon A, Altavilla G, Pagotto
U, Boscaro M, Fallo F. Inactivation of the p16 tumor suppressor gene in
adrenocortical tumors. J Clin Endocrinol Metab. 1999;84:27762779.
29. Reincke M. Mutations in adrenocortical tumors. Horm Metab Res. 1998;30:447455.[Medline] [Order article via Infotrieve]
This article has been cited by other articles:
![]() |
E. Ritz How Little Aldosterone is Able to Raise Blood Pressure? Clin. J. Am. Soc. Nephrol., April 1, 2009; 4(4): 703 - 710. [Full Text] [PDF] |
||||
![]() |
N. Makhanova, J. Hagaman, H.-S. Kim, and O. Smithies Salt-Sensitive Blood Pressure in Mice With Increased Expression of Aldosterone Synthase Hypertension, January 1, 2008; 51(1): 134 - 140. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Mulatero, F. Veglio, P. Maffei, M. Bondanelli, S. Bovio, F. Daffara, G. Leotta, A. Angeli, C. Calvo, C. Martini, et al. CYP11B2 -344T/C Gene Polymorphism and Blood Pressure in Patients with Acromegaly J. Clin. Endocrinol. Metab., December 1, 2006; 91(12): 5008 - 5012. [Abstract] [Full Text] [PDF] |
||||
![]() |
H. Tanahashi, T. Mune, Y. Takahashi, M. Isaji, T. Suwa, H. Morita, N. Yamakita, K. Yasuda, T. Deguchi, P. C. White, et al. Association of Lys173Arg Polymorphism with CYP11B2 Expression in Normal Adrenal Glands and Aldosterone-Producing Adenomas J. Clin. Endocrinol. Metab., November 1, 2005; 90(11): 6226 - 6231. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Meneton, X. Jeunemaitre, H. E. de Wardener, and G. A. Macgregor Links Between Dietary Salt Intake, Renal Salt Handling, Blood Pressure, and Cardiovascular Diseases Physiol Rev, April 1, 2005; 85(2): 679 - 715. [Abstract] [Full Text] [PDF] |
||||
![]() |
C. E. Grim, A. W. Cowley Jr, P. Hamet, D. Gaudet, M. L. Kaldunski, J. M. Kotchen, S. Krishnaswami, Z. Pausova, R. Roman, J. Tremblay, et al. Hyperaldosteronism and Hypertension: Ethnic Differences Hypertension, April 1, 2005; 45(4): 766 - 772. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. C. White and W. E. Rainey Polymorphisms in CYP11B Genes and 11-Hydroxylase Activity J. Clin. Endocrinol. Metab., February 1, 2005; 90(2): 1252 - 1255. [Full Text] [PDF] |
||||
![]() |
T. A. Williams, P. Mulatero, M. Bosio, S. Lewicka, M. Palermo, F. Veglio, and D. Armanini A Particular Phenotype in a Girl with Aldosterone Synthase Deficiency J. Clin. Endocrinol. Metab., July 1, 2004; 89(7): 3168 - 3172. [Abstract] [Full Text] [PDF] |
||||
![]() |
J. M.C. Connell, R. Fraser, S. MacKenzie, and E. Davies Is Altered Adrenal Steroid Biosynthesis a Key Intermediate Phenotype in Hypertension? Hypertension, May 1, 2003; 41(5): 993 - 999. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. O. Lim, T. M. Macdonald, C. Holloway, E. Friel, N. H. Anderson, E. Dow, R. T. Jung, E. Davies, R. Fraser, and J. M. C. Connell Variation at the Aldosterone Synthase (CYP11B2) Locus Contributes to Hypertension in Subjects with a Raised Aldosterone-to-Renin Ratio J. Clin. Endocrinol. Metab., September 1, 2002; 87(9): 4398 - 4402. [Abstract] [Full Text] [PDF] |
||||
![]() |
P. Mulatero, T. A. Williams, A. Milan, C. Paglieri, F. Rabbia, F. Fallo, and F. Veglio Blood Pressure in Patients with Primary Aldosteronism Is Influenced by Bradykinin B2 Receptor and {alpha}-Adducin Gene Polymorphisms J. Clin. Endocrinol. Metab., July 1, 2002; 87(7): 3337 - 3343. [Abstract] [Full Text] [PDF] |
||||
![]() |
S.-J. Shi, H. T. Nguyen, G. D. Sharma, L. G. Navar, and K. N. Pandey Genetic disruption of atrial natriuretic peptide receptor-A alters renin and angiotensin II levels Am J Physiol Renal Physiol, October 1, 2001; 281(4): F665 - F673. [Abstract] [Full Text] [PDF] |
||||
![]() |
A. H. El-Gharbawy, V. S. Nadig, J. M. Kotchen, C. E. Grim, K. B. Sagar, M. Kaldunski, P. Hamet, Z. Pausova, D. Gaudet, F. Gossard, et al. Arterial Pressure, Left Ventricular Mass, and Aldosterone in Essential Hypertension Hypertension, March 1, 2001; 37(3): 845 - 850. [Abstract] [Full Text] [PDF] |
||||
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
|
Hypertension Home | Subscriptions | Archives | Feedback | Authors | Help | AHA Journals Home | Search Copyright © 2000 American Heart Association, Inc. All rights reserved. Unauthorized use prohibited. |