bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal Injury and Salt-Sensitive Hypertension After Exposure to Catecholamines
Authors: Johnson Richard J. , Gordon Katherine L. , Suga Shinichi , Duijvestijn Adrian M. , Griffin Karen , Bidani Anil
Published: June 2012

Abstract
—We investigated whether chronic infusion of phenylephrine could induce structural and functional changes in the kidney of rats with the subsequent development of salt-sensitive hypertension. Rats were infused with phenylephrine (0.15 mmol/kg per day) by minipump, resulting in a moderate increase in systolic blood pressure (BP) (17 to 25 mm Hg) and a marked increase in BP variability as measured by an internal telemetry device. After 8 weeks, the phenylephrine infusion was stopped with the return of BP to normal, and a nephrectomy was performed for histological studies. Glomeruli were largely spared, but focal tubulointerstitial fibrosis was present, with the de novo expression of osteopontin by injured tubules, macrophage and “myofibroblast” accumulation, and focal increases in mRNA for transforming growth factor β by in situ hybridization. Peritubular capillaries at sites of injury had distorted morphology with shrinkage, rounding, and focal rarefaction, and endothelial cell proliferation was also identified. Rats were randomized to a high (8% NaCl or 1.36 mol/kg) or low (0.1% NaCl or 17 mmol/kg) salt diet. After 4 to 8 weeks, phenylephrine-treated rats on a high salt diet developed marked hypertension, which was in contrast with phenylephrine-treated rats placed on a low salt diet or vehicle-treated rats given a high salt diet. Hypertension after phenylephrine exposure correlated with the initial mean systolic BP (
r
2
=0.99) and the degree of BP lability (
r
2
=0.99) during the phenylephrine infusion, the amount of osteopontin expressed in the initial biopsy/nephrectomy (
r
2
=0.74), and the final glomerular filtration rate (
r
2
=0.58). These studies provide a mechanism by which a markedly elevated sympathetic nervous system can induce salt-dependent hypertension even when the hyperactive sympathetic state is no longer engaged.
Endothelial Nitric Oxide Gene Knockout Mice
Authors: Yang Xiao-Ping , Liu Yun-He , Shesely Edward G. , Bulagannawar Manohar , Liu Fang , Carretero Oscar A.
Published: June 2012

Abstract
—We tested the hypothesis that nitric oxide (NO) released by endothelial NO synthase (eNOS) is not only important in blood pressure regulation but also involved in cardiac function and remodeling and in the cardioprotective effect of angiotensin-converting enzyme inhibitors (ACEi). With the use of a 2D Doppler echocardiography system equipped with a 15-MHz linear transducer, we evaluated left ventricular (LV) morphology and function in conscious eNOS knockout mice (eNOS
−/−
; n=15) and their wild-type littermates (eNOS
+/+
; n=16). We also studied whether in eNOS
−/−
mice (1) myocardial ischemia/reperfusion injury is more severe and (2) the cardioprotective effect of ACEi is diminished or absent. In comparison with the wild type, eNOS
−/−
mice had significantly increased systolic blood pressure (128±3 versus 108±5 mm Hg;
P
<0.001) and decreased heart rate (531±22 versus 629±18 bpm;
P
<0.001) associated with increased LV posterior wall thickness (0.80±0.04 versus 0.64±0.02 mm;
P
<0.001) and LV mass (18.3±0.9 versus 13.1±0.5 mg/10 g body weight;
P
<0.01). Despite hypertension and LV hypertrophy, LV chamber dimension, shortening fraction and ejection fraction (indicators of LV contractility), and cardiac output did not differ between the 2 strains, which indicates that LV function in eNOS
−/−
mice is well compensated. We also found that in eNOS
+/+
mice, ACEi decreased the ratio of myocardial infarct size to area at risk from 62.7±3.9% to 36.3±1.6% (
P
<0.001), whereas in eNOS
−/−
mice this effect of ACEi was almost abolished: the ratio of myocardial infarct size to area at risk was 67.2±2.9% in the vehicle-treated group and 62.7±3.9% in mice treated with ACEi. Moreover, infarct size in vehicle-treated eNOS
−/−
mice was not significantly different from eNOS
+/+
mice given the same treatment. We concluded that (1) endothelium-derived NO plays an important role in the regulation of blood pressure homeostasis; (2) NO released under basal conditions has no significant impact on cardiac function; and (3) ACEi protect the heart against ischemia/reperfusion injury in mice and that this effect is mediated in part by endothelium-derived NO.
Rat Angiotensin-Converting Enzyme Promoter Regulation by β-Adrenergics and cAMP in Endothelium
Authors: Xavier-Neto José , Pereira Alexandre C. , Junqueira Maria de Lourdes , Carmona Renata , Krieger José E.
Published: June 2012

Abstract
—To shed light on mechanisms of angiotensin-converting enzyme (ACE) upregulation, we used a rabbit endothelial cell model to characterize intracellular pathways of β-adrenergic stimulation. In these cells, ACE activity is increased by isoproterenol (ISO). The stably transfected 1273-bp ACE promoter is stimulated by ISO in the presence of isobutyl methylxanthine. This effect is abolished by propranolol. Promoter stimulation is mimicked by cholera toxin, forskolin, and 8BrcAMP, but not by 8BrcGMP. Promoter stimulation by ISO and isobutyl methylxanthine is blocked by protein kinase A inhibitors, indicating that β-adrenergic stimulation of the ACE gene depends on phosphorylation of protein kinase A targets. Activation by cAMP, resistance to phorbol ester, and lack of synergism between cAMP and phorbol ester suggest that promoter regulation is due to cAMP responsive element rather than to activating protein-2 sequences. Okadaic acid potentiation of 8BrcAMP induction indicated that promoter activation by cAMP is regulated by phosphatases controlling activation of typical cAMP responsive element regulated genes. In summary, β-adrenergic activation of rat ACE promoter is specific; uses G
s
proteins, adenylyl cyclase, protein kinase A; and probably includes cAMP responsive element–like sequences.
Blood Pressure and the Progression of Carotid Atherosclerosis in Middle-Aged Men
Authors: Lakka Timo A. , Salonen Riitta , Kaplan George A. , Salonen Jukka T.
Published: June 2012

Abstract
—Elevated blood pressure has consistently been associated with increased prevalence of preclinical atherosclerosis and with increased risk of clinical atherosclerotic cardiovascular disease (CVD). However, there is no prospective evidence of the association between blood pressure and the progression of preclinical atherosclerosis. We therefore investigated the relationships of systolic blood pressure (SBP), diastolic blood pressure (DBP), and pulse pressure to the 4-year increase in the measures of early carotid atherosclerosis, the mean and maximal common carotid intima-media thickness (IMT), assessed by B-mode ultrasonography, in 1026 men aged 42 to 60 years. Men with the SBP of <120, 120 to 126, 127 to 134, 135 to 143, and >143 mm Hg (fifths) had an increase in the mean IMT of 0.074, 0.090, 0.110, 0.136, and 0.158 mm per 4 years (
P
<0.001 for difference between groups,
P
<0.001 for linear trend) and in the maximal IMT of 0.212, 0.221, 0.279, 0.286, and 0.315 mm per 4 years, (
P
<0.001,
P
<0.001), respectively, adjusting for other atherosclerotic risk factors, including DBP. Also, pulse pressure, when adjusted for other risk factors including mean arterial pressure, was directly associated with the IMT increase. DBP was not independently related to the IMT increase. This is the first documentation to show that mildly elevated SBP and pulse pressure accelerate the progression of preclinical atherosclerosis. This study provides further evidence for the finding that systolic hypertension is a more important risk factor for atherosclerosis and consequent CVD than diastolic hypertension. Therefore, more attention should be paid to the level of SBP in the evaluation of CVD risk and in the treatment of hypertension.
Bioactivity and Interactions of Adrenomedullin and Brain Natriuretic Peptide in Patients With Heart Failure
Authors: Lainchbury John G. , Nicholls M. Gary , Espiner Eric A. , Yandle Timothy G. , Lewis Lynley K. , Richards A. Mark
Published: June 2012

Abstract
—Plasma concentrations of the recently discovered hormones adrenomedullin (ADM), from vascular tissue, and brain natriuretic peptide (BNP), secreted by myocardium, are elevated in patients with heart failure. We tested the hypotheses that short-term increments in circulating levels of these hormones, within the pathophysiological range, would have biological effects and that the 2 hormone systems interact. Eight patients with heart failure (left ventricular ejection fractions <35%) received 4-hour infusions of BNP (3.0 pmol · kg
−1
· min
−1
) alone, ADM (2.7 pmol · kg
−1
· min
−1
and 5.4 pmol · kg
−1
· min
−1
for 2 hours each) alone, ADM and BNP combined, and placebo. BNP and ADM infusions raised plasma levels of the respective peptide within the pathophysiological range. Arterial blood pressure fell (
P
<0.05) with all peptide infusions, but cardiac output was unchanged. Heart rate increased with ADM and combined infusions (
P
<0.01). Sodium excretion rose (
P
<0.05), and creatinine clearance was sustained during both BNP and combined infusions. Urine volume increased in response to BNP alone (
P
=0.02). Despite a >2-fold increase in plasma renin with both ADM and combined infusions (
P
<0.05), plasma aldosterone remained lower than time-matched placebo levels. Plasma noradrenaline was increased by combined, BNP, and higher dose ADM infusions (
P
<0.05). ADM suppressed plasma cGMP (
P
<0.05) and inhibited the plasma cGMP response to BNP (
P
<0.05). The vascular hormones ADM and BNP, produced by myocardium, at plasma concentrations within the pathophysiological range have hemodynamic, renal, and hormonal effects and measurable interactions in patients with heart failure.
Early Onset Salt-Sensitive Hypertension in Bradykinin B
2
Receptor Null Mice
Authors: Cervenka Ludek , Harrison-Bernard Lisa M. , Dipp Susana , Primrose Ginny , Imig John D. , El-Dahr Samir S.
Published: June 2012

Abstract
—Kinins have been implicated in the hemodynamic adaptation to postnatal life. The present study examined the impact of bradykinin B
2
receptor (B
2
R) gene disruption on the postnatal changes in blood pressure (BP) and the susceptibility to early onset salt-sensitive hypertension in mice. B
2
R null (−/−) and wild-type (+/+) mice were fed normal (NS, 1% NaCl) or high (HS, 5% NaCl) salt diets during pregnancy. After birth, the pups remained with their mothers until they were weaned and were subsequently continued on the respective maternal salt intake until 4 months of age. The age-related changes at 3 and 4 months in tail-cuff BP and anesthetized mean arterial pressure at 4 months were not different in NS/B
2
R
−/−
and NS/B
2
R
+/+
mice. However, there was a mild increase in BP in NS/B
2
R
−/−
at 2 months versus NS/B
2
R
+/+
. In contrast, HS/B
2
R
−/−
mice manifested early onset and persistent elevations of tail-cuff BP (
P
<0.05) at 2, 3, and 4 months versus other groups. MAP was also higher in HS/B
2
R
−/−
than HS/B
2
R
+/+
, NS/B
2
R
−/−
, and NS/B
2
R
+/+
(91±3 versus 75±5, 74±2, and 70±2 mm Hg, respectively;
P
<0.05). Kidney renin and angiotensin type 1 receptor mRNA levels were not different. Additional studies showed that a delay in the initiation of HS until after birth was accompanied by later development of hypertension, although postnatal discontinuation of HS resulted in a gradual return of BP to normal values by 4 months of age. The results demonstrate that (1) kinins protect the developing animal from salt-sensitive hypertension, (2) lack of B
2
R from early development does not alter the maturation of BP under conditions of normal sodium intake, and (3) exposure to a HS diet during fetal life is not sufficient in itself to induce long-term hypertension in either wild-type or B
2
R null mice.
Impaired Isoproterenol-Induced Hyperpolarization in Isolated Mesenteric Arteries of Aged Rats
Authors: Fujii Koji , Onaka Uran , Goto Kenichi , Abe Isao , Fujishima Masatoshi
Published: June 2012

Abstract
—Stimulation of vascular β-adrenoceptors leads to membrane hyperpolarization, presumably via the β-adrenoceptor/G
s
protein/adenylate cyclase signaling cascade; the ionic mechanisms of this phenomenon remain unclear. β-Adrenoceptor–mediated vascular relaxation is impaired with aging; however, little is known concerning whether β-adrenoceptor–mediated hyperpolarization is altered with aging. We sought to determine the ionic mechanisms of isoproterenol-induced hyperpolarization in the rat mesenteric resistance artery, as well as the age-related changes in isoproterenol-induced hyperpolarization and their underlying mechanisms. Isoproterenol-induced hyperpolarization was inhibited by high-K
+
solution and glibenclamide (10
−6
mol/L), an inhibitor of ATP-sensitive K
+
channels (K
ATP
), but not by apamin, iberiotoxin, or charybdotoxin, inhibitors of Ca
2+
-activated K
+
channels. Isoproterenol-induced hyperpolarization was markedly less in aged rats (≥24 months) than in adults rats (12 to 20 weeks) (3×10
−6
mol/L; −3.1 versus −9.9 mV;
P
<0.001; n=8 to 9). Cholera toxin (10
−9
g/mL), an activator of G
s
, evoked hyperpolarization only in adult rats. Hyperpolarization to forskolin, a direct activator of adenylate cyclase, was also reduced to some extent in aged rats (10
−5
mol/L; −8.8 versus −13 mV;
P
<0.05; n=6), whereas hyperpolarization to levcromakalim, a K
ATP
opener, was comparable in both groups. These findings suggest that isoproterenol elicits hyperpolarization via an opening of K
ATP
in the rat resistance artery and that isoproterenol-induced hyperpolarization is attenuated in aged rats mainly because of a defective coupling of β-adrenoceptors to adenylate cyclase and partly because of a defect at the level of adenylate cyclase, but not because of an alteration of K
ATP
per se.
Apoptosis During Regression of Cardiac Hypertrophy in Spontaneously Hypertensive Rats
Authors: Tea Bun-Seng , Dam Than-Vinh , Moreau Pierre , Hamet Pavel , deBlois Denis
Published: June 2012

Abstract
—We previously reported that increased apoptosis participates in the regression of aortic hypertrophy in spontaneously hypertensive rats. To further document the potential role of apoptosis in cardiovascular therapy, we examined apoptosis during regression of hypertrophy in the heart of spontaneously hypertensive rats receiving the antihypertensive drug enalapril (30 mg · kg
−1
· d
−1
), losartan (30 mg · kg
−1
· d
−1
), nifedipine (35 mg · kg
−1
· d
−1
), hydralazine (40 mg · kg
−1
· d
−1
), propranolol (50 mg · kg
−1
· d
−1
), or hydrochlorothiazide (75 mg · kg
−1
· d
−1
) for 1 to 4 weeks, starting at 10 to 11 weeks of age. Systolic blood pressure and heart rate were measured by the tail-cuff method. Markers of apoptosis included oligonucleosomal DNA fragmentation in extracted cardiac DNA or in situ in ventricular cross sections labeled with terminal deoxynucleotidyl transferase. Cardiac DNA synthesis was evaluated by [
3
H]-thymidine incorporation in vivo. All drugs reduced cardiac workload, defined as the product of blood pressure and heart rate, by >20% at 4 weeks. However, only nifedipine, enalapril, losartan, and propranolol reduced cardiac mass (>19%) within 4 weeks. Regression of cardiac hypertrophy was accompanied by a 50% to 300% increase in DNA fragmentation and a >20% reduction in DNA synthesis, resulting in a >20% reduction in cardiac DNA content after 4 weeks. Apoptosis induction occurred early and was transient within 4 weeks of nifedipine, enalapril, or losartan administration. With all regression-inducing drugs, the increase in DNA fragmentation occurred mainly in the subepicardium. Thus, transient induction of apoptosis in the subepicardium appears to be a characteristic feature of the early response to drug-induced regression of cardiac hypertrophy in spontaneously hypertensive rats.
Autonomic Modulation and QT Interval Dispersion in Hypertensive Subjects With Anxiety
Authors: Piccirillo Gianfranco , Viola Emanuela , Nocco Marialuce , Santagada Elvira , Durante Michele , Bucca Carmela , Marigliano Vincenzo
Published: June 2012

Abstract
—Anxiety is associated with an increased risk of sudden death. QT dispersion is a marker of cardiac repolarization instability and is seen in conditions of high risk of sudden death. The purpose of this study was to evaluate autonomic nervous system control and QT dispersion in hypertensive subjects with anxiety symptoms. In a recent preliminary study, we observed that hypertensive individuals reporting high scores on a self-assessment anxiety scale had more marked left ventricular hypertrophy. In 105 hypertensive subjects divided into 3 groups according to severity of anxiety, we evaluated autonomic control by short-term power spectral analysis of RR and arterial pressure variability at rest (baseline) and during sympathetic stress (tilt test), left ventricular mass index, and heart rate–corrected QT (QTc) dispersion. At baseline, hypertensive subjects with higher anxiety symptom scores had significantly lower high-frequency RR values expressed in absolute terms (
P
<0.05) and in normalized units (
P
<0.05) than their counterparts without anxiety symptoms. Hypertensive subjects with anxiety also had a higher mean left ventricular mass index (
P
<0.001) and greater QTc dispersion (
P
<0.001). Both indexes and high frequency (
P
<0.05) correlated with severity of anxiety. These findings suggest that anxiety is associated with autonomic imbalance. This condition could favor an increase in left ventricular mass. Myocardial hypertrophy alone or combined with neuroautonomic imbalance may lead to QT dispersion.
Late Treatment With Ramipril Increases Survival in Old Spontaneously Hypertensive Rats
Authors: Linz Wolfgang , Wohlfart Paulus , Schoelkens Bernward A. , Becker Reinhard H. A. , Malinski Tadeusz , Wiemer Gabriele
Published: June 2012

Abstract
—Spontaneously hypertensive rats (SHR) begin to die from cardiovascular complications at ≈15 months of age. We tested whether chronic ACE-inhibitor treatment would extend the lifespan of such old animals. We also studied cardiac hypertrophy and function, endothelial function and expression, and activity of NO synthase (eNOS). One hundred 15-month-old SHR were randomized into 3 groups, control (n=10), placebo-treated (n=45), and ramipril-treated with an antihypertensive dose of 1 mg · kg
−1
· d
−1
in drinking water (n=45). Ex vivo experiments were performed after 15 months (control) and 21 months, when ≈80% of the placebo group had died. Late treatment with ramipril significantly extended lifespan of the animals from 21 to 30 months. Fully established cardiac hypertrophy, observed in placebo-treated animals and in controls, was significantly reversed by ramipril treatment. In isolated working hearts, a significantly improved function associated with increased cardiac eNOS expression was seen versus placebo and control hearts. Endothelial dysfunction in isolated aortic rings from control and placebo-treated SHR was significantly improved by ACE inhibition and associated with enhanced NO release. Late treatment of SHR with the ACE inhibitor ramipril extended lifespan from 21 to 30 months, which is comparable to the lifespan of untreated normotensive Wistar-Kyoto rats. This lifespan extension, probably due to blood pressure reduction, correlated with increased eNOS expression and activity followed by a regression of left ventricular hypertrophy and cardiac and vascular dysfunction.
Renin Activity and Blood Pressure in Response to Chronic Episodic Hypoxia
Authors: Fletcher Eugene C. , Bao Gang , Li Rena
Published: June 2012

Abstract
—Previous studies in several strains of rats have demonstrated that 35 days of recurrent episodic hypoxia (EH) (7 hours per day), with a fractional concentration of inspired oxygen that produces desaturation equivalent to the recurrent hypoxemia of sleep apnea, results in an 8 to 13 mm Hg persistent increase in diurnal systemic blood pressure (BP). Carotid chemoreceptors and the sympathetic nervous system have been shown to be necessary for development of this BP increase. Both renal artery denervation and adrenal demedullation block the BP response to chronic EH. The present study was undertaken to define further the role of the kidneys and the renin-angiotensin system in this BP increase. Separate groups of male Sprague-Dawley rats had either (1) bilateral renal artery denervation with EH, (2) sham surgery with EH, (3) sham surgery with sham EH (compressed air), (4) EH with losartan, (5) unhandled with losartan, or (6) unhandled. The experimental period lasted 35 days. Both renal-artery denervated and losartan-treated animals showed no BP change or a lowering of BP in response to EH, whereas the sham-operated EH animals showed a progressive, sustained increase in resting room air BP. BP remained at basal levels or fell in unhandled and unhandled losartan-treated animals. Plasma renin activity was elevated 4-fold versus basal levels in EH animals with renal nerves intact but remained at baseline levels in denervated animals. At the end of the experiment, renal tissue catecholamines confirmed renal denervation in those animals. In conclusion, EH causes a progressive increase in BP, mediated in part through renal sympathetic nerve activity that acts to increase renin-angiotensin system activity through angiotensin II type 1 receptors.
Genotype-Phenotype Relationships for the Renin-Angiotensin-Aldosterone System in a Normal Population
Authors: Paillard Françoise , Chansel Dominique , Brand Eva , Benetos Athanase , Thomas Frédérique , Czekalski Stanislaw , Ardaillou Raymond , Soubrier Florent
Published: June 2012

Abstract
—The renin-angiotensin-aldosterone system plays an important role in blood pressure regulation by influencing salt-water homeostasis and vascular tone. The purpose of the present study was to search for associations of single nucleotide polymorphisms on 3 major candidate genes of this system with the plasma concentrations of the corresponding renin-angiotensin-aldosterone system components considered as quantitative phenotypes. Genotyping was performed in 114 normotensive subjects for different variants of the angiotensinogen (
AGT
) gene (C-532T, G-6A, M235T), the angiotensin I–converting enzyme (
ACE
) gene [4656(CT)
2/3
], the aldosterone synthase (CYP11B2), and the type 1 angiotensin II receptor (
AT1R
) gene (A1166C) by hybridization with allele-specific oligonucleotides (ASO) or enzymatic digestion of polymerase chain reaction products. Plasma levels of AGT, ACE, angiotensin II (Ang II), aldosterone, and immunoreactive active renin were measured according to standard techniques. Platelet binding sites for Ang II were analyzed by the binding of radioiodinated Ang II to purified platelets. B
max
and
K
D
values of the Ang II binding sites on platelets of each individual were calculated to examine a possible relationship between these parameters and the
AT1R
genotype. A highly significant association of the
ACE
4656(CT)
2/3
variant with plasma ACE levels was observed (
P
<0.0001). ANOVA showed a significant effect of the
AGT
C-532T polymorphism on AGT plasma levels (
P
=0.017), but no significant effect was detectable with the other
AGT
polymorphisms tested, such as the G-6A or the M235T. A significant effect association was also found between the C-344T polymorphism of the CYP11B2 gene and plasma aldosterone levels, with the T allele associated with higher levels (
P
=0.02). No genotype effect of the
AT1R
A1166C polymorphism was detected either on the B
max
or the
K
D
value of the Ang II receptors on platelets.
Sympathetic Nerve Traffic Responses to Surgical Removal of Pheochromocytoma
Authors: Grassi Guido , Seravalle Gino , Turri Carlo , Mancia Giuseppe
Published: June 2012

Abstract
—Pheochromocytoma is usually characterized by a marked increase in peripheral catecholamine secretion. Whether this is accompanied by an alteration in central sympathetic drive has not been clarified. In 6 patients with adrenal pheochromocytoma (mean±SEM age, 49.3±7.2 years), we measured systolic and diastolic blood pressure (photoplethysmographic device), heart rate (ECG), venous plasma catecholamines (high-performance liquid chromatography), and postganglionic muscle sympathetic nerve activity (microneurography) before and 78.3±13 days after surgical removal of the tumor. In each experimental session, measurements were performed during (1) a 60-minute resting period to compare several values of sympathetic nerve traffic at similar blood pressures before and after surgery and (2) voluntary end-expiratory apnea, ie, a maneuver inducing sympathetic activation. Tumor removal significantly (
P
<0.05 at least) reduced plasma catecholamines, blood pressure, and heart rate. In contrast, muscle sympathetic nerve activity was significantly (
P
<0.01) increased, both when quantified as bursts per minute (from 28.1±5.7 to 54.3±7.5) and as bursts per 100 heartbeats (from 33.4±5.6 to 65.1±6.5). This was also the case when data were evaluated in periods of 2 experimental sessions characterized by similar diastolic blood pressure values. The apnea maneuver induced sympathetic nerve traffic responses that were significantly (
P
<0.05) greater after surgery than before surgery. These data provide the first direct evidence that in pheochromocytoma central sympathetic outflow is markedly reduced and that this reduction cannot be ascribed to a reflex inhibitory response to elevated blood pressures. It is likely that this sympathoinhibition is rather due to a central depression of sympathetic outflow induced by high circulating catecholamines.
Inhibition of the Renin-Angiotensin System Upregulates Cyclooxygenase-2 Expression in the Macula Densa
Authors: Wolf Konrad , Castrop Hayo , Hartner Andrea , Goppelt-Strübe Margarete , Hilgers Karl F. , Kurtz Armin
Published: June 2012

Abstract
—The expression of cyclooxygenase 2 (COX-2) in the late thick ascending limb, including the macula densa, is found to be upregulated in an activated renin-angiotensin system. How this upregulation is managed is not yet known. We therefore considered the possibility that the stimulation of COX-2 expression is triggered by the activation of the renin-angiotensin system. For this purpose, we treated male Sprague-Dawley rats with the angiotensin I–converting enzyme inhibitor ramipril (10 mg/kg per day), the angiotensin II type 1 (AT
1
) receptor blocker losartan (30 mg/kg per day), and the angiotensin II type 2 (AT
2
) receptor blocker PD123319 (6 mg/kg per day) for 4 days. We determined the expression of COX-2 mRNA and protein in the renal cortex. We found that ramipril and the AT
1
receptor blocker losartan increased COX-2 mRNA and COX-2 immunoreactivity in the macula densa ≈4-fold, whereas the AT
2
blocker PD123319 showed no effect. A low-salt diet (0.02% wt/wt) stimulated COX-2 expression in the kidney cortex <2-fold. The combination of a low-salt diet with ramipril led to a further increase of COX-2 mRNA and COX-2 immunoreactivity compared with low salt or ramipril alone. These data indicate that endogenous angiotensin II apparently inhibits COX-2 expression in the macula densa via AT
1
receptors and can therefore not account for the stimulation of COX-2 expression associated with an activated renin-angiotensin system. Because macula densa–derived prostaglandins are considered stimulators of renin secretion and renin synthesis, inhibition of macula densa COX-2 by angiotensin II could form a novel indirect negative feedback control of the renin system.
Endothelial Function in Hypertension
Authors: McIntyre Martin , Bohr David F. , Dominiczak Anna F.
Published: June 2012

Abstract
—Much attention has been focused on the role of nitric oxide in hypertension and cardiovascular disease. More recently, the role of superoxide anion and its interaction with nitric oxide has been investigated in this context. This review will concentrate on the role of superoxide in human and experimental hypertension, paying particular attention to the potential sources of superoxide within the vasculature and discussing some of the molecular mechanisms surrounding its production and dismutation. We discuss what is known about the human superoxide dismutase enzymes. We conclude that the balance between nitric oxide and superoxide is more important than the absolute levels of either alone.
Pathogenic Role of Oxidative Stress in Vascular Angiotensin-Converting Enzyme Activation in Long-Term Blockade of Nitric Oxide Synthesis in Rats
Authors: Usui Makoto , Egashira Kensuke , Kitamoto Shiro , Koyanagi Masamichi , Katoh Makoto , Kataoka Chu , Shimokawa Hiroaki , Takeshita Akira
Published: June 2012

Abstract
—Inhibition of nitric oxide (NO) synthesis with
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) activates vascular angiotensin-converting enzyme (ACE) and causes oxidative stress. We investigated the role of oxidative stress in the pathogenesis of ACE activation in rats. Studies involved aortas of rats receiving no treatment, L-NAME, L-NAME plus
l
-arginine, or L-NAME plus an antioxidant drug (
N
-acetylcysteine, allopurinol, or ebselen) for 7 days. L-NAME significantly increased oxidative stress (O
2
−
) and ACE activity. The increased O
2
−
production was normalized by removal of endothelium. Immunohistochemistry showed the increased ACE activity in the endothelial layer. Treatment with antioxidant drugs did not affect the L-NAME–induced increase in systolic arterial pressure but did prevent increases in vascular O
2
−
production and ACE activity. These results implicate oxidative stress in the pathogenesis of vascular ACE activation in rats with long-term inhibition of NO synthesis. The observed effects of antioxidant drugs on ACE activation do not appear to involve the hypertension induced by L-NAME.
N
-Acetyl-
l
-Cysteine Enhances Interleukin-1β–Induced Nitric Oxide Synthase Expression
Authors: Jiang Bingbing , Haverty Michael , Brecher Peter
Published: June 2012

Abstract
—The effect of
N
-acetyl-
l
-cysteine on interleukin-1β–induced nitric oxide synthase expression was studied in rat vascular smooth muscle cells to determine if the reduction/oxidation state would modulate cytokine-induced changes. Interleukin-1β induced the production of nitrite, a stable metabolite of nitric oxide in a time- and dose-dependent manner. Cytokine-induced nitrite production was enhanced by the addition of
N
-acetyl-
l
-cysteine in a dose-dependent manner, with a >50% increase produced by the addition of 1 mmol/L
N-
acetyl-
l
-cysteine. There was no influence on nitrite production when the cells were treated with
N
-acetyl-
l
-cysteine alone. Northern and Western blot analyses revealed that the upregulation of interleukin-1β–induced nitric oxide production by
N
-acetyl-
l
-cysteine resulted from an enhanced expression of inducible nitric oxide synthase. Interferon-γ or tumor necrosis factor-α when used alone had no influence on nitrite production in the absence or presence of
N-
acetyl-
l
-cysteine. Nitrite accumulation was higher by the cells treated with interleukin-1β combined with either interferon-γ or tumor necrosis factor-α compared with those treated with interleukin-1β alone.
N
-Acetyl-
l
-cysteine upregulated nitrite production and inducible nitric oxide synthase expression induced by combination treatment with interleukin-1β and either interferon-γ or tumor necrosis factor-α. However,
N
-acetyl-
l
-cysteine had no significant influence in cytokine-induced activation of nuclear factor-κB or signal transducer and activator of transciption-1, as assessed by electrophoretic mobility shift assays. These results demonstrate that
N-
acetyl-
l
-cysteine possibly acted as a thiol-containing reducing agent and facilitated the expression of inducible nitric oxide synthase in rat vascular smooth muscle cells by cytokines through a mechanism that is independent of nuclear factor-κB or signal transducer and activator of transciption-1.
Sex Steroids, Insulin, and Arterial Stiffness in Women and Men
Authors: Giltay Erik J. , Lambert Jan , Gooren Louis J. G. , Elbers Jolanda M. H. , Steyn Mieke , Stehouwer Coen D. A.
Published: June 2012

Abstract
—Arterial stiffness may be influenced by sex steroids and insulin; the association with fasting insulin level may be stronger in women than in men. Therefore, we analyzed the effects of sex steroid administration on (1) arterial stiffness and (2) the relationship between fasting insulin level and arterial stiffness. Twelve male-to-female transsexuals were treated with ethinyl estradiol and cyproterone acetate, and 18 female-to-male transsexuals were treated with testosterone esters, with assessments made at baseline and after 4 and 12 months. Changes in distensibility and compliance coefficients (DC and CC, respectively) of the common carotid artery, femoral artery (FA), and brachial artery (BA) were analyzed in relation to changes in fasting plasma levels of glucose, insulin, HDL-cholesterol, and triglycerides. After 4 months of estrogens and antiandrogens in men, significant reductions in the CC and DC of the FA (
P
=0.006 and
P
=0.04, respectively) and BA (
P
=0.04 and
P
=0.04, respectively) were observed. In women, testosterone, on average, did not affect DC or CC, but the changes in fasting insulin level were strongly negatively associated with changes in the CC and DC, especially in the FA and BA. These associations were significantly less strong in genetic men and were independent of age, mean arterial pressure, and glucose and lipid levels. This experimental study shows (1) that short-term administration of estrogens and antiandrogens increases FA and BA stiffness in men and (2) that the fasting insulin level is a stronger determinant of arterial stiffness in women than in men.
Heart Rate-Dependent Stiffening of Large Arteries in Intact and Sympathectomized Rats
Authors: Mircoli Luca , Mangoni Arduino A. , Giannattasio Cristina , Mancia Giuseppe , Ferrari Alberto U.
Published: June 2012

Abstract
—In the anesthetized rat, acute increases in heart rate are accompanied by a reduction in arterial distensibility, which is a significant phenomenon in elastic-type vessels such as the common carotid but much less evident in muscle-type vessels such as the femoral artery. Because the sympathetic nervous system importantly reduces arterial distensibility, the present study aimed to determine whether sympathetic influences (1) are involved in the heart rate–dependent changes in arterial distensibility and (2) exert differential effects on elastic-type versus muscle-type arteries. To address this issue, 9 sympathectomized (6-hydroxydopamine) and 10 vehicle-treated, 12-week-old, pentobarbitone-anesthetized Wistar-Kyoto rats were subjected to atrial pacing via a transjugular catheter at 5 different randomly sequenced rates (280, 310, 340, 370, and 400 bpm). After each step, spontaneous sinus rhythm was allowed to return to normal. Common carotid and femoral artery diameters were measured by an echo Doppler device (NIUS 01), and blood pressure was measured via catheter inserted into the contralateral vessel. Arterial distensibility was calculated over the systolic-diastolic pressure range according to the Langewouters formula. In the common carotid artery, progressive increases in heart rate determined progressive and marked reductions of distensibility (range, 15% to 43%) in sympathectomized and intact rats. In the femoral artery, the stiffening effect of tachycardia was present in sympathectomized rats (range, 21% to 42%), at variance with the inconsistent changes observed in intact rats. In conclusion, our experiments support the notions (1) that in predominantly elastic-type arteries, the stiffening effect of tachycardia is exerted independently of sympathetic modulation of the vessel wall properties and (2) that in predominantly muscle-type arteries, removal of sympathetic influences unmasks the stiffening effect of tachycardia.
In Vivo Study of AT
1
and AT
2
Angiotensin Receptors in Apoptosis in Rat Blood Vessels
Authors: Diep Quy N. , Li Jin-Sheng , Schiffrin Ernesto L.
Published: June 2012

Abstract
—In vitro experiments suggest that angiotensin II (Ang II) may cause growth via angiotensin type 1 (AT
1
) receptors and apoptosis via angiotensin type 2 (AT
2
) receptors. To answer the question of whether AT
1
or AT
2
receptor activation could induce apoptosis in the vasculature in vivo, Wistar rats were infused for 7 days with Ang II (120 ng · kg
−1
· min
−1
subcutaneously) and treated with the AT
2
receptor antagonist PD 123319 (30 mg · kg
−1
· d
−1
subcutaneously) or the AT
1
receptor antagonist losartan (10 mg · kg
−1
· d
−1
orally). Apoptosis in thoracic aorta was quantified by radiolabeled DNA laddering and by terminal deoxynucleotide transferase–mediated dUTP nick end-labeling. The expression of p53, bax, bcl-2, and caspase-3, which play critical roles in apoptotic signaling, was examined by Western blot analysis. The mRNA expression of AT
1
and AT
2
receptors was determined by reverse transcription–polymerase chain reaction. The increase in systolic blood pressure and aortic growth induced by Ang II infusion was completely prevented by losartan alone or losartan given with PD 123319, whereas PD 123319 resulted in a greater increase in systolic blood pressure and aortic growth than Ang II alone. Radiolabeled DNA laddering showed that Ang II infusion±losartan or PD 123319 significantly increased apoptosis (147±8%, 178±20%, and 238±41%, respectively,
P
<0.05 compared with control). Expression of bax and active forms of caspase-3 was increased in the Ang II+PD 123319 group, whereas the expression of p53 and bcl-2 was not significantly different in all groups. The expression of AT
1
and AT
2
receptor mRNA was downregulated by losartan and PD 123319, respectively. Thus, when AT
1
or AT
2
receptors are stimulated in vivo, apoptosis is enhanced in the media of blood vessels. In the case of AT
1
receptor stimulation, this may occur secondary to vascular growth and modulate the latter. Both bax and caspase-3 participate in the pathways of apoptosis triggered by in vivo AT
1
receptor stimulation.
Genetic Variants in the Epithelial Sodium Channel in Relation to Aldosterone and Potassium Excretion and Risk for Hypertension
Authors: Ambrosius Walter T. , Bloem Laura J. , Zhou Lifen , Rebhun John F. , Snyder Peter M. , Wagner Mary Anne , Guo Chunlu , Pratt J. Howard
Published: June 2012

Abstract
—Renin and aldosterone secretion is often lower in blacks than in whites, characteristics that resemble a milder form of Liddle syndrome in which a mutation in the amiloride-sensitive epithelial sodium channel (ENaC) of the kidney results in enhanced resorption of sodium. In the present study, we looked for evidence that the intrinsic level of ENaC activity is indeed higher in blacks than in whites. In overnight urine samples collected from young people (249 white and 181 black subjects, mean age 13.4 years), the urinary aldosterone/potassium ratio, which is typically very low in Liddle syndrome, was lower in blacks than in whites: 0.421±0.024 (mean±SE) versus 0.582±0.016 nmol/mmol (
P
<0.0001). In addition, all but 1 of 5 molecular variants in ENaC were much more common in blacks than in whites. G442V in the β-subunit, present in 16% of the blacks and in only 1 white, was associated with parameters reflective of a greater Na retention and potentially a higher ENaC activity: a lower plasma aldosterone concentration (
P
=0.070), a lower urinary aldosterone excretion rate (
P
=0.052), a higher potassium excretion rate (
P
=0.048), and a lower urinary aldosterone/potassium ratio (
P
=0.027). In a second cohort consisting of 126 black and 161 white normotensive subjects and 232 black and 188 white hypertensive subjects, βG442V did not show a significant association with hypertension (
P
=0.089). On the other hand, a variant that was twice as common in whites, αT663A, was associated with being normotensive both in blacks (
P
=0.018) and in whites (
P
=0.034). Expression of either βG442V or αT663A in
Xenopus
oocytes did not result in a change in basal Na current, consistent with the variants being in linkage disequilibrium with alleles at active loci. In conclusion, several lines of evidence are presented to suggest that ENaC activity is higher in blacks than in whites, which could contribute to racial differences in Na retention and the risk for hypertension.
Risk Mechanisms in Hypertensive Heart Disease
Authors: Frohlich Edward D.
Published: June 2012

Abstract
—In this report, some of the underlying pathophysiological alterations associated with the independent risk from hypertensive heart disease and left ventricular hypertrophy are discussed. Emphasized are the classically described coronary hemodynamic alterations of decreased coronary blood flow and flow reserve with increased coronary vascular resistance and minimal coronary resistance; more recent concepts of endothelial dysfunction are emphasized. Additionally, increased collagen deposition within the ventricular walls and perivascularly participates importantly. These changes are exacerbated by the aging process and perhaps by increased dietary salt intake. Consequences of these functional and structural changes include further endothelial dysfunction, impairment of coronary hemodynamics, and ventricular contractile function (diastolic as well as systolic). The clinical consequences of these alterations are angina pectoris (with or without atherosclerosis), myocardial infarction, cardiac failure, lethal dysrhythmias, and sudden cardiac death. Thus, not all that is clinically recognized as “left ventricular hypertrophy” is true myocytic hypertrophy with structural remodeling; other important comorbid changes occur that directly affect risk, including ventricular fibrosis, impaired coronary hemodynamics, and endothelial dysfunction.
Cardiac Microvasculature in DOCA-Salt Hypertensive Rats
Authors: Larouche Isabelle , Schiffrin Ernesto L.
Published: June 2012

Abstract
—The cardiac abnormalities associated with hypertension include left ventricular hypertrophy and vascular changes. The latter may affect the cardiac microvasculature and predispose to myocardial ischemia. To test the hypothesis that endothelin-1 contributes to changes in the microcirculation of the heart, we studied cardiac microvessels of the deoxycorticosterone acetate–salt (DOCA-salt) model of hypertension in the rat, in which the endothelin system is activated, and the effect of the endothelin-A (ET
A
) subtype–selective endothelin receptor antagonist A-127722. A-127722 (30 mg · kg
−1
· d
−1
) was administered for 4 weeks. Arterioles (≤20 μm in lumen diameter) were identified in the myocardium by use of immunolabeling with an anti–smooth muscle α-actin antibody, and capillaries with an anti-laminin antibody with nuclear counterstaining by nuclear fast red. Systolic blood pressure was 103±1.6 mm Hg in unilaterally nephrectomized rats (UniNx), 202±3.2 mm Hg in DOCA-salt (
P
<0.01 versus UniNx), and 182±3.1 mm Hg in ET
A
antagonist–treated DOCA-salt (
P
<0.01 versus DOCA-salt or UniNx). Arteriolar and capillary densities were altered significantly in the subendocardial myocardium but not in the subepicardial myocardium of the left ventricle. Arteriolar density per square millimeter was 18.1±1.48 in UniNx, 31.9±3.26 in DOCA-salt (
P
<0.01 versus UniNx), and 24.2±1.36 in ET
A
antagonist–treated DOCA-salt (
P
<0.05 versus DOCA-salt or UniNx). Capillary density per square millimeter was 2395±148 in UniNx, 1576±107 in DOCA-salt (
P
<0.01 versus UniNx), and 1982±31 in ET
A
antagonist–treated DOCA-salt (
P
<0.01 versus DOCA-salt or UniNx). In conclusion, in DOCA-salt hypertensive rats, subendocardial arteriolar growth and capillary rarefaction were observed in the left ventricular myocardium, and both were partially corrected by ET
A
receptor antagonism. This suggests a role for endothelin-1 in cardiac arteriolar growth and capillary rarefaction, which may have pathophysiological implications by contributing to myocardial ischemia in hypertension.
Long-Term Nitric Oxide Synthase Inhibition in Rat Pregnancy Reduces Renal Kallikrein
Authors: Salas Sofía P. , Vuletin José F. , Giacaman Andrea , Rosso Pedro , Vío Carlos P.
Published: June 2012

Abstract
—This study was performed to test the hypothesis that long-term nitric oxide synthase (NOS) inhibition during pregnancy may alter the predominance of the vasodilator kallikrein system. Sprague-Dawley rats were treated with the competitive inhibitor of NOS
N
ω
-nitro-
l
-arginine (L-NNA, 50 mg · kg
−1
· d
−1
, dissolved in water) from days 7 to 21 of pregnancy. Rats were studied before treatment (day 5), at days 11, 17, and 21 of pregnancy (during treatment), and at postpartum days 7 and 21 (after the drug was withdrawn at delivery). Each group (n=5 to 8) had its corresponding control group (C) that received only vehicle. Additional rats were treated with
N
G
-nitro-
l
-arginine methyl ester (L-NAME) alone or with an excess of
l
-arginine. At each study day, we measured blood pressure, collected urine overnight, obtained blood samples, and processed the kidneys for conventional histology and immunohistochemistry. In L-NNA rats, fetal and placental weights were reduced at days 17 and 21. Blood pressure was higher at days 17 and 21, returning to normal after L-NNA was removed. Urinary kallikrein activity was lower at days 11 and 17 (L-NNA=1147±213 and C=2317±146 nmol/16 h,
P
<0.001). Plasma renin activity was reduced at day 21 (L-NNA=9.6±2.1 and C=25.9±5 ng · mL
−1
· h
−1
,
P
<0.05) and remained lower at postpartum day 7. L-NNA rats exhibited glomerular lesions and tubular atrophy, particularly of connecting tubules that displayed reduced kallikrein staining. Tubulointerstitial infiltrating macrophages (ED1+) were also observed. Renal lesions were present as early as day 11 and persisted at day 7 postpartum. L-NAME rats exhibited similar alterations that were attenuated with an excess of
l
-arginine. We postulate that the reduction in renal kallikrein may contribute to the hemodynamic alterations described in this model.
Identification of Diadenosine Hexaphosphate in Human Erythrocytes
Authors: Luo Jiankai , Jankowski Joachim , Tepel Martin , von der Giet Markus , Zidek Walter , Schlüter Hartmut
Published: June 2012

Abstract
—Diadenosine polyphosphates have been identified as important regulators of vascular tone and blood pressure. In reference to the background of the well-known vasoconstriction induced by hemolysate, we questioned whether this action may be due in part to the presence of diadenosine polyphosphates in human erythrocytes. Therefore, erythrocytes were separated from other blood cells and deproteinated. To concentrate and purify nucleotides, the extract was chromatographed by anion exchange, affinity, and reversed-phase columns. In one of the purified fractions, diadenosine hexaphosphate (diadenosine 5′, 5′-P
1
, P
6
hexaphosphate [AP
6
A]) was identified by matrix-assisted laser desorption/ionization mass spectrometry, ultraviolet spectroscopy, and enzymatic analysis. Hemolysate of erythrocytes injected into the isolated perfused rat kidney induced a dose-dependent vasoconstriction, which was partially inhibited by P
2
-purinoceptor antagonist. The data document the existence of AP
6
A in erythrocytes. AP
6
A may be involved in the pathogenesis of vasospasm induced by free hemoglobin.