bluuebunny/crossref_metadata_2025 huggingface dataset:
Low-Dose Angiotensin II Increases Free Isoprostane Levels in Plasma
Authors: Haas John A. , Krier James D. , Bolterman Rodney J. , Juncos Luis A. , Romero J. Carlos
Published: June 2012

Abstract
—Chronic intravenous infusion of subpressor doses of angiotensin II causes blood pressure to increase progressively over the course of several days. The mechanisms underlying this response, however, are poorly understood. Because high-dose angiotensin II increases oxidative stress, and some compounds that result from the increased oxidative stress (eg, isoprostanes) produce vasoconstriction and antinatriuresis, we tested the hypothesis that a subpressor dose of angiotensin II also increases oxidative stress, as measured by 8-epi-prostaglandin F
2α
(isoprostanes), which may contribute to the slow pressor response to angiotensin II. To test this hypothesis, we infused angiotensin II (10 ng/kg per minute for 28 days via an osmotic pump) into 6 conscious normotensive female pigs (30 to 35 kg). We recorded mean arterial pressure continuously with a telemetry system and measured plasma isoprostanes before starting the angiotensin II infusion (baseline) and again after 28 days with an enzyme immunoassay. Angiotensin II infusion significantly increased mean arterial pressure from 121±4 to 153±7 mm Hg (
P
<0.05) without altering total plasma isoprostane levels (180.0±24.3 versus 147.0±29.2 pg/mL;
P
=NS). However, the plasma concentrations of free isoprostanes increased significantly, from 38.3±5.8 to 54.7±10.4 pg/mL (
P
<0.05). These results suggest that subpressor doses of angiotensin II increase oxidative stress, as implied by the increased concentration of free isoprostanes, which accompany the elevation in mean arterial pressure elevation. Thus, isoprostane-induced vasoconstriction and antinatriuresis may contribute to the hypertension induced by the slow pressor responses of angiotensin II.
Hemodynamic Function at Rest, During Acute Stress, and in the Field
Authors: Kapuku Gaston K. , Treiber Frank A. , Davis Harry C. , Harshfield Gregory A. , Cook Barton B. , Mensah George A.
Published: June 2012

Abstract
—Left ventricular hypertrophy is an independent predictor of cardiovascular morbidity and mortality. However, predictors of cardiac structure and function in youth are not completely understood. On 2 occasions (2.3 years apart), we examined 146 youth aged initially 10 to 19 years (mean age, 14.2±1.8 years). On the initial visit, hemodynamic function was assessed at rest, during laboratory stress (ie, orthostasis, car-driving simulation, video game, and forehead cold), and in the field (ie, ambulatory blood pressure). Quantitative M-mode echocardiograms were obtained on both visits. On both visits, black compared with white youth had higher resting laboratory systolic blood pressure (
P
<0.02), greater relative wall thickness (
P
<0.003), greater left ventricular mass indexed by either body surface area or height
2.7
(
P
<0.01 for both), and lower midwall fractional shortening ratio (
P
<0.05). Hierarchical stepwise regression analysis indicated that significant independent predictors of follow-up left ventricular mass/height
2.7
were the initial evaluation of left ventricular mass/height
2.7
, body mass index, gender (males more than females), and supine resting total peripheral resistance (final model
R
2
=0.53). Left ventricular mass/body surface area was predicted by initial left ventricular mass/body surface area, weight, gender, mean supine resting total peripheral resistance, and systolic pressure response to car-driving simulation (final model
R
2
=0.48). Midwall fractional shortening was predicted by initial midwall fractional shortening, race (white more than black), and lower mean supine total peripheral resistance (final model
R
2
=0.13). The clinical significance of these findings and their implications for improved prevention of cardiovascular diseases are yet to be determined.
Plasma Leptin Level Is Associated With Myocardial Wall Thickness in Hypertensive Insulin-Resistant Men
Authors: Paolisso Giuseppe , Tagliamonte Maria Rosaria , Galderisi Maurizio , Zito Guido Antonio , Petrocelli Antonio , Carella Carlo , de Divitiis Oreste , Varricchio Michele
Published: June 2012

Abstract
—Leptin, the product of the
ob
gene, has been shown to increase heart rate and blood pressure through a stimulation of cardiac sympathetic nervous system activity, a phenomenon also involved in the pathogenesis of left ventricular hypertrophy in hypertensives. Thus, we hypothesize that plasma leptin concentration is associated with left ventricular hypertrophy. Forty hypertensive males and 15 healthy male subjects underwent anthropometric and echocardiographic evaluations, assessment of insulin sensitivity through euglycemic glucose clamp combined with indirect calorimetry, and determination of fasting plasma leptin concentration. Fasting plasma leptin levels were higher in hypertensives than in controls (6.48±2.9 versus 4.62±1.5 ng/mL,
P
<0.05); these results were unchanged after adjustment for body mass index (
P
<0.05). In the whole group of patients (n=55), fasting plasma leptin concentration was correlated with body mass index (
r
=0.46,
P
<0.001) and waist/hip ratio (
r
=0.50,
P
<0.001); independent of body mass index and waist/hip ratio, fasting plasma leptin concentration was correlated (n=55) with whole-body glucose disposal (
r
=−0.27,
P
<0.04), interventricular septum thickness (
r
=0.34,
P
<0.001), posterior wall thickness (
r
=0.38,
P
<0.003), and the sum of wall thicknesses (
r
=0.68,
P
<0.001). In a multivariate analysis (n=55), age, body mass index, fasting plasma leptin concentration, plasma Na
+
concentration, whole-body glucose disposal, and diastolic blood pressure explained 68% of the variability of the sum of wall thicknesses with fasting plasma leptin concentration (
P
<0.03), whole body glucose disposal (
P
<0.002), and diastolic blood pressure (
P
<0.001), which were significantly and independently associated with the sum of wall thicknesses. In conclusion, our study demonstrates that fasting plasma leptin levels are associated with increased myocardial wall thickness independent of body composition and blood pressure levels in hypertensives.
Impaired Atrial M
2
-Cholinoceptor Function in Obesity-Related Hypertension
Authors: Pelat Michel , Verwaerde Patrick , Merial Christelle , Galitzky Jean , Berlan Michel , Montastruc Jean-Louis , Senard Jean-Michel
Published: June 2012

Abstract
—The aim of this study was to investigate the activity of the parasympathetic limb of the baroreflex arch in a canine model of obesity-related hypertension. Twelve male beagle dogs were randomized into 2 groups. Six dogs were fed with normal canine food and 6 were submitted to a 10-week high-fat diet (HFD). We have evaluated the consequences of HFD on heart rate (HR) and blood pressure (BP) circadian cycles and methylscopolamine dose-response curves. Binding of [
3
H]-AF-DX 384 and adenylyl cyclase activity were investigated to determine the density and functionality of M
2
-cholinoceptors on right atrial membranes from control and HFD dogs. HFD induced a significant increase in body weight (15±1 vs 12±1 kg), systolic BP (161±5 vs 145±4 mm Hg), diastolic BP (92±3 vs 79±2 mm Hg), and HR (96±4 vs 81±3 bpm). Circadian rhythms of HR and BP observed in the baseline period were abolished after 9 weeks of HFD. After propranolol (1 mg/kg) pretreatment, the dose of methylscopolamine able to induce 50% maximum tachycardia was significantly increased after 9 weeks of HFD (7.4±0.3 vs 4.7±0.1 μg/kg). In the control group, the experimental period failed to modify these parameters. The numbers of M
2
-cholinoceptors measured in right atrial membranes were significantly lower in HFD than in control groups (54±6 vs 27±6 fmol/mg protein). The ability of carbachol to inhibit isoproterenol-stimulated adenylyl cyclase activity was significantly lower in HFD than in control groups (IC
50
=47±12 vs 6.4±1.4 μmol/L). However, the basal activity of adenylyl cyclase was unchanged by HFD. HFD decreases M
2
-cholinoceptor number and function in cardiomyocytes. This could explain the abolition of circadian rhythm of HR and the changes in chronotropic effect brought about by methylscopolamine.
Genetic Polymorphisms of the Renin-Angiotensin System and Atheromatous Renal Artery Stenosis
Authors: Olivieri Oliviero , Trabetti Elisabetta , Grazioli Silvia , Stranieri Chiara , Friso Simonetta , Girelli Domenico , Russo Carla , Pignatti Pier Franco , Mansueto Giancarlo , Corrocher Roberto
Published: June 2012

Abstract
—Genes that influence the renin-angiotensin system have been investigated in recent years as potential etiologic candidates of cardiovascular and renal diseases. In atheromatous renal artery stenosis (RAS), a condition characterized by persistent activation of the renin-angiotensin system, the study of these genes may be of particular relevance. We evaluated angiotensin-converting enzyme (ACE) insertion/deletion, angiotensinogen (AGT) M235T, and angiotensin II receptor (ATR) A1166C polymorphisms in relation to the occurrence of RAS. We studied 58 patients with angiographically documented RAS; 102 normotensive subjects with normal coronary arteries and no history or clinical or instrumental evidence of atherosclerosis in other vascular districts were considered the control group. Patients had a significantly higher D allele frequency (0.70 versus 0.55; χ
2
6.88,
P
=0.01; odds ratio [OR] 1.9, 95% CI 1.17 to 3.07) than did the control population; 48.3% of patients were homozygous for DD (χ
2
6.62,
P
<0.05; OR 2.04, 95% CI 1.05 to 3.95); and only 8.6% carried the II genotype (OR 0.34, 95% CI 0.19 to 1.47). No significant association was found for AGT M235T and ATR A1166C. Our results suggest a predisposing role for ACE genetic polymorphism in the development and progression of atheromatous RAS.
Impaired Prostaglandin E
2
/Prostaglandin I
2
Receptor–G
s
Protein Interactions in Isolated Renal Resistance Arterioles of Spontaneously Hypertensive Rats
Authors: Ruan Xiaoping , Chatziantoniou Christos , Arendshorst William J.
Published: June 2012

Abstract
—The protective effect of vasodilator agents linked to the cAMP pathway is less effective for buffering the vasoconstrictor effect of angiotensin II in young animals with genetic hypertension. To determine the underlying cellular mechanism, experiments were performed on freshly isolated preglomerular resistance arterioles obtained from kidneys of 7-week-old spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). Specific high-affinity saturable binding of
3
H-prostaglandin (PG) E
2
revealed 1 receptor class in renal microvessels; PGE
2
receptor density was similar in SHR and WKY (106 versus 115 fmol/mg;
P
>0.8), as was receptor affinity (3.6 versus 3.5 nmol/L;
P
>0.7). Basal cAMP activity was similar in renal arterioles from SHR and WKY. A major finding was that PGE
2
, PGI
2
, and isoproterenol produced weaker stimulation of cAMP formation in arteriolar cells of SHR (
P
<0.02). In contrast, GTPγs and forskolin stimulated cAMP generation to a similar degree in both rat strains, which suggests normal adenylate cyclase activity in hypertension-prone SHR. Immunoblots revealed the presence of 3 classes of G proteins (G
s
, G
i
, and G
q
) in preglomerular arterioles. The relative amounts of discernible G-protein α-subunits in renal resistance vessels did not differ between SHR and WKY. These results extend previous in vivo studies of abnormal renal vascular reactivity in SHR and more directly localize defective coupling of the prostaglandin and β-adrenergic receptors to a stimulatory G protein and cAMP production in freshly isolated preglomerular arteriolar cells of young SHR. This dysfunction may be due to an abnormal interaction between prostaglandin receptors and G
s
protein that leads to inefficient coupling of initiating steps in the cAMP–protein kinase A cascade during the development of hypertension.
Sodium Pump Inhibition and Regional Expression of Sodium Pump α-Isoforms in Lens
Authors: Tao Qing-Feng , Hollenberg Norman K. , Graves Steven W.
Published: June 2012

Abstract
—Both hypertension and cataract formation have been associated with reductions in sodium pump activity, possibly as a result of an endogenous inhibitor. The objective of the present study was to answer 4 closely related questions: (1) Is the lens sodium pump effectively inhibited by a labile, digitalis-like factor we have identified in the peritoneal dialysate from hypertensive patients in end-stage renal failure? (2) How does that inhibition compare to that induced by ouabain? (3) Does sodium pump isoform distribution determine the degree of lens sodium pump inhibition? (This question was precipitated by the unanticipated finding that the labile DLF was more effective in inhibiting lens sodium pump than was anticipated.) (4) Is sodium pump activity altered in lens in response to increased salt intake, a maneuver known to increase endogenous digitalis-like factor? We found that whereas ouabain produced equivalent or significantly less inhibition of lens Na
+
,K
+
-ATPase from calf or rabbit, respectively, compared with brain, labile digitalis-like factor preferentially inhibited lens compared with brain. Analysis of whole-lens preparations from rabbit, calf, and normal human lens revealed substantial α2- and α3-isoforms of the sodium pump but little α1-isoform. Ouabain inhibition of whole-lens Na
+
,K
+
-ATPase from rabbit and calf were comparable: for rabbit lens,
K
i
=5.2×10
−7
mol/L; for calf lens,
K
i
=1.0×10
−6
mol/L. Limited quantities of labile digitalis-like factor prohibited similar determinations; however, its concentration-activity profile paralleled that of ouabain. Na
+
,K
+
-ATPase activity, measured in the 3 major anatomic regions of lens and normalized to nucleus, was greatest in epithelium (56.9±17.9) compared with cortex (5.8±1.4) and nucleus (1.0±0.0;
P
=0.01). Immunohistochemistry of rabbit lens found abundant α2- and α3-isoforms in epithelium and limited α3 but undetectable α1 in cortex and nucleus. Finally, rats randomized to a high Na diet showed significantly reduced lens Na
+
,K
+
-ATPase activity compared with those on a low Na diet, consistent with the effects of a sodium pump inhibitor. In conclusion, the present study suggests that digitalis-like factor may provide a link between hypertension and cataract formation.
Association and Linkage Analyses of Glucocorticoid Receptor Gene Markers in Essential Hypertension
Authors: Lin Ruby C. Y. , Wang William Y. S. , Morris Brian J.
Published: June 2012

Abstract
—Suggestive evidence has been obtained in a “4-corners” study for involvement of the glucocorticoid receptor gene (
GRL
) in genetic variation in blood pressure. Therefore, we tested markers at the
GRL
locus for association and linkage with essential hypertension (HT). For the association study, we used a well-characterized group of 129 white Australians of Anglo-Celtic extraction who had HT, a strong family history of HT (2 parents with the disease), and early-onset moderate-to-severe disease. Controls were 195 normotensive white subjects whose parents were normotensive past the age of 50 years. For the linkage study, we used 175 sibling pairs of similar ancestry. The case-control groups were genotyped for an Asn363Ser variant in exon 2, a G/T variant in intron 4, and a microsatellite marker (
D5S207
) tightly linked (<200 kb) to
GRL
. For the groups as a whole, no association or linkage was observed after analysis of data by a variety of statistical tests. Analysis of sibling-pair data gave an exclusion score of −3.8 for the logarithm of the odds for linkage, indicating significant nonlinkage. However, in females, weak association of the intron 4 polymorphism with HT (
P
=0.03), as well as with systolic and diastolic blood pressure in all subjects (
P
=0.04 and 0.03), was observed, and in the case of the
D5S207
marker, association with HT was apparent in males (
P
=0.0001). Thus, although our results provide no overall support for
GRL
in HT etiology, apparent gender-specific associations could exist in this genomic region, possibly reflecting correlated occurrence with (an)other metabolic syndrome disorder(s).
Interaction Between Nitric Oxide and Endogenous Vasoconstrictors in Control of Renal Blood Flow
Authors: Berthold Heike , Just Armin , Kirchheim Hartmut R. , Ehmke Heimo
Published: June 2012

Abstract
—The level of renal blood flow (RBF) is controlled by opposing vasoconstrictor and vasodilator influences. In a recent investigation in normotensive dogs, we found that combined blockade of endothelin type A (ET
A
) receptors and angiotensin II formation induces marked increases in RBF that were much larger than the effects of blocking either system alone. The aim of the present study was to determine the contribution of nitric oxide (NO) to this vasodilator response. Experiments were made in 6 conscious, chronically instrumented dogs subjected to 5 different experimental treatments on separate days. Blockade of ET
A
receptors alone by the selective antagonist LU 135252 had only minor effects on RBF compared with time-control experiments. Additional blockade of angiotensin II formation by angiotensin-converting enzyme inhibition with trandolaprilat caused a substantial increase of RBF by ≈50%. This vasodilation was entirely suppressed when NO formation was prevented by inhibition of NO synthase with
N
G
-nitro-
l
-arginine methyl ester HCl. However, when during NO synthase inhibition renal vascular NO concentrations were clamped at control levels by infusing the NO donor
S
-nitroso-
N
-acetyl-
d
,
l
-penicillamine, the vasodilator response to combined blockade of ET
A
receptors and angiotensin II formation was completely restored (ΔRBF ≈60%). These results indicate that the vasodilation after combined ET
A
receptor blockade and angiotensin-converting enzyme inhibition is not mediated by an increase in NO release but results from the unmasking of the tonic influence that is normally exerted by constitutively released NO. Accordingly, the tonic activity of endothelial NO synthase appears to be of major importance in the physiological regulation of renal vascular resistance by determining the vasomotor responses to endothelin and angiotensin II.
Effects of the Nonpeptide V
1
Vasopressin Receptor Antagonist SR49059 in Hypertensive Patients
Authors: Thibonnier Marc , Kilani Ahmad , Rahman Mahboob , DiBlasi Tina Pilumeli , Warner Kelly , Smith Michael C. , Leenhardt Anne Françoise , Brouard Rémi
Published: June 2012

Abstract
—We assessed the clinical and pharmacological profile of the orally active V
1
vascular vasopressin (AVP) receptor nonpeptide antagonist SR49059 (SR) during the osmotic stimulation of AVP release in hypertensive patients. In a double-blind crossover-versus-placebo study, 24 untreated stage I or II essential hypertensive patients (12 whites and 12 blacks) received a single 300 mg oral dose of SR 2 hours before the stimulation of AVP secretion with a 5% hypertonic saline infusion. Hemodynamic, humoral, and hormonal parameters were monitored for up to 28 hours after drug administration. SR did not alter blood pressure or heart rate before the saline infusion and did not reduce the blood pressure increment induced by the hypertonic saline infusion. However, the blood pressure peak at the end of the hypertonic saline infusion was slightly lower in the presence of SR (
P
=0.04). Heart rate was significantly faster between 4 and 6 hours after SR administration (
P
=0.02). The rise in plasma sodium and osmolality triggered by the saline infusion was not modified by SR, but AVP release was slightly greater in the presence of SR (
P
<0.0003). AVP-induced aggregation of blood platelets in vitro was significantly reduced by SR, with a peak effect 2 hours after drug administration that coincided with the SR peak plasma concentration. Plasma renin activity and aldosterone before and after the saline infusion were not modified by SR. Urine volume and osmolality were not altered by SR administration. SR effects were similar in the 2 ethnic groups as well as in salt-sensitive versus salt-resistant patients. In a situation of AVP osmotic release and volume expansion in hypertensive patients, a single oral dose of the V
1
vascular AVP receptor nonpeptide antagonist SR49059, which is able to block AVP-induced platelet aggregation, exerts a transient vasodilation effect that is not associated with a sustained blood pressure reduction. SR49059 is a pure V
1
vascular receptor antagonist that is devoid of V
2
renal receptor actions.
Metformin Improves Vascular Function in Insulin-Resistant Rats
Authors: Katakam Prasad V. G. , Ujhelyi Michael R. , Hoenig Margarethe , Miller Allison W.
Published: June 2012

Abstract
—This study assessed the effect of metformin treatment on insulin, mean arterial pressure (MAP), and endothelial function in insulin-resistant (IR) rats. In addition, we assessed the direct effect of metformin in vitro. Sprague-Dawley rats were randomized to control (n=28) or IR (n=28) groups. Rats were further randomized to receive metformin (300 mg/kg) or placebo for 2 weeks. MAP and insulin were measured. Subsequently, a third-order branch of the superior mesenteric artery was isolated, and endothelial function was assessed. Specifically, dose-response experiments of acetylcholine (ACh) with or without
N
-nitro-
l
-arginine (LNNA) were performed. For in vitro experiments, mesenteric arteries were removed from untreated control and IR rats and treated with metformin (100 μmol/L) before ACh±LNNA. MAP and insulin levels were improved in IR-metformin compared with IR-placebo rats. Maximal relaxation (E
max
) to ACh was enhanced in IR-metformin (92±2%) compared with IR-placebo rats (44±4%) (
P
<0.05). Relaxation in response to ACh+LNNA was greater in IR-metformin (33±4%) than in IR-placebo rats (12±4%) but remained depressed compared with control rats (E
max
=68±5%). The control group was not affected by metformin. In vitro treatment of arteries with metformin in response to ACh produced results similar to those in the experiments with metformin-treated rats. Although metformin improves metabolic abnormality in IR rats, this action does not appear to mediate its effect on vascular function. Both in vivo and in vitro metformin improved ACh-induced relaxation in IR rats to control levels, apparently through nitric oxide–dependent relaxation. These data suggest that metformin improves vascular function through a direct mechanism rather than by improving metabolic abnormalities.
Increased Nitrovasodilator Sensitivity in Endothelial Nitric Oxide Synthase Knockout Mice
Authors: Brandes Ralf P. , Kim Do-yei , Schmitz-Winnenthal Friedrich-Hubertus , Amidi Mojgan , Gödecke Axel , Mülsch Alexander , Busse Rudi
Published: June 2012

Abstract
—Endogenously produced nitric oxide (NO) modulates nitrovasodilator-induced relaxation. We investigated the underlying mechanism in wild-type (WT) mice and endothelial NO synthase knockout (eNOS
−/−
) mice to determine whether a chronic lack of endothelial NO alters the soluble guanylyl cyclase (sGC) pathway. In aortic segments from eNOS
−/−
mice, the vasodilator sensitivity to sodium nitroprusside (SNP) was significantly greater than that in WT mice. There was no difference in sensitivity to the G-kinase I activator 8-para-chlorophenylthio-cGMP or to cromakalim.
N
ω
-Nitro-
l
-arginine had no effect on the SNP-induced relaxation in eNOS
−/−
but increased the sensitivity in WT mice so it was no longer different than that of eNOS
−/−
. Basal cGMP levels in aortic rings were significantly lower in eNOS
−/−
mice than in WT mice. SNP (300 nmol/L) induced a significantly greater cGMP accumulation in eNOS
−/−
mice than in WT mice. The maximal SNP-induced (10 μmol/L) increase in cGMP was similar in both strains. SNP-stimulated sGC activity was significantly greater in eNOS
−/−
mice than in WT mice. Incubation of aortic segments from WT mice with
N
ω
-nitro-
l
-arginine increased sGC activity, an effect prevented by coincubation with SNP (10 μmol/L). The aortic expressions of the sGC α1 and β1 subunits in WT and eNOS
−/−
mice were identical as determined with Western blot analysis. These data suggest that chronic exposure to endothelium-derived NO, as well as acute exposure to nitrovasodilator-derived NO, desensitizes sGC to activation by NO but does not alter sGC expression. Both the acute cessation of endothelial NO formation in WT mice and the chronic deficiency of NO in eNOS
−/−
mice restore the NO sensitivity of sGC and enhance vascular smooth muscle relaxation in response to nitrovasodilator agents.
Kallikrein Gene Delivery Attenuates Myocardial Infarction and Apoptosis After Myocardial Ischemia and Reperfusion
Authors: Yoshida Hideaki , Zhang Jenny J , Chao Lee , Chao Julie
Published: June 2012

Abstract
—The tissue kallikrein-kinin system is present in the heart, and kinin has been shown to have cardioprotective effects. In this study, we investigated the potential role of tissue kallikrein in myocardial ischemia/reperfusion injury through adenovirus-mediated human kallikrein gene delivery. One week after gene delivery, the rats were subjected to a 30-minute coronary occlusion followed by a 2-hour reperfusion. Kallikrein gene delivery caused significant decreases in the ratio of infarct size to ischemic area at risk (from 69.6% to 44.5%, n=10 and 8,
P
<0.01) and in the incidence of ventricular fibrillation (from 64.3% to 16.7%, n=14 and 24,
P
<0.01) compared with the group injected with control adenovirus. Kallikrein gene delivery also attenuated programmed cell death in the ischemic area compared with the control area as assessed with the terminal deoxynucleotidyl transferase–mediated nick end labeling assay (n=6,
P
<0.01). Icatibant, a specific bradykinin B
2
receptor antagonist, abolished these kallikrein-mediated beneficial effects. The expression of human tissue kallikrein mRNA was identified in rat heart, kidney, lung, liver, and adrenal gland. After kallikrein gene delivery, cardiac kinin and cGMP levels were significantly elevated compared with the control (29.6±12.7 versus 6.1±2.1 pg/mg protein, n=7,
P
<0.01; 1.30±0.06 versus 0.86±0.09 pmol/mg protein, n=5,
P
<0.05). These results indicate that kallikrein gene delivery protects against myocardial infarction, ventricular arrhythmias, and apoptosis in ischemia/reperfusion injury via kinin-cGMP signal pathway. The successful application of this technology may have potential therapeutic value in the treatment of coronary artery diseases.
Endothelin-Mediated Calcium Signaling in Preglomerular Smooth Muscle Cells
Authors: Schroeder Alan C. , Imig John D. , LeBlanc Elizabeth A. , Pham Bao Thang , Pollock David M. , Inscho Edward W.
Published: June 2012

Abstract
—This study was performed to test the hypothesis that endothelin peptides differentially influence intracellular calcium concentration ([Ca
2+
]
i
) in preglomerular microvascular smooth muscle cells (MVSMC), in part through activation of endothelin (ET)
A
receptors. Experiments were performed in vitro with the use of single MVSMC freshly isolated from rat preglomerular microvessels. The effect of ET-1, ET-2, and ET-3 on [Ca
2+
]
i
was measured with the use of the calcium-sensitive dye, fura 2, and standard fluorescence microscopy techniques. Baseline [Ca
2+
]
i
averaged 84±3 nmol/L (n=141 cells from 23 dispersions). ET-1 concentrations of 1, 10, and 100 nmol/L evoked peak increases in [Ca
2+
]
i
of 48±16, 930±125, and 810±130 nmol/L, respectively. The time course of the [Ca
2+
]
i
response was biphasic, beginning with a rapid initial increase followed by a sustained plateau phase or a period during which [Ca
2+
]
i
oscillated sharply. Similar responses were observed after ET-2 administration. In contrast, ET-3 stimulated monophasic increases in [Ca
2+
]
i
of only 14±5, 33±16, and 44±19 nmol/L at peptide concentrations of 1, 10, and 100 nmol/L, respectively. These responses are significantly smaller than responses to ET-1 or ET-2, respectively. The relative contributions of calcium mobilization and calcium influx in the response to ET-1 were also evaluated. Removal of calcium from the bathing medium did not significantly alter the peak response to 10 nmol/L ET-1 but abolished the late phase elevation of [Ca
2+
]
i
. These data demonstrate that endothelin peptides increase [Ca
2+
]
i
in preglomerular MVSMC. The concentration-response profiles are consistent with the response involving activation of ET
A
receptors. Furthermore, these results suggest that ET-1 increases [Ca
2+
]
i
by stimulating both the release of intracellular calcium and the influx of calcium from the extracellular medium.
Downregulation of Angiotensin II Type 1 Receptor by All-
trans
Retinoic Acid in Vascular Smooth Muscle Cells
Authors: Takeda Kotaro , Ichiki Toshihiro , Funakoshi Yuko , Ito Kiyoko , Takeshita Akira
Published: June 2012

Abstract
—All-
trans
retinoic acid (atRA) is a biologically active metabolite of vitamin A that plays an important role in cell differentiation and proliferation. Although neointimal formation after balloon injury of rat carotid artery is inhibited by atRA, the mechanisms are not clearly understood. Because the renin-angiotensin system is one of the crucial components of atherosclerosis, we examined the effects of atRA on the expression of angiotensin II type 1 receptor (AT
1
-R) in vascular smooth muscle cells. atRA (1 μmol/L) decreased the AT
1
-R mRNA level by 50% after 24 hours; AT
1
-R number was also reduced to the same extent after 48 hours. atRA markedly suppressed promoter activity of the AT
1
-R promoter-luciferase construct, but AT
1
-R mRNA stability was not affected. Cycloheximide blocked the atRA-induced decrease in AT
1
-R mRNA expression, suggesting that this process requires de novo protein synthesis. Simultaneous treatment with an agonist (Ro40-6055) specific for retinoic acid receptor (RAR) and an agonist (Ro25-7836) specific for retinoid X receptor (RXR) suppressed the AT
1
-R mRNA expression comparable to that with treatment with atRA, suggesting that the RAR/RXR heterodimer mediates the effect of atRA in AT
1
-R downregulation. These results suggest that atRA suppressed AT
1
-R mRNA transcription through new protein synthesis induced by RAR/RXR-dependent transcription. This study provides novel insight into a role of atRA as an important molecule that regulates AT
1
-R gene expression and provides possible mechanisms for the suppression of neointimal formation by atRA.
Insulin Inhibits Migration of Vascular Smooth Muscle Cells With Inducible Nitric Oxide Synthase
Authors: Kahn Andrew M. , Allen Julius C. , Seidel Charles L. , Zhang Sui
Published: June 2012

Abstract
—Vascular smooth muscle cell (VSMC) migration participates in atherosclerosis and arterial restenosis after balloon angioplasty. Because these processes are enhanced in insulin-resistant states, our goal was to determine whether insulin affects VSMC migration and, if so, how. The migration of primary cultured VSMCs from canine femoral artery was measured with the use of a wound migration assay and related to cGMP levels. Insulin (1 nmol/L) did not affect migration or cGMP production in control cells. When inducible nitric oxide synthase (iNOS) was induced by 24-hour preincubation with lipopolysaccharide and interleuken-1β, basal migration decreased, cGMP production increased, and insulin inhibited migration by >90% and stimulated cGMP production by 3-fold. The nitric oxide synthase inhibitor
N
G
-monomethyl-
l
-arginine blocked the affect of insulin on the migration of VSMCs with iNOS. 8-Bromo-cGMP inhibited VSMC migration in control cells, and 1-
H
-1[1,2,4]oxadiazolo-[4,3
a
]quinoxolin-1-one, a selective inhibitor of guanylate cyclase, blocked the inhibition by insulin of migration of cells with iNOS. We conclude that insulin does not normally affect cGMP production or the migration of these VSMCs. However, after the induction of iNOS, insulin stimulates cGMP production and inhibits migration via an NOS-and a cGMP-dependent mechanism.
Cyclosporin A Protects Against Angiotensin II–Induced End-Organ Damage in Double Transgenic Rats Harboring Human Renin and Angiotensinogen Genes
Authors: Mervaala Eero , Müller Dominik N. , Park Joon-Keun , Dechend Ralph , Schmidt Folke , Fiebeler Anette , Bieringer Markus , Breu Volker , Ganten Detlev , Haller Hermann , Luft Friedrich C.
Published: June 2012

Abstract
—Leukocyte infiltration and adhesion molecule activation play a central role in the pathogenesis of angiotensin II (Ang II)–induced end-organ damage in double transgenic rats (dTGR) harboring human renin and angiotensinogen genes. We tested the hypothesis that the immunosuppressive agent cyclosporine (CsA) protects against the Ang II–induced myocardial and renal damage in dTGR. Furthermore, we investigated the influence of CsA on interleukin-6 (IL-6) and inducible nitric oxide synthase (iNOS) expression and the DNA binding activity of transcription factor necrosis factor-κB (NF-κB). The 4-week-old rats were divided into 4 groups: (1) control dTGR (n=20), (2) dTGR plus CsA (5 mg/kg SC for 3 weeks, n=15), (3) normotensive Sprague-Dawley (SD) rats (n=10), and (4) SD rats plus CsA (n=8). In dTGR, CsA completely prevented cardiovascular death (0 of 15 versus 9 of 20), decreased 24-hour albuminuria by 90% and systolic blood pressure by 35 mm Hg, and protected against the development of cardiac hypertrophy. Whole blood CsA concentrations 24 hours after the last drug treatment were 850±15 ng/mL. Semiquantitative ED-1 and Ki-67 (a nuclear cell proliferation–associated antigen) scoring showed that CsA prevented perivascular monocyte/macrophage infiltration and prevented cell proliferation in the kidneys and hearts of dTGR, respectively. The beneficial effects of CsA were, at least in part, mediated by the suppression of IL-6 and iNOS expression. Electrophoretic mobility shift assay revealed that CsA regulated inflammatory response in part through the NF-κB transcriptional pathway. In contrast to dTGR, CsA increased blood pressure in normotensive SD rats by 10 mm Hg and had no effect on cardiac mass or 24-hour urinary albumin excretion. Perivascular monocyte/macrophage infiltration, IL-6, and iNOS expression or cell proliferation were not affected by CsA in SD rats. Our findings indicate that CsA protects against Ang II–induced end-organ damage and underscore the central role of vascular inflammatory response in the pathogenesis of myocardial and renal damage in dTGR. The beneficial effects of CsA in the kidney and heart are mediated, at least in part, by suppression of IL-6 and iNOS expression via NF-κB transcriptional pathway.
Cyclooxygenase-2 Involved in Stimulation of Renal Mechanosensitive Neurons
Authors: Kopp Ulla C. , Cicha Michael Z. , Smith Lori A. , Haeggström Jesper Z. , Samuelsson Bengt , Hökfelt Tomas
Published: June 2012

Abstract
—Stretching of the renal pelvic wall activates renal mechanosensitive neurons, resulting in an increase in afferent renal nerve activity (ARNA). Prostaglandin (PG)E
2
plays a crucial role in the activation of renal mechanosensitive neurons through facilitation of the release of substance P from the sensory neurons in the renal pelvic wall. Because wall stretch may induce cyclooxygenase-2 activity, we examined whether cyclooxygenase-2 was expressed in the renal pelvic wall and whether activation of cyclooxygenase-2 contributed to the ARNA response produced through increased renal pelvic pressure. In situ hybridization showed a strong cyclooxygenase-2 mRNA signal in the papilla and subepithelial layer of the renal pelvic wall from time control kidneys and from kidneys exposed to 15 minutes of increased renal pelvic pressure in anesthetized surgically operated rats. In anesthetized rats, an increase in renal pelvic pressure increased ARNA by 40±2% and increased renal pelvic release of PGE
2
from 289±46 to 1379±182 pg/min (
P
<0.01). Renal pelvic perfusion with the cyclooxygenase-2 inhibitor etodolac reduced the increases in ARNA and PGE
2
by 66±7% and 55±13%, respectively (
P
<0.01). Likewise, the cyclooxygenase-2 inhibitor 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulfonyl)phenyl-2(5
H
)-furanone reduced the increases in ARNA and PGE
2
by 43±5% and 47±8%, respectively. We conclude that cyclooxygenase-2 is expressed in the renal pelvic wall and that the activation of cyclooxygenase-2 contributes to the stimulation of renal mechanosensitive neurons in the pelvic wall.
Inhibition of Nitric Oxide Synthesis Potentiates Hypertension During Chronic Glucose Infusion in Rats
Authors: Claxton Christie R. , Brands Michael W. , Fitzgerald Sharyn M. , Cameron Joseph A.
Published: June 2012

Abstract
—Endothelial dysfunction has been proposed to contribute to impaired blood flow control or hypertension in many conditions characterized by hyperinsulinemia or hyperglycemia. However, most studies have focused on whether endothelial dysfunction is present in the established phases of these various hypertensive states, and there is little known concerning the role of the endothelium in the initial stages. This study tested whether nitric oxide production, before endothelial dysfunction develops, plays an important role in counteracting the hypertensive response to chronic glucose infusion. Glucose was infused (18.6 mg/kg per minute IV) for 7 days in 8 normal rats (G) and in 9 rats with a long-term background intravenous infusion of
N
G
-nitro-
l
-arginine methyl ester (L-NAME) at 10 μg/kg per minute (G+L). Mean arterial pressure (MAP), measured 24 hours per day, increased an average of ≈11 mm Hg in the G rats. L-NAME treatment increased MAP an average of 28±2 mm Hg in the G+L rats, and glucose infusion raised MAP >30 mm Hg above that, averaging 155±8 mm Hg by day 6. In addition, heart rate increased from an average of 389±8 bpm to 441±16 bpm by day 6, whereas there was no significant change in the G rats. Glomerular filtration rate decreased significantly with L-NAME treatment and decreased in both groups by day 3 of glucose infusion, reaching lower levels in the G+L rats. These results show that NO is required to minimize the increase in MAP during glucose infusion and suggest that renal and neural mechanisms may be important in mediating that effect.
Induction of Cyclooxygenase-2 by Angiotensin II in Cultured Rat Vascular Smooth Muscle Cells
Authors: Ohnaka Keizo , Numaguchi Kotaro , Yamakawa Tadashi , Inagami Tadashi
Published: June 2012

Abstract
—Angiotensin II (Ang II) stimulates the release of prostaglandins (PGs) in various cells and tissues. Recently, cyclooxygenase-2 (COX-2) emerged as a new key regulator for PG synthesis. In the present study, we investigated whether Ang II regulates COX-2 expression in cultured rat vascular smooth muscle cells (VSMCs). Ang II markedly increased the expression of COX-2 mRNA in a time- and dose-dependent manner. This effect was completely blocked by the Ang II type 1 receptor antagonist losartan but not by the Ang II type 2 receptor antagonist PD123319. The p42/44 mitogen-activated protein kinase (MAPK) kinase-1 inhibitor PD98059 and the p38 MAPK inhibitor SB203580 significantly suppressed Ang II–induced COX-2 mRNA and protein expression. Ang II did not increase transcription of the COX-2 gene, as examined with a COX-2 promoter/luciferase chimeric plasmid construct. Instead, it suppressed the degradation of COX-2 mRNA. PD98059 and SB203580 markedly enhanced the decay of COX-2 mRNA induced by Ang II, implying that p42/44 and p38 MAPK activated by Ang II play a role in the regulation of COX-2 through stabilization of its mRNA. The COX-2–specific inhibitor NS-398 attenuated Ang II–stimulated DNA and protein synthesis, as well as PGE
2
production by VSMCs. These results suggest that Ang II regulates COX-2 expression and PG production and modulates cell proliferation through MAPK-mediated signaling pathways in rat VSMCs.
Platelet Ca
2+
ATPases
Authors: Martin Virginie , Bredoux Raymonde , Corvazier Elisabeth , Papp Béla , Enouf Jocelyne
Published: June 2012

Abstract
—Gaining insight into nonmuscle Ca
2+
signaling requires basic knowledge of the major structures involved. We investigated the expression of platelet Ca
2+
ATPases in normal and hypertension-associated abnormal Ca
2+
signaling. First, overall identification of normotensive Wistar-Kyoto rat Ca
2+
ATPases was attempted by looking for newly described human platelet 3′-end alternatively spliced sarco/endoplasmic reticulum Ca
2+
ATPases (SERCA) 3b mRNA and plasma membrane Ca
2+
ATPase (PMCA) 1b and 4b proteins, in addition to SERCA2b and SERCA3a isoforms. For SERCAs, comparative analyses of human and Wistar-Kyoto rat SERCA3 platelet mRNA by reverse transcription–polymerase chain reaction (RT-PCR) followed by sequencing established that human platelets coexpressed SERCA3b and a third SERCA3c, while rat cells were devoid of them but expressed a still unknown splice variant that we termed rSERCA3b/3c. Its identification using 3′-end SERCA3 gene and rapid amplification of cDNA ends (RACE)–PCR studies showed that it results from an additional SERCA3 alternative splicing process, which uses a second alternative polyadenylation site located in the last intron. For PMCAs, with the use of gene-specific RT-PCR followed by sequencing and Western blotting using 5F10 monoclonal antibody, expression of human and rat platelet PMCA1b and PMCA4b was similar. Second, comparative analysis of these newly identified Ca
2+
ATPases and SERCA3a in age-matched spontaneously hypertensive rat platelets demonstrated (1) a marked downregulation of rSERCA3b/3c, which became null, and a 1.71-fold increase in SERCA3a and (2) an opposite regulation of the 2 PMCAs, namely, a 3.3-fold decrease in PMCA1b mRNA and a 3.7-fold increase in PMCA4b mRNA. Hence, platelets coexpress multiple, diverse, and species-specific Ca
2+
ATPases, including a novel fourth SERCA3. Moreover, expression of PMCA (1b and 4b), SERCA3a, and rSERCA3b/3c was modulated in rat hypertension. Hence, Ca
2+
ATPases should be regarded as constituting a new rational basis for the understanding of nonmuscle cell Ca
2+
signaling.
Effects of Systemic Inhibition of Neuronal Nitric Oxide Synthase in Diabetic Rats
Authors: Komers Radko , Oyama Terry T. , Chapman Justin G. , Allison Kristen M. , Anderson Sharon
Published: June 2012

Abstract
—Diabetes is associated with alterations in nitric oxide–mediated vasomotor function. The role of nitric oxide generated via the neuronal nitric oxide synthase pathway in the control of systemic and renal hemodynamics in diabetes has not been studied. To explore the hypothesis that diabetic vascular dysfunction is in part caused by altered neuronal nitric oxide synthase activity, systemic and renal hemodynamics were assessed before and after acute inhibition of this enzyme with a specific inhibitor,
S
-methyl-
l
-thiocitrulline, in control and diabetic rats. The interaction of this pathway and the renin-angiotensin system was studied in separate groups of rats pretreated with the angiotensin II receptor blocker losartan; these rats were compared with rats treated with losartan alone. Diabetic animals demonstrated higher baseline glomerular filtration rates and filtration fractions. At a low dose, the neuronal nitric oxide synthase inhibitor induced similar dose-dependent pressor responses in control and diabetic rats. Losartan abolished the pressor response in both groups. No changes in renal plasma flow or renal vascular resistance occurred in control rats. In contrast, diabetic rats responded with significant renal vasoconstriction. At a high dose, the renal vasoconstriction was similar in both groups and was not affected by losartan. In conclusion, neuronal nitric oxide synthase–derived nitric oxide plays a role in the control of systemic and renal hemodynamics in normal and diabetic rats. Diabetic rats are more sensitive to the inhibitor, suggesting increased activity of this pathway in the diabetic kidney. Furthermore, renal responses in diabetic rats were attenuated by angiotensin II receptor blockade, whereas losartan alone induced hemodynamic changes that were opposite those seen with neuronal nitric oxide synthase inhibition. This observation implicates angiotensin II as an important modulator of this nitric oxide pathway in diabetes.
Angiotensin II Type 1 Receptor A1166C Gene Polymorphism Is Associated With an Increased Response to Angiotensin II in Human Arteries
Authors: van Geel Peter Paul , Pinto Yigal M. , Voors Adriaan A. , Buikema Hendrik , Oosterga Margreeth , Crijns Harry J. G. M. , van Gilst Wiek H.
Published: June 2012

Abstract
—An adenine/cytosine (A/C) base substitution at position 1166 in the angiotensin II type 1 receptor (AT
1
R) gene is associated with the incidence of essential hypertension and increased coronary artery vasoconstriction. However, it is still unknown whether this polymorphism is associated with a difference in angiotensin II responsiveness. Therefore, we assessed whether the AT
1
R polymorphism is associated with different responses to angiotensin II in isolated human arteries. Furthermore, we evaluated whether inhibition of the renin-angiotensin system modifies the effect of the AT
1
R polymorphism. One hundred twelve patients who were undergoing coronary artery bypass graft surgery were prospectively randomized to receive an ACE inhibitor or a placebo for 1 week before surgery. Excess segments of the internal mammary artery were exposed to angiotensin II (0.1 nmol/L to 1 μmol/L) and KCl (60 mmol/L) in organ bath experiments. Patients homozygous for the C allele (n=17) had significantly greater angiotensin II responses (percentage of this maximal KCl-induced response) than did patients genotyped with AA+AC (n=95,
P
<0.05). Although ACE inhibition increased the response to angiotensin II, the difference in the response to angiotensin II, between CC and AA+AC patients remained intact in ACE inhibitor–treated patients. These results indicate increased responses to angiotensin II in patients with the CC genotype. The mechanism is preserved during ACE inhibition, which in itself also increased the response to angiotensin II. This reveals that the A1166C polymorphism may be in linkage disequilibrium with a functional mutation that alters angiotensin II responsiveness, which may explain the described relation between this polymorphism and cardiovascular abnormalities.
ET
B
Receptor Blockade Potentiates the Pressor Response to Big Endothelin-1 But Not Big Endothelin-2 in the Anesthetized Rabbit
Authors: Gratton Jean-Philippe , Rae Giles A. , Bkaily Ghassan , D’Orléans-Juste Pedro
Published: June 2012

Abstract
—The precursor of endothelin-1, big endothelin-1, is considered to be a more reliable marker of systemic production of vasoactive peptide. However, it is largely unclear whether ET
B
receptor–dependent clearance and endothelium-derived relaxing factors affect the precursor in a similar manner to mature ET-1. These ET
B
-dependent modulations of big ET-1 and big ET-2 pressor properties were therefore studied in the anesthetized rabbit. When injected into the left cardiac ventricle, ET-1 and ET-2 (0.01 to 1 nmol/kg) each induced biphasic responses (a depressor followed by a pressor response), whereas big ET-1 and big ET-2 (0.1 to 3 nmol/kg) caused only protracted pressor responses. The highest dose of big ET-1 caused significantly greater responses than ET-1, ET-2, or big ET-2. A selective ET
A
receptor antagonist, BQ-123 (1 mg/kg), markedly reduced pressor responses to all 4 peptides, whereas blockade of ET
B
receptors with BQ-788 (0.25 mg/kg) sharply potentiated the responses to ET-1, ET-2, and big ET-1, but not to big ET-2. Indomethacin (10 mg/kg) sharply potentiated the pressor response to ET-1 (1 nmol/kg), but not big ET-1, at all time points. In control animals, ET-1, but not big ET-1, also triggered an indomethacin-sensitive increase in circulating prostacyclin. Finally, systemically administered big ET-1, but not big ET-2, induced a phosphoramidon-sensitive increase in plasma IR-ET. Our results suggest a significant limiting role of ET
B
receptors on pressor responses to big ET-1. In contrast, the same receptor entities do not modulate the hemodynamic properties of the ET-2 precursor, given that, unlike big ET-1, it is poorly converted in the pulmonary or systemic circulation in anesthetized rabbits.