bluuebunny/crossref_metadata_2025 huggingface dataset:
Applicability of a “Speed” Congenic Strategy to Dissect Blood Pressure Quantitative Trait Loci on Rat Chromosome 2
Authors: Jeffs Baxter , Negrin Cervantes D. , Graham Delyth , Clark James S. , Anderson Niall H. , Gauguier Dominique , Dominiczak Anna F.
Published: June 2012

Abstract
—The identification of any quantitative trait locus (QTL) via a genome scan is only the first step toward the ultimate goal of gene identification. The next step is the production of congenic strains by which the existence of a QTL may be verified and the implicated chromosomal region be reduced to a size applicable to positional cloning of the causal gene. We used a speed congenic breeding protocol previously verified in mice for 2 blood pressure QTLs on rat chromosome 2. Four congenic strains were produced through introgression of various segments of chromosome 2 from Wistar-Kyoto rats from Glasgow colonies [WKY
(Gla)
rats] into the recipient stroke-prone spontaneously hypertensive rats from Glasgow colonies [SHRSP
(Gla)
], and vice versa. The number of backcross generations required for each strain to achieve complete homozygosity at 83 background genetic markers in a “best” male varied between 3 and 4. Transfer of the region of rat chromosome 2 containing both QTLs from WKY
(Gla)
into an SHRSP
(Gla)
genetic background lowered both baseline and salt-loaded systolic blood pressure by ≈20 and ≈40 mm Hg in male congenic rats compared with the SHRSP parental strain (
F
=53.4,
P
<0.005;
F
=28.0,
P
< 0.0005, respectively). In contrast, control animals for stowaway heterozygosity presented no deviation from the blood pressure values recorded for the SHRSP
(Gla)
, indicating that if such heterozygosity exists, its effect on blood pressure is negligible. A reciprocal strategy in which 1 or both QTLs on rat chromosome 2 were transferred from SHRSP
(Gla)
into a WKY
(Gla)
genetic background resulted in statistically significant but smaller blood pressure increases for 1 of these QTLs. These results confirm the existence of blood pressure QTLs on rat chromosome 2 and demonstrate the applicability of a speed congenic strategy in the rat and emphasize the important role of the genetic background.
Endothelin-Dependent and -Independent Components of Strain-Activated Brain Natriuretic Peptide Gene Transcription Require Extracellular Signal Regulated Kinase and p38 Mitogen-Activated Protein Kinase
Authors: Liang Faquan , Lu Shan , Gardner David G.
Published: June 2012

Abstract
—The application of mechanical strain to cultured cardiac myocytes in vitro leads to activation of the brain natriuretic peptide (BNP) gene promoter, a marker of cardiac hypertrophy. We have previously shown that this activation results from both a direct mechanostimulatory event and an indirect autocrine/paracrine stimulation involving the sequential production of angiotensin II and endothelin (ET). In the present study, we examined the role of p38 mitogen-activated protein kinase (MAPK) and extracellular signal regulated kinase (ERK) in signaling the increase in promoter activity trafficking through each of these pathways. ET was shown to stimulate both p38 MAPK and ERK activity in these cultures and to activate human BNP (hBNP) promoter activity. Activation of the promoter was inhibited ≈45% by SB-203580, a p38 MAPK inhibitor, and ≈70% by PD98059, an inhibitor of the ERK-activating kinase MAPK kinase. The ET-independent (ie, direct) stimulation of the hBNP promoter by mechanical strain was inhibited ≈70% by SB-203580 and ≈60% by PD98059, implying that similar signaling circuitry is used, albeit to different degrees, by the direct and indirect pathways. The p38 MAPK component of both the ET-dependent and the ET-independent responses to strain appears to operate through a series of nuclear factor-κB binding, shear stress response element–like structures in the hBNP gene promoter. Collectively, these data suggest that activation of the BNP promoter by hypertrophic stimuli involves the participation of several independent signaling pathways. Such redundancy would help to guarantee generation of the full hypertrophic phenotype independently of the nature of the hypertrophic stimulus.
Angiotensin II and PDGF-BB Stimulate β
1
-Integrin–Mediated Adhesion and Spreading in Human VSMCs
Authors: Kappert Kai , Schmidt Gunther , Doerr Gesine , Wollert-Wulf Brigitte , Fleck Eckart , Graf Kristof
Published: June 2012

Abstract
—β
1
-Integrins play an important role for adhesion and spreading of human smooth muscle cells. In the present study we examined the influence of angiotensin II and platelet-derived growth factor (PDGF)-BB on β
1
-integrin–dependent functions of human smooth muscle cells obtained from iliac arteries. Treatment of these cells with PDGF-BB (20 ng/mL) and Angiotensin II (1 μmol/L) did not change β
1
-integrin expression up to 48 hours as analyzed by flow cytometry and reverse transcription polymerase chain reaction. β
1
-integrins predominantly mediated adhesion of human smooth muscle cells to collagen I (79.7±4.4%,
P
<0.01) and fibronectin (66.6±2.4%,
P
<0.01). Treatment of smooth muscle cells with Angiotensin II (1 μmol/L) and PDGF-BB (20 ng/mL) significantly increased the adhesion to collagen I by 56.5% and 44.3%, respectively, and to fibronectin by 49.6% and 36.4%, respectively (all
P
<0.05). Angiotensin II–induced effects were mediated by the AT
1
receptor. The PDGF-BB mediated increase of adhesion was inhibited in the presence of genestein, a tyrosine-kinase inhibitor and by protein kinase C downregulation with phorbol 12-myristate 13-acetate. Spreading of smooth muscle cells also was β
1
-integrin dependent on collagen I and α
5
β
1
-integrin dependent on fibronectin. Angiotensin II and PDGF-BB increased cell spreading on fibronectin up to 276% and 318%, respectively, and on collagen I up to 133% and 138% (all
P
<0.05). These increases were significantly inhibited by blocking antibodies against β
1
-integrin, α
5
-integrin on fibronectin, the AT
1
receptor blocker irbesartan, and genestein. The present data demonstrate that angiotensin II and as well PDGF-BB enhance β
1
-integrin–dependent adhesion and spreading of human vascular smooth muscle cells. Furthermore, the experiments with PDGF suggest an involvement of protein kinase C activation leading to these enhanced effects.
Potentiation of the Vascular Response to Kinins by Inhibition of Myocardial Kininases
Authors: Dendorfer Andreas , Wolfrum Sebastian , Schäfer Ulrich , Stewart John M. , Inamura Noriaki , Dominiak Peter
Published: June 2012

Abstract
—Inhibitors of angiotensin I–converting enzyme (ACE) are very efficacious in the potentiation of the actions of bradykinin (BK) and are able to provoke a B
2
receptor–mediated vasodilation even after desensitization of this receptor. Because this activity cannot be easily explained only by an inhibition of kinin degradation, direct interactions of ACE inhibitors with the B
2
receptor or its signal transduction have been hypothesized. To clarify the significance of degradation-independent potentiation, we studied the vasodilatory effects of BK and 2 degradation-resistant B
2
receptor agonists in the isolated rat heart, a model in which ACE and aminopeptidase P (APP) contribute equally to the degradation of BK. Coronary vasodilation to BK and to a peptidic (B6014) and a nonpeptidic (FR190997) degradation-resistant B
2
agonist was assessed in the presence or absence of the ACE inhibitor ramiprilat, the APP inhibitor mercaptoethanol, or both. Ramiprilat or mercaptoethanol induced leftward shifts in the BK dose-response curve (EC
50
=3.4 nmol/L) by a factor of 4.6 or 4.9, respectively. Combined inhibition of ACE and APP reduced the EC
50
of BK to 0.18 nmol/L (ie, by a factor of 19) but potentiated the activity of B6014 (EC
50
=1.9 nmol/L) only weakly without altering that of FR190997 (EC
50
=0.34 nmol/L). Desensitization of B
2
receptors was induced by the administration of BK (0.2 μmol/L) or FR190997 (0.1 μmol/L) for 30 minutes; the vascular reactivity to ramiprilat or increasing doses of BK was tested thereafter. After desensitization with BK, but not FR190997, an additional application of ramiprilat provoked a B
2
receptor–mediated vasodilation. High BK concentrations were still effective at the desensitized receptor. The process of desensitization was not altered by ramiprilat. These results show that in this model, all potentiating actions of ACE inhibitors on kinin-induced vasodilation are exclusively related to the reduction in BK breakdown and are equivalently provoked by APP inhibition. The desensitization of B
2
receptors is overcome by increasing BK concentrations, either directly or through the inhibition of ACE. These observations do not suggest any direct interactions of ACE inhibitors with the B
2
receptor or its signal transduction but point to a very high activity of BK degradation in the vicinity of the B
2
receptor in combination with a stimulation-dependent reduction in receptor affinity.
Decreased Endothelium-Dependent Vascular Relaxation During Reduction of Uterine Perfusion Pressure in Pregnant Rat
Authors: Crews Janice K. , Herrington Jason N. , Granger Joey P. , Khalil Raouf A.
Published: June 2012

Abstract
—Reduction in uterine perfusion and the ensuing placental ischemia during late pregnancy have been proposed to trigger increases in systemic vascular resistance and pregnancy-induced hypertension; however, the intermediary mechanisms involved are unclear. The purpose of the present study was to test the hypothesis that reduced uterine perfusion pressure during late pregnancy is associated with impaired endothelium-dependent vascular relaxation and, consequently, enhanced systemic vascular reactivity. Active stress was measured in aortic strips isolated from late pregnant Sprague-Dawley rats and a hypertensive pregnant rat model produced through the long-term reduction in uterine perfusion pressure (RUPP). Phenylephrine (Phe, 10
−5
mol/L) caused an increase in active stress to 4.5±0.4×10
3
N/m
2
in normal pregnant rats and a larger increase to 9.4±0.7×10
3
N/m
2
in RUPP rats. Removal of the endothelium significantly enhanced Phe-induced stress in pregnant (6.4±0.6×10
3
N/m
2
) but not RUPP (9.95±0.95×10
3
N/m
2
) rats. In endothelium-intact strips, acetylcholine (ACh) was more potent in inducing relaxation of Phe contraction in pregnant (ED
50
0.1×10
−6
mol/L) than in RUPP (ED
50
1.2×10
−6
mol/L) rats. Pretreatment of endothelium-intact strips with
N
G
-nitro-
l
-arginine methyl ester(100 μmol/L), to inhibit nitric oxide (NO) synthase, significantly inhibited ACh-induced relaxation and enhanced Phe-induced stress in pregnant (6.2±0.5×10
3
N/m
2
) but not RUPP (9.5±0.85×10
3
N/m
2
) rats. Pretreatment of endothelium-intact strips with methylene blue (10 μmol/L), to inhibit cGMP production in smooth muscle, also inhibited ACh-induced relaxation and enhanced Phe-induced stress in pregnant (6.9±0.65×10
3
N/m
2
) but not RUPP (9.3±0.7×10
3
N/m
2
) rats. In endothelium-denuded strips, relaxation of Phe contraction with the exogenous NO donor sodium nitroprusside was not significantly different between pregnant and RUPP rats. These results suggest that an endothelium-dependent relaxation pathway involving the release of NO from endothelial cells and increased cGMP production in smooth muscle is inhibited in systemic vessels of late pregnant rats with reduced uterine perfusion pressure and may in part explain the increased vascular resistance in pregnancy-induced hypertension.
Increased Blood Pressure in α-Calcitonin Gene–Related Peptide/Calcitonin Gene Knockout Mice
Authors: Gangula Pandu R. R. , Zhao Huwai , Supowit Scott C. , Wimalawansa Sunil J. , Dipette Donald J. , Westlund Karin N. , Gagel Robert F. , Yallampalli Chandra
Published: June 2012

Abstract
—Nerves that contain calcitonin gene–related peptide
(CGRP)
are components of the sensory nervous system. Although these afferent nerves have traditionally been thought to sense stimuli in the periphery and transmit the information centrally, they also have an efferent vasodilator function. Acute administration of a
CGRP
receptor antagonist increases the blood pressure (BP) in several models of hypertension, which indicates that this potent vasodilator plays a counterregulatory role to attenuate the BP increase in these settings. To determine the role of this peptide in the long-term regulation of cardiovascular function, including hypertension, we obtained mice that have a deletion of the α-calcitonin gene–related peptide (α-
CGRP
) gene. Although the β-calcitonin gene–related peptide (β-
CGRP
) gene is intact in these mice, α-
CGRP
is by far the predominant species of
CGRP
produced in dorsal root ganglia (DRG) sensory neurons. Initially, we examined the effect of deletion of the α-
CGRP
on baseline BP and β-
CGRP
and substance P mRNA expression. Systolic BP was significantly higher in the knockout mice (n=7) compared with wild-type in both male (160±6.1 vs 125±4.8 mm Hg) and female (163±4.8 vs 135±33 mm Hg) mice. Next, groups (n=7) of knockout and wild-type mice had catheters surgically placed in the right carotid artery for mean arterial pressure recording. With the animals fully awake and unrestrained, the knockout mice displayed an elevated mean arterial pressure compared with wild-type in both male (139±4.9 vs 118±4.9 mm Hg) and female (121±3.4 vs 107±3.1 mm Hg) mice. Northern blot analysis of DRG RNA samples confirmed the absence of α-
CGRP
mRNA in the knockout mice. Substance P mRNA content in DRG was unchanged between the 2 groups; however, β-
CGRP
mRNA levels were reduced 2-fold in the knockout mice. These results indicate for the first time that α-
CGRP
may be involved in the long-term regulation of resting BP and suggest that these mice are particularly sensitive to challenges to BP homeostasis because of the loss of a compensatory vasodilator mechanism.
Role of Female Sex Hormones in the Development and Reversal of Dahl Hypertension
Authors: Hinojosa-Laborde Carmen , Lange Darrell L. , Haywood Joseph R.
Published: June 2012

Abstract
—Female sex hormones protect against the development of Dahl hypertension mediated by increases in dietary sodium. The role of female sex hormones in the reversal of Dahl hypertension mediated by decreases in dietary sodium is unknown. The goal of this study was to identify sex differences in the reversal of Dahl hypertension and the associated changes in water and electrolyte homeostasis. Male (M, n=8), female (F, n=8), and ovariectomized female (OVX, n=9) Dahl salt-sensitive rats were instrumented with an abdominal radiotelemetry device for 24-hour monitoring of blood pressure (BP) and heart rate. Daily measurements of food intake, water intake, and urine output were recorded as diet was changed from a low-sodium diet (0.15% NaCl) to a diet containing 8% NaCl. The diet was then changed back to 0.15% NaCl. The responses to changes in the salt diet were compared with responses observed in rats (M, n=4; F, n=4; OVX, n=4) that were maintained on 0.15% NaCl during the experiment. Sex differences in BP were observed when M, F, and OVX rats were fed 8% NaCl diet for 2 weeks (152±4, 141±3, and 154±5 mm Hg, respectively). BP was significantly greater (
P
<0.05) in M and OVX rats than in F rats. Fluid balance (water intake minus urine volume) and sodium balance (sodium intake minus sodium excretion) were similar in all groups on the 8% NaCl diet. BP in time-control M, F, and OVX rats was 121±3, 130±4, and 162±11 mm Hg, respectively. Compared with time-control groups, differences in BP while rats were eating the 8% NaCl diet were observed in M and F rats but not OVX rats. Reinstatement of an NaCl-deficient diet reversed the hypertension in M and F but not OVX rats (124±4, 124±2, and 145±5 mm Hg, respectively). The changes in dietary sodium caused similar changes in renal handling of sodium and water in all groups of rats; therefore, the effect on blood pressure was independent of renal excretory function. The inability to reverse the hypertension by decreasing sodium intake in OVX rats and the development of spontaneous hypertension in OVX females maintained on a low-sodium diet indicates that removal of the female sex hormones predisposes the animal to the development of hypertension that is sodium independent. We conclude that female sex hormones protect Dahl S rats against the development of sodium-dependent and -independent hypertension.
Renin-Angiotensin System Genetic Polymorphisms and Salt Sensitivity in Essential Hypertension
Authors: Giner Vicente , Poch Esteban , Bragulat Ernesto , Oriola Josep , González Daniel , Coca Antonio , Alejandro de la Sierra
Published: June 2012

Abstract
—We evaluated the association between salt-sensitive hypertension and 3 different genetic polymorphisms of the renin-angiotensin system. Fifty patients with essential hypertension were classified as salt sensitive or salt resistant, depending on the presence or absence of a significant increase (
P
<0.05) in 24-hour ambulatory mean blood pressure (BP) after high salt intake. The insertion/deletion
(I/D)
angiotensin-converting enzyme
(ACE)
gene, the
M235T
angiotensinogen
(AGT)
gene, and the
A1166C
angiotensin II type 1
(AT1)
receptor gene polymorphisms were determined with the use of standard polymerase chain reaction methods. Twenty-four (48%) patients with significantly increased (
P
<0.05) 24-hour mean BP with high salt intake (from 107.3±9.4 to 114.8±10.6 mm Hg) were classified as salt sensitive. In the remaining 26 patients (52%), high salt intake did not significantly modify 24-hour mean BP (from 107.6±10 to 107.8±9 mm Hg), and they were classified as having salt-resistant hypertension. We did not find any significant association between either
M235T AGT
or
A1166C AT1
receptor genotypes and the BP response to high salt intake. However, patients with essential hypertension homozygous for the insertion allele of the
ACE
gene
(II)
had a significantly higher BP increase with high salt intake (9.8±8.1 mm Hg for systolic BP and 5.2±4.2 mm Hg for diastolic BP) than that observed in patients homozygous for the deletion allele
(DD)
(1.2±5.9 mm Hg for systolic BP;
P
=0.0118 and −0.2±4.2 mm Hg for diastolic BP;
P
=0.0274). Heterozygous patients
(ID)
exhibited an intermediate response. The prevalence of salt-sensitive hypertension also was significantly higher (
P
=0.012) in
II
(67%) and
DI
patients (62%) compared with
DD
hypertensives (19%). We conclude that a significant association exists between the
I/D
polymorphism of the
ACE
gene and salt-sensitive hypertension. Patients with
II
and
DI
genotypes have significantly higher prevalence of salt sensitivity than
DD
hypertensives.
Age-Related Changes in Renal Cyclic Nucleotides and Eicosanoids in Response to Sodium Intake
Authors: Millatt Lesley J. , Siragy Helmy M.
Published: June 2012

Abstract
—The signaling molecules cGMP, cAMP, prostaglandin E
2
(PGE
2
), and prostaglandin F
2α
(PGF
2α
) play important roles in mediating the response of the kidney to changes in dietary sodium intake. We used a renal microdialysis technique in conscious rats to address the hypothesis that the renal ability to produce these mediators in response to dietary sodium intake is altered during maturation. Young (4-week-old) or adult (6-month-old) rats were studied after the consumption for 5 days of diets containing low (0.04% NaCl), normal (0.28% NaCl), or high (4.0% NaCl) levels of sodium. Plasma renin activity was significantly increased by low-sodium diet and significantly decreased by high-sodium diet, with no significant difference between the responses of the 2 age groups. Renal interstitial fluid (RIF) levels of cGMP, cAMP, PGE
2
, and PGF
2α
on normal-sodium diet were similar in the 2 age groups. Low-sodium diet caused a significant increase in RIF levels of all 4 mediators, with no significant differences between the responses of the 2 age groups. High-sodium diet also caused a significant increase in RIF levels of all 4 mediators. However, RIF production of cGMP, cAMP, and PGE
2
was significantly greater, and RIF PGF
2α
production was significantly lower, in young rats compared with adult rats. These data demonstrate that the kidneys of young and adult rats respond to dietary sodium restriction in a similar manner but that there are age-related changes in the renal response to sodium loading.
Progressive Resistance Exercise and Resting Blood Pressure
Authors: Kelley George A. , Kelley Kristi Sharpe
Published: June 2012

Abstract
—Hypertension is a major public health problem affecting an estimated 43 million civilian, noninstitutionalized adults in the United States (24% of this population). The purpose of this study was to use the meta-analytic approach to examine the effects of progressive resistance exercise on resting systolic and diastolic blood pressure in adult humans. Studies were retrieved via (1) computerized literature searches, (2) cross-referencing from original and review articles, and (3) review of the reference list by 2 experts on exercise and blood pressure. Inclusion criteria were as follows: (1) trials that included a randomized nonexercise control group; (2) progressive resistance exercise as the only intervention; (3) adult humans; (4) journal articles, dissertations, and masters theses published in the English-language literature; (5) studies published and indexed between January 1966 and December 1998; (6) resting systolic and/or diastolic blood pressure assessed; and (7) training studies lasting a minimum of 4 weeks. Across all designs and categories, fixed-effects modeling yielded decreases of ≈2% and 4% for resting systolic and diastolic blood pressure, respectively (mean±SD systolic, −3±3 mm Hg; 95% bootstrap CI, −4 to −1 mm Hg; mean±SD diastolic, −3±2 mm Hg; 95% bootstrap CI, −4 to −1 mm Hg). It was concluded that progressive resistance exercise is efficacious for reducing resting systolic and diastolic blood pressure in adults. However, a need exists for additional studies that limit enrollment to hypertensive subjects as well as analysis of data with an intention-to-treat approach before the effectiveness of progressive resistance exercise as a nonpharmacological intervention can be determined.
Association of Insulin Resistance With Salt Sensitivity and Nocturnal Fall of Blood Pressure
Authors: Suzuki Masaaki , Kimura Yuko , Tsushima Motoo , Harano Yutaka
Published: June 2012

Abstract
—Insulin resistance was demonstrated in hypertensive patients and in salt-sensitive subjects. It was recently reported that the salt-sensitive state was related to a reduced fall in blood pressure during the night in essential hypertension. In the present study, the relationship among insulin sensitivity, blood pressure response to salt intake, and nocturnal fall in blood pressure was examined in 20 subjects with nondiabetic and nonobese essential hypertension during a low-salt and a high-salt diet. The subjects were maintained on a low-salt diet (50 mmol/d) and a high-salt diet (255 mmol/d) for 1 week each, in random order. On the sixth day of each diet, blood pressure was measured every hour for 24 hours with an automatic device. Insulin sensitivity was measured according to the steady-state plasma glucose (SSPG) method on the seventh day of each diet. Salt-induced increase in blood pressure, which we defined as the change in 24-hour mean arterial pressure between the low and the high dietary salt intakes, was significantly correlated with SSPG (
r
=0.60,
P
<0.01) during the high-salt period. There was a significant negative correlation (
r
=−0.61,
P
<0.01) between SSPG and a nocturnal fall in mean arterial pressure during the high-salt period. Salt-induced increase in blood pressure was inversely correlated with a nocturnal fall in mean arterial pressure (
r
=−0.52,
P
<0.02) with the high-salt diet. These results suggest that insulin resistance, salt sensitivity, and failed nocturnal fall in blood pressure are associated with each other in subjects with essential hypertension.
Effects of Work Stress on Ambulatory Blood Pressure, Heart Rate, and Heart Rate Variability
Authors: Vrijkotte Tanja G. M. , van Doornen Lorenz J. P. , de Geus Eco J. C.
Published: June 2012

Abstract
—Work stress has repeatedly been associated with an increased risk for cardiovascular disease. This study tested whether this relationship could be explained by exaggerated cardiovascular reactivity to work or impaired recovery in leisure time. Vagal tone was assessed as a possible determinant of these work stress effects. Participants included 109 male white-collar workers (age, 47.2±5.3) who were monitored on 2 workdays and 1 nonworkday for ambulatory blood pressure, heart rate, and heart rate variability. Chronic work stress was defined according to Siegrist’s model as (1) high imbalance, a combination of high effort and low reward at work, or (2) high overcommitment, an exhaustive work-related coping style indexing the inability to unwind. All findings were adjusted for possible differences in posture and physical activity between the work stress groups. High imbalance was associated with a higher heart rate during work and directly after work, a higher systolic blood pressure during work and leisure time, and a lower 24-hour vagal tone on all 3 measurement days. Overcommitment was not associated with an unfavorable ambulatory profile. Logistic regression analysis revealed that heart rate [odds ratio 1-SD increase 1.95 (95% CI, 1.02 to 3.77)] and vagal tone [odds ratio 1-SD decrease 2.67 (95% CI, 1.24 to 5.75)] were independently associated with incident mild hypertension. Surprisingly, the values during sleep were more predictive for mild hypertension than the values during work. The results from the present study suggest that the detrimental effects of work stress are partly mediated by increased heart rate reactivity to a stressful workday, an increase in systolic blood pressure level, and lower vagal tone.
Angiotensin II and α
v
β
3
Integrin Expression in Rat Neonatal Cardiac Fibroblasts
Authors: Graf Kristof , Neuss Michael , Stawowy Philipp , Hsueh Willa A. , Fleck Eckart , Law Ronald E.
Published: June 2012

Abstract
—We recently demonstrated that α
v
β
3
integrins are involved in the mechanisms of angiotensin II (Ang II)–induced DNA synthesis and collagen gel contractions in rat cardiac fibroblasts (CFBs), cellular mechanisms that are relevant for cardiac remodeling. The aim of the present study was to elucidate the effect of Ang II and other growth factors on the regulation of the α
v
β
3
integrins in fibroblasts from neonatal rat hearts. The α
v
β
3
integrin receptor expression was significantly increased (
P
<0.05) at the mRNA level after treatment with Ang II, transforming growth factor-β
1
(TGF-β
1
), and platelet-derived growth factor (PDGF) for 8 and 16 hours. The surface expression of the α
v
and β
3
integrin subunits was elevated after 32 and 48 hours (
P
<0.05) as determined with flow cytometry. To investigate fibroblast motility, we performed chemotaxis experiments with transwell chambers. Ang II was chemotactic for CFBs, as tested with checkerboard experiments. The chemotactic effect was concentration dependent and was completely blocked by Ang II type 1 receptor blockers but not by Ang II type 2 receptor blocker PD 123319. Ang II– and PDGF-BB–mediated chemotaxis could be significantly inhibited by RGD peptides and the blocking antibodies against α
v
β
3
integrin (both
P
<0.01). Adhesion of CFBs to vitronectin was partially inhibited by an antibody to α
v
β
3
integrin but was mainly mediated by an α
v
β
5
integrin. Relevant in vivo expression of α
v
β
3
integrin by CFBs was confirmed with in situ hybridization with probes for α
v
and β
3
mRNA in rat hearts. The present study demonstrates that the expression of α
v
β
3
integrin is augmented by Ang II, PDGF, and TGF-β
1
in neonatal CFBs. Furthermore, this integrin is involved in the chemotaxis, motility, and adhesion of CFBs. The present findings support the current concept that integrins participate in the control of fibroblast behavior during cardiac remodeling mechanisms.
In Vitro and In Vivo Inhibition of the 2 Active Sites of ACE by Omapatrilat, a Vasopeptidase Inhibitor
Authors: Azizi Michel , Massien Christine , Michaud Annie , Corvol Pierre
Published: June 2012

Abstract
—The vasopeptidase inhibitor omapatrilat inhibits both neutral endopeptidase and angiotensin-converting enzyme (ACE). The in vitro and in vivo inhibitory potency of omapatrilat and the specific ACE inhibitor fosinopril toward the 2 active sites of ACE (called N- and C
-
domains) was investigated with the use of 3 substrates: angiotensin I, which is equally cleaved by the 2 ACE domains; hippuryl-histidyl-leucine, specific synthetic substrate of the C-domain in high- salt conditions; and a newly synthesized specific substrate of the N-domain designed by acetylating the lysine residue of AcSDKP. In vitro, omapatrilat was 5 times more potent than fosinoprilat in inhibiting angiotensin I hydrolysis. Omapatrilat inhibited similarly both N- and C-domain hydrolysis, whereas fosinoprilat was slightly more specific for the N-domain. The in vivo selective inhibitory potency of single oral doses of 10 mg omapatrilat and 20 mg fosinopril were investigated in a double-blind, placebo-controlled, cross-over study in 9 mildly sodium-depleted normotensive subjects. In accordance with the in vitro results, fosinopril appeared to be more specific for the N-domain than the C-domain in vivo, since plasma and urine AcSDKP concentrations were significantly higher than those observed with omapatrilat. This study shows that it is possible to assess separately in vitro and in vivo the selectivity of ACE or ACE/neutral endopeptidase inhibitors. A differential selectivity may explain some peculiar properties observed with some ACE inhibitors.
Angiotensin-(1-7) Reduces Norepinephrine Release Through a Nitric Oxide Mechanism in Rat Hypothalamus
Authors: Gironacci Mariela M. , Vatta Marcelo , Rodriguez-Fermepín Martín , Fernández Belisario E. , Peña Clara
Published: June 2012

Abstract
—Angiotensin (Ang)-(1-7) elicits a facilitatory presynaptic effect on peripheral noradrenergic neurotransmission, and because biological responses to the heptapeptide on occasion are tissue specific, the present investigation was undertaken to study its action on noradrenergic neurotransmission at the central level. In rat hypothalamus labeled with [
3
H]-norepinephrine, 100 to 600 nmol/L Ang-(1-7) diminished norepinephrine released by 25 mmol/L KCl. This effect was blocked by the selective angiotensin type 2 receptor antagonist PD 123319 (1 μmol/L) and by the specific Ang-(1-7) receptor antagonist [
d
-Ala
7
]Ang-(1-7) (1 μmol/L) but not by losartan (10 nmol/L to 1 μmol/L), a selective angiotensin type 1 receptor antagonist. The inhibitory effect on noradrenergic neurotransmission caused by Ang-(1-7) was prevented by 10 μmol/L
N
ω
-nitro-
l
-arginine methylester, an inhibitor of nitric oxide synthase activity, and was restored by 100 μmol/L
l
-arginine, precursor of nitric oxide synthesis. Methylene blue (10 μmol/L), an inhibitor of guanylate cyclase considered as the target of nitric oxide action, as well as Hoe 140 (10 μmol/L), a bradykinin B
2
-receptor antagonist, prevented the inhibitory effect of the heptapeptide on neuronal norepinephrine release, whereas no modification was observed in the presence of 0.1 to 10 μmol/L indomethacin, a cyclooxygenase inhibitor. Our results indicate that Ang-(1-7) has a tissue-specific neuromodulatory effect on noradrenergic neurotransmission, being inhibitory at the central nervous system by a nitric oxide–dependent mechanism that involves angiotensin type 2 receptors and local bradykinin production.
Modulatory Effects of Carbon Monoxide on Baroreflex Activation in Nucleus Tractus Solitarii of Rats
Authors: Lo Wan-Chen , Jan Chung-Ren , Chiang Hung-Ting , Tseng Ching-Jiunn
Published: June 2012

Abstract
—Recent studies suggest that carbon monoxide (CO), which is produced in significant quantities in many brain regions, may function as a neurotransmitter. Heme oxygenase catalyzes the metabolism of heme to CO and biliverdin; however, the physiological role of CO in central cardiovascular regulation was not well understood. In the present study, we evaluated the baroreflex response of CO in the nucleus tractus solitarii (NTS) of rats. Male Sprague-Dawley rats were anesthetized with urethane, and blood pressure and heart rate were monitored intra-arterially. Unilateral microinjection (60 nL) of hematin, a heme molecule cleaved by heme oxygenase to yield CO, into the NTS produced prominent dose-related depressor and bradycardic effects. Baroreflex responses were elicited by increasing doses of phenylephrine (10 to 30 μg/kg IV) before and after intra-NTS administration of zinc deuteroporphyrin 2,4-
bis
-glycol (ZnDPBG) (1 nmol), an inhibitor of heme oxygenase activity, or vehicle alone. The reflex bradycardia elicited by phenylephrine was significantly inhibited by pretreatment with ZnDPBG. Furthermore, the inhibitory effect of ZnDPBG on baroreflex activation was dose dependent. These results suggest CO formed by brain heme oxygenase plays a significant role in central cardiovascular regulation and that inhibition of heme oxygenase attenuated baroreflex activation.
Study of Arterial and Autonomic Effects of Cyclosporine in Humans
Authors: Lucini Daniela , Milani Richard V. , Ventura Hector O. , Mehra Mandeep R. , Messerli Franz , Pagani Massimo
Published: June 2012

Abstract
—Altered sympathetic activity and peripheral vascular function are suspected as a mechanism of the development of arterial hypertension in organ transplantation recipients treated with cyclosporine. We assessed whether cyclosporine might alter peripheral vascular properties or autonomic modulation of the sinus node and the vasculature during rest and standing. We examined 17 orthotopic heart transplantation recipients, 8 solid organ transplantation recipients, 17 patients with essential hypertension, and 42 normotensive control subjects. All except the normotensive control subjects were treated with a long-acting dihydropyridine calcium entry blocker; transplantation recipients also received cyclosporine-based immunosuppression. Radial artery compliance was reduced in patients with essential hypertension and in patients with heart and solid organ transplantation as compared with normotensive control subjects, with this reduction being more marked in heart transplantation recipients. At rest, R-R variance was lowest in heart transplantation recipients, denoting denervation. The spectral profile of both R-R and systolic blood pressure variability as well as the index of baroreflex gain was normal at rest in patients with solid organ transplantation. On standing, both transplantation groups demonstrated reduced responsiveness in markers of autonomic modulation. The decrease in arterial compliance in cyclosporine-induced hypertension seems to imply a degree of ventricular vascular uncoupling more apparent in heart transplantation recipients. These changes are associated with alterations in autonomic modulation that are evidenced by an orthostatic stimulus.
Resting Metabolic Rate and Substrate Use in Obesity Hypertension
Authors: Kunz Iris , Schorr Ulrike , Klaus Susanne , Sharma Arya M.
Published: June 2012

Abstract
—There is substantial evidence that obesity is a prime risk factor for the development of hypertension. Although hyperinsulinemia and an increased activity of the sympathetic nervous system have been implicated in the pathogenesis of “obesity hypertension,” their effects on energy metabolism have not been studied thus far. In the present study, we therefore examined resting metabolic rate (RMR) and basal substrate oxidation in subjects with obesity and obesity-related hypertension. A total of 166 subjects were characterized for RMR and basal substrate use through indirect calorimetry. Blood pressure was measured at rest and with 24-hour ambulatory monitoring. Blood samples were collected for the measurement of plasma catecholamines, leptin, and the insulin response to an oral glucose load. In our study population, 116 subjects were defined as hypertensive and 91 were defined as obese. Hypertensive patients under β-adrenergic blockade (n=42) had a significantly lower RMR than did patients without β-blockade (
P
<0.05) and were therefore excluded from further analyses. Univariate regression analysis revealed a significant relationship between RMR and body fat mass, as well as body fat–free mass, in both groups. Compared with obese normotensive control subjects (n=27), obese hypertensives (n=43) had a 9% higher RMR (
P
<0.05), higher plasma catecholamine (
P
<0.05) and leptin (
P
<0.05) levels, and an increased insulin response to oral glucose (
P
<0.01). Together, these findings are compatible with the idea that chronic neurogenic and metabolic adaptations related to obesity may play a role in the development of obesity hypertension in susceptible individuals.
Blood Flow Regulates the Development of Vascular Hypertrophy, Smooth Muscle Cell Proliferation, and Endothelial Cell Nitric Oxide Synthase in Hypertension
Authors: Ueno Hitoshi , Kanellakis Peter , Agrotis Alex , Bobik Alex
Published: June 2012

Abstract
—Blood flow participates in vascular remodeling during development and growth by regulating cell apoptosis and proliferation. However, its significance in the development of vascular hypertrophy and vascular remodeling in hypertensive patients is not known. We investigated how changing blood flow through the common carotid artery (CA) of young adult rats rendered hypertensive via aortic coarctation affects CA hypertrophy and/or remodeling responses to hypertension. Blood flow was reduced by ≈50% as a result of ligation of the external CA immediately after hypertension was induced, and the effects of that procedure were compared with those in similarly treated normotensive rats. Reducing blood flow in the hypertensive animals markedly augmented the development of CA hypertrophy over the ensuing 14 days by increasing the vessel wall cross-sectional area. In those animals, CA lumen size was unaltered by reducing blood flow, as was CA structure in normotensive animals. The greater hypertrophy in the hypertensive animals with reduced blood flow was associated with enhanced smooth muscle cell (SMC) proliferation 3 days after the hemodynamic changes were induced. There also appeared to be more extensive remodeling of the endothelium in the hypertensive animals with normal flow; this was indicated by the greater frequency of apoptotic endothelial cells at that time. This reduction in blood flow also attenuated endothelial cell nitric oxide synthase expression in hypertensive animals but not in normotensive animals. Severe reductions in blood flow (≈90%) were required to reduce endothelial cell nitric oxide synthase in the normotensive animals. Increasing CA nitric oxide levels by perivascular application of
S
-nitroso-
N
-acetylpenicillamine (SNAP) to the CAs of hypertensive animals with reduced endothelial cell nitric oxide synthase attenuated the greater SMC proliferation. Thus, reduced blood flow in hypertensive animals promotes hypertrophy by enhancing SMC proliferation via mechanisms that reduce the inhibitory effects of nitric oxide on SMC proliferation.
Mechanisms of Reduced Nitric Oxide/cGMP–Mediated Vasorelaxation in Transgenic Mice Overexpressing Endothelial Nitric Oxide Synthase
Authors: Yamashita Tomoya , Kawashima Seinosuke , Ohashi Yoshitaka , Ozaki Masanori , Rikitake Yoshiyuki , Inoue Nobutaka , Hirata Ken-ichi , Akita Hozuka , Yokoyama Mitsuhiro
Published: June 2012

Abstract
—NO, constitutively produced by endothelial NO synthase (eNOS), plays a key regulatory role in vascular wall homeostasis. We generated transgenic (Tg) mice overexpressing eNOS in the endothelium and reported the presence of reduced NO-elicited relaxation. The purpose of this study was to clarify mechanisms of the reduced response to NO-mediated vasodilators in eNOS-Tg mice. Thoracic aortas of Tg and control mice were surgically isolated for vasomotor studies. Relaxations to acetylcholine and sodium nitroprusside were significantly reduced in Tg vessels compared with control vessels. Relaxations to atrial natriuretic peptide and 8-bromo-cGMP were also significantly reduced in Tg vessels. Reduced relaxations to these agents were restored by chronic
N
G
-nitro-
l
-arginine methyl ester treatment. Basal cGMP levels of aortas were higher in Tg mice than in control mice, whereas soluble guanylate cyclase (sGC) activity in Tg vessels was ≈50% of the activity in control vessels. Moreover, cGMP-dependent protein kinase (PKG) protein levels and PKG enzyme activity were decreased in Tg vessels. These observations indicate that chronic overexpression of eNOS in the endothelium resulted in resistance to the NO/cGMP-mediated vasodilators and that at least 2 distinct mechanisms might be involved: one is reduced sGC activity, and the other is a decrease in PKG protein levels. We reported for the first time that increased NO release from the endothelium reduces sGC and PKG activity in mice. These data may provide a new insight into the mechanisms of nitrate tolerance and cross tolerance to nitrovasodilators.
Modulation of Blood Pressure and Obesity With the Dopamine D2 Receptor Gene
Taq
I Polymorphism
Authors: Thomas G. Neil , Tomlinson Brian , Critchley Julian A. J. H.
Published: June 2012

Abstract
—Pharmacological data suggest that obesity and blood pressure (BP) may be modulated through the dopamine D2 receptor (DD2R), which may represent an underlying mechanism that links these conditions. A
Taq
I polymorphism near the DD2R gene has been associated with indices of obesity in white populations. We compared anthropometric and fasting plasma biochemical parameters between 209 nondiabetic hypertensive and 174 gender-matched normotensive Chinese subjects. The hypertensives had increased dyslipidemia, increased fasting plasma glucose concentrations, and a greater degree of obesity. The A1 and A2 alleles of the DD2R gene
Taq
I polymorphism were identified with a polymerase chain reaction–based restriction fragment length polymorphism protocol. The A1 allele frequency was decreased in the hypertensives (42.0%) compared with the control subjects (52.0%,
P
=0.006), and genotype frequencies were different (
P
=0.05) between the 2 groups. In the combined population (n=383), systolic, diastolic, and mean arterial BPs were 6, 5, and 6 mm Hg lower, respectively, in subjects with the A1A1 genotype relative to the A2A2 genotype (all
P
<0.05), whereas skinfold thickness was increased at the iliac (
P
<0.001) and triceps (
P
<0.03) sites but not at the biceps or subscapular sites. Furthermore, this DD2R gene polymorphism was shown to be a significant independent predictor of diastolic BP and iliac and triceps skinfold thicknesses (all
P
<0.03). These contrasting associations of the DD2R
Taq
I polymorphism A1 allele with lower BP but increased markers of “gynoidal” or peripheral subcutaneous obesity (iliac and triceps skinfold thicknesses) in our Chinese population may provide some insight into the underlying relationship between BP and body fat distribution, but the exact nature of this link remains to be determined.
Deconvolution Analysis of Cardiac Natriuretic Peptides During Acute Volume Overload
Authors: Pemberton Chris J. , Johnson Michael L. , Yandle Tim G. , Espiner Eric A.
Published: June 2012

Abstract
—Cardiac natriuretic peptides, especially amino terminal pro–Brain Natriuretic Peptide (NT-proBNP), are emerging as powerful circulating markers of cardiac function. However, the in vivo secretion and elimination (t1/2) of these peptides during acute volume overload have not been studied. We present the first report of the secretion and elimination of cardiac natriuretic peptides, based on deconvolution analysis of endogenous ovine plasma levels measured by specific radioimmunoassay. Four normal, conscious sheep underwent rapid right ventricular pacing (225 bpm) for 1 hour to stimulate acute cardiac natriuretic peptide release. Plasma samples and right atrial pressure measurements were taken at regular intervals 30 minutes before, during, and 4 hours after pacing. Baseline right atrial pressure significantly increased (
P
=0.02) during the 1 hour of pacing in association with a prompt increase in plasma BNP (
P
=0.03), atrial natriuretic peptide (
P
=0.01), and NT-proBNP (
P
=0.02). Deconvolution analysis showed that the t1/2 of NT-proBNP (69.6±10.8 minutes) was 15-fold longer than BNP (4.8±1.0 minutes). Despite sustained increases in atrial pressure, cardiac secretion of natriuretic peptides (particularly atrial natriuretic peptide) fell during the pacing period, suggesting a finite source of peptide for secretion. Size-exclusion high-performance liquid chromatography revealed NT-proBNP to be a single immunoreactive peak, whereas BNP comprised at least 2 immunoreactive forms. These findings, especially the prompt secretion of BNP and the prolonged t1/2 of NT-proBNP, clarify the metabolism of BNP forms and help to explain the diagnostic value of NT-proBNP measurement as a sensitive marker of ventricular function.
Probucol Reduces Oxysterol Formation in Hypertensive Rabbits
Authors: Hodis Howard N. , Hashimoto Sam , Mack Wendy J. , Sevanian Alex
Published: June 2012

Abstract
—The role of lipid peroxidation during the pathogenesis of atherosclerosis has been described through numerous studies and has provided compelling evidence for free radical–mediated processes that link hypertension with atherosclerosis. However, there remains only limited information concerning peroxidative processes in hypertension and their modulation by antioxidants. In the present study, the formation of cholesterol oxidation products was used as a measure of in vivo lipid peroxidation after hypertension induced by coarctation of the aorta in New Zealand White rabbits. The rabbits were fed a standard chow diet devoid of cholesterol or cholesterol oxidation products such that the measured cholesterol oxides in the plasma and aortic tissues would most plausibly arise from endogenous oxidation of cholesterol. After 12 weeks of hypertension, all of the measured cholesterol oxides increased significantly over baseline levels in the surgically coarctated animals; however, this increase was significantly less in hypertensive probucol-treated animals. Similarly, the cholesterol oxide content of aortic tissue from the surgically coarctated animals was significantly greater than that found in normotensive control aortas, and probucol treatment significantly reduced the increase in cholesterol oxide content of aortic tissue relative to that of hypertensive animals not receiving the antioxidant. These findings in hypertensive animals suggest that cholesterol oxidation products measured in plasma and aortic tissue can be derived from endogenous free radical activity and that this activity is enhanced under specific pathological conditions.