bluuebunny/crossref_metadata_2025 huggingface dataset:
Advanced Hypertensive Heart Disease in Spontaneously Hypertensive Rats
Authors: Brilla Christian G. , Matsubara Luiz , Weber Karl T.
Published: June 2012

Left ventricular hypertrophy (LVH) in spontaneously hypertensive rats (SHR) is accompanied by a structural remodeling of the myocardium that includes myocyte hypertrophy and interstitial and perivascular fibrosis of intramyocardial coronary arteries. The structural abnormalities related to fibrous tissue accumulation lead to increased myocardial diastolic stiffness and ultimately impaired systolic function of the left ventricle. It has been shown in 14-week-old SHR with early hypertensive heart disease that myocardial fibrosis could be reversed and myocardial diastolic stiffness normalized by 12-week treatment with the angiotensin-converting enzyme inhibitor lisinopril. Whether such functional defects of the myocardium, based on adverse structural changes, are also reversible in advanced hypertensive heart disease has been questioned. Therefore, we treated 78-week-old male SHR that had chronic hypertension and advanced LVH with severe myocardial fibrosis and age- and sex-matched normotensive Wistar-Kyoto rats (WKY) with 20 mg/kg per day oral lisinopril for 8 months. Compared with untreated SHR or WKY, we found the following: (1) Systolic arterial pressure was normalized (
P
<.025) and LVH completely reversed (
P
<.025) in SHR, with no significant reduction in systolic arterial pressure or left ventricular mass in WKY; (2) morphometrically determined myocardial fibrosis in SHR was significantly reversed (
P
<.025) and associated with improved diastolic stiffness (
P
<.05), which was measured in the isolated heart by calculation of the stiffness constant of the myocardium; no significant changes occurred in WKY; (3) reversal of myocardial fibrosis was accompanied by an increase (
P
<.025) in myocardial matrix metalloproteinase 1 activity determined by degradation of [
14
C]collagen with myocardial tissue extracts after trypsin activation of myocardial promatrix metalloproteinase 1; matrix metalloproteinase 1 activity remained unchanged in WKY treated with lisinopril; and (4) systolic dysfunction, measured by a significantly (
P
<.025) diminished slope of the systolic stress-strain relation under isovolumic conditions of the left ventricle, was found in 110-week-old SHR, and it could be prevented by lisinopril treatment. Thus, long-term angiotensin-converting enzyme inhibition with lisinopril normalized arterial pressure and LVH, reversed myocardial fibrosis, and improved abnormal myocardial diastolic stiffness in advanced hypertensive heart disease in SHR. In addition, systolic dysfunction of the left ventricle could be prevented. The fibrolytic response to lisinopril was at least partly due to enhanced collagen degradation by activation of tissue matrix metalloproteinase 1.
An E-Box Motif Conveys Inhibitory Activity on the Atrial Natriuretic Peptide Gene
Authors: Garami Miklós , Gardner David G.
Published: June 2012

Atrial natriuretic peptide (ANP) is a potent diuretic, natriuretic, and vasorelaxant hormone that is expressed early in ventricular hypertrophy. Expression of human ANP is controlled by a series of regulatory elements located in the 5′ flanking sequence of its gene. We generated a series of 5′ deletion mutations extending from −2600 to −1150 relative to the transcription start site and linked them to a chloramphenicol acetyltransferase reporter gene. Using transient transfection analysis, we have identified a negative regulatory element between −1206 and −1152 relative to the start site. Each of a series of 5′ deletion mutants, when introduced into fibroblast cultures, expressed the reporter function at a level that was significantly less (<20%) than that seen with the −1152 reporter construct, whereas comparably transfected atrial cardiocytes demonstrated no change in reporter activity, implying that the repressor function is specific to cell type. The critical region (from −1206 to −1152) associates with a soluble protein present in cardiac fibroblast extracts in a sequence-specific fashion. Deoxyribonuclease I footprint analysis demonstrated the presence of several protected regions, including one that overlies an E-box motif (CAACTG), an element that in other systems has been implicated in promoting differentiation in the myocyte lineage. Site-directed mutagenesis of the E-box motif suppressed both the protein-binding and inhibitory activities of the 54-bp fragment. In summary, we have found a region in the 5′ flanking sequence of the human ANP gene that represses transcriptional activity in nonmyocardial cells. This element may play an important role in the restriction of ANP gene expression to cardiac myocytes.
Use-Dependent Loss of Active Sympathetic Neurogenic Vasodilation After Nitric Oxide Synthase Inhibition in Conscious Rats
Authors: Davisson Robin L. , Shaffer Richard A. , Johnson A. Kim , Lewis Stephen J.
Published: June 2012

In this study, we examined whether air-jet stress–induced active sympathetic hindlimb vasodilation in conscious rats involves the release of preformed stores of nitric oxide–containing factors. We determined the effects of repeated episodes of air-jet stress (six episodes given 5 minutes apart) on mean arterial pressure and vascular resistances in the mesenteric bed and intact and sympathetically denervated hindlimb beds of conscious rats treated with saline or the nitric oxide synthesis inhibitor
N
ω
-nitro-
l
-arginine methyl ester (L-NAME, 25 μmol/kg IV). In saline-treated rats, air-jet stress produced alerting behavior, minor changes in blood pressure, pronounced mesenteric vasoconstriction, and immediate and marked vasodilation in the sympathetically intact hindlimb but a minor vasodilation in the sympathetically denervated hindlimb. Each air-jet stress produced virtually identical responses. In L-NAME–treated rats, the first air-jet stress produced vasodilator responses in the sympathetically intact and sympathetically denervated hindlimbs that were similar to those in the saline-treated rats. However, each subsequent air-jet stress produced progressively smaller vasodilator responses in the sympathetically intact but not the sympathetically denervated hindlimb. There was no loss of air-jet stress–induced alerting behavior or mesenteric vasoconstriction, suggesting that L-NAME did not interfere with the central processing of the air-jet or the resultant changes in autonomic nerve activity. The progressive diminution of air-jet stress–induced vasodilation in the intact hindlimb of L-NAME–treated rats may be due to the use-dependent depletion of preformed stores of nitric oxide–containing factors that cannot be replenished in the absence of nitric oxide synthesis.
Impairment of Endothelium-Dependent Relaxation by Increasing Percentages of Glycosylated Human Hemoglobin
Authors: Angulo Javier , Sánchez-Ferrer Carlos F. , Peiró Concepción , Marín Jesús , Rodríguez-Mañas Leocadio
Published: June 2012

High levels of glycosylated human hemoglobin impair nitric oxide–mediated responses. However, the percentage of glycosylation for which this effect is observed and the mechanisms involved are unknown. We tested endothelium-dependent relaxations caused by acetylcholine in rat aortic segments either in control conditions or after preincubation with increasing percentages of glycosylated human hemoglobin. Human hemoglobin (1 and 10 nmol/L) inhibited endothelium-dependent relaxations only when glycosylated at 9% or higher. We evaluated the effect of 14% glycosylated human hemoglobin on acetylcholine-evoked responses in vessels preincubated with scavengers of superoxide anions, hydroxyl radical, or hydrogen peroxide (superoxide dismutase, deferoxamine, and catalase, respectively); with inhibitors of xanthine oxidase, cyclooxygenase, or thromboxane synthase (allopurinol, indomethacin, and dazoxiben, respectively); with blockers of thromboxane A
2
/prostaglandin H
2
or endothelin receptors (SQ 30741 and BQ-123); and with the precursor of nitric oxide synthesis
l
-arginine. Superoxide dismutase abolished the effect of glycosylated hemoglobin, and the other substances did not have any effect. Glycosylated hemoglobin at 14% did not modify either the vasoconstrictions induced by the blocker of nitric oxide synthase
N
G
-nitro-
l
-arginine methyl ester or the relaxations evoked in deendothelialized vessels by sodium nitroprusside and 8-bromo-cGMP. However, it inhibited the vasodilations evoked by exogenous nitric oxide. Superoxide dismutase abolished this latter effect. We conclude that the threshold for glycosylated human hemoglobin (Hb A
1
) to inhibit endothelium-dependent relaxation is 9%. This effect is due to interference with endothelial nitric oxide by means of superoxide anion production.
Role of Angiotensin-Converting Enzyme, Adrenergic Receptors, and Blood Pressure in Cardiac Gene Expression of Spontaneously Hypertensive Rats During Development
Authors: Ohta Kensuke , Kim Shokei , Iwao Hiroshi
Published: June 2012

We undertook this study to investigate the regulatory mechanism of cardiac gene expression in spontaneously hypertensive rats (SHR) during development. We measured cardiac mRNAs by Northern blot analysis. In 9-week-old SHR at the very early stage of cardiac hypertrophy, the expression of various cardiac genes related to the regulation of cardiac contraction and relaxation was already significantly changed compared with control Wistar-Kyoto rats, indicating that cardiac molecular changes are responsible for cardiac remodeling or the modulation of cardiac performance in SHR. We gave various types of antihypertensive drugs, at oral doses causing a mild and comparable hypotensive effect, to 27-week-old SHR to examine the effects on the altered cardiac gene expression. Imidapril, an angiotensin-converting enzyme inhibitor, normalized the increased gene expression of atrial natriuretic polypeptide and collagen types I and III and the decreased expression of α-myosin heavy chain in SHR heart. Atenolol (a β
1
-blocker) combined with doxazosin did not affect cardiac ANP and α-myosin heavy chain expression of SHR but normalized the increased collagen expression. In contrast, despite a hypotensive effect comparable to these two drug treatments, doxazosin (an α
1
-blocker) alone or manidipine (a calcium antagonist) did not normalize these altered gene expressions of SHR. These results show that the cardiac renin-angiotensin system is involved in the altered cardiac gene expression in SHR. The β
1
- but not α
1
-adrenergic receptor is also responsible for the increased cardiac collagen expression in SHR.
Role of Type 1 and Type 2 Angiotensin Receptors in Angiotensin II–Induced Cardiomyocyte Hypertrophy
Authors: Booz George W. , Baker Kenneth M.
Published: June 2012

We compared the ability of angiotensin II (Ang II) to induce hypertrophy of neonatal rat ventricular myocytes with that of endothelin-1. Over 72 hours, Ang II (1 μmol/L) increased the ratio of protein to DNA by less than 10%, whereas endothelin-1 (100 nmol/L) produced a 28% increase. The growth effects of either agonist occurred independently of chronotropic actions. Radioligand binding studies showed that myocytes have nearly 300-fold more receptors for endothelin-1 than Ang II, and type 1 and type 2 Ang II receptor subtypes (AT
1
and AT
2
) are present in near equal proportions. Cotreatment with a 10-fold molar excess of AT
2
antagonists (PD 123177 or CGP 42112) for 72 hours augmented the Ang II–induced increase in the protein-to-DNA ratio to levels nearly as high (23%) as those with endothelin-1 (28%). AT
2
antagonists enhanced Ang II stimulation of protein synthesis, as indexed by [
3
H]leucine incorporation, whereas an AT
1
antagonist blocked Ang II–induced incorporation. An AT
2
antagonist also prevented Ang II–induced protein degradation. In conclusion, Ang II–induced myocyte growth is tempered because of low AT
1
levels and an antigrowth effect of AT
2
. These findings have potential clinical significance in that regression of hypertension-induced cardiac hypertrophy by AT
1
antagonists may be in part due to an unopposed antigrowth effect of Ang II mediated via AT
2
.
Beneficial Effects of Pravastatin on Fasting Hyperinsulinemia in Elderly Hypertensive Hypercholesterolemic Subjects
Authors: Chan Paul , Tomlinson Brian , Lee Ching-Bing , Pan Wen-Harn , Lee Ying-Shiung
Published: June 2012

We undertook this prospective double-blind, placebo-controlled study to evaluate the efficacy and safety of low-dose (15 mg) pravastatin in elderly hypercholesterolemic hypertensive subjects with concurrent antihypertensive treatment and to determine whether fasting hyperinsulinemia could also be improved. At three hypertension and lipid clinics of two medical centers, 96 elderly (49 women, 47 men) ambulatory subjects were randomized to active treatment or placebo for 12 months after a 3-month single-blind lead-in period. Hypertensive subjects with plasma total cholesterol levels of at least 6.47 mmol/L (250 mg/dL) and triglyceride levels less than 3.39 mmol/L (300 mg/dL) were treated with 15 mg pravastatin for 12 months after receiving 3 months of the American Heart Association step I diet. Lipid, glucose, and fasting insulin levels were measured; clinical laboratory tests included liver function and creatine kinase determinations. After 12 months of pravastatin therapy, plasma total cholesterol concentration decreased by 25.1% (from a mean of 7.29 to 5.47 mmol/L,
P
<.05), low-density lipoprotein cholesterol decreased by 30.2% (from 5.27 to 3.68 mmol/L,
P
<.05), and triglycerides decreased by 10.7% (from 1.68 to 1.50 mmol/L,
P
<.05). High-density lipoprotein cholesterol increased by 9.2% (from 1.20 to 1.31 mmol/L,
P
<.05). Fasting insulin levels decreased from 89.0 to 61.5 pmol/L (
P
<.05). All of these changes were greater (
P
<.05) than any tendency toward change in the placebo group. Adverse events and clinical laboratory abnormalities were generally mild and transient in both placebo and pravastatin groups. Study drugs were withdrawn from one subject in each group with asymptomatic creatine kinase elevations. We conclude that low-dose pravastatin was effective and safe in the treatment of hypercholesterolemic hypertensive subjects on concurrent antihypertensive therapy. It also improved fasting hyperinsulinemia despite the use of β-blockers and diuretics in these hypertensive subjects.
Pressure-Dependent Renin Release During Chronic Blockade of Nitric Oxide Synthase
Authors: Knoblich Penny R. , Freeman Ronald H. , Villarreal Daniel
Published: June 2012

We evaluated pressure-dependent stimulation of renin release in rats with sustained hypertension induced by chronic blockade of nitric oxide synthase with
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) for 5 to 7 days. Rats were anesthetized and catheters were inserted into the carotid artery and abdominal aorta for measurement of arterial pressures. An adjustable snare was placed around the suprarenal aorta, and this snare was tightened to reduce renal perfusion pressure. Pressure-dependent renin release was evaluated in hypertensive rats by reducing renal perfusion pressure to 125, 85, and 65 mm Hg. Renin release was also evaluated in normotensive control rats at these same pressures. Basal systemic arterial pressures averaged 159±3 and 124±4 mm Hg (
P
<.001), respectively, in the L-NAME–treated (n=22) and normotensive control (n=18) rats. Basal plasma renin activity was lower in L-NAME than control rats (5.0±0.3 versus 9.5±1.3 U,
P
<.01), and plasma renin activity was markedly attenuated at all comparable levels of renal perfusion pressure. Maximal plasma renin activity levels were achieved at perfusion pressures reduced to 65 mm Hg, and plasma renin activity averaged 14±2 and 34±7 U (
P
<.01) in L-NAME hypertensive and control rats, respectively. However, infusion of the nitric oxide donor sodium nitroprusside similarly stimulated plasma renin activity levels to 39±3 and 45±3 U (
P
>.05), in the hypertensive and normal control groups, respectively. Overall, these findings are consistent with the hypothesis that prolonged L-NAME administration attenuates pressure-dependent renin release by inhibiting nitric oxide formation, which may function as a paracrine mechanism inversely linking renal perfusion pressure with the stimulation of renin release.
Translational Regulation of Angiotensin II Type 1A Receptor
Authors: Mori Yasukiyo , Matsubara Hiroaki , Murasawa Satoshi , Kijima Kazuhisa , Maruyama Katsuya , Tsukaguchi Hiroyasu , Okubo Naohiko , Hamakubo Takao , Inagami Tadashi , Iwasaka Toshiji , Inada Mitsuo
Published: June 2012

The cDNA sequence of rat angiotensin II type 1A receptor (AT
1A
R) shows that AT
1A
R transcripts have AUG triplets in the 5′-leader region that may begin a short open reading frame encoding an 11–amino acid peptide. In this study, the mutational inactivation of the start codon of the short open reading frame in AT
1A
R–chloramphenicol acetyltransferase (CAT) reporter gene constructs resulted in a 2.6-fold increase in CAT activity, whereas CAT transcript levels were not affected. Furthermore, experiments with rat AT
1A
R cDNA–transfected Cos-7 cells revealed that mutagenesis of the upstream AUG increased the AT
1A
R protein up to 2.5-fold, although AT
1A
R transcript levels showed no changes. The synthetic peptide corresponding to the sequence of the short open reading frame significantly suppressed the amount of AT
1A
R product in the in vitro translation system. The inhibiting effect of the short open reading frame appears to operate at least in part at the level of translation initiation, because polysome analysis with transfected Cos-7 cells showed that mutagenesis of the upstream AUG resulted in a shift of AT
1A
R mRNA distribution from a smaller to larger fraction of polysomes. Taken together, these results show that the upstream AUG inhibits translational regulation, suggesting that the short open reading frame in the 5′-leader region of AT
1A
R transcripts has a certain role in the translation of AT
1A
R protein.
Erectile Dysfunction in Hypertensive Subjects
Authors: Jaffe Anat , Chen Yuza , Kisch Eldad S. , Fischel Beno , Alon Malbina , Stern Naftali
Published: June 2012

Hypertension is often cited as a risk factor for erectile dysfunction. To clarify the relation between hypertension and erectile dysfunction, we evaluated 32 consecutive hypertensive and 78 normotensive impotent men with respect to multiple potential determinants and parameters of erectile function, including medical and sexual history, depression, hormonal profile, penile nocturnal tumescence, penile vascular supply, and pudendal nerve conduction. The hypertensive men were older, had higher body mass index, and used more medications than the normotensive men. The groups were not different with respect to the prevalence of smoking and peripheral vascular disease, but the hypertensive men had a marginally higher rate of ischemic heart disease (
P
=.06). The prevalence of depression, abnormal nocturnal penile tumescence, anomalous pudendal nerve conduction, and impairment in arterial supply as determined by penile brachial index were similar in the two groups. Testosterone and bioavailable testosterone levels were lower in the hypertensive men. After stratification by age and body mass index, hypertensive men younger than 50 years with body mass index less than 30 kg/m
2
had significantly lower testosterone levels (12.0±1.7 versus 21.3±1.4 nmol/L,
P
<.02) but not bioavailable testosterone levels (3.9±0.7 versus 6.4±0.7 nmol/L,
P
<.17) than the corresponding normotensive group. Prolactin, follicle-stimulating hormone, and luteinizing hormone levels of the two groups were not significantly different. Contrary to common belief and with the exception of lower circulating testosterone levels, the overall analysis showed little difference between hypertensive and normotensive men with respect to a wide range of classic determinants of erectile function. Direct study of the local vascular erectile apparatus appears necessary for further elucidation of the mechanisms underlying erectile dysfunction in hypertensive men.
Blood Pressure and the M235T Polymorphism of the Angiotensinogen Gene
Authors: Hingorani Aroon D. , Sharma Pankaj , Jia Haiyan , Hopper Ruth , Brown Morris J.
Published: June 2012

The angiotensinogen gene locus (1q42-43) has been linked to hypertension in affected relative-pair studies (including a previous UK study), but the role of the Met→Thr polymorphism at position 235 remains controversial. Using this marker, we investigated the relationship between angiotensinogen genotype and blood pressure in two data sets from the East Anglia region of the United Kingdom. Two hundred twenty-three untreated hypertensive and 187 normotensive control subjects were recruited through local general practices. Blood pressure (including pretreatment measurements in the hypertensive group), age, sex, body mass index, alcohol consumption, cholesterol level, and angiotensinogen genotype were recorded for all subjects. The influence of angiotensinogen genotype on blood pressure was assessed with a general linear model ANOVA with adjustment for age, sex, body mass index, and alcohol consumption. There was no evidence for an association between angiotensinogen genotype and blood pressure level in either the hypertensive or normotensive data set. Angiotensinogen genotype did not influence blood pressure in subjects aged <50 years, women, or those with a body mass index <26 kg/m
2
. We conclude that the angiotensinogen Met→Thr polymorphism is not a marker for blood pressure level in these East Anglian subjects. Further studies are required to confirm the involvement of the 1q locus in the development of hypertension in UK subjects and to delineate the functional variant(s) in this chromosomal region that influences blood pressure.
Experimental Studies on the Role of Intercellular Adhesion Molecule-1 and Lymphocyte Function–Associated Antigen-1 in Hypertensive Nephrosclerosis
Authors: Mai Monika , Hilgers Karl F. , Geiger Helmut
Published: June 2012

T helper cells and macrophages infiltrate into the renal cortical interstitium during the course of hypertensive nephrosclerosis. To investigate the mechanisms of mononuclear cell infiltration, we examined the expression of the intercellular adhesion molecule-1 (ICAM-1) and its counterpart lymphocyte function–associated antigen-1 (LFA-1) in the progression of hypertensive renal injury. We studied nonclipped kidneys of two-kidney, one clip renovascular hypertensive and sham-operated control rats immunohistochemically at 4, 7, 14, and 28 days after clipping (n=5 per group and time point). Systolic pressure was significantly elevated by day 7 (154±4 versus 117±6 mm Hg in sham,
P
<.05). The development of hypertension resulted in a progressive increase of ICAM-1 expression in the perivascular and interstitial areas of the renal cortex and on proximal tubular brush borders. Only a few glomeruli showed augmented ICAM-1 staining. Increased ICAM-1 was associated with an accumulation of LFA-1–positive mononuclear cells in the perivascular region (day 14: 15±4 versus 2±0.2 cells/mm
2
in sham,
P
<.005) and intertubular region (127±11 versus 32±3 cells per millimeter squared in sham,
P
<.005). The maximum was obtained at day 14 and remained elevated until day 28. In addition, the number of interstitial LFA-1–positive infiltrating cells was related to the degree of interstitial and tubular ICAM-1 expression and correlated with blood pressure (
r
=.75,
P
<.001, n=18). Our data suggest that ICAM-1 is involved in the recruitment of macrophages/lymphocytes via specific interaction of ICAM-1 and LFA-1 in this model of hypertensive target-organ damage.
Essential Hypertension Is Associated With Decreased Insulin Clearance and Insulin Resistance
Authors: Lender Dan , Arauz-Pacheco Carlos , Adams-Huet Beverley , Raskin Philip
Published: June 2012

Essential hypertension is associated with multiple metabolic abnormalities, among them, hyperinsulinemia. This hyperinsulinemia is attributed to the presence of decreased insulin sensitivity (insulin resistance) with consequent compensatory insulin secretion. We tested the hypothesis that decreased insulin clearance is present in hypertensive subjects and contributes to hyperinsulinemia independently of the degree of insulin resistance. Seventy-five subjects were studied (48 hypertensive and 27 normotensive). Both groups were comparable in terms of age, body fat content, waist-to-hip ratio, and sex distribution. A primed continuous insulin infusion at 40 mU/m
2
per minute was performed. Glucose was maintained at baseline levels with the euglycemic clamp technique. Hypertensive subjects were characterized by decreased insulin sensitivity (insulin-mediated glucose uptake: 5.14±0.28 versus 7.26±0.61 mg glucose/kg fat-free mass per minute, hypertensive versus normotensive,
P
=.002), increased insulin levels during the insulin infusions (804±36 versus 510±38 pmol/L, hypertensive versus normotensive,
P
<.001), and decreased insulin metabolic clearance rate (328±15 versus 521±30 mL/min per meter squared, hypertensive versus normotensive,
P
<.001). In an ANCOVA (including sex, degree of obesity, waist-to-hip ratio, and insulin sensitivity as covariates) the differences in insulin metabolic clearance rate between normotensive and hypertensive subjects remained highly significant (
P
<.001). Insulin metabolic clearance rate was significantly associated with fasting insulin levels. We conclude that essential hypertension is independently associated with decreased insulin metabolic clearance rate in addition to insulin resistance. A low insulin metabolic clearance rate may be a contributory factor to the hyperinsulinemia observed in essential hypertension.
Senescent Heart Compared With Pressure Overload–Induced Hypertrophy
Authors: Assayag Patrick , Charlemagne Danièle , de Leiris Joël , Boucher François , Valère Paul-Etienne , Lortet Sylviane , Swynghedauw Bernard , Besse Sophie
Published: June 2012

Although systolic left ventricular (LV) function is normal in the elderly, aging is associated in rat papillary muscle with mechanical and sarcoplasmic reticulum Ca
2+
ATPase alterations similar to those observed in the hypertrophied heart. However, alterations in the other calcium-regulating proteins implicated in contraction and relaxation are still unknown. To investigate alterations in LV function and calcium-regulating proteins, we measured hemodynamics and Na
+
-Ca
2+
exchanger (NCx), ryanodine receptor (RyR2), and sarcoplasmic reticular Ca
2+
ATPase (SERCA2) mRNA levels (expressed in densitometric scores normalized to that of poly(A
+
) mRNA) in left ventricle from 4-month-old (adult, n=13) and 24-month-old (senescent, n=15) rats. For ex vivo contractile function, active tension was measured during isolated heart perfusion in adult (n=11) and senescent (n=11) rats. For comparison of age-dependent effects of moderate hypertension on both hemodynamics and calcium proteins, renovascular hypertension was induced or a sham operation performed at 2 (n=11 and n=6) and 22 (n=26 and n=5) months of age. In senescent rats, LV systolic pressure and maximal rates of pressure development were unaltered, although active tension was depressed (4.7±0.4 versus 8.3±0.7 g/g heart weight in adults,
P
<.0001). SERCA2 mRNA levels were decreased in senescent left ventricle (0.98±0.05 versus 1.18±0.05 in adults,
P
<.01), without changes in NCx and RyR2 mRNA accumulation. Renovascular hypertension resulted in 100% mortality in aged rats; in adults, renovascular hypertension resulted, 2 months later, in an increase of LV systolic pressure (170±7 versus 145±3 mm Hg in sham-operated rats,
P
<.05) and in mild LV hypertrophy (+18%,
P
<.01) associated with a decrease in SERCA2 mRNA levels (1.02±0.03 versus 1.18±0.03 in sham-operated rats,
P
<.001). Contractile dysfunction in senescent isolated heart and decreased SERCA2 mRNA levels were associated with in vivo normal LV function at rest, indicating the existence of in vivo compensatory mechanisms. RyR2 and NCx gene expressions were not implicated in the observed contractile dysfunction. In aged rats, renovascular hypertension resulted in 100% mortality, probably related to elevated levels of circulating angiotensin II, whereas in adult rats, renovascular hypertension induced a mild LV hypertrophy associated with a selective alteration in SERCA2 gene expression.
Angiotensin-Converting Enzyme and Angiotensinogen Gene Polymorphisms, Plasma Levels, Cardiac Dimensions A Twin Study
Authors: Busjahn Andreas , Knoblauch Hans , Knoblauch Margit , Bohlender Jürgen , Menz Marianne , Faulhaber Hans-Dieter , Becker Albert , Schuster Herbert , Luft Friedrich C.
Published: June 2012

We tested the hypotheses that angiotensin-converting enzyme insertion/deletion (I/D) and angiotensinogen 235 methionine/threonine (M/T) substitution gene polymorphisms influence angiotensin-converting enzyme and angiotensinogen serum concentrations and cardiac dimensions in 91 monozygotic and 41 dizygotic twin pairs. Cardiac dimensions were determined echo-cardiographically. Angiotensin-converting enzyme levels were 24±11, 43±18, and 58±24 U/L for the II, ID, and DD genotypes, respectively (
P
<.01). Posterior wall thickness was 8.1±1.3, 8.6±1.7, and 8.9±1.9 mm for these genotypes (
P
<.05). Angiotensin-converting enzyme levels were correlated with posterior wall thickness (
r
=.15,
P
<.05). The intrapair differences in angiotensin converting enzyme levels for monozygotic, concordant dizygotic, and discordant dizygotic twins were 1.36±1.6, 1.86±1.6, and 17.25±4.3 U/L, respectively. The angiotensinogen M/T genotypes exerted no influence on cardiac dimensions or on angiotensinogen concentrations. The additive genetic effect on angiotensin-converting enzyme levels (0.49), on posterior wall thickness (0.26), and on septum thickness (0.37) was significant (
P
<.01), although shared and nonshared environmental effects were also identified. Our data confirm the impressive effect that the angiotensin-converting enzyme D allele exerts on angiotensin-converting enzyme plasma levels. Furthermore, our data also suggest that the angiotensin-converting enzyme gene locus is primarily responsible for angiotensin-converting enzyme plasma levels. Our twin study also indicates that the angiotensin-converting enzyme gene locus is genetically linked to posterior wall thickness. The correlation between angiotensin-converting enzyme levels and posterior wall thickness suggests that this effect is exerted by angiotensin-converting enzyme. We were unable to demonstrate genetic linkage between the angiotensinogen gene locus and cardiac dimensions in this study.
Temporal Influence of the Renal Nerves on Renal Excretory Function During Chronic Inhibition of Nitric Oxide Synthesis
Authors: Reinhart Glenn A. , Lohmeier Thomas E. , Mizelle H. Leland
Published: June 2012

To determine whether the sympathetic nervous system contributes to the hypertension induced by long-term suppression of nitric oxide synthesis, we determined the neurally induced changes in renal excretory function during chronic administration of
N

g

-nitro-
l
-arginine methyl ester (L-NAME). Studies were carried out in six conscious chronically instrumented dogs subjected to unilateral renal denervation and surgical division of the urinary bladder into two hemibladders to allow separate 24-hour urine collection from denervated and innervated kidneys. Animals were studied during acute (100 minutes) and chronic (5 days) intravenous infusion of L-NAME at 37.1 nmol/kg per minute (10 μg/kg per minute). During the first 100 minutes of L-NAME, there were no significant changes in mean arterial pressure (control: 96±3 mm Hg), but heart rate fell from 66±6 to 55±7 beats per minute. Changes in glomerular filtration rate were not significant, but renal plasma flow and urinary sodium excretion decreased to ≈75% and 50% of control values, respectively; however, these changes were comparable in both kidneys. In association with these responses, plasma concentrations of norepinephrine (control: 887±130 pmol/L or 150±22 pg/mL) and epinephrine (control: 691±192 pmol/L or 108±30 pg/mL) tended to decrease. In contrast to the acute responses, mean arterial pressure increased from 92±3 to 106±3 mm Hg and heart rate decreased from 72±4 to 57±5 beats per minute by day 5 of L-NAME infusion, while renal plasma flow and glomerular filtration rate were not significantly different from control values. Most importantly, there were no significant differences in urinary sodium excretion between innervated (control: 31±2 mmol/d) and denervated (control 33±2 mmol/d) kidneys during chronic L-NAME infusion or during the recovery period. These results indicate that the renal sympathetic nerves do not play an important role in promoting sodium retention during either acute or chronic inhibition of nitric oxide synthesis in conscious dogs. Thus, increased renal sympathetic nerve activity does not contribute significantly to L-NAME-induced hypertension.
Relationship Between Insulin Resistance and Endothelium-Dependent Vascular Relaxation in Patients With Essential Hypertension
Authors: Higashi Yukihito , Oshima Tetsuya , Sasaki Nobuo , Ishioka Norio , Nakano Yukiko , Ozono Ryoji , Yoshimura Mitsuisa , Ishibashi Katsuhiko , Matsuura Hideo , Kajiyama Goro
Published: June 2012

The infusion of
l
-arginine induces the production of nitric oxide and stimulates the immediate secretion of insulin. To examine the relationship between insulin resistance and endothelium-dependent vascular relaxation in patients with essential hypertension, we evaluated the renal and insulin responses to
l
-arginine, 500 mg/kg infused intravenously over 30 minutes, in 23 patients with mild essential hypertension who were neither obese nor diabetic and in 20 normotensive control subjects. We found no difference between the two groups in blood glucose or insulin in the fasting condition. The renovascular relaxation induced by
l
-arginine was significantly less in patients with essential hypertension than in normotensive control subjects. The increase in plasma cyclic GMP in response to
l
-arginine was lower in hypertensive patients than in normotensive subjects. Although the serum concentrations of glucose in response to
l
-arginine were similar in the two groups, the serum insulin response of the essential hypertensives was significantly higher than that of the normotensive subjects. In all subjects, the peak cyclic GMP response to
l
-arginine was significantly correlated with the peak Δglucose/ Δinsulin ratio response to
l
-arginine (
r
=.69,
P
<.001). Findings suggested that an impairment of endothelium-dependent renal vascular relaxation and a reduced sensitivity to insulin are present in patients with essential hypertension. A link may be present between the abnormality of the
l
-arginine/nitric oxide/cyclic GMP pathway and insulin resistance in patients with essential hypertension.
Cyclooxygenase-2 Mediates Increased Renal Renin Content Induced by Low-Sodium Diet
Authors: Harding Pamela , Sigmon David H. , Alfie Marcos E. , Huang Paul L. , Fishman Mark C. , Beierwaltes William H. , Carretero Oscar A.
Published: June 2012

We hypothesized that neuronal nitric oxide synthase and cyclooxygenase-2, which both exist in the renal cortex, predominantly in the macula densa, play a role in the control of renal renin tissue content. We studied the possible role of neuronal nitric oxide synthase in regulating renal renin content by using mice in which the neuronal nitric oxide synthase gene has been disrupted (nNOS -/-) compared with its two progenitor strains, the 129/SvEv and the C57BL/6, to determine if the absence of neuronal nitric oxide synthase would result in decreased renal renin content or blunt the increase observed during low sodium intake. Renal renin content from cortical slices was determined in adult mice from all three strains maintained on a normal sodium diet. Renal renin content was significantly reduced in the nNOS -/- mice compared with the 129/SvEv and the C57BL/6 mice (3.11±0.23 versus 5.66±0.50 and 7.55±1.17 μg angiotensin I/mg dry weight, respectively;
P
<.005), suggesting that neuronal nitric oxide synthase may stimulate renal renin content under basal conditions. Neither selective pharmacological inhibition of neuronal nitric oxide synthase using 7-nitroin-dazole or disruption of the neuronal nitric oxide synthase gene affected the increase in renal renin content observed during dietary sodium restriction. The influence of cyclooxygenase-2 on renal renin content through a macula densa-mediated pathway was studied using a selective cyclooxygenase-2 inhibitor, NS398, in 129/SvEv mice. A low-sodium diet increased renal renin content from 6.97±0.52 to 11.59±0.79 μg angiotensin I/mg dry weight (
P
<.005); but this increase was blocked by NS398. In addition, treatment with NS398 reduced renin mRNA in response to a low-sodium diet. Thus, increased renal renin content in response to dietary sodium restriction appears to require the induction of cyclooxygenase-2, while neuronal nitric oxide synthase appears to affect basal but not stimulated renal renin content.
Mitogen-Activated Protein Kinase Activation Is Involved in Platelet-Derived Growth Factor-Directed Migration by Vascular Smooth Muscle Cells
Authors: Graf Kristof , Xi Xiao-Ping , Yang Dong , Fleck Eckart , Hsueh Willa A. , Law Ronald E.
Published: June 2012

Migration of vascular smooth muscle cells (VSMCs) is a crucial response to vascular injury resulting in neointima formation and atherosclerosis. Platelet-derived growth factor (PDGF-BB) functions as a potent chemoattractant for VSMCs and enhances these pathologies in the vasculature. However, little is known about the intracellular pathways that mediate VSMC migration. In the present study, we investigated the role of mitogen-activated protein kinase (MAPK) activation in this function, since PDGF-BB as well as other growth factors activate this pathway. Using an in-gel kinase assay, we observed that PD 98059, an inhibitor of MEK that activates MAP kinase, inhibited PDGF-BB-induced activation of ERK-1 and ERK-2 in cultured rat aortic smooth muscle cells in a concentration-dependent manner. In contrast, PDGF-mediated activation of intracellular calcium release was not affected by PD 98059. The chemotactic response of both rat aortic smooth muscle cells (RASMCs) and human umbilical vein smooth muscle cells (HUSMCs) toward PDGF-BB (10 ng/mL) was significantly reduced by PD 98059 (10 μmol/L) to 41.7±7.1% in RASMCs (
P
>.01) and to 47.2 ±5.3% in HUSMCs (
P
>.01). Similar inhibition was seen at 30 μmol/L, less at 1 μmol/L. To further confirm the specificity of these results implicating the MAPK pathway, an antisense oligodeoxynucleotide (ODN) directed against the initiation translation site of rat ERK-1 and ERK-2 mRNA was used to suppress MAP kinase synthesis and function in rat VSMCs. Liposomal transfection with 0.4 μmol/L antisense ODN reduced ERK-1 and ERK-2 protein by 65% (
P
>.01) after 48 hours. The chemotactic response to PDGF-BB (10 ng/mL) was reduced by 75% (
P
>.01) in rat VSMCs transfected with the same antisense ODN concentration. Sense and scrambled control ODNs (0.4 μmol/L) did not affect ERK-1 and ERK-2 protein concentrations or chemotaxis of VSMCs induced by PDGF-BB. These experiments provide the first evidence that activation of MAPK is a critical event in PDGF-mediated signal transduction regulating VSMC migration.
Angiotensin II Signaling in Vascular Smooth Muscle
Authors: Griendling Kathy K. , Ushio-Fukai Masuko , Lassègue Bernard , Alexander R. Wayne
Published: June 2012

Angiotensin II is a multifunctional hormone that affects both contraction and growth of vascular smooth muscle cells through a complex series of intracellular signaling events initiated by the interaction of angiotensin II with the AT
1
receptor. The cellular response to angiotensin II is multiphasic, involving stimulation within seconds of phospholipase C and Ca
2+
mobilization; activation within minutes of phospholipase D, A
2
, protein kinase C, and MAP kinase; and stimulation after a period of hours of gene transcription and NADH/NADPH oxidase activity. Angiotensin II also activates numerous intracellular tyrosine kinases. In this respect, it shares some aspects of signaling with growth factor and cytokine receptors, including activation of phospholipase C-γ, src, and ras; association of shc with grb2; and stimulation of the Jak/STAT pathway. The cellular events responsible for this unique series of events may involve receptor movement and the creation of a signaling domain. Elucidation of these pathways is important to our understanding of AT
1
receptor function as a final effector of the renin-angiotensin system.
Prolonged Reduction of High Blood Pressure With an In Vivo, Nonpathogenic, Adeno-Associated Viral Vector Delivery of AT
1
-R mRNA Antisense
Authors: Phillips M. Ian , Mohuczy-Dominiak Dagmara , Coffey Mark , Galli Sara M. , Kimura Birgitta , Wu Ping , Zelles Tibor
Published: June 2012

To produce a prolonged decrease in blood pressure, we have developed a nonpathogenic adeno-associated viral vector (AAV) with the antisense DNA for AT
1
-R. AAV has many advantages over other viral vectors. AAV does not stimulate inflammation or immune reaction. AAV enters nondividing cells and does not replicate. Therefore, it is an appropriate choice for gene therapy. Recombinant AAV was prepared with a cassette containing a cytomegalovirus promoter and the cDNA for the AT
1
receptor inserted in the antisense direction. The cassette was packaged in the virion. Stable transfection of NG108-15 cells with the pAAV-AS (plasmid AAV) antisense to AT
1
-R produced a significant reduction in AT
1
receptors. A single injection of the rAAV-AS (viral vector) was made in adult spontaneously hypertensive rats, either directly in the hypothalamus (1 μL) or in the lateral ventricles (5 μL). The result shows that there is a significant decrease of blood pressure (≈23±2 mm Hg) for up to 9 weeks after injection. Control injections of mock vector produced no change in blood pressure during the same time period in age-matched controls. In young spontaneously hypertensive rats (3 weeks), a single intracardiac injection of recombinant rAAV-AS reduced blood pressure and slowed the development of hypertension compared with controls (
P
<.01). The results suggest that a prolonged reduction in high blood pressure can be achieved with AAV vectors delivering antisense to inhibit AT
1
receptors with a single administration.
Opposite Regulation of Gax Homeobox Expression by Angiotensin II and C-Type Natriuretic Peptide
Authors: Yamashita Jun , Itoh Hiroshi , Ogawa Yoshihiro , Tamura Naohisa , Takaya Kazuhiko , Igaki Toshio , Doi Kentaro , Chun Tae-Hwa , Inoue Mayumi , Masatsugu Ken , Nakao Kazuwa
Published: June 2012

Growth arrest-specific homeobox (Gax) gene was isolated from rat aorta cDNA library and its expression was largely confined to the cardiovascular tissues. Gax gene was rapidly downregulated by platelet-derived growth factor in vascular smooth muscle cells (VSMCs) and overexpressed Gax was reported to reduce the neointimal thickening after balloon injury in vivo. We have demonstrated that angiotensin II (Ang II) stimulates vascular growth. In contrast, we also reported that C-type natriuretic peptide (CNP) is secreted from vascular endothelial cells to act as a novel endothelium-derived relaxing peptide and inhibits vascular growth via cGMP cascade. In the present study, we examined the effects of Ang II and CNP on Gax gene expression in VSMCs. In quiescent rat aortic VSMCs, Gax mRNA (2.3 kb) level became negligible 6 hours after the addition of Ang II (10
−6
mol/L). The inhibitory action of Ang II on Gax mRNA expression (ED
50
: 10
−11
mol/L) was almost completely blocked by an AT
1
R antagonist, CV11974. In contrast, CNP 10
−6
mol/L augmented Gax mRNA expression to exhibit 1.8-fold increase of the control 12 hours after the stimulation. This effect of CNP was mimicked by the addition of 8-bromoadenosine 3′:5′-cyclic monophosphate. The addition of C-ANF[4–23], an atrial natriuretic peptide-C receptor-specific agonist and devoid of stimulating cGMP production, exhibited no effect on Gax mRNA expression. Simultaneous administration of Ang II and CNP revealed that CNP (10
−6
mol/L) significantly attenuated the inhibitory action of Ang II (10
−10
mol/L) on Gax mRNA expression. These results suggest that Gax is a common transcription factor involved in the signaling pathway of vascular growth for Ang II and CNP and regulates the cell cycle and/or phenotype of VSMCs for vascular remodeling in hypertension and atherosclerosis.
Pulsatile Compression of the Rostral Ventrolateral Medulla in Hypertension
Authors: Morimoto Satoshi , Sasaki Susumu , Miki Shigeyuki , Kawa Tetsuyoshi , Itoh Hiroshi , Nakata Tetsuo , Takeda Kazuo , Nakagawa Masao , Naruse Shoji , Maeda Tomoho
Published: June 2012

The rostral ventrolateral medulla (RVLM) has been known to be a major regulating center of sympathetic and cardiovascular activities. An association between essential hypertension and neurovascular compression of the RVLM has been reported in clinical observations, including magnetic resonance imaging (MRI) studies. To reconfirm this relationship, we performed MRI using a high-resolution 512×512 matrix in patients with essential and secondary hypertension and in normotensive subjects. The duration of hypertension and the degree of organ damage by hypertension were not significantly different between the two hypertension groups. Neurovascular compression of the RVLM was observed in 74% of the essential hypertension group, and the incidence of compression was significantly higher than in the secondary hypertension group (11%) or in the normotensive group (13%) (
P
<.01). These results from the clinical studies suggest that neurovascular compression of the RVLM is, at least in part, causally related to essential hypertension. Although blood pressure elevation by pulsatile compression of the RVLM in an experimental baboon model has already been reported, its underlying mechanism is not well known. Accordingly, we performed experiments to investigate whether pulsatile compression of the RVLM would increase arterial pressure and to elucidate the mechanism of the pressor response in rats. Sympathetic nerve activity, arterial pressure, heart rate, and plasma levels of epinephrine and norepinephrine were increased by pulsatile compression of the RVLM. The pressor response was abolished by intravenous treatment with hexamethonium or RVLM injection of kainic acid. In summary, the results from the MRI studies suggest that neurovascular compression of the RVLM is, at least in part, causally related to essential hypertension. This was supported by the results from experimental studies using rats indicating that pulsatile compression of the RVLM increases arterial pressure by enhancing sympathetic outflow.