bluuebunny/crossref_metadata_2025 huggingface dataset:
Neutral Endopeptidase Regulates C-Type Natriuretic Peptide Metabolism But Does Not Potentiate Its Bioactivity In Vivo
Authors: Brandt Roland R. , Mattingly Michael T. , Clavell Alfredo L. , Barclay Paul L. , Burnett John C.
Published: June 2012

Abstract
C-type natriuretic peptide (CNP) is a newly described 22–amino acid peptide of endothelial and renal cell origin with selective cardiovascular actions. Recent in vitro studies have reported that CNP is the most susceptible of all natriuretic peptides to enzymatic degradation by neutral endopeptidase 24.11 (NEP). The present study was undertaken to define the role of NEP in total and regional CNP metabolism and the modulatory actions of NEP inhibition on the biological actions of CNP. CNP (10 ng · kg
−1
· min
−1
) followed by candoxatrilat (240 μg · kg
−1
bolus and 8 μg · kg
−1
· min
−1
), a potent and selective NEP inhibitor, was administered intravenously to a group of anesthetized mongrel dogs (group 1) to permit calculation of total metabolic clearance rate (MCR); results were compared with those in a group receiving vehicle infusion followed by candoxatrilat (group 2; both groups, n=7). NEP inhibition increased circulating CNP achieved by exogenous infusion and reduced total MCR in group 1. The regional CNP MCRs increased after CNP administration. While the pulmonary MCR did not change during concomitant candoxatrilat infusion, renal MCR was suppressed. Hemodynamic changes were not different between groups. A mild natriuretic and diuretic effect in association with an increase in circulating and urinary ANP levels was not different between groups. Urinary CNP excretion did not change with CNP infusion but markedly increased after NEP inhibition. We conclude that (1) circulating CNP achieved by exogenous CNP infusion is regulated by NEP in vivo, (2) regional MCRs are heterogeneous with NEP inhibition, (3) NEP inhibition does not potentiate acute cardiovascular actions of CNP, and (4) a mild natriuretic and diuretic effect observed with CNP and NEP inhibition may be ANP dependent.
Myogenic Tone Attenuates Pressure-Induced Gene Expression in Isolated Small Arteries
Authors: Allen Steven P. , Wade Suzanne S. , Prewitt Russell L.
Published: June 2012

Abstract
This study was designed to determine whether pressure-induced expression of early response genes in the arterial wall is dependent on an increase in cell stretch or an increase in wall stress. Mesenteric arteries (245 to 385 μm in diameter) were isolated from Wistar rats and subjected to static pressures of either 90 mm Hg (control), 140 mm Hg, or 165 mm Hg for a period of 3 hours. Arteries developed a range of myogenic tone such that wall stresses in the 140 and 165 mm Hg arteries (1.60 to 4.44×10
6
dynes/cm
2
) were equivalent in some cases to those of controls (1.76 to 2.63×10
6
dynes/cm
2
). Vessels subjected to 140 or 165 mm Hg intraluminal pressure had diameters ranging from 74% to 104% of their relaxed diameter at 90 mm Hg, whereas control vessel diameters ranged from 88% to 100%. At the end of each experiment, vessels were fixed in 10% formalin, embedded in paraffin, and sectioned for in situ hybridization. Wall stress significantly correlated with c-
myc
mRNA and 18S rRNA expression. Gene expression did not correlate with vessel diameter, expressed as a percentage of the relaxed diameter at 90 mm Hg, ie, cell stretch. The expression of β-actin mRNA did not differ between vessels and showed no correlation with wall stress, suggesting that the induction of c-
myc
mRNA and 18S rRNA was part of a specific response. These findings show that in an isolated artery, a pressure stimulus can be perceived as an increase in wall stress, independently of cell stretch. Therefore, wall stress may be the signaling parameter in hypertension where arteries are tonically constricted. The inhibition of gene expression by myogenic constriction may explain why hypertrophy takes place in large arteries during hypertension but not in arterioles where increased tone reduces wall stress.
Flow-Mediated Vasodilatation Is Enhanced in Normal Pregnancy but Reduced in Preeclampsia
Authors: Cockell Anna P. , Poston Lucilla
Published: June 2012

Abstract
Endothelium-derived nitric oxide is proposed to play an important role in the lowering of peripheral vascular resistance in normal pregnancy. In women with preeclampsia, the function of the endothelium is compromised, and it is suggested that reduced nitric oxide synthesis may contribute to the elevation of blood pressure and activation of coagulation pathways. In this study, we have compared responses to increments of intraluminal flow, considered to be a physiological stimulus to nitric oxide release, in arteries from normotensive nonpregnant and pregnant women and women with preeclampsia. Small subcutaneous arteries from normotensive pregnant women showed substantial flow-induced relaxation, which was attenuated by the nitric oxide synthase inhibitor
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) (mean relaxation, 48.3±8.0% [absence of L-NAME] versus 19.2±10.6% [presence of L-NAME]), whereas those from nonpregnant women and women with preeclampsia demonstrated modest constriction (mean constriction, 10.1±7.3% and 1.2±7.2%, respectively). Shear stress, the frictional force that is the stimulus for flow responses, was calculated from parameters of flow, viscosity, and artery diameter. Arteries from pregnant women showed greater relaxation to shear than those from nonpregnant women or those with preeclampsia. We conclude that flow-induced shear stress is a potent stimulus to vasodilatation in arteries from pregnant women and that this mechanism may lead to a fall in peripheral vascular resistance in normal pregnancy. Failure of this flow-induced dilatation may contribute to the gestational hypertension of preeclampsia.
Birth Weight, Growth, and Blood Pressure
Authors: Uiterwaal Cuno S. P. M. , Anthony Sabine , Launer Lenore J. , Witteman Jacqueline C. M. , Trouwborst Ada M. W. , Hofman Albert , Grobbee Diederick E.
Published: June 2012

Abstract
Associations between birth weight and blood pressure have been found in children and adults. In this longitudinal study, the objective was to assess the relation between birth weight and blood pressure level and the change in blood pressure from childhood and young adolescence into adulthood. A cohort of 483 children from a middle-class community in the town of Zoetermeer in the Netherlands had annual measurements of blood pressure during an average follow-up period of 14 years. For 330 of these participants, initially aged 5 through 21 years, birth weight data were collected, which were related to blood pressure level and blood pressure change. An inverse association between birth weight and systolic blood pressure was found, with adjustment for current body height and weight, sex, and use of alcohol, cigarettes, and oral contraceptives. This inverse association was found for the total follow-up in 5- to 37- year-olds (regression coefficient: −2.4 mm Hg/kg; 95% confidence interval: −3.9 to −1.0, as well as in most individual age groups: 5 through 9 years (−0.6 mm Hg/kg, −3.2 to 2.0); 10 through 14 years (−2.5 mm Hg/kg, −4.7 to −0.4); 15 through 19 years (−3.1 mm Hg/kg, −4.9 to −1.2); 20 through 24 years (−2.7 mm Hg/kg, −4.6 to −0.9); 25 through 29 years (−2.0 mm Hg/kg, −3.9 to −0.01); and 30 through 37 years (−1.9 mm Hg/kg, −4.6 to 0.7). For diastolic blood pressure, there appeared to be an inverse association with birth weight in the age group of 30 through 37 years, both unadjusted (−2.0 mm Hg/kg, −4.6 to 0.5) and adjusted for risk factors other than sex (−2.3 mm Hg/kg, −4.7 to 0.1), although these findings were of borderline statistical significance. The results were independent of gestational age and were similar in the group of subjects with low birth weight but normal gestational age (−2.7 mm Hg/kg, −4.3 to −1.0). In relation to systolic blood pressure, birth weight showed a significant interaction with body mass index (regression coefficient, 0.02; SE=0.01;
P
=.05). There was no relation between birth weight and change in systolic or diastolic blood pressure with age. Our longitudinal study shows that birth weight is consistently inversely associated with systolic blood pressure level from childhood to young adulthood and with diastolic blood pressure in young adulthood. Birth weight is not related to change of blood pressure with increasing age. Low birth weight in combination with high current body mass index seems to be of particular importance in the development of high blood pressure.
Early Induction of Angiotensin I–Converting Enzyme in Rat Carotid Artery After Balloon Injury
Authors: Fernandez-Alfonso Maria S. , Martorana Piero A. , Licka Ivo , van Even Paul , Trobisch Dieter , Schölkens Bernward A. , Paul Martin
Published: June 2012

Abstract
Several studies have demonstrated the effectiveness of angiotensin I–converting enzyme (ACE) inhibitors in preventing the neointima formation found after denudation of the rat carotid artery by balloon injury. The aim of the present study was to determine the role of ACE in this model and to compare the treatment with the ACE inhibitor ramiprilat with that with the angiotensin II antagonist HR 720. The endothelial layer of the left carotid artery was removed using an inflated balloon catheter. Injured and control vessels were both submitted to histomorphological analysis and DNA content quantification at 2, 4, 6, 8, 12, and 14 days after injury. Evaluation of neointima thickening demonstrated a slow but steady increase of neointima that was significant after day 6 and reached 30% of the lumen in 2 weeks. This was paralleled by an increase in DNA content, which was significant 4 days after injury. ACE mRNA levels were quantified by polymerase chain reaction after reverse transcription. Measurement of ACE mRNA levels revealed a significant upregulation 2 and 8 days after injury, with no significant difference when compared with control tissue at later time points. ACE activity was also significantly enhanced at 2 and 8 days after injury, with no significant difference when compared with control tissue at later time points. In addition, the treatment with ramiprilat was more efficient in reducing neointima formation than that with HR 720. These data underlie the role of ACE in this model of restenosis. The early induction of ACE expression after endothelial injury but before significant changes in the vessel structure suggests that ACE activity might be one of the mechanisms that trigger neointima formation in the rat.
Initial Characterization of Hamsters With Spontaneous Hypertension
Authors: Thomas Crystal L. , Artwohl James E. , Suzuki Hideyuki , Gao Xiao-pei , White Edward , Saroli Andres , Bunte Ralph M. , Rubinstein Israel
Published: June 2012

Abstract
The purpose of this study was to begin to characterize a new inbred strain of adult male hamsters with established spontaneous hypertension along with their genetically/age-matched normotensive controls. We found that mean arterial pressure was 162±3 mm Hg in hypertensive hamsters and 94±4 mm Hg in controls (mean±SEM;
P
<.05). Body weight was significantly lower in hypertensive hamsters relative to normotensive hamsters (
P
<.05). Hypertension was associated with a significant increase in heart weight, thickness of the left ventricular wall, and amplitude of the QRS complex in standard electrocardiographic leads I and aVR (
P
<.05). No gross or microscopic abnormalities were observed in other organs. Plasma renin activity and the number of circulating neutrophils were significantly increased in hypertensive hamsters relative to controls (
P
<.05). Serum concentrations of creatinine, blood urea nitrogen, sodium, potassium, and calcium as well as urinalysis were similar in both groups. Overall, these data suggest that the spontaneously hypertensive hamster could be a suitable model for the study of spontaneous hypertension.
Enhanced Endothelium-Dependent Relaxations After Gene Transfer of Recombinant Endothelial Nitric Oxide Synthase to Rabbit Carotid Arteries
Authors: Kullo Iftikhar J. , Mozes Geza , Schwartz Robert S. , Gloviczki Peter , Tsutsui Masato , Katusic Zvonimir S. , O’Brien Timothy
Published: June 2012

Abstract
We tested the effects of overexpression of the endothelial nitric oxide synthase (eNOS) gene in the normal arterial wall by adenoviral-mediated gene transfer. Rabbit carotid arteries were surgically isolated and exposed to adenoviral vectors encoding eNOS (AdeNOS) or β-galactosidase (AdβGal) on the contralateral side. Vector solutions at a concentration of 1×10
10
plaque forming units/mL were instilled for 20 minutes before restoration of flow. Arteries were harvested 4 days later for immunostaining, measurement of cGMP, and vasomotor studies. Endothelium-specific gene transfer was confirmed by staining for β-galactosidase in the AdβGal arteries. Immunostaining of en face endothelial cell imprints from AdeNOS-transduced arteries with a monoclonal antibody to eNOS showed increased immunoreactivity. Basal cGMP levels were significantly greater in the AdeNOS-transduced arteries (18.4±4.6 versus 4.2±0.5 pmol/mg protein;
P
<.05). Contractions to phenylephrine were significantly reduced in the AdeNOS-transduced arteries (area under curve, 106±5 versus 119±7;
P
<.05), but in the presence of the eNOS inhibitor,
N
G
-monomethyl-
l
-arginine (L-NMMA, 3×10
−4
mol/L), there was no difference between the two (area under curve, 148±5 versus 153±6;
P
=NS). Relaxations to acetylcholine obtained during submaximal contractions to phenylephrine were significantly enhanced in the AdeNOS-transduced arteries (EC
50
, 7.45±0.05 versus 7.23±0.03;
P
<.05). We conclude that overexpression of eNOS in the endothelium results in diminished contractile responses, as well as enhanced endothelium-dependent relaxations. These findings imply a possible role for vascular eNOS gene transfer in the treatment of vasospasm and endothelial dysfunction.
Sympathoinhibitory Response to Clonidine Is Blunted in Patients With Heart Failure
Authors: Lang Chim C. , Stein C. Michael , Nelson Richard A. , He Huai B. , Belas Frank J. , Blair Ian A. , Wood Margaret , Wood Alastair J. J.
Published: June 2012

Abstract
To determine whether α
2
-adrenergic–mediated sympathoinhibition was altered in chronic heart failure, sympathoinhibitory sensitivity was assessed using the α
2
-adrenergic agonist clonidine in 7 patients with heart failure and in 10 healthy control subjects. Basal norepinephrine spillover was significantly higher in patients with heart failure (1.3±0.3 μg/min) than in control subjects (0.7±0.1 μg/min,
P
=.05). Compared with control subjects, the decrement in norepinephrine spillover to cumulative doses of clonidine (1, 2, and 3 μg/kg administered intravenously) was significantly less in patients with heart failure (
P
<.05). Blood pressure also tended to decrease less in patients with heart failure (
P
=.06). The doses of clonidine required to produce a 10% decrease in blood pressure and a 25% decrease in norepinephrine spillover were significantly higher in heart failure (
P
<.01 and
P
=.05, respectively). Thus, although clonidine lowers norepinephrine spillover significantly in patients with heart failure, such patients are less sensitive to clonidine than healthy control subjects. This difference in sensitivity suggests that doses of clonidine provide effective sympathoinhibition will need to be selected for studies that will evaluate the potential therapeutic effect of clonidine in heart failure.
Blunted Cardiovascular Growth Induction During Prolonged Nitric Oxide Synthase Blockade
Authors: Banting James D. , Thompson Karen E. , Friberg Peter , Adams Michael A.
Published: June 2012

Abstract
The goal of the present study was to characterize the activation profile of the growth-related enzyme ornithine decarboxylase (ODC) in cardiovascular tissue during hypertension induced by chronic NO synthase blockade in relation to the development of structurally based changes in the heart and blood vessels. In previously instrumented conscious rats, mean arterial pressure and ODC activation were measured in cardiovascular tissue of rats treated with
N
ω
-nitro-
l
-arginine methyl ester (L-NAME; 100 mg/kg per day PO) for 4 hours and 1, 6, and 12 days. After 12 days of L-NAME treatment alone or in combination with 3% L-ornithine, structurally based hindlimb resistance properties were assessed. A marginal activation of ODC in the left ventricle and aorta was seen at 4 hours but returned to control levels at 1, 6, and 12 days of L-NAME treatment. A slightly prolonged yet transient activation of ODC occurred in the mesenteric vascular bed. Structurally based hindlimb vascular resistance was enhanced by 15% at maximum vasoconstrictor tone, and no change in cardiac mass occurred with L-NAME treatment. L-NAME+3% L-ornithine treatment resulted in a similar level of structural upregulation compared with L-NAME treatment alone. In summary, 12 days of L-NAME treatment resulted in only a modest change in vascular resistance, and only at maximum constriction, and no cardiac hypertrophy despite the presence of marked hypertension. The results of the present study indicate that either (1) pressure alone is not a sufficient stimulus to induce cardiovascular growth processes or (2) L-NAME may be “nonspecifically” inhibiting cardiovascular growth processes.
Opposite Feedback Control of Renin and Aldosterone Biosynthesis in the Adrenal Cortex by Angiotensin II AT
1
-Subtype Receptors
Authors: Gigante Bruna , Rubattu Speranza , Russo Rosaria , Porcellini Antonio , Enea Iolanda , De Paolis Paola , Savoia Carmine , Natale Armando , Piras Ornella , Volpe Massimo
Published: June 2012

Abstract
The aims of this study were to identify whether tissue renin is regulated by a negative-feedback mechanism produced by locally generated angiotensin (Ang II) in the adrenal cortex and to detect the pathway of Ang II modulation. For this purpose, in 36 12-week old, salt-restricted, nephrectomized Sprague-Dawley rats, we studied the effects of the Ang II AT
1
-subtype receptor antagonist losartan and of the Ang II AT
2
-subtype receptor antagonist
PD123319
on renin mRNA and activity, aldosterone synthase mRNA, and AT
1a
-, AT
1b
-, and AT
2
-subtype receptor expression in the adrenal cortex. Ten additional rats, kept on a regular diet and then nephrectomized, were also studied. In salt-restricted, nephrectomized rats, losartan administration caused increases of adrenal renin mRNA (
P
<.05) and activity (
P
<.05) and a concomitant reduction of aldosterone synthase mRNA (
P
<.05). In addition, after losartan AT
1b
, receptor mRNA was reduced (
P
<.05), AT
1a
receptor mRNA was unchanged, and AT
2
mRNA was increased (
P
<.05).
PD123319
did not significantly modify any of these parameters. In conclusion, in salt-restricted, nephrectomized rats, selective antagonism of AT
1
-subtype receptors stimulates the expression and the activity of renin in the adrenal cortex. This observation demonstrates that Ang II locally formed in the adrenal cortex exerts a modulatory negative-feedback action on adrenal renin biosynthesis independent of the influence of the circulating renin-Ang system; this action is largely mediated through the AT
1b
-subtype receptors.
Possible Involvement of Endothelium-Derived Hyperpolarizing Factor in Vascular Responses of Abdominal Aorta From Pregnant Rats
Authors: Bobadilla Rosa Amalia , Henkel Carlos Castillo , Henkel Enrique Castillo , Escalante Bruno , Hong Enrique
Published: June 2012

Abstract
Increased relaxant response to acetylcholine during pregnancy is proposed to be due to an estrogen-mediated increase in nitric oxide release. We studied acetylcholine-induced pathways of relaxation in the thoracic and abdominal aortic rings from pregnant and nonpregnant Wistar-Kyoto rats and measured basal and stimulated release of nitrites in these vessels. Endothelium-dependent relaxation was significantly greater in pregnant than in nonpregnant rats. Acetylcholine provoked a concentration-dependent relaxation on thoracic and abdominal aortic rings from nonpregnant and pregnant rats. After
N
118
-nitro-
l
-arginine methyl ester pretreatment, the relaxation was significantly inhibited in the two preparations of nonpregnant and pregnant rodents. The relaxation was not inhibited by indomethacin in any of the aortic segments from pregnant and nonpregnant rats. After cytochrome P450 arachidonic acid metabolism inhibitor clotrimazole, a nonsignificant decrease in the E
max
to acetylcholine-induced relaxation was observed in the thoracic segments of pregnant and nonpregnant rats. On the other hand, in abdominal aorta, clotrimazole decreased maximal relaxation in rings from pregnant rats (
P
<.05) but did not change the acetylcholine-induced relaxation from nonpregnant rats. Our results show an increase in the acetylcholine-stimulated release of nitrites in thoracic aortic rings from pregnant rats compared with rings from nonpregnant rats, which cannot be evidenced in abdominal aortic rings. These results suggest that acetylcholine-induced vasodilation in the abdominal segment from pregnant rats is mediated only in part by nitric oxide, the remainder apparently due to an endothelium-derived vasodilator, cytochrome P450-dependent, which may be endothelium-derived hyperpolarizing factor/epoxyeicosatrienoic acid.
Lipid Metabolism Alterations in Normotensive Subjects With Positive Family History of Hypertension
Authors: Lopes Heno Ferreira , Silva Hélio Bernardes , Soares José Augusto , Filho Barreto , Consolim-Colombo Fernanda Marciano , Giorgi Dante Marcelo Artigas , Krieger Eduardo Moacyr
Published: June 2012

Abstract
Metabolic abnormalities are usually reported in hypertensive patients. These metabolic alterations seem to begin in childhood. The young offspring of hypertensive parents have not been studied thoroughly for metabolic alterations. The aim of this study was to examine the level of total cholesterol, LDL cholesterol, VLDL cholesterol, HDL cholesterol, uric acid, glycemia, aldosterone, and plasma renin activity in a population of 42 young, slender normotensive subjects with positive family history of hypertension (FH+) or negative family history of hypertension (FH−). Measurements were made in 20 young normotensive subjects (age 21.1±2.2 years, 11 males, 15 white, 5 oriental, body mass index of 22.1±2.3 kg/m
2
) with FH+ and 22 young normotensive subjects (age 19.9±1.4 years, 17 males, 17 white, 5 oriental, body mass index of 22.1±2.3 kg/m
2
) with FH−. The total cholesterol (4.47±0.8 versus 3.95±0.6 mmol/L), LDL cholesterol (2.74±0.63 versus 2.36±0.61 mmol/L), VLDL cholesterol (0.5±0.25 versus 0.35±0.09 mmol/L), and triglycerides (2.52±1.26 versus 1.76±0.5 mmol/L) were significantly elevated (
P
<.05) in the FH+ group compared with the FH− group. The total cholesterol/HDL cholesterol ratio was significantly higher in the group with a positive family history of hypertension (3.75±0.02 versus 3.11±0.02,
P
<.05). Glycemia was slightly elevated in the FH+ group (2.16±0.29 mmol/L) but was not significantly different from that of the FH− group (2±0.2 mmol/L). Uric acid, plasma renin activity, and aldosterone were similar in both groups. We conclude that young, slender normotensive subjects with a positive history of hypertension show alterations in lipid metabolism, suggesting a positive correlation between lipid metabolism and hypertension heredity.
Is Insulin or Its Precursor Independently Associated With Hypertension?
Authors: Ferreira Sandra R. G. , Franco Laércio J. , Gimeno Suely G. A. , Iochida Lúcia C. , Iunes Magid
Published: June 2012

Abstract
Japanese individuals living outside Japan are more susceptible to chronic diseases included in the insulin resistance syndrome. Hyperinsulinemia and hypertension are associated, but large studies adjusting for confounders are still required. The present evaluated if insulin (I) or proinsulin (PI) was associated with hypertension after adjustment for other risk factors, in first (n=238) and second (n=292) generation Japanese-Brazilians, aged 40 to 79 years, living in a developed city in Brazil. Blood pressure (BP) was measured by random-zero sphygmomanometry. People with mean systolic/diastolic BP >140/90 mm Hg or taking antihypertensive drugs were considered hypertensive. Diagnosis of diabetes was based on results of an oral glucose tolerance test using WHO criteria. I and PI after fasting and 2 hours after glucose load were determined by specific immunofluorimetric assays. The first generation was older than the second (65.6±9.2 versus 53.6±8.4 years,
P
<.01) and male/female ratios were 1.14 and 0.87, respectively. The age-adjusted prevalence of hypertension was 29.2% with no difference between sexes or generations. Higher body mass index (25.2±4.3 versus 23.8±3.3 kg/m
2
), waist-to-hip ratio (0.939±0.067 versus 0.919±0.073), plasma glucose (6.3±2.3 versus 5.6±1.8 mmol/L), cholesterol (5.74±1.19 versus 5.48±1.08 mmol/L), and creatinine (74±26 versus 83±36 μmol/L) were found among the hypertensives (
P
<.05). Univariate analyses showed associations of obesity, diabetes, and dyslipidemia with hypertension. Logistic regression analyses demonstrated that 2-hour I (OR, 1.22; 95% CI, 1.02 to 1.46) and fasting PI (OR, 1.14; 95% CI, 1.00 to 1.31) remained significantly associated with hypertension, after adjustment for age, sex, generation, family history of hypertension, smoking habits, waist-to-hip ratio, serum creatinine, glucose intolerance, and dyslipidemia. Japanese-Brazilians have a higher prevalence of hypertension than the general population in Brazil. High levels of 2-hour I, seen in hypertensives, may be interpreted as independent risk factors for hypertension in this population. Our findings suggest that fasting PI should be useful, in addition to insulin, to assess risk factors for hypertension in epidemiological studies.
Hyperglycemia, Hyperinsulinemia, Overweight, and High Blood Pressure in Young Adults
Authors: Pozzan Roberto , Brandão Andréa Araujo , da Silva Sergio Luz Domingues , Brandão Ayrton Pires
Published: June 2012

Abstract
Children and adolescents (n=3906, 10-15 years old) have been participating in a screening program for high blood pressure. Sixty-four individuals (17-23 years old) from this population were followed up for 8 years and four consecutive screenings and were stratified into three groups according to blood pressure: group 1 (n=23), ≥95th percentile for at least three of four evaluations; group 2 (n=28), <50th percentile for at least three of four screenings; and group 3 (n=13), with unstable blood pressure percentiles. All 64 individuals underwent an oral glucose tolerance test after a 12-hour fast. Blood samples were collected at 0, 30, 60, 90, and 120 minutes for insulin and glucose measurements. Group 1 had a greater body mass index and higher systolic and diastolic blood pressures, basal glucose and insulin levels, and peak values of insulin and glucose levels than the other groups (
P
<.05). Group 1 also had a higher prevalence of overweight and abnormal values of basal insulin than the other groups (
P
<.05) and a higher proportion of glucose-intolerant individuals when compared with group 2 (
P
<.05). Systolic and diastolic blood pressures were positively related to body mass index (
P
<.05) and insulin variables (
P
<.05); however, when body mass index was controlled for, only systolic blood pressure demonstrated a significant correlation with insulin variables (
P
<.05). The association of overweight, hyperinsulinemia, glucose intolerance, and high blood pressure can be detected early, but the significance of these findings would be better explained by longitudinal studies.
Gene Transfer to Carotid Sinus In Vivo
Authors: Meyrelles Silvana S. , Mao Hui Z. , Heistad Donald D. , Chapleau Mark W.
Published: June 2012

Abstract
Baroreceptor nerve endings are located in the adventitia of the carotid sinuses and aortic arch. The goal of the present study was to develop a method for gene transfer to the carotid sinus adventitia. Replication-deficient adenovirus containing the gene for
Escherichia coli
β-galactosidase (β-Gal) was applied topically to the carotid sinuses of anesthetized rabbits. Transgene expression was localized by histochemical staining and quantified by chemiluminescence assay (Galacto-Light). Possible effects of adenovirus on baroreceptor sensitivity were investigated by recording baroreceptor activity from the vascularly isolated carotid sinus over a pressure range of 0 to 160 mm Hg. β-Gal expression in carotid sinus was evident 1 day after virus application, was dose dependent, and was markedly enhanced after 4 days. Expression was restricted to the adventitia of the vessel wall and was not present in vehicle-treated carotid sinuses. Baroreceptor sensitivity measured from carotid sinuses exposed to adenovirus 4 to 5 days beforehand was not altered compared with that measured from control carotid sinuses. In summary, topical application of adenoviral vectors to the carotid sinus provides transgene expression restricted to the region of baroreceptor innervation. The technique provides a novel approach to delineate mechanisms involved in baroreceptor activation and to deliver neuroactive gene products to the baroreceptors.
Moderately Obese, Insulin-Resistant Women Exhibit Abnormal Vascular Reactivity to Stress
Authors: Sung Bong Hee , Wilson Michael F. , Izzo Joseph L. , Ramirez Lalaine , Dandona Paresh
Published: June 2012

Abstract
To define the hemodynamic implications of insulin resistance (IR), we compared 10 normotensive, insulin-resistant women who had abnormal glucose tolerance tests with 10 age-matched healthy normotensive women with normal glucose tolerance tests with respect to mental arithmetic and handgrip responses. Hemodynamic variables obtained at baseline and during stress included heart rate, blood pressure, cardiac output, and systemic vascular resistance. The IR group weighed more (84 versus 66 kg). Screening BP was similar (123/72 versus 120/68 mm Hg,
P
=NS) between groups although baseline diastolic BP at testing day was higher in the IR group than control group (75 versus 65 mm Hg,
P
<.05). The IR group showed a significantly greater increase in systolic (18% versus 10%,
P
<.01) and diastolic (24% versus 12%,
P
<.01) blood pressure responses to mental stress than the control group. During mental stress, the control group demonstrated increased cardiac output (1.4 L/min) and decreased systemic vascular resistance (−120 dyne · s · cm
−5
), whereas IR subjects demonstrated increased systemic vascular resistance (119 dyne · s · cm
−5
; group difference,
P
<.02) with only a small increase in cardiac output (0.5 L/min). Handgrip also caused a greater increase in systemic vascular resistance in the IR group (252 versus 64 dyne · s · cm
−5
,
P
<.05), with a correspondingly greater increase in blood pressure than control subjects. Baseline blood pressure was correlated with weight (
r
=.41,
P
<.02) and stress blood pressure with fasting insulin (
r
=.51,
P
<.001) and glucose-to-insulin ratio (
r
=−.55,
P
<.001). We conclude that insulin resistance is associated with an exaggerated blood pressure response to stress; an enhanced vasoconstriction to stress may mediate this response. This hyperreactivity may be a marker for future hypertension in obese, normotensive, hyperinsulinemic individuals.
Insulin Acutely Inhibits Cultured Vascular Smooth Muscle Cell Contraction by a Nitric Oxide Synthase–Dependent Pathway
Authors: Kahn Andrew M. , Husid Annat , Allen Julius C. , Seidel Charles L. , Song Tom
Published: June 2012

Abstract
Insulin acutely decreases contractile agonist-induced Ca
2+
influx and contraction in endothelium-free cultured vascular smooth muscle (VSM) cells, but the mechanism is not known. Since it has been reported that insulin-induced vasodilation in humans is linked to nitric oxide synthase activity, we wished to determine whether insulin inhibits Ca
2+
influx and contraction of cultured vascular smooth muscle cells by a nitric oxide synthase–dependent pathway. Primary cultures of endothelial cell–free VSM cells from canine femoral artery were preincubated with and without 1 nmol/L insulin for 30 minutes, and the 5-minute production of cGMP was measured. Insulin alone did not affect cGMP production, but in the presence of 10
−5
mol/L serotonin insulin stimulated cGMP production by 60%.
N
G
-monomethyl-
l
-arginine (0.1 mmol/L), an inhibitor of nitric oxide synthase, inhibited the conversion of arginine to citrulline by these cells, blocked insulin-stimulated cGMP production, and blocked the inhibition by insulin of 5-hydroxytryptamine (5-HT)–stimulated Mn
+2
(a Ca
2+
surrogate) influx and contraction. Insulin did not affect contraction of VSM cells grown under conditions designed to deplete the cells of tetrahydrobiopterin, an essential cofactor of nitric oxide synthase. These studies demonstrate that insulin acutely inhibits 5-HT–stimulated Ca
2+
influx and contraction of endothelium-free cultured VSM cells by a nitric oxide synthase–dependent mechanism.
Endothelial Dysfunction Coincides With an Enhanced Nitric Oxide Synthase Expression and Superoxide Anion Production
Authors: Bouloumié Anne , Bauersachs Johann , Linz Wolfgang , Schölkens Bernward A. , Wiemer Gabriele , Fleming Ingrid , Busse Rudi
Published: June 2012

Abstract
We investigated the effects of aortic banding–induced hypertension on the endothelium-dependent vasodilator responses in the aorta and coronary circulation of Sprague-Dawley rats. We studied the influence of hypertension on the endothelial nitric oxide synthase (NOS III) expression, assessed by Western blot and reverse transcription–polymerase chain reactions experiments, and on the superoxide anion (O
2
−
) production. Two weeks after aortic banding, the endothelium-dependent relaxations were not altered. At this time, the expression of NOS III in the aorta and in confluent coronary microvascular endothelial cells (RCMECs) exhibited no marked changes, whereas O
2
−
production was enhanced 1.9-fold in aortas from aortic-banded rats. Six weeks after aortic banding, the endothelium-dependent dilations were markedly impaired in the heart (50% decrease) and aorta (35% decrease). Analysis of NOS III protein and mRNA levels revealed marked increases in both aortas and confluent RCMECs (2.6- to 4-fold) from aortic-banded compared with sham-operated rats. There was no further increase in O
2
−
production in both the aorta and confluent RCMECs from aortic-banded rats. An enhanced nitrotyrosine protein level was also detected in the aorta from 6-week aortic-banded rats. These findings indicate that in hypertension induced by aortic banding, an enhanced O
2
−
production alone is not sufficient to produce endothelial dysfunction. Endothelial vasodilator hyporesponsiveness was observed only when NOS III expression and O
2
−
production were increased and was associated with the appearance of enhanced nitrotyrosine residues. This would suggest that the development of endothelial dysfunction is linked to an overproduction of not one, but two, endothelium-derived radicals that might lead to the formation of peroxynitrite.
Cardiomyocyte Apoptosis and Cardiac Angiotensin-Converting Enzyme in Spontaneously Hypertensive Rats
Authors: Díez Javier , Panizo Angel , Hernández Marta , Vega Francisco , Sola Iosu , Fortuño María Antonia , Pardo Javier
Published: June 2012

Abstract
Increased apoptosis has been reported in the heart of rats with spontaneous hypertension and cardiac hypertrophy. This study was designed to investigate the relationship between apoptosis and hypertrophy in cardiomyocytes from the left ventricle of spontaneously hypertensive rats (SHR). In addition, we evaluated whether the development of cardiomyocyte apoptosis is related to blood pressure or to the activity of the local angiotensin-converting enzyme (ACE) in SHR. The study was performed in 16-week-old SHR, 30-week-old untreated SHR, and 30-week-old SHR treated with quinapril (10 mg · kg
−1
· d
−1
) during 14 weeks before they were killed. Cardiomyocyte apoptosis was assessed by direct immunoperoxidase detection of digoxigenin-labeled 3′-hydroxyl ends of DNA. Nuclear polyploidization measured by DNA flow cytometry was used to assess cardiomyocyte hypertrophy. Compared with 16-week-old normotensive Wistar-Kyoto rats, 16-week-old SHR exhibited increased blood pressure (
P
<.001), increased rate of tetraploidy (
P
<.05), and similar levels of ACE activity and apoptosis. Compared with 30-week-old Wistar-Kyoto rats, 30-week-old SHR showed increased blood pressure (
P
<.001), increased ACE activity (
P
<.05), increased rate of tetraploidy (
P
<.01), and increased apoptosis (
P
<.01). Untreated 30-week-old SHR exhibited similar values of blood pressure and tetraploidy and higher ACE activity (
P
<.05) and apoptosis (
P
<.001) than 16-week-old SHR. A direct correlation (
P
<.01) was found between ACE activity and the apoptotic index in untreated 30-week-old SHR. The long-term administration of quinapril was associated with the normalization of ACE activity and apoptosis in treated SHR. These results suggest that the timing and mechanisms responsible for apoptosis and hypertrophy of cardiomyocytes are different in SHR. Whereas hypertrophy seems to be an earlier alteration that develops in parallel with hypertension, apoptosis develops later in association with overactivity of the local ACE. Our data suggest that cell death dysregulation may be a novel target for antihypertensive agents that interfere with the renin-angiotensin system in hypertension.
Norepinephrine Release in the Human Forearm
Authors: Stein C. Michael , Nelson Richard , He Huai B. , Wood Margaret , Wood Alastair J. J.
Published: June 2012

Abstract
It has been postulated that delayed facilitation of norepinephrine release by epinephrine is causally related to the development of hypertension. It has been proposed that a brief increase in epinephrine concentrations results in the uptake of epinephrine into the sympathetic nerve terminal. Subsequent rerelease of epinephrine stimulates presynaptic β-adrenergic receptors, resulting in a prolonged increase in plasma norepinephrine (NE) concentrations, with amplified sympathetic responses and vasoconstriction. To determine whether such epinephrine-induced, delayed facilitation of NE release occurs in a vascular bed draining resistance vessels and, if it occurs, whether that facilitation differs in hypertension, we used a radioisotope dilution method to measure unstimulated and isoproterenol-stimulated forearm NE spillover before, during, and after a 50 ng/min infusion of epinephrine for 30 minutes directly into the brachial artery. No delayed facilitatory effects of epinephrine on forearm NE spillover were observed in either 6 normotensive (NT) or 8 borderline hypertensive (BHT) subjects (NT unstimulated forearm NE spillover preepinephrine 1.79±0.41 ng/min versus postepinephrine 2.36±0.65 ng/min,
P
=.38; BHT preepinephrine 2.24±0.70 ng/min versus postepinephrine 1.93±0.46 ng/min,
P
=.51; NT isoproterenol-stimulated forearm NE spillover preepinephrine 4.61±1.01 ng/min versus postepinephrine 4.4±0.98 ng/min,
P
=.9; BHT preepinephrine 4.04±1.36 ng/min versus postepinephrine 4.69±1.49 ng/min
P
=.5). We conclude that the short-term local infusion of epinephrine does not have a delayed facilitatory effect on forearm NE spillover in NT or BHT subjects. Therefore, the prolonged increase in NE concentrations after epinephrine infusion previously shown systemically, and not seen locally in the forearm, suggests that the delayed facilitatory response to epinephrine may occur in other organs.
Effects of Chronic Nitric Oxide Synthase Inhibition on Cerebral Arterioles in Rats
Authors: Chillon Jean-Marc , Ghoneim Shams , Baumbach Gary L.
Published: June 2012

Abstract
We examined the effects of nitric oxide (NO) synthase inhibition on the structure and mechanics of cerebral arterioles. We measured pressure, diameter, and cross-sectional area of the vessel wall (histologically) in maximally dilated cerebral arterioles in Sprague-Dawley rats that were untreated or treated for 3 months with the NO synthase inhibitor
N
G
-nitro-
l
-arginine methyl ester (L-NAME; 10 mg/kg per day). Treatment with L-NAME increased cerebral arteriolar mean (87±6 versus 42±2 mm Hg,
P
<.05) and pulse (25±2 versus 13±2 mm Hg,
P
<.05) pressures, as well as cross-sectional area of the vessel wall (1839±70 versus 1019±58 μm
2
,
P
<.05) and external diameter (101±4 versus 87±2 μm,
P
<.05). These findings suggest that hypertension induced by NO synthase inhibition is accompanied by hypertrophy of the vessel wall and enlargement of cerebral arterioles in rats. To determine the role of cerebral arteriolar pulse pressure in hypertrophy of cerebral arterioles during inhibition of NO synthase, we measured the cross-sectional area of the vessel wall in rats treated with L-NAME that underwent unilateral carotid clipping. Unilateral carotid clipping failed to prevent increases in cross-sectional area of the vessel wall (1507±173 and 1613±148 μm
2
in the clip and sham sides, respectively) in rats treated with L-NAME, even though increases in pulse pressure were prevented (16±1 and 27±1 mm Hg in the clip and sham sides, respectively,
P
<.05). These findings suggest that inhibition of NO synthase may promote hypertrophy of cerebral arterioles independently of increases in arteriolar pulse pressure.
Fatty Acids, Not Insulin, Modulate α
1
-Adrenergic Reactivity in Dorsal Hand Veins
Authors: Stepniakowski Konrad T. , Lu Gang , Miller Gregory D. , Egan Brent M.
Published: June 2012

Abstract
Resistance to the vasodilator action of insulin and its capacity to antagonize vascular α-adrenergic reactivity may contribute to the increased neurovascular tone and blood pressure in obese hypertensive subjects. We showed that nonesterified fatty acids (NEFAs) were elevated in obese hypertensive subjects and that raising NEFAs locally in dorsal hand veins of healthy normotensive subjects enhances α
1
-adrenoceptor reactivity. Research by others suggests that insulin antagonizes α
1
-adrenoceptor tone in dorsal hand veins. Taken together with evidence that NEFAs antagonize several of the metabolic actions of insulin, these observations raise the possibility that NEFAs participate in resistance to the vascular effects of insulin and suggest that dorsal hand veins represent a good model for studying these interactions. Thus, we produced local hyperinsulinemia in the dorsal hand veins of six lean normal volunteers and quantified changes of venous distensibility in response to phenylephrine in the presence and absence of a local elevation of NEFAs. We confirmed that raising NEFAs locally decreased by twofold to threefold the phenylephrine ED
50
(
P
<.01), but this α
1
-sensitizing action of NEFAs was not antagonized by insulin concentrations up to ≈1000 μU/mL. Moreover, local hyperinsulinemia alone did not affect vascular α
1
-adrenergic sensitivity as measured by the phenylephrine ED
50
. To address the possibility that the absence of an insulin effect reflected a lack of nitric oxide–mediated, endothelium-dependent dilation in hand veins, responses to acetylcholine were obtained. Acetylcholine relaxed preconstricted hand veins by 60% to 80% (
P
<.01) in the presence and absence of indomethacin, which suggests substantial endothelium-dependent, cyclooxygenase-independent vasodilation. The results confirm that raising NEFAs locally enhances vascular α
1
-adrenoceptor sensitivity. Despite the presence of significant endothelium-dependent dilation in dorsal hand veins, insulin does not antagonize vascular α
1
-adrenoceptor sensitivity in the presence of either ambient or locally elevated fatty acids.
Angiotensin II Affects Basal, Pulsatile, and Glucose-Stimulated Insulin Secretion in Humans
Authors: Fliser Danilo , Schaefer Franz , Schmid Daniela , Veldhuis Johannes D. , Ritz Eberhard
Published: June 2012

Abstract
Angiotensin II (Ang II) modulates the tissue response to insulin (insulin sensitivity), but the effect of Ang II on the secretion of insulin has not been investigated thus far. Nineteen healthy volunteers (17 male; mean age, 26±1 years) were studied. In a double-blind, randomized, placebo-controlled study, seven volunteers were allocated on three occasions in random order after an overnight fast to three interventions: (1) solvent (placebo) infusion; (2) infusion of 1.0 ng Ang II · kg
−1
· min
−1
(subpressor dose); and (3) infusion of 5.0 ng Ang II · kg
−1
· min
−1
(pressor dose). Frequent blood samples (each minute) were obtained for estimation of plasma insulin concentrations over a period of 120 minutes to assess basal and pulsatile insulin secretion. In an ancillary study, plasma glucose and insulin levels were measured after an oral glucose tolerance test while solvent (placebo) or Ang II was infused in 12 fasting healthy volunteers. Plasma insulin concentrations were measured immunoenzymatically (enzyme-linked immunosorbent assay). Insulin secretion pulses were analyzed with the deconvolution technique, and the regularity of insulin secretion was analyzed with the approximate entropy technique. Plasma insulin half-life was assessed using the hyperinsulinemic euglycemic clamp method. The pressor dose of Ang II reduced total, basal, and pulsatile insulin secretion, and this effect was highly significant (
P
<.01). The subpressor dose tended to suppress insulin secretion. The burst frequency (number of peaks) and the regularity of insulin secretion were not affected by administration of Ang II. After the oral glucose load, the insulinemic response was significantly lower and plasma glucose concentrations were significantly higher with infusion of Ang II compared with placebo. Ang II affects both the basal (nonpulsatile) and the pulsatile component of spontaneous insulin secretion and the glucose-stimulated insulin secretion in humans. This observation is of potential interest with respect to the interaction of Ang II and insulin, eg, in the genesis of hyperinsulinemia and hypertension.
Endothelin-1 as an Autocrine/Paracrine Apoptosis Survival Factor for Endothelial Cells
Authors: Shichiri Masayoshi , Kato Hiroki , Marumo Fumiaki , Hirata Yukio
Published: June 2012

Abstract
Endothelin-1 (ET-1), an endothelium-derived vasoactive peptide, functions as a potent vasoconstrictor as well as mitogen. We show here a novel role for ET-1 as an apoptosis survival factor for cultured rat endothelial cells. When we rendered endothelial cells obtained from rat aorta quiescent by serum starvation, significant portions of cultured cells underwent apoptotic death as demonstrated by nucleosomal laddering on agarose gel electrophoresis, flow cytometry analysis with FACS, and the TdT-mediated dUTP biotin nick-end labeling (TUNEL) method. ET-1 dose-dependently (10
−12
to 10
−6
mol/L) suppressed the apoptosis induced by serum starvation. The ET
B
receptor antagonist (BQ788; 10
−6
mol/L) and ET
A/B
receptor antagonists (PD142893 and PD145065; 10
−6
mol/L), but not the ET
A
receptor antagonist (BQ123; 10
−6
mol/L), blocked the apoptosis protective effect of 10
−7
mol/L ET-1. Nonimmune rabbit serum reduced the apoptotic event induced by serum deprivation, whereas neutralization of endogenous ET-1 by polyclonal anti–ET-1 antiserum abrogated this protective effect. The ET
B
receptor antagonist (BQ788; 10
−8
to 10
−6
mol/L), but not the ET
A
receptor antagonist (BQ123; 10
−8
to 10
−6
mol/L), significantly inhibited proliferation of endothelial cells. These data suggest that ET-1, as well as mitogen, functions as an apoptosis survival factor for endothelial cells in an autocrine/paracrine manner via the ET
B
receptor.