bluuebunny/crossref_metadata_2025 huggingface dataset:
Angiotensin AT
1B
Receptor Mediates Calcium Signaling in Vascular Smooth Muscle Cells of AT
1A
Receptor–Deficient Mice
Authors: Zhu Zhiming , Zhang Sunny H. , Wagner Charlotte , Kurtz Armin , Maeda Nobuyo , Coffman Thomas , Arendshorst William J.
Published: June 2012

Abstract
—Our studies on angiotensin II receptor subtype 1A (AT
1A
) knockout mice define how endogenous receptors other than AT
1A
receptors stimulate changes in cytosolic calcium concentration ([Ca
2+
]
i
) in cultured aortic vascular smooth muscle cells (VSMCs). Wild-type cells have a 1.7 ratio of AT
1A
/AT
1B
receptor mRNA as determined by semiquantitative reverse transcriptase–polymerase chain reaction. Mutant cells express AT
1B
receptor mRNA but not that for the AT
1A
receptor. In wild-type cells with AT
1A
present, Ang II (10
−7
mol/L) produces a characteristic rapid peak increase in [Ca
2+
]
i
of 150 to 180 nmol/L, followed by a plateau phase characterized by a sustained 70 to 80 nmol/L increase in [Ca
2+
]
i
. An unexpected finding was that the magnitude and time-dependent pattern of [Ca
2+
]
i
changes produced by Ang II were similar in cells that lacked AT
1A
receptors but possessed AT
1B
receptors. The response in mutant cells indicates effective coupling of an Ang II receptor to one or more second messenger systems. The similarity of response patterns between cells with and without AT
1A
receptors suggests that non-AT
1A
receptors are functionally linked to similar signal transduction pathways in mutant cells. The fact that mutant and wild-type cells exhibit similar patterns of calcium mobilization and entry supports the notion that AT
1A
and non-AT
1A
receptors share common signal transduction pathways. The AT
2
receptor ligands PD-123319 and CGP-42112 do not alter Ang II effects in either VSMC type, suggesting a paucity of AT
2
receptors and/or an absence of their linkage to [Ca
2+
]
i
pathways. The nonpeptide AT
1
receptor blocker losartan antagonizes Ang II–induced [Ca
2+
]
i
increases in both cell groups, supporting mediation by native AT
1B
receptors and effective coupling of this subtype to second messenger systems leading to calcium entry and mobilization. Our results demonstrate that Ang II causes calcium signaling in AT
1A
–deficient VSMCs that is mediated by an endogenous losartan-sensitive AT
1B
receptor.
Relaxin Activates the
l
-Arginine–Nitric Oxide Pathway in Vascular Smooth Muscle Cells in Culture
Authors: Bani Daniele , Failli Paola , Bello Maria Grazia , Thiemermann Christoph , Sacchi Tatiana Bani , Bigazzi Mario , Masini Emanuela
Published: June 2012

Abstract
—The peptide hormone relaxin (RLX) has been shown to elicit a powerful vasodilatory response in several target organs. This response is mediated by the stimulation of intrinsic nitric oxide (NO) generation. The present study was designed to clarify whether RLX directly promotes the relaxation of vascular smooth muscle cells through stimulation of NO generation. Vascular smooth muscle cells from bovine aortas were incubated with RLX at concentrations ranging from 1 nmol/L to 1 μmol/L. The expression and activity of NO synthase, production of NO, and the intracellular levels of cGMP and Ca
2+
were determined. The cell morphology and signal transduction mechanisms of these bovine aortic smooth muscle cells in response to RLX were also studied. RLX stimulated the expression of immunoreactive inducible NO synthase and increased significantly and in a concentration-related fashion inducible NO synthase activity, NO generation, and intracellular cGMP levels. Concurrently, RLX significantly decreased cytosolic Ca
2+
concentrations and caused changes in cell shape and the actin cytoskeleton that were consistent with cell relaxation. The signal transduction mechanisms leading to the enhanced expression of inducible NO synthase protein and activity caused by RLX involve the activation of tyrosine kinase, phosphatidylcholine–phospholipase C, and the transcription factor nuclear factor-κB, similar to bacterial endotoxins and proinflammatory cytokines. This study suggests that RLX is an endogenous agent capable of regulating vascular tone by activation of the
l
-arginine–NO pathway in vascular smooth muscle cells.
Reduction of Cold-Induced Hypertension by Antisense Oligodeoxynucleotides to Angiotensinogen mRNA and AT
1
-Receptor mRNA in Brain and Blood
Authors: Peng Jian-Feng , Kimura Birgitta , Fregly Melvin J. , Phillips M. Ian
Published: June 2012

Abstract
—Rats exposed chronically to mild cold (5°C/41°F) develop hypertension and cardiac hypertrophy. This provides a unique model of hypertension that is environmentally induced. The blood renin-angiotensin system (RAS) has been shown to play a role in both initiating and maintaining the high blood pressure (BP) in cold-induced hypertension. The mechanism also appears to involve both the tissue and brain RAS because there is increased mRNA for angiotensinogen (AGT) and angiotensin type 1 (AT
1
) receptors in brain and peripheral tissues, an increased spontaneous drinking response, and an increased dipsogenic response to acute administration of angiotensin II (Ang II) in cold-treated rats. Antisense oligodeoxynucleotides (AS-ODN), targeted to the RAS, have been shown to reduce BP in spontaneously hypertensive rats. Therefore, we injected AS-ODN in rats with cold-induced hypertension to test whether antisense inhibition was effective in reducing this nongenetic nonsurgical hypertension. Sprague-Dawley rats were made hypertensive by cold exposure and injected intracerebroventricularly with AS-ODN to AGT mRNA (n=6) or AT
1
receptor mRNA (n=6). Systolic BP was recorded by tail cuff 24 hours later for 2 or 7 days, respectively. Systolic BP decreased significantly in response to AGT–AS-ODN (40±6 mm Hg,
P
<0.01) within 1 day after injection and to AT
1
receptor–AS-ODN (
P
<0.05) for 3 days after injection. The maximum decrease was 41±10 mm Hg. Systolic BP then gradually increased to the preinjection level. The spontaneous drinking response to cold treatment also decreased significantly (
P
<0.05) after AGT–AS-ODN or AT
1
receptor–AS-ODN intracerebroventricular injection. Intracardiac injection of AT
1
–AS-ODN (n=6) reduced systolic BP by 36±8 mm Hg (
P
<0.05) and decreased AT
1
receptor as measured by autoradiography in aorta, adrenal glands, and kidneys 24 hours after injection. These data show that AS-ODN reduces BP in cold-induced hypertension and that the hypertension involves both peripheral tissues and central RAS in addition to blood-borne RAS mechanisms.
Angiotensin II Induces Vascular Smooth Muscle Cell Replication Independent of Blood Pressure
Authors: Su Enming J. , Lombardi Donna M. , Siegal Justin , Schwartz Stephen M.
Published: June 2012

Abstract
—The purpose of this investigation was to evaluate the role of blood pressure in the proliferative response of vascular smooth muscle cells to systemic infusion of angiotensin II (Ang II). Our laboratory has previously shown that infusion of Ang II induces smooth muscle cell proliferation in rat mesenteric vessels and carotid arteries. Ang II, a strong vasopressor, raised systolic blood pressure in rats from 120 to 200 mm Hg at a dose of 435 ng · kg
−1
· min
−1
after 1 week of treatment. The question arises as to whether this development of hypertension is a primary contributor to the replicative activities observed in the arterial wall of the mesenteric arteries or the carotid arteries or whether Ang II alone, without an increase in blood pressure, is sufficient to stimulate proliferation in these vessels. In the previous studies, we found that Ang II stimulated smooth muscle cell replication in the carotid artery and in type III and type I mesenteric microvessels. This study demonstrates that although administration of hydralazine normalizes the animals’ blood pressures, it does not suppress the mitogenic effect of Ang II. Thus, it appears that Ang II has a direct effect on cell proliferation.
Connection of Smooth Muscle Cells to Elastic Lamellae in Aorta of Spontaneously Hypertensive Rats
Authors: Bezie Yvonnick , Lacolley Patrick , Laurent Stéphane , Gabella Giorgio
Published: June 2012

Abstract
—We have recently demonstrated that in large arteries of spontaneously hypertensive rats (SHR), there is no increase of stiffness despite the increase in wall thickness, a sign of mechanical adaptation of the arterial wall to the higher level of stress. Because the dense plaques of smooth muscle are a major site of anchorage between the muscle cells and extracellular matrix, we determined by electron microscopy the distribution of dense plaques and their connections to elastic lamellae in the abdominal aorta of 1-year-old SHR and control Wistar rats. In vivo echo-tracking measurement of aortic distensibility and elastic modulus indicates a reduction of arterial stiffness in SHR compared with Wistar rats when they are studied over a common range of blood pressure. The media thickness to body weight ratio was higher in SHR than in Wistar rats. In the media, the percentage of sectional area occupied by extracellular matrix was not different between Wistar rats and SHR. The average number of dense plaques per muscle cell was not different between Wistar rats and SHR. However, the percentage of cell surface occupied by dense plaques was increased in SHR, and the percentage of cell surface connected to the elastic lamellae was twice as high in SHR compared with Wistar rats (9.4±1.5% versus 3.8±1.1%). These results suggest that the elastin network plays a major role in the mechanical adaptation of the arterial wall in SHR, not through variations of its total amount but through variations of the extent of anchorage to the muscle cells.
Quantification of Alterations in Structure and Function of Elastin in the Arterial Media
Authors: Avolio Alberto , Jones Deanna , Tafazzoli-Shadpour Mohammad
Published: June 2012

Abstract
—The structure of medial elastin determines arterial function and affects wall mechanical properties. The aim of this study was to (1) characterize the structure of elastin in terms of textural features, (2) relate structural parameters to total number of cardiac cycles (TC), and (3) determine the contribution of medial elastin to lumen mechanical stress. Images of pressure-fixed aortic sections stained for elastin were obtained from specimens collected postmortem from 35 animals of different species with a wide range of age, heart rate, and TC and divided into 2 groups: TC
low
=3.69±0.38×10
8
(n=17) and TC
high
=15.8±2.38×10
8
(n=18) (
P
<0.001). A directional fractal curve was generated for each image, and image texture was characterized by directional fractal curve parameters. Elastin volume fraction and interlamellar distance were obtained by image analysis. Wall stress distribution was determined from a finite element model of the arterial wall with multiple layers simulating elastin lamellae. DFC amplitude was related to elastin volume fraction. Increased TC (TC
low
versus TC
high
) was associated with lower directional fractal curve amplitude (0.23±0.02 versus 0.14±0.02;
P
<0.001), reduced elastin volume fraction (36.5±2.6% versus 25.7±2.1%;
P
<0.01), and increased interlamellar distance (8.5±0.5 versus 11.5±1.0 μm;
P
<0.05). Loss of medial elastic function increased pressure-dependent maximal circumferential stress. Structural alterations of medial elastin, quantified by fractal parameters, are associated with cumulative effects of repeated pulsations due to the combined contribution of age and heart rate. Loss of medial functional elasticity increases luminal wall stress, increasing the possibility of endothelial damage and predisposition to atherosclerosis.
Endothelial Function and Common Carotid Artery Wall Thickening in Patients With Essential Hypertension
Authors: Ghiadoni Lorenzo , Taddei Stefano , Virdis Agostino , Sudano Isabella , Di Legge Virgilio , Meola Mario , Di Venanzio Lorenzo , Salvetti Antonio
Published: June 2012

Abstract
—Intimal-medial thickening of the carotid wall is considered an early marker of atherosclerosis. Endothelial function is impaired in the presence of various cardiovascular risk factors that are implicated in the pathogenesis of atherosclerosis. To evaluate the relationship between vascular reactivity and carotid intimal-medial thickening, in 44 (mean±SD age, 45.7±8.8 years; range, 28 to 60 years; 31 men and 13 women) patients with essential hypertension who had never been treated and whose history of increased blood pressure was no longer than 12 months, we evaluated several parameters: intimal-medial thickening of the common carotid arteries (by B-mode ultrasound); forearm vascular response (by strain-gauge plethysmography) to intrabrachial infusion of acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 μg/100 mL forearm tissue per minute), an endothelium-dependent vasodilator, or sodium nitroprusside (1, 2, and 4 μg/100 mL forearm tissue per minute), an endothelium-independent vasodilator; calculated minimal forearm vascular resistances (the ratio between mean arterial pressure and maximal forearm vasodilation induced by 13 minutes of ischemia and 1 minute of exercise); and left ventricular mass index (on echocardiography profile). Carotid wall intimal-medial thickening showed a significant (
P
<0.001) inverse correlation with vasodilation to acetylcholine (
r
=−0.58) and age (
r
=−0.40), whereas no correlation was observed with the response to sodium nitroprusside or with minimal forearm vascular resistances, left ventricular mass index, systolic and diastolic blood pressures, and plasma cholesterol and glucose levels. Moreover, vasodilation to acetylcholine showed no correlation with minimal forearm vascular resistances or left ventricular mass index. Although comparison of different vascular “districts,” such as the forearm microcirculation and carotid artery, does not allow for a conclusive interpretation, the present data indicate that in patients with essential hypertension, carotid wall thickening is associated with reduced endothelium-dependent vasodilation and suggest that endothelial dysfunction might be involved in early arterial structural alterations.
Endothelial Nitric Oxide Synthase Gene Is Positively Associated With Essential Hypertension
Authors: Miyamoto Yoshihiro , Saito Yoshihiko , Kajiyama Noboru , Yoshimura Michihiro , Shimasaki Yukio , Nakayama Masafumi , Kamitani Shigeki , Harada Masaki , Ishikawa Masahiro , Kuwahara Koichiro , Ogawa Emiko , Hamanaka Ichiro , Takahashi Nobuki , Kaneshige Toshihiko , Teraoka Hiroshi , Akamizu Takashi , Azuma Nobuyuki , Yoshimasa Yasunao , Yoshimasa Takaaki , Itoh Hiroshi , Masuda Izuru , Yasue Hirofumi , Nakao Kazuwa
Published: June 2012

Abstract
—Essential hypertension has a genetic basis. Accumulating evidence, including findings of elevation of arterial blood pressure in mice lacking the endothelial nitric oxide synthase (eNOS) gene, strongly suggests that alteration in NO metabolism is implicated in hypertension. There are, however, no reports indicating that polymorphism in the eNOS gene is associated with essential hypertension. We have identified a missense variant, Glu298Asp, in exon 7 of the eNOS gene and demonstrated that it is associated with both coronary spastic angina and myocardial infarction. To explore the genetic involvement of the eNOS gene in essential hypertension, we examined the possible association between essential hypertension and several polymorphisms including the Glu298Asp variant, variable number tandem repeats in intron 4 (eNOS4b/4a), and two polymorphisms in introns 18 and 23. We performed a large-scale study of genetic association using two independent populations from Kyoto (n=458; 240 normotensive versus 218 hypertensive subjects) and Kumamoto (n=421; 223 normotensive versus 187 hypertensive subjects), Japan. In both groups, a new coding variant, Glu298Asp, showed a strong association with essential hypertension (Kyoto: odds ratio, 2.3 [95% confidence interval, 1.4 to 3.9]; Kumamoto: odds ratio, 2.4 [95% confidence interval, 1.4 to 4.0]). The allele frequencies of 298Asp in hypertensive subjects were significantly higher than those in normotensive subjects in both groups (Kyoto: 0.103 versus 0.050,
P
<0.0017; Kumamoto: 0.120 versus 0.058,
P
<0.0013, respectively). No such disequilibrium between genotypes was significantly associated with any other polymorphisms we examined; the Glu298Asp variant was also not linked to any other polymorphisms. In conclusion, the Glu298Asp missense variant was significantly associated with essential hypertension, which suggests that it is a genetic susceptibility factor for essential hypertension.
Hepatic Denervation Chronically Elevates Arterial Pressure in Wistar-Kyoto Rats
Authors: Carlson Scott H. , Osborn John W. , Wyss J. Michael
Published: June 2012

Abstract
—Several lines of evidence suggest that peripheral osmoreceptors respond to alterations in dietary NaCl by adjusting renal sympathetic nerve activity, but the impact of this reflex on the long-term regulation of mean arterial pressure (MAP) remains unclear. The present study tested the hypothesis that denervation of peripheral osmoreceptors elevates arterial pressure and induces NaCl-sensitive hypertension in normotensive rats. Hepatic denervated and sham-operated Wistar-Kyoto rats were instrumented with telemetry probes for continuous monitoring of MAP and heart rate. After 1 week on a basal (0.6%) NaCl diet, the rats were fed a high (8%) NaCl diet for 2 weeks. On the basal NaCl diet, MAP in hepatic denervated rats was 15±1 mm Hg higher than in sham-operated rats. The high NaCl diet did not significantly increase MAP above baseline levels in either denervated or sham-operated rats, but the amplitude of the 24-hour rhythm of arterial pressure increased significantly more in the denervated than in the sham-operated rats. In a second experiment, two similar groups of rats were fed a very low (0.05%) NaCl diet. Mean arterial pressure of the denervated group was significantly higher than that of the sham-operated rats on either the basal or the very low NaCl diet, but the very low NaCl diet did not affect arterial pressure in either group. These results suggest that in the rat, although hepatic osmoreceptors contribute to long-term arterial pressure regulation, they contribute much less to dietary NaCl–induced changes in arterial pressure.
Immunolocalization of Subtype 2 Angiotensin II (AT
2
) Receptor Protein in Rat Heart
Authors: Wang Zhi-Qin , Moore Allan F. , Ozono Ryoji , Siragy Helmy M. , Carey Robert M.
Published: June 2012

Abstract
—Angiotensin II exerts its effects on cardiovascular function and water and sodium homeostasis by interacting with plasma membrane receptors on target organs. The existence of subtype 2 angiotensin II (AT
2
) receptors in the rat heart has been demonstrated by ligand binding and reverse transcription–polymerase chain reaction. In the present study, the expression and localization of AT
2
receptor protein in the rat heart was investigated using an antipeptide polyclonal antibody against the native rat AT
2
receptor by light microscopic immunocytochemistry and Western blot analysis. In frozen tissue sections, positive immunostaining was observed in the myocardium and coronary vessels throughout the ventricle and atrium of neonatal and young rat hearts. Coronary vessels of the neonatal heart were more intensely stained compared with the surrounding myocardium. Positive immunoreactivity in the coronary vessels of young rats was localized to vascular endothelium but not in the smooth muscle cells. Preadsorption controls were all negative. Western blot analysis showed that the AT
2
receptor protein (≈44 kDa) was detectable from the AT
2
receptor–transfected COS-7 cells and neonatal rat cardiac myocytes but not from fibroblasts or young rat aortic smooth muscle cells. The neonatal rat heart expressed significantly more AT
2
receptors than young rat heart. These data provide the first direct evidence for the expression and localization of AT
2
receptor protein in the rat heart.
Contribution of Nitric Oxide to Reactive Hyperemia
Authors: Dakak Nader , Husain Syed , Mulcahy David , Andrews Neil P. , Panza Julio A. , Waclawiw Myron , Schenke William , Quyyumi Arshed A.
Published: June 2012

Abstract
—Our objectives were to (1) test the hypothesis that nitric oxide (NO) contributes to peak reactive hyperemia (RH) in the human peripheral vasculature, (2) examine the impact of atherosclerosis and its risk factors on RH, and (3) investigate whether
l
-arginine will improve RH in patients with endothelial dysfunction. The endothelium contributes to shear stress–mediated vasomotion by releasing a variety of dilating factors, including NO, but the contribution of NO to peak RH in patients with and without endothelial dysfunction is unknown. Endothelium-dependent and endothelium-independent function was assessed with intrafemoral arterial acetylcholine (ACh) and sodium nitroprusside. RH was produced by occlusion of blood flow to the leg for 3 minutes. The study was repeated after
N
G
-monomethyl-
l
-arginine (L-NMMA) in 44 subjects and
l
-arginine in 9 patients with atherosclerosis. There were 15 normal control subjects without risk factors for atherosclerosis and 29 patients with risk factors or angiographic atherosclerosis. Microvascular vasodilation in response to ACh, but not to sodium nitroprusside, was lower in the patients with risk factors or atherosclerosis compared with normal control subjects,
P
=0.048, and the inhibition of ACh-induced microvascular dilation by L-NMMA was also greater in normal control subjects (
P
=0.045). Similarly, RH, including the peak response, was inhibited by L-NMMA in normal control subjects (
P
=0.0011) but not in patients with risk factors or atherosclerosis, suggesting that the contribution of NO to both ACh-induced dilation and RH was diminished in patients with risk factors or atherosclerosis.
l
-Arginine did not affect vasodilation in response to ACh, sodium nitroprusside, or RH. We concluded that (1) NO contributes to all phases of RH in the normal human peripheral vasculature, (2) patients with atherosclerosis or its risks have abnormal NO bioactivity in response to pharmacological and physiological stimulation, and (3)
l
-arginine does not improve RH in atherosclerosis. Reduced physiological vasodilation in atherosclerosis may contribute to or exacerbate hypertension and ischemia.
Conditioned Medium From HepG2 Cells Transfected With Human Apolipoprotein(a) Gene Stimulates Growth of Human Vascular Smooth Muscle Cells
Authors: Morishita Ryuichi , Yamada Shingo , Higaki Jitsuo , Tomita Naruya , Kida Iwao , Aoki Motokuni , Moriguchi Atsushi , Hayashi Shin-ichiro , Sakurabayashi Ikunosuke , Kaneda Yasufumi , Ogihara Toshio
Published: June 2012

Abstract
—Lipoprotein(a) [Lp(a)] is well known to stimulate growth of vascular smooth muscle cells (VSMCs), resulting in atherosclerosis. Its mechanism is postulated to be decreased in active transforming growth factor (TGF)-β. However, the exact mechanisms and cellular processing from apolipoprotein(a) [apo(a)] to Lp(a) have not yet been clarified because no cultured cells producing apo(a) are available. Therefore, it is necessary to establish apo(a)-producing cells to study the role of apo(a). We evaluated the effects of overexpression of human apo(a) gene on human aortic VSMC growth. First, we tested whether transfection of apo(a) gene into human hepatoma cells, HepG2 cells, producing human apoB resulted in the formation of Lp(a). Transfection of apo(a) gene into HepG2 cells resulted in detectable levels of Lp(a) in the medium, as assessed by ELISA and Western blot, whereas no Lp(a) was detected in the medium of HepG2 cells transfected with control vector and untransfected HepG2 cells. Expression of apo(a) mRNA was also confirmed by reverse transcription–polymerase chain reaction. In contrast, Western blotting showed a single band detected by specific anti-apo(a) antibody, but not anti-apoB antibody, in the medium of apo(a)-transfected VSMCs. These results demonstrate that Lp(a) can be formed from apo(a) on HepG2 cells, whereas transfection of apo(a) gene into VSMCs resulted in the production of apo(a) alone but not Lp(a). Next, we examined the biological effects of overexpression of apo(a) gene on growth of VSMCs and endothelial cells. Incubation of cultured medium of HepG2 cells transfected with apo(a) gene with human VSMCs or endothelial cells resulted in a significant increase in cell number compared with the conditioned medium of HepG2 cells transfected with control vector. In contrast, transfection of apo(a) gene directly into VSMCs caused no significant effect on VSMC growth. Therefore, we measured TGF-β concentration in the conditioned medium of VSMCs. However, using ELISA, only latent but not active TGF-β was detected in the medium of VSMCs. Moreover, addition of neutralizing anti–TGF-β antibody did not alter VSMC growth. These results suggest that Lp(a) could stimulate growth of VSMCs via the independent mechanisms from the inhibition of TGF-β activation. Overall, these data demonstrate that overexpression of apo(a) gene in cells producing apoB results in formation of Lp(a), resulting in a mitogenic action on human endothelial cells and VSMCs. These results provide new information to understand the mechanisms of the mitogenic action of Lp(a) and suggest the role of Lp(a) in the pathogenesis of atherosclerosis.
Insulin and Insulin-like Growth Factor-I Cause Coronary Vasorelaxation In Vitro
Authors: Hasdai David , Rizza Robert A. , Holmes David R. , Richardson Darcy M. , Cohen Pinchas , Lerman Amir
Published: June 2012

Abstract
—Insulin and insulin-like growth factor-I (IGF-I) may play a role in the modulation of coronary artery tone, yet there are few data regarding their vasoactive effects on the coronary vascular bed. We evaluated the vasorelaxation effects of insulin and IGF-I on porcine coronary epicardial vessels in vitro and elucidated possible mechanisms. Porcine epicardial arteries were contracted with 10
−7
mol/L endothelin-1 and relaxed with cumulative concentrations of either insulin or IGF-I (10
−12
to 10
−7
mol/L). The above experiments were repeated in vessels without endothelium. Vessels were also incubated with the nitric oxide synthase inhibitor
N
G
-monomethyl-
l
-arginine (L-NMMA; 10
−4
mol/L) with and without 10
−3.5
mol/L
l
-arginine, the potassium channel blocker tetraethylammonium (TEA; 10
−2
mol/L), and the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-α]quinoxalin-1-one (ODQ; 10
−5.5
mol/L); vessels were then contracted with endothelin-1 and relaxed with insulin or IGF-I. Insulin and IGF-I were also added after contraction with 60 mmol/L KCl. Insulin and IGF-I caused a similar decrease in coronary epicardial tension after contraction with endothelin-1 (relaxation of 28±4% [n=7] and 25±3% [n=8] with insulin and IGF-I, respectively;
P
<0.0001 for both peptides). Removal of the endothelium did not affect these responses. Incubation with L-NMMA, but not ODQ, attenuated the vasorelaxation response to insulin and IGF in vessels without endothelium.
l
-Arginine did not reverse this effect of L-NMMA. KCl and TEA attenuated the vasorelaxation effect of both insulin and IGF-I. Thus, both insulin and IGF-I caused non–endothelium-dependent coronary vasorelaxation in vitro, probably through a mechanism involving the activation of potassium channels. These findings suggest that insulin and IGF-I participate in the regulation of coronary vasomotor tone.
Reference Values for 24-Hour Ambulatory Blood Pressure Monitoring Based on a Prognostic Criterion
Authors: Ohkubo Takayoshi , Imai Yutaka , Tsuji Ichiro , Nagai Kenichi , Ito Sadayoshi , Satoh Hiroshi , Hisamichi Shigeru
Published: June 2012

Abstract
—Although reference values for ambulatory blood pressure (ABP) monitoring have been investigated in several population studies, these values were derived from cross-sectional observations and were based merely on the statistical distribution of blood pressure values. Therefore, we conducted a prospective cohort study to identify reference values for 24-hour ABP in relation to prognosis. We obtained measurements of 24-hour ABP for 1542 subjects (565 men) aged 40 years and over in a general population of a rural Japanese community and then followed-up their survival status. There were 117 deaths during the follow-up period (mean, 6.2 years). The association between baseline 24-hour ABP values and mortality, examined by the Cox proportional hazards regression model adjusted for possible confounding factors, showed a better fit with a second-degree equation than with a first-degree equation. On the basis of the results of this analysis, we identified the following reference values as the optimal blood pressure ranges that predict the best prognosis: 120 to 133 mm Hg for systolic blood pressure and 65 to 78 mm Hg for diastolic blood pressure. 24-Hour ABP values >134/79 mm Hg and <119/64 mm Hg were related to increased risks for cardiovascular and noncardiovascular mortality, respectively. This is the first report to propose reference values for 24-hour ABP based on a prognostic criterion.
Reduced Heart Rate Variability and New-Onset Hypertension
Authors: Singh Jagmeet P. , Larson Martin G. , Tsuji Hisako , Evans Jane C. , O’Donnell Christopher J. , Levy Daniel
Published: June 2012

Abstract
—Heart rate variability (HRV) is a useful noninvasive tool to assess cardiac autonomic function. The purpose of this study was to (1) compare measures of HRV between hypertensive and normotensive subjects and (2) examine the role of HRV as a predictor of new-onset hypertension. The first 2 hours of ambulatory ECG recordings obtained from 931 men and 1111 women attending a routine examination at the Framingham Heart Study were processed for HRV. Three time-domain and 5 frequency-domain variables were studied: standard deviation of normal RR intervals (SDNN), percentage of differences between adjacent normal RR intervals exceeding 50 milliseconds, square root of the mean of squared differences between adjacent normal RR intervals, total power (0.01 to 0.40 Hz), high frequency power (HF, 0.15 to 0.40 Hz), low frequency power (LF, 0.04 to 0.15 Hz), very low frequency power (0.01 to 0.04 Hz), and LF/HF ratio. On cross-sectional analysis, HRV was significantly lower in hypertensive men and women. Among 633 men and 801 women who were normotensive at baseline (systolic blood pressure <140 mm Hg and diastolic blood pressure <90 mm Hg and not receiving antihypertensive treatment), 119 men and 125 women were newly hypertensive at follow-up 4 years later. After adjustment for factors associated with hypertension, multiple logistic regression analysis revealed that LF was associated with incident hypertension in men (odds ratio per SD decrement [OR], 1.38; 95% confidence interval [CI], 1.04 to 1.83) but not in women (OR, 1.12; 95% CI, 0.86 to 1.46). SDNN, HF, and LF/HF were not associated with hypertension in either sex. HRV is reduced in men and women with systemic hypertension. Among normotensive men, lower HRV was associated with greater risk for developing hypertension. These findings are consistent with the hypothesis that autonomic dysregulation is present in the early stage of hypertension.
Augmented Cardiopulmonary and Integrative Sympathetic Baroreflexes but Attenuated Peripheral Vasoconstriction With Age
Authors: Davy Kevin P. , Seals Douglas R. , Tanaka Hirofumi
Published: June 2012

Abstract
—Based on observations of smaller increases in limb vascular resistance during acute incremental hypovolemia in older adults, cardiopulmonary and integrative (combined cardiopulmonary and arterial) baroreflex control of sympatho-circulatory function is thought to be impaired with aging in humans. We tested this hypothesis directly by making intraneural measurements of skeletal muscle sympathetic nerve activity (MSNA; peroneal microneurography) in groups of young (23±1 years; n=11) and older (64±1 years; n=12) healthy adult men during progressive hypovolemia produced by graded (−5 to −40 mm Hg) lower body negative pressure (LBNP). Baseline levels of MSNA and arterial blood pressure were higher and heart rate was lower in the older subjects (
P
<0.05). Lower levels of LBNP (−5 to −20 mm Hg) did not affect arterial blood pressure or heart rate in either group; systolic and pulse pressures declined during higher levels of LBNP (−30 and −40 mm Hg) but only in the young subjects (
P
<0.05). Graded LBNP evoked progressive, linear reductions in peripheral venous pressure (PVP) and increases in MSNA, plasma norepinephrine concentration (PNE), and forearm vascular resistance (FVR) in both groups (all
P
<0.05). ΔMSNA/ΔPVP was ≈150% greater in the older versus young men during both lower and higher levels of hypovolemia (
P
<0.01); however, ΔFVR/ΔPVP was ≈50% smaller in the older men (
P
<0.05). There was no difference in the MSNA-PNE relation with age, but ΔFVR/ΔMSNA was ≈65% to 70% smaller in the older subjects (
P
<0.05). Our findings indicate that cardiopulmonary and integrative baroreflex control of central sympathetic outflow during hypovolemia is augmented, not impaired, with age in healthy humans. However, the reflex-mediated increases in limb vascular resistance during hypovolemia are smaller in older adults because of attenuated vasoconstrictor responsiveness to sympathetic stimulation.
Nitric Oxide Synthase Expression in Endothelial Cells Exposed to Mechanical Forces
Authors: Ziegler Thierry , Silacci Paolo , Harrison Vanessa J. , Hayoz Daniel
Published: June 2012

Abstract
—Nitric oxide (NO) has been demonstrated to play a central role in vascular biology and pathobiology. The expression of endothelial NO synthase (eNOS) is regulated in part by blood flow–induced mechanical factors. The purpose of this study was to evaluate how the expression of eNOS mRNA correlates with the activation of its promoter in both arterial and venous endothelial cells (ECs) exposed to mechanical forces, ie, shear stress and cyclic circumferential stretch. Bovine aortic ECs (BAECs) and EA hy.926, a cell line derived from human umbilical vein ECs, were grown on the inside of elastic tubes and subjected to combinations of pressure, pulsatile shear stress, and cyclic circumferential stretch for 24 hours. Two patterns of shear stress were used: unidirectional (mean of 6, ranging from 3 to 9 dyne/cm
2
) and oscillatory (mean of 0.3, ranging from −3 to +3 dyne/cm
2
). The expression of eNOS mRNA was quantified by Northern blot analysis. Activation of the promoter was assessed by luciferase activity after the cells were transiently transfected before the flow experiments with a plasmid construct containing the fully functional eNOS promoter coupled to a luciferase reporter gene. Expression of eNOS mRNA was increased and promoter activity was enhanced by unidirectional shear stress compared with static control. Oscillatory shear slightly upregulated eNOS mRNA in BAECs, whereas it downregulated eNOS mRNA in EA hy.926. In both BAECs and EA hy.926, there was a good correlation between the increase in eNOS mRNA expression and promoter activation by unidirectional shear stress. In contrast, in both BAECs and EA hy.926 cells exposed to shear stress, cyclic stretch did not change eNOS mRNA expression, but the activation of eNOS promoter was significantly lower. Moreover, when ECs were exposed to oscillatory shear stress, there was a dramatic activation of the eNOS promoter. These results demonstrate that unidirectional shear stress increases eNOS mRNA expression via a transcriptional mechanism. However, oscillatory shear stress and cyclic stretch appear to control eNOS expression through posttranscriptional regulatory events.
Smooth Muscle Tone and Arterial Wall Viscosity
Authors: Boutouyrie Pierre , Boumaza Saliha , Challande Pascal , Lacolley Patrick , Laurent Stéphane
Published: June 2012

Abstract
—The relationships between steady and pulsatile pressures, smooth muscle tone, and arterial viscoelastic behavior remain a matter of controversy. We previously showed that arterial wall viscosity (AWV) was 3-fold lower in vivo than in vitro and suggested that in vivo active mechanisms could minimize intrinsic AWV to improve the efficiency of heart-vessel coupling energy balance. The aim of the present study was to determine the role of smooth muscle tone on AWV, under various levels of steady and pulsatile pressures, both in vivo and in vitro. AWV of rat abdominal aorta was studied first in vivo after bolus injections of phenylephrine (PE) or sodium nitroprusside (SNP), then in vitro in response to PE or SNP. In vitro, arterial segments were submitted first to steady pressure (0 to 200 mm Hg) by increments of 20 mm Hg, then to increasing levels of pulse pressure (20 to 50 mm Hg) at various mean arterial pressures (75 to 150 mm Hg). AWV was quantified as the area of the pressure/diameter relationship hysteresis, issued from the simultaneous measurements of pressure (Millar micromanometer) and diameter (NIUS echotracking device). In vivo, AWV increased after PE and decreased after SNP, in parallel with pressure changes. In vitro, AWV was not significantly influenced by PE and SNP. After both PE and SNP, AWV increased with pulse pressure but was not influenced by mean arterial pressure. At any given pulse pressure, AWV was higher in vitro than in vivo. The relation between AWV and pulse pressure was significantly steeper in vitro than in vivo. These results show that AWV is strongly influenced by steady and pulsatile mechanical load but not by smooth muscle tone, both in vivo and in vitro. Factors other than sustained smooth muscle activation should be explored to explain the minimization of AWV in vivo compared with intrinsic in vitro values.
Pathways for Angiotensin II Generation in Intact Human Tissue
Authors: Hollenberg Norman K. , Fisher Naomi D. L. , Price Deborah A.
Published: June 2012

Abstract
—Multiple lines of evidence have suggested that alternative pathways to the angiotensin-converting enzyme (ACE) exists for angiotensin II (Ang II) generation in the heart, large arteries, and the kidney. In vitro studies in intact tissues, homogenates, or membrane isolates from the heart and large arteries have repeatedly demonstrated such pathways, but the issue remains unresolved because the approaches used have not made it possible to extrapolate from the in vitro to the in vivo situation. For our in vivo model, we studied young and healthy human volunteers, for the most part white and male; when these subjects achieved balance on a low salt diet to activate the renin system, the response of renal perfusion to pharmacological interruption of the renin system was studied. With this approach, we studied the renal vasodilator response to 3 ACE inhibitors, 2 renin inhibitors, and 2 Ang II antagonists at the top of their respective dose-response relationships. When these studies were initiated, our premise was that a kinin-dependent mechanism contributed to the renal hemodynamic response to ACE inhibition; therefore, the renal vasodilator response to ACE inhibition would exceed the alternatives. To our surprise, both renin inhibitors and both Ang II antagonists that were studied induced a renal vasodilator response of 140 to 150 mL/min/1.73 m
2
, ≈50% larger than the maximal renal hemodynamic response to ACE inhibition, which was 90 to 100 mL/min/1.73 m
2
. In light of the data from in vitro systems, our findings indicate that in the intact human kidney, virtually all Ang II generation is renin-dependent but at least 40% of Ang I is converted to Ang II by pathways other than ACE, presumably a chymase, although other enzyme pathways exist. Preliminary data indicate that the non-ACE pathway may be substantially larger in disease states such as diabetes mellitus. One implication of the studies is that at the tissue level, Ang II antagonists have much greater potential for blocking the renin-angiotensin system than does ACE inhibition—with implications for therapeutics.
Angiotensinogen Genotype, Sodium Reduction, Weight Loss, and Prevention of Hypertension
Authors: Hunt Steven C. , Cook Nancy R. , Oberman Albert , Cutler Jeffrey A. , Hennekens Charles H. , Allender P. Scott , Walker W. Gordon , Whelton Paul K. , Williams Roger R.
Published: June 2012

Abstract
—The angiotensinogen gene has been linked to essential hypertension and increased blood pressure. A functional variant believed to be responsible for hypertension susceptibility occurs at position −6 in the promoter region of the gene in which an A for G base pair substitution is associated with higher angiotensinogen levels. To test whether an allele within the angiotensinogen gene is related to subsequent incidence of hypertension and blood pressure response to sustained sodium reduction, 1509 white male and female subjects participating in phase II of the Trials of Hypertension Prevention were genotyped at the angiotensinogen locus. Participants had diastolic blood pressures between 83 and 89 mm Hg and were randomized in a 2×2 factorial design to sodium reduction, weight loss, combined intervention, or usual care groups. Persons in the usual care group with the AA genotype at nucleotide position −6 had a higher 3-year incidence rate of hypertension (44.6%) compared with those with the GG genotype (31.5%), with a relative risk of 1.4 (95% confidence interval [0.87, 2.34], test for trend across all 3 genotypes,
P
=0.10). In contrast, the incidence of hypertension was significantly lower after sodium reduction for persons with the AA genotype (relative risk=0.57 [0.34, 0.98] versus usual care) but not for persons with the GG genotype (relative risk=1.2 [0.79, 1.81], test for trend
P
=0.02). Decreases of diastolic blood pressure at 36 months in the sodium reduction group versus usual care showed a significant trend across all 3 genotypes (
P
=0.01), with greater net blood pressure reduction in those with the AA genotype (−2.2 mm Hg) than those with the GG genotype (+1.1 mm Hg). A similar trend across the 3 genotypes for net systolic blood pressure reduction (−2.7 for AA versus −0.2 mm Hg for GG) was not significant (
P
=0.17). Trends across genotypes for the effects of weight loss on hypertension incidence and decreases in blood pressure were similar to those for sodium reduction. We conclude that the angiotensinogen genotype may affect blood pressure response to sodium or weight reduction and the development of hypertension.
A Population-Based Study on Blood Pressure and Brain Atrophy in 85-Year-Olds
Authors: Skoog Ingmar , Andreasson Lars-Arne , Landahl Sten , Lernfelt Bodil
Published: June 2012

Abstract
—In the general population, mean systolic and diastolic blood pressure increases up to age 75 years but decreases thereafter. The brain has a role in blood pressure regulation; it is not clear whether the cerebral changes that occur with aging contribute to the decline in blood pressure in the very elderly. We examined a population-based sample of 484 85-year-old persons (344 nondemented and 140 demented, 61 with Alzheimer’s disease, 65 with vascular dementia, and 14 with other types of dementia) with a neuropsychiatric examination and blood pressure measurements. Dementia was diagnosed according to the criteria proposed in the
Diagnostic and Statistical Manual of Mental Disorders, edition 3, revised
. Brain atrophy was measured by CT of the brain. In the nondemented group, frontal (
r
=−0.18,
P
=0.037) and parietal (
r
=−0.23,
P
=0.008) cortical atrophy and bifrontal ratio (
r
=−0.20,
P
=0.013) were associated with lower systolic blood pressure, and frontal (
r
=−0.23,
P
=0.010) and parietal (
r
=−0.24,
P
=0.008) cortical atrophy and bifrontal ratio (
r
=−0.23,
P
=0.006) with lower diastolic blood pressure. Systolic blood pressure was lower in subjects with Alzheimer’s disease and vascular dementia, and diastolic blood pressure was lower in those with vascular dementia compared with the nondemented. Systolic (
r
=−0.27,
P
<0.0001) and diastolic (
r
=−0.10,
P
=0.020) blood pressure was negatively correlated to dementia severity. In the demented subjects, frontal cortical atrophy was correlated to lower diastolic blood pressure (
r
=−0.21,
P
=0.043). Our findings suggest that age-related changes in brain structure may contribute to the decrease in blood pressure in the very elderly and that low blood pressure in dementia disorders is mainly a secondary phenomenon.
Renovascular Hypertension in Bradykinin B
2
-Receptor Knockout Mice
Authors: Madeddu Paolo , Milia Anna Franca , Salis Maria Bonaria , Gaspa Leonardo , Gross Wolkmar , Lippoldt Andrea , Emanueli Costanza
Published: June 2012

Abstract
—We evaluated whether kinins exert a protective action against the development of two-kidney, one clip (2K1C) hypertension, a model characterized by an activated renin-angiotensin system in the ischemic kidney and increased expression of the bradykinin (BK) B
2
receptor in the contralateral kidney. BK B
2
-receptor knockout (B
2
−/−
), wild-type (B
2
+/+
), and heterozygous (B
2
+/−
) mice underwent clipping of the left renal artery, with the other kidney remaining untouched. Basal systolic blood pressure (SBP, via tail-cuff plethysmography) was higher in B
2
−/−
mice than in B
2
+/−
or B
2
+/+
mice (121±2 versus 113±2 and 109±1 mm Hg;
P
<0.05 for both comparisons). SBP did not change from basal values after sham operation, but it increased in mice that underwent clipping. The increase in SBP was greater in 2K1C B
2
−/−
mice than in B
2
+/−
or B
2
+/+
mice (28±2 versus 14±2 and 14±2 mm Hg, respectively, at 2 weeks;
P
<0.05 for both comparisons). Blockade of the BK B
2
receptor by Icatibant enhanced the pressure response to clipping in B
2
+/+
mice (29±2 mm Hg at 2 weeks). Intra-arterial mean blood pressure (MBP) was higher in 2K1C than in respective sham-operated mice, with the MBP difference being higher in B
2
−/−
mice (32 and 38 mm Hg, at 2 and 4 weeks, respectively), and higher in B
2
+/+
mice given Icatibant (30 and 32 mm Hg) than in B
2
+/+
mice without Icatibant (17 and 18 mm Hg). At 4 weeks, acute injection of an angiotensin type 1 receptor antagonist normalized the MBP of 2K1C hypertensive mice. A tachycardic response was observed 1 week after clipping in B
2
−/−
and B
2
+/−
mice, but this effect was delayed in B
2
+/+
mice. However, the HR response to clipping in B
2
+/+
mice was enhanced by Icatibant. Within each strain, heart weight to body weight ratio was greater in 2K1C hypertensive mice than in sham-operated control animals (B
2
−/−
: 5.7±0.1 versus 5.2±0.1; B
2
+/+
: 5.1±0.1 versus 4.5±0.1;
P
<0.01 for both comparisons). The clipped kidney weight to nonclipped kidney weight ratio was consistently reduced in mice with 2K1C hypertension. Our results indicate that kinins acting on the BK B
2
receptor exert a protective action against excessive blood pressure elevation during early phases of 2K1C hypertension.
Human Spiral Artery Renin-Angiotensin System
Authors: Morgan Terry , Craven Catherine , Ward Kenneth
Published: June 2012

Abstract
—Pregnancy induces uterine spiral arteries to remodel into dilated uteroplacental vessels by an unknown mechanism called “physiological change.” In women who develop preeclampsia, however, many spiral arteries remain unchanged or develop medial hyperplasia and atherosis. We recently demonstrated that angiotensinogen is expressed by remodeling spiral arteries in first-trimester decidua. We hypothesize that a local spiral artery renin-angiotensin system mediates pregnancy-induced remodeling of these vessels. In this study we tested for expression of renin, angiotensin-converting enzyme, and angiotensin II type 1 receptor genes in the first-trimester uterus using reverse-transcription polymerase chain reaction. Expression was localized by in situ hybridization and immunohistochemistry. Renin, angiotensin-converting enzyme, and the angiotensin II type 1 receptor are all expressed in and around remodeling spiral arteries. These observations suggest that a local spiral artery renin-angiotensin system may play a role in pregnancy-induced remodeling of these vessels. Elevated angiotensinogen expression in women homozygous for the A(−6) variant in the angiotensinogen promoter may promote abnormal remodeling, whereas relatively lower levels in women homozygous for G(−6) may permit enough normal remodeling to protect these women from preeclampsia.