bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Cholecalciferol Treatment on the Relaxant Responses of Spontaneously Hypertensive Rat Arteries to Acetylcholine
Authors: Borges Antonio C. R. , Feres Teresa , Vianna L. M. , Paiva Therezinha B.
Published: June 2012

Abstract
—We studied the effect of oral cholecalciferol treatment on the endothelium-dependent vascular relaxation and hyperpolarization induced by acetylcholine (ACh), which is impaired in spontaneously hypertensive rats (SHR). Adult female SHR and normotensive Wistar-Kyoto rat (WKY) controls received 125 μg of cholecalciferol per kilogram body weight per day for 6 weeks. The responses to ACh of the isolated mesenteric vascular bed and mesenteric artery rings were measured, as well as the smooth muscle cell membrane potential. After cholecalciferol treatment, the systolic blood pressure and basal perfusion pressure of the mesenteric vascular bed of the SHR fell to control levels. The relaxant and hyperpolarizing effects of ACh, which are reduced in SHR, were also brought to control levels after cholecalciferol treatment. These effects of ACh were inhibited by
N
ω
-nitro-
l
-arginine in SHR and by apamin in WKY. After cholecalciferol treatment, SHR hyperpolarizing responses showed the same inhibition pattern as those of WKY. This indicates that, after cholecalciferol treatment, SHR vascular mesenteric preparation responses to ACh are mediated by endothelium-derived hyperpolarizing factor, which induces activation of Ca
2+
-dependent K
+
channels, as in WKY. In untreated SHR, the ACh-mediated response is entirely due to ACh acting via the release of nitric oxide.
Gender Differences in Hypertension in Spontaneously Hypertensive Rats
Authors: Reckelhoff Jane F. , Zhang Huimin , Srivastava Kumud , Granger Joey P.
Published: June 2012

Abstract
—Males are at greater risk of cardiovascular and renal disease than are females. For example, male spontaneously hypertensive rats (SHR) have higher blood pressures than females. Androgens have been strongly implicated in the hypertension of male SHR, because castration attenuates the hypertension. This study determined whether the androgen receptor plays a role in hypertension in male SHR and whether testosterone alone can cause the hypertension or whether conversion to dihydrotestosterone is necessary. Male SHR, aged 10 weeks, were given the androgen receptor antagonist flutamide (8 mg/kg SC; n=8) or the 5α-reductase inhibitor finasteride (30 mg · kg
−1
· d
−1
SC; n=11) daily for 5 to 6 weeks. Control rats (n=10) received vehicle (20% benzyl benzoate or ethanol in castor oil). After 5 to 6 weeks, blood pressure (mean arterial pressure) and glomerular filtration rate were measured. Long-term flutamide treatment caused a reduction in mean arterial pressure (control 178±5 mm Hg; flutamide 159±3 mm Hg;
P
<0.01), but finasteride had no effect (180±5 mm Hg). There were no differences in glomerular filtration rate among the groups. These data indicate that hypertension in male SHR is mediated via the androgen receptor and does not require conversion of testosterone to dihydrotestosterone.
Antiproliferative Actions of Angiotensin-(1-7) in Vascular Smooth Muscle
Authors: Tallant E. Ann , Diz Debra I. , Ferrario Carlos M.
Published: June 2012

Abstract
—Hemodynamic factors, circulating hormones, paracrine factors, and intracrine factors influence vascular smooth muscle growth and plasticity. The well-characterized role of angiotensin II in the modulation of vascular tone and cell function may be critically involved in the mechanisms by which vascular smooth muscle responds to signals associated with vascular endothelial dysfunction and increases in oxidative stress. Studies from this laboratory suggest that the trophic actions of angiotensin II may be intrinsically regulated by angiotensin-(1-7), a separate product of the angiotensin system derived from the common substrate, angiotensin I. Exposure of cultured vascular smooth muscle cells to angiotensin-(1-7) inhibited the trophic actions of angiotensin II and reduced the expression of the mitogenic effects of both normal serum and platelet-derived growth factor. The growth-inhibitory actions of angiotensin-(1-7) were blocked by the selective
d
-alanine
7
-angiotensin-(1-7) antagonist and the nonselective angiotensin receptor blocker sarcosine
1
-threonine
8
-angiotensin II. In contrast, subtype-selective antagonists for the AT
1
and AT
2
receptors had no effect on the inhibitory actions of angiotensin-(1-7), a finding that is consistent with the pharmacological characterization of a high-affinity
125
I-labeled angiotensin-(1-7) binding site in the vasculature by use of selective and nonselective angiotensin II receptor antagonists. The relevance of these findings to the proliferative response of vascular smooth muscle cells after endothelial injury was confirmed by assessment of the effect of a 12-day infusion of angiotensin-(1-7) on neointimal formation. In these experiments, the proliferative response produced by injuring the carotid artery was inhibited by angiotensin-(1-7) through a mechanism that could not be explained by changes in arterial pressure. Because plasma angiotensin-(1-7) increased to levels comparable to those found in animals and human subjects given therapeutic doses of angiotensin-converting enzyme inhibitors, angiotensin-(1-7) may be one factor participating in the reversal of vascular proliferation during inhibition of angiotensin II formation or activity.
Effect of Estrogen Replacement on Vasoconstrictor Responses in Rat Mesenteric Arteries
Authors: Zhang Yunlong , Davidge Sandra T.
Published: June 2012

Abstract
—Recent studies have shown that estrogen can increase endothelial nitric oxide synthase expression and/or activity and that nitric oxide may play a role in attenuating vasoconstrictor responses. Yet there are still controversies in this field. Our hypothesis was that the role of nitric oxide in modulating vasoconstrictor responses in estrogen-replaced animals depends on the agonist. The aim of the study was to determine the effect of long-term estrogen replacement on vascular reactivity of resistance-sized mesenteric arteries in ovariectomized rats with the use of a variety of vasoconstrictors. Female Sprague-Dawley rats were ovariectomized at 11 weeks of age. 17β-estradiol pellets (0.5 mg/pellet) were implanted in the estrogen-replaced group (n=9) for 4 weeks; placebo pellets were used in the ovariectomized group (n=10). Resistance-sized mesenteric arteries were dissected and mounted onto a dual-chamber arteriograph system. Estradiol replacement did not alter the response of mesenteric arteries to either arginine vasopressin or the thromboxane mimetic U46619. Inhibition of nitric oxide synthase with
N
G
-monomethyl-
l
-arginine (100 μmol/L) did not modulate these vasoconstrictor responses in either group of rats. In contrast, the dose-response curve of the adrenergic agonist phenylephrine was significantly attenuated for the estradiol-replaced rats compared with the ovariectomized group (EC
50
=0.90±0.17 vs 0.44±0.08 μmol/L,
P
<0.05). After incubation with
N
G
-monomethyl-
l
-arginine, the EC
50
of phenylephrine significantly decreased in both groups, but a significant difference remained between the 2 groups (EC
50
=0.41±0.08 vs 0.28±0.02 μmol/L,
P
<0.05). Importantly, Western immunoblotting demonstrated that the expression of α
1
-adrenergic receptors was significantly suppressed by estradiol replacement. We conclude that estrogen may have a specific effect on adrenergic vasoconstriction by modulating its receptors.
Orthostatic Stimuli Rapidly Change Plasma Adrenomedullin in Humans
Authors: Rössler Andreas , László Zoltán , Haditsch Bernd , Hinghofer-Szalkay Helmut G.
Published: June 2012

Abstract
—The aim of this study was to evaluate the effect of orthostasis on the time course of plasma adrenomedullin concentration. On 5 different days, normotensive subjects were randomized to undergo for 30 minutes either 12°, 30°, 53°, or 70° passive head-up tilt or to remain supine. Venous blood was collected from each subject in the supine position before tilting, at 3 and 27 minutes during tilting, and at 2 and 50 minutes after orthostasis. Plasma adrenomedullin increased significantly with tilt of ≥30° in a stimulus-dependent manner. Approximately half of the increase seen at 27 minutes occurred during the first 2 minutes of upright positioning; the maximum effect with 70° tilt was +70%. Elevations in norepinephrine, epinephrine, aldosterone, plasma renin activity, vasopressin, heart rate, and mean arterial pressure were also significant. Hematocrit, blood density, plasma density, and plasma volume loss rose (
P
<0.05) at 53° and 70° tilt. Our results indicate that adrenomedullin may play an important role in stabilization of hemodynamics during passive orthostasis. In conclusion, plasma adrenomedullin rapidly increases with orthostatic challenge in a stimulus-dependent manner and also swiftly returns to baseline levels after the subject resumes the supine position.
Time-Dependent Effects of the Neuropeptide PACAP on Catecholamine Secretion
Authors: Taupenot Laurent , Mahata Manjula , Mahata Sushil K. , O’Connor Daniel T.
Published: June 2012

Abstract
—Pituitary adenylyl cyclase-activating polypeptide (PACAP) is a potent endogenous secretagogue for chromaffin cells. We previously reported that PACAP coupled to the PAC1 receptor to evoke dihydropyridine-sensitive early (15 to 20 minutes) catecholamine secretion and cAMP response element binding protein–mediated
trans-
activation of the secretory protein chromogranin A promoter in PC12 pheochromocytoma cells. In this report, we studied whether the secretory and transcriptional responses elicited by PACAP were subject to desensitization. We found that PACAP evoked distinct immediate (initial, 0 to 20 minutes) and long-lasting (20 to 180 minutes) effects on catecholamine secretion. Initial secretory and chromogranin A
trans
-activation responses induced by PACAP were desensitized in a dose-dependent fashion after preexposure of cells to PACAP, and the IC
50
doses of PACAP for desensitization were ≈18- to ≈32-fold lower than the EC
50
activating doses for secretion or transcription. Desensitization of the initial secretion response was associated with decreased Ca
2+
influx through L-type voltage-operated Ca
2+
channels. Acute exposure to PACAP also triggered long-lasting (up to 3 hours), extracellular Ca
2+
-dependent, pertussis toxin–insensitive catecholamine secretion; indeed, even after short-term (20 minutes) exposure to PACAP and removal of the secretagogue, PC12 cells continued to secrete norepinephrine up to 76.9±0.22% of cellular norepinephrine content after 3 hours. A phospholipase C-β inhibitor (U-73122) blocked this extended secretory response, which was dependent on low-magnitude Ca
2+
influx resistant to several L-, N-, P/Q-, or T-type Ca
2+
channel antagonists, but sensitive to Zn
2+
, Ni
2+
, Cd
2+
, or to the store-operated Ca
2+
channel blocker
SKF96365
. A less than additive effect of the sarco-endoplasmic reticulum Ca
2+
-ATPase inhibitor thapsigargin plus PACAP on this sustained secretion also supported a contribution of store-operated Ca
2+
entry to the sustained secretory response. We propose that PACAP-evoked secretion and transcription are subject to homologous desensitization in PC12 cells; however, PACAP also induces long-lasting secretion, even under dose and time circumstances in which acute, dihydropyridine-sensitive secretion has been desensitized. Although initial secretion is mediated by an L-type voltage-operated Ca
2+
channel, extended secretion may involve a store-operated Ca
2+
channel that is activated through a G
q/11
/phospholipase C-β/phosphoinositide signaling pathway.
Epoxyeicosatrienoic Acids Increase Intracellular Calcium Concentration in Vascular Smooth Muscle Cells
Authors: Fang Xiang , Weintraub Neal L. , Stoll Lynn L. , Spector Arthur A.
Published: June 2012

Abstract
—Epoxyeicosatrienoic acids (EETs) are cytochrome P450–derived metabolites of arachidonic acid. They are potent endogenous vasodilator compounds produced by vascular cells, and EET-induced vasodilation has been attributed to activation of vascular smooth muscle cell (SMC) K
+
channels. However, in some cells, EETs activate Ca
2+
channels, resulting in Ca
2+
influx and increased intracellular Ca
2+
concentration ([Ca
2+
]
i
). We investigated whether EETs also can activate Ca
2+
channels in vascular SMC and whether the resultant Ca
2+
influx can influence vascular tone. The 4 EET regioisomers (1 μmol/L) increased porcine aortic SMC [Ca
2+
]
i
by 52% to 81%, whereas arachidonic acid, dihydroxyeicosatrienoic acids, and 15-hydroxyeicosatetraenoic acid (1 μmol/L) produced little effect. The increases in [Ca
2+
]
i
produced by 14,15-EET were abolished by removal of extracellular Ca
2+
and by pretreatment with verapamil (10 μmol/L), an inhibitor of voltage-dependent (L-type) Ca
2+
channels. 14,15-EET did not alter Ca
2+
signaling induced by norepinephrine and thapsigargin. When administered to porcine coronary artery rings precontracted with a thromboxane mimetic, 14,15-EET produced relaxation. However, when administered to rings precontracted with acetylcholine or KCl, 14,15-EET produced additional contractions. In rings exposed to 10 mmol/L KCl, a concentration that did not affect resting ring tension, 14,15-EET produced small contractions that were abolished by EGTA (3 mmol/L) or verapamil (10 μmol/L). These observations indicate that 14,15-EET enhances [Ca
2+
]
i
influx in vascular SMC through voltage-dependent Ca
2+
channels. This 14,15-EET–induced increase in [Ca
i
2+
] can produce vasoconstriction and therefore may act to modulate EET-induced vasorelaxation.
Effect of Continuous Positive Airway Pressure on Blood Pressure
Authors: Dimsdale Joel E. , Loredo Jose S. , Profant Judi
Published: June 2012

Abstract
—This study examined the effect of continuous positive airway pressure (CPAP) treatment on blood pressure in patients with obstructive sleep apnea. Thirty-nine patients with sleep apnea were studied. Ambulatory blood pressure monitoring was obtained before and after patients were randomized to receive either 1 week of CPAP or placebo CPAP (CPAP administered at ineffective pressure). Blood pressure was examined over daytime hours (6
am
to 10
pm
) and during nighttime hours (10
pm
to 6
am
). Daytime mean arterial blood pressure decreased significantly but equally in both the active treatment group and the placebo treatment group (
P
=0.001). Nighttime mean arterial pressure levels decreased to a much greater extent over time in the patients who received active CPAP treatment (
P
=0.032). CPAP does appear to decrease nighttime blood pressure. However, the decrease in daytime blood pressure may reflect a nonspecific response (ie, placebo), since both the active treatment group and the placebo treatment group developed comparable decreases in blood pressure.
Implications of Species Difference for Clinical Investigation
Authors: Hollenberg Norman K.
Published: June 2012

Abstract
—The justification for clinical investigation has its roots in the fact that physiological mechanisms and disease pathogenesis in animal models replicate mechanisms and pathogenesis in humans only in part. In the case of the renin-angiotensin system, there is species variation in the anatomic distribution of the renin-angiotensin system, in the active site of the renin enzyme, and in the structure of angiotensin and the AT
1
receptor. The conversion of angiotensin I (Ang I) to angiotensin II (Ang II) may prove to be the most important aspect of species variation. In plasma, all the conversion occurs through a single enzyme, angiotensin-converting enzyme (ACE), and species variation in structure and function have not been reported. Non–ACE-dependent pathways, which occur only at the tissue level, show unambiguous, striking species variation. Specifically, chymase, the most important enzyme responsible for non-ACE conversion of Ang I to Ang II, shows striking species variation. In humans and a number of species, including the hamster, quantitatively important chymase-independent Ang II formation from Ang I occurs in the heart, arteries, and kidney. In rats and rabbits, on the other hand, chymase differs, is not active in the conversion of Ang I to Ang II, and indeed is involved in Ang II degradation. Consequently, one would anticipate that blockade of the system at the ACE step would be equivalent to that at the Ang II receptor in the rat. This has been widely reported. In humans, on the other hand, one would anticipate that the AT
1
receptor blockers will be more effective than ACE inhibitors. Again, preliminary evidence favors this possibility. The implications for therapeutics are clear.
G-Protein β
3
Subunit Gene Variant and Left Ventricular Hypertrophy in Essential Hypertension
Authors: Poch Esteban , González Daniel , Gómez-Angelats Elisenda , Enjuto Montserrat , Paré Joan Carles , Rivera Francisca , de la Sierra Alejandro
Published: June 2012

Abstract
—A functional genetic variant consisting of a C825T substitution in the
GNB3
gene, encoding for the G-protein β
3
subunit, has been associated with enhanced G-protein activation and cell growth. The aim of the study was to investigate the association of this polymorphism with left ventricular hypertrophy (LVH) in a sample of patients with essential hypertension. Left ventricular mass was assessed by 2-mode echocardiography in 86 patients with essential hypertension, and
GNB3
C825T genotype was determined by polymerase chain reaction and restriction digestion. Thirty-seven (0.43) patients were homozygous for the C allele (CC), 40 (0.47) were heterozygous (CT), and 9 (0.10) were homozygous for the T allele (TT). The genotype distribution among the patients was in Hardy-Weinberg equilibrium. Values of left ventricular end-diastolic diameter (52.0±0.7 versus 48.9±0.9 mm,
P
=0.007), posterior wall thickness (11.3±0.2 versus 10.6±0.2 mm,
P
=0.042), and left ventricular mass index (152.7±4.4 versus 135.2±6.4 g/m
2
,
P
=0.023) were significantly higher in patients with CT and TT genotypes considered together (CT+TT) than in CC patients. The distribution of the genotypes was significantly different when comparing patients with LVH: 20 (0.33) CC and 40 (0.67) CT+TT patients had this complication, and 17 (0.65) CC and 9 (0.35) CT+TT patients did not (
P
<0.01). The frequency of the T allele was significantly different among patients with (0.40) and without (0.20) LVH (
P
<0.01). A logistic regression analysis showed that the association between the T allele and LVH was independent of age, mean blood pressure, body mass index, and alcohol consumption. The relative risk of LVH in patients bearing the T allele (CT+TT group) compared with CC hypertensive patients was 3.03 (95% CI 1.14 to 8.05). The findings suggest an association between LVH and the 825T allele in hypertensive patients.
Genetic Analysis of Rat Chromosome 1 and the
Sa
Gene in Spontaneous Hypertension
Authors: St. Lezin Elizabeth , Liu Weizhong , Wang Jia-Ming , Yang Ying , Qi Nianning , Kren Vladimir , Zidek Vaclav , Kurtz Theodore W. , Pravenec Michal
Published: June 2012

Abstract
—Linkage studies in segregating populations derived from the spontaneously hypertensive rat (SHR) indicate that a blood pressure quantitative trait locus exists on rat chromosome 1 in the vicinity of the
Sa
gene. On the basis of these findings and the observation of increased renal expression of the
Sa
gene in SHR versus normotensive rats, the
Sa
gene has been proposed as a candidate gene for spontaneous hypertension. In SHR congenic strains, we and others have found that replacement of a segment of SHR chromosome 1 that contains the
Sa
gene with the corresponding chromosome segment from a normotensive Brown Norway (BN) rat or Wistar-Kyoto rat can reduce blood pressure. To test whether the
Sa
gene is necessary for the effect of this region of chromosome 1 on blood pressure, we studied a new SHR congenic subline that harbors a smaller segment of BN chromosome 1 that does not include the
Sa
gene. Transfer of this subregion of chromosome 1 from the BN rat onto the SHR background was associated with significant reductions in blood pressure comparable to those previously observed on transfer of a larger region of chromosome 1 that included the
Sa
gene. Thus, in the SHR-BN model of hypertension, the results of these mapping studies (1) demonstrate that molecular variation in the
Sa
gene is not required for the effect of this region of chromosome 1 on blood pressure and (2) should direct attention toward other candidate genes within the differential chromosome segment of the new congenic subline.
Interleukin-1β Regulates the Human Brain Natriuretic Peptide Promoter via Ca
2+
-Dependent Protein Kinase Pathways
Authors: He Quan , LaPointe Margot C.
Published: June 2012

Abstract
—We have shown that interleukin-1β (IL-1β) activates the human brain natriuretic peptide (hBNP) promoter via a transcriptional mechanism. Others have reported that changes in intracellular calcium (Ca
2+
) mediate the action of IL-1β. We questioned whether Ca
2+
and Ca
2+
-dependent pathways mediate IL-1β regulation of the hBNP promoter in cardiac myocytes. The hBNP promoter (−1818 to +100) coupled to a luciferase cDNA reporter gene was transferred into neonatal cardiac myocytes. Cells were then treated with agents that modify Ca
2+
levels or inhibit Ca
2+
-dependent kinases, and luciferase activity was measured as an index of hBNP promoter activity. The Ca
2+
ionophore A23187 increased hBNP promoter activity; however, neither EGTA nor nifedipine reduced IL-1β–stimulated promoter activity. Long-term treatment with thapsigargin, which depletes intracellular Ca
2+
stores, decreased basal promoter activity and blocked the effect of IL-1β. Inhibition of protein kinase C completely blocked IL-1β–stimulated hBNP promoter activity, whereas inhibition of Ca
2+
/calmodulin-dependent kinase II decreased promoter activity by 40%. In contrast, inhibition of the Ca
2+
-regulated phosphatase calcineurin by cyclosporin A had no effect. These data suggest that (1) Ca
2+
activates the hBNP promoter; (2) release of Ca
2+
from intracellular stores is important to IL-1β regulation of the hBNP promoter, but transport via voltage-sensitive Ca
2+
channels is not; (3) protein kinase C and Ca
2+
/calmodulin-dependent kinase II mediate the action of IL-1β; and (4) the phosphatase calcineurin is not involved in IL-1β regulation of the hBNP promoter. Thus, Ca
2+
and Ca
2+
-dependent pathways are critical to IL-1β regulation of the hBNP promoter.
Involvement of Rho-Kinase in Angiotensin II–Induced Hypertrophy of Rat Vascular Smooth Muscle Cells
Authors: Yamakawa Tadashi , Tanaka Shun-ichi , Numaguchi Kotaro , Yamakawa Yuko , Motley Evangeline D. , Ichihara Sahoko , Inagami Tadashi
Published: June 2012

Abstract
—Angiotensin II (Ang II) is now believed to play a critical role in the pathogenesis of hypertrophy and/or hyperplasia of vascular smooth muscle cells (VSMCs). Several G
i
- and G
q
-coupled receptors, including the Ang II type 1 (AT
1
) receptor, activate Rho and Rho-associated kinase in Swiss 3T3 cells and cardiac myocytes. However, little is known about the role of Rho-kinase in Ang II–induced vascular hypertrophy in VSMCs. In the present study, we explored the role of Rho and Rho-kinase in Ang II–induced protein synthesis in VSMCs. In unstimulated cells, RhoA was observed predominantly in the cytosolic fraction, but it was translocated in part to the particulate fraction in response to Ang II (100 nmol/L). This effect was completely blocked by the AT
1
receptor blocker candesartan but not by the Ang II type 2 (AT
2
) receptor antagonist PD123319. Botulinum C
3
exoenzyme, which inactivated RhoA, attenuated Ang II–induced [
3
H]leucine incorporation. The specific Rho-kinase inhibitor, Y-27632, dose-dependently abolished Ang II–induced protein synthesis and also suppressed Ang II–induced c-
fos
mRNA expression. On the other hand, Y-27632 had no effect on Ang II–stimulated phosphorylation of p70 S6 kinase and extracellular signal—regulated kinase 1/2, which are reported to be involved in Ang II–induced protein synthesis, nor had it any effect on the Ang II–induced phosphorylation of PHAS-I, a heat- and acid-stable eIF-4E–binding protein. The phosphorylation of PHAS-I is regulating for translation initiation. These observations suggest that the Rho, Rho-kinase, and c-fos pathways may play a role in Ang II–induced hypertrophic changes of VSMCs through a novel pathway.
eNOS Mediates
l
-Arginine–Induced Inhibition of Thick Ascending Limb Chloride Flux
Authors: Plato Craig F. , Shesely Edward G. , Garvin Jeffrey L.
Published: June 2012

Abstract
—We recently reported that the rat thick ascending limb (THAL) possesses an active isoform of nitric oxide synthase (NOS) that is substrate-limited in vitro. NO produced by THAL NOS inhibits chloride flux. Protein and transcript for each of the primary NOS isoforms−endothelial (eNOS), inducible (iNOS), and neuronal (nNOS)−have been demonstrated in THALs. However, the NOS isoform that mediates NO-induced inhibition of chloride flux is unknown. We hypothesized that NO produced from eNOS in the THAL inhibits NaCl transport. THALs from male eNOS, iNOS, and nNOS knockout mice and C57BL/6J wild-type controls were perfused in vitro and the response of transepithelial chloride flux (J
Cl
) to
l
-arginine (L-Arg), the substrate for NOS, and spermine NONOate (SPM), an NO donor was measured. We first tested whether isolated mouse THALs could synthesize NO and whether this NO inhibits transport. Addition of 0.5 mmol/L L-Arg to the bath decreased J
Cl
from 105.8±17.5 to 79.2±15.8 pmol/mm per minute (
P
<0.01) in C57BL/6J wild-type mice, whereas addition of
d
-Arginine had no effects on J
Cl.
In contrast, addition of 0.5 mmol/L L-Arg to the bath did not alter J
Cl
of THALs from eNOS knockout mice. When 10 μmol/L SPM was added to the bath of eNOS knockout THALs, J
Cl
decreased from 89.1±8.6 to 74.8±7.5 pmol/mm/min (
P
<0.05). Thus the lack of responsiveness of eNOS knockout THALs to L-Arg was not due to an inability to respond to NO. We next evaluated the role of iNOS and nNOS in the response to L-Arg. Addition of 0.5 mmol/L L-Arg to the bath decreased J
Cl
in THALs from iNOS and nNOS knockout mice by 37.7±6.4% (
P
<0.05) and 31.8±8.3% (
P
<0.01), respectively. We conclude that eNOS is the active isoform of NOS in the THAL under basal conditions. Mouse THAL eNOS responds to exogenous L-Arg by increasing NO production, which, in turn, inhibits J
Cl
.
Release of Angiotensin-(1-7) From the Rat Hindlimb
Authors: Chappell Mark C. , Gomez Martina N. , Pirro Nancy T. , Ferrario Carlos M.
Published: June 2012

Abstract
—The results of recent studies have demonstrated that angiotensin (Ang)-(1-7) contributes to the antihypertensive actions of either combined ACE/Ang II type 1 receptor blockade or ACE inhibition alone. The vasculature is a key site of action for either drug regimen, and evidence favors a local Ang system within these tissues. Because ACE may degrade Ang-(1-7), we determined whether ACE inhibition alters Ang-(1-7) release from the rat hindlimb perfused with Krebs-Ringer buffer containing Ficoll. Ang-(1-7) release averaged 36±13 fmol (period 1, 15-minute collection) and 44±11 fmol (period 2) in the control buffer. The addition of the ACE inhibitor lisinopril to the perfusion buffer augmented levels of Ang-(1-7) in periods 3 (144±39 fmol) and 4 (163±35 fmol;
P
<0.05 versus 1 or 2, n=8). HPLC and radioimmunoassay of effluent from control or lisinopril treatment demonstrated a single immunoreactive peak with a retention time identical to that of Ang-(1-7). The addition of the neprilysin inhibitor SCH 39370 reduced Ang-(1-7) release in the lisinopril buffer from 177±32 (period 1) and 173±39 (period 2) fmol to 112±24 (period 3) and 87±23 fmol (period 4;
P
<0.05 versus 1 or 2, n=6). Ang I metabolism in the collected perfusate revealed the formation of Ang-(1-7) that was sensitive only to thimet oligopeptidase inhibition; Ang II generation was not detected. The present study demonstrates the recovery of endogenous Ang-(1-7) from the perfused hindlimb. The release of Ang-(1-7) is significantly influenced by inhibition of ACE, which may reflect both increased substrate (Ang I) levels and reduced metabolism of the peptide. Neprilysin inhibition reduced but did not abolish Ang-(1-7) release, which suggests that other endopeptidases may contribute to the release of the peptide.
Angiotensin II Type 1 Receptor Blockade Prevents Cardiac Remodeling in Bradykinin B
2
Receptor Knockout Mice
Authors: Madeddu Paolo , Emanueli Costanza , Maestri Roberta , Salis Maria Bonaria , Minasi Alessandra , Capogrossi Maurizio C. , Olivetti Giorgio
Published: June 2012

Abstract
—Knockout mice (B
2
−/−
) lacking the bradykinin (BK) B
2
receptor gene develop mild hypertension, cardiac hypertrophy, and myocardial damage. We hypothesized that these effects are due to the hypertrophying and damaging actions of angiotensin II (Ang II) in the absence of the balancing protection of BK. To verify this hypothesis, B
2
−/−
or wild-type mice (B
2
+/+
) were administered a nonpeptide antagonist of Ang II type 1 (AT
1
) receptors (
A81988
) from conception through 180 days of age. Untreated B
2
+/+
and B
2
−/−
served as controls. Blood pressure (BP) and heart rate were monitored with the use of tail-cuff plethysmography at regular intervals. Ventricular weights, diameters, wall thickness, chamber volume, and myocardial fibrosis were measured at 40 and 180 days. No differences were observed in BP, heart rate, and cardiac weight and dimensions between treated and untreated B
2
+/+
. The BP of AT
1
antagonist–treated B
2
−/−
was reduced until 70 days; then, it increased to the levels found in untreated B
2
−/−
. AT
1
receptor blockade resulted in a reduction in left ventricular mass, chamber volume, and wall thickness and abrogated myocardial fibrosis in B
2
−/−
. These results indicate that Ang II is the major factor responsible for ventricular remodeling and myocardial damage in mice with disruption of BK B
2
receptor signaling. The interaction of Ang II and BK appears to be essential for the development of a normal heart.
Aging and Chronic Hypertension Decrease Expression of Rat Aortic Soluble Guanylyl Cyclase
Authors: Klöß Stephan , Bouloumié Anne , Mülsch Alexander
Published: June 2012

Abstract
—We analyzed the influence of aging and genetic hypertension on the function and expression of soluble guanylyl cyclase (sGC) in the aortas of prehypertensive and old spontaneously hypertensive rats (SHR) as well as in age-matched normotensive Wistar-Kyoto rats (WKY). The expression of heterodimeric sGC (α
1
and β
1
) was assessed at the mRNA and protein level, and its function was assessed by the relaxant responses of phenylephrine-contracted endothelium-denuded aortic rings to the nitric oxide (NO) donor sodium nitroprusside. The vasodilator potency of sodium nitroprusside was significantly reduced (
P
<0.05) with age (3- to 6-fold increase in the EC
50
in old WKY and SHR compared with their young counterparts) as well as with hypertension (3-fold increase in old SHR compared with age-matched WKY), whereas the vasodilator potency of sodium nitroprusside did not differ between young SHR and WKY. A similar influence of aging and hypertension on NO-stimulated GC activity was revealed at the GC expression level: Whereas the β
1
protein content was similar in young rats of both strains, old WKY exhibited 60% lower and old SHR exhibited 80% lower β
1
subunit protein compared with young rats (
P
<0.05). Moreover, the abundance of α
1
and β
1
mRNA (assessed by reverse transcriptase—polymerase chain reaction) was similar in young rats but was 2.5-fold (α
1
) and 4.3-fold (β
1
) lower in old SHR compared with old WKY. In conclusion, our findings show that both aging and hypertension decrease sGC expression and its NO-dependent activation in aortic tissue. Downregulation of sGC may therefore contribute to arterial dysfunction in senescence and chronic hypertension.
Subpressor Doses of Angiotensin II Increase Plasma F
2
-Isoprostanes in Rats
Authors: Reckelhoff Jane F. , Zhang Huimin , Srivastava Kumud , Roberts L. Jackson , Morrow Jason D. , Romero J. Carlos
Published: June 2012

Abstract
—The present study was performed to determine whether physiologically relevant doses of angiotensin II (Ang II), which do not affect renal hemodynamics but do cause slow response hypertension, result in oxidative stress as measured by production of vasoconstrictor F
2
-isoprostane, a prostaglandin-like non–cyclooxygenase-produced arachidonic acid metabolite that is the end product of lipid peroxidation. Rats were instrumented with abdominal aortic and left femoral venous catheters, and before and throughout Ang II (or saline) infusion, all rats received enalapril (250 mg/L). Four days after the initiation of enalapril, rats were infused with Ang II (10 ng · kg
−1
· min
−1
, n=6) or saline (n=6) for 14 days. Mean arterial pressure was measured 24 hours per day, and on day 12, glomerular filtration rate and renal plasma flow were measured. Mean arterial pressure in control rats averaged 85±1 mm Hg, and with Ang II infusion, mean arterial pressure increased slowly and reached a plateau on day 3, averaging 117±2 mm Hg (
P
<0.0001 compared with enalapril alone). Glomerular filtration rate and renal plasma flow were not affected by Ang II. Free F
2
-isoprostanes in plasma increased by 54% with Ang II (
P
<0.01), and the production of F
2
-isoprostanes esterified in plasma lipids tended to be higher with Ang II also but did not reach significance (
P
=0.1). These studies suggest that low doses of Ang II are capable of producing oxidative stress in animals. Whether oxidative stress plays a causative role in Ang II–mediated slow-response hypertension or is secondary to the hypertension is not clear from these data and will require further study.
Influence of the I/D Polymorphism of the Angiotensin-Converting Enzyme Gene on the Outcome of Microalbuminuria in Essential Hypertension
Authors: Redon Josep , Chaves Felipe Javier , Liao Youlian , Pascual Jose Maria , Rovira Eduardo , Armengod Maria Eugenia , Cooper Richard S.
Published: June 2012

Abstract
—The objective of the present study was to analyze the influence of the I/D polymorphism of the ACE gene on the outcome of microalbuminuria in essential hypertensive patients who were receiving antihypertensive treatment. One hundred thirty-six essential hypertensive patients who were <50 years old and had never previously received treatment with antihypertensive drugs were included in the study. During a 3-year period, patients received nonpharmacological treatment consisting of moderate salt restriction and a low-calorie diet they were obese, with or without a regimen of antihypertensive drugs based on β-blockers or ACE inhibitors. Hydrochlorothiazide was added when necessary to maintain the blood pressure goal of <135/85 mm Hg. At the beginning of the study and at yearly intervals, systolic and diastolic blood pressures (SBP and DBP, respectively), 24-hour urinary albumin excretion (UAE), renal function, and biochemical profile measurements were made. The insertion/deletion (I/D) polymorphism of the ACE gene was determined through the use of polymerase chain reaction. The variables used in the statistical analysis were the measurements at the start of the study and the increase or decrease detected during the follow-up, estimated as individual specific regression line slope values. At baseline, no differences in blood pressure or UAE values were observed among genotypes. Likewise, the genotype or allele frequency was not significantly different between normoalbuminurics and microalbuminurics. After the 3 treatment years, significant reductions in SBP, DBP, and UAE were found (SBP 151.6±17.3 reduced to 137.2±14.3 mm Hg,
P
<0.001; DBP 96.6±8.9 reduced to 84.5±9.8 mm Hg,
P
<0.001; UAE 36.7±71.5 reduced to 28.3±78.6 mg/24 h,
P
<0.05). The slopes of these parameters over time did not differ significantly among genotypes. The slope of SBP was the main factor related to the slope of logUAE (
P
<0.003). A significant positive correlation coefficient between the SBP and logUAE slopes was observed for the DD patients (
r
=0.57,
P
<0.0001) but was absent in patients carrying the I allele (II
r
=−0.03,
P
=NS; I/D
r
=0.01,
P
=NS). Follow-up studies should be used to achieve a better understanding of the impact of candidate gene polymorphisms on the development of hypertension-induced organ damage. Assessment of the I/D polymorphism of the ACE gene may identify subjects who require a greatly lowered blood pressure to prevent organ damage and to reduce hypertension-associated complications and death.
Impact of Different Partition Values on Prevalences of Left Ventricular Hypertrophy and Concentric Geometry in a Large Hypertensive Population
Authors: Wachtell Kristian , Bella Jonathan N. , Liebson Philip R. , Gerdts Eva , Dahlöf Björn , Aalto Tapio , Roman Mary J. , Papademetriou Vasilios , Ibsen Hans , Rokkedal Jens , Devereux Richard B.
Published: June 2012

Abstract
—Left ventricular (LV) hypertrophy and concentric remodeling have been defined by using a variety of indexation methods and partition values (PVs) for LV mass and relative wall thickness (RWT). The effects of these methods on the distribution of LV geometric patterns in hypertensive subjects remain unclear. Echocardiograms were obtained in 941 patients with stage I to III hypertension and LV hypertrophy by ECG. LV mass was calculated by using different methods of indexation for body size and different PVs to identify hypertrophy: LV mass/body surface area (g/m
2
) PV for men/women 116/104, 125/110, or 125/125; LV mass/height (g/m) PV 143/102 or 126/105; and LV mass/height
2.7
(g/m
2.7
) PV 51/51 or 49.2/46.7. RWT was calculated by either 2×end-diastolic posterior wall thickness (PWT)/end-diastolic LV internal dimension (LVID) or end-diastolic interventricular septum dimension+end-diastolic PWT/end-diastolic LVID. LV hypertrophy or remodeling was present in 63% to 86% of subjects, and LV hypertrophy was present in 42% to 77%. By any index, eccentric hypertrophy was the common LV geometric pattern. Use of interventricular septum dimension+PWT/LVID to calculate RWT slightly increased the prevalence of normal geometry and eccentric hypertrophy compared with the use of 2×PWT/LVID. Subjects with LV hypertrophy identified by only LV mass/height
2.7
PV 49.2/46.7 were more obese, whereas those identified by only LV mass/body surface area PV 116/104 were taller and thinner than those in the 2 concordant groups with or without LV hypertrophy by both criteria. By either criterion, there were no significant differences between different LV geometric patterns in clinical cardiovascular disease. Hypertensive patients with LV hypertrophy by ECG have a high prevalence of geometric abnormalities, especially eccentric hypertrophy, irrespective of method of indexation or PV. LV mass indexation by body surface area or height
2.7
identifies lean and obese subjects, respectively. We found no difference in prevalent cardiovascular disease in subjects identified by either criterion, suggesting a similar high risk.
Role of Transforming Growth Factor-β1 in Cardiovascular Inflammatory Changes Induced by Chronic Inhibition of Nitric Oxide Synthesis
Authors: Koyanagi Masamichi , Egashira Kensuke , Kubo-Inoue Mayuko , Usui Makoto , Kitamoto Shiro , Tomita Hideharu , Shimokawa Hiroaki , Takeshita Akira
Published: June 2012

Abstract
—We previously reported that chronic inhibition of nitric oxide (NO) synthesis with
N
ω
-nitro-
l
-arginine methyl ester (L-NAME) induces inflammatory changes (monocyte infiltration, myofibroblast formation, and monocyte chemoattractant protein-1 [MCP-1] and transforming growth factor-β1 [TGF-β1] expression) in the rat heart and vessel. There is debate regarding whether TGF-β1 exhibits proinflammatory or anti-inflammatory activities. We used the rat model to investigate the role of TGF-β in the pathogenesis of such inflammatory changes. We show here that infiltrating monocytes and myofibroblasts in the inflammatory lesions produced TGF-β1 on the third day of L-NAME administration. Cotreatment with a monoclonal antibody against TGF-β1, but not with control IgG, prevented the L-NAME–induced cardiac inflammation. The antibody also significantly inhibited the gene expression of MCP-1, P-selectin, and intercellular adhesion molecule-1. In summary, the antibody against TGF-β1 prevented inflammatory changes in rat heart and vessel induced by chronic inhibition of NO synthesis, suggesting that increased production of TGF-β1 is involved in the inflammatory changes in this model.
Blood Pressure–Independent Effects in Rats With Human Renin and Angiotensinogen Genes
Authors: Mervaala Eero , Müller Dominik N. , Schmidt Folke , Park Joon-Keun , Gross Volkmar , Bader Michael , Breu Volker , Ganten Detlev , Haller Hermann , Luft Friedrich C.
Published: June 2012

Abstract
—The blood pressure–independent effects of angiotensin II (Ang II) were examined in double transgenic rats (dTGR) harboring human renin and human angiotensinogen genes, in which the end-organ damage is due to the human components of the renin angiotensin system. Triple-drug therapy (hydralazine 80 mg/L, reserpine 5 mg/L, and hydrochlorothiazide 25 mg/L in drinking water) was started immediately after weaning. Triple-drug therapy normalized blood pressure and coronary resistance, only partially prevented cardiac hypertrophy, and had no effect on ratio of renal weight to body weight. Although triple-drug therapy delayed the onset of renal damage, severe albuminuria nevertheless occurred. Semiquantitative scoring of ED-1–positive and MIB-5–positive (nuclear cell proliferation–associated antigen Ki-67) cells showed profound perivascular monocyte/macrophage infiltration and cell proliferation in kidneys and hearts of untreated dTGR. Triple-drug therapy had only a minimal effect on local inflammatory response or vascular cell proliferation. In contrast, a novel orally active human renin inhibitor (HRI), 30 mg/kg by gavage for 4 weeks, normalized blood pressure and coronary resistance and also prevented cardiac hypertrophy and albuminuria. ED-1–positive cells and MIB-5–positive cells were decreased by HRI in hearts and kidneys almost to levels observed in normotensive Sprague-Dawley rats. The renoprotective effects of HRI were at least in part due to improved renal hemodynamics and distal tubular function, since HRI shifted renal pressure-diuresis/natriuresis curves leftward by ≈35 mm Hg, increased glomerular filtration rate and renal blood flow, and shifted the fractional water and sodium excretion curves leftward. In untreated dTGR, plasma Ang II was increased by 400% and renal Ang II level was increased by 300% compared with Sprague-Dawley rats. HRI decreased plasma human renin activity by 95% and normalized Ang II levels in both plasma and kidney compared with triple-drug therapy. Our findings indicate that in dTGR harboring human renin and angiotensinogen genes, Ang II causes end-organ damage and promotes inflammatory response and cellular growth largely independent of blood pressure.
Gene Transfer of Endothelial Nitric Oxide Synthase Reduces Angiotensin II–Induced Endothelial Dysfunction
Authors: Nakane Hiroshi , Miller Francis J. , Faraci Frank M. , Toyoda Kazunori , Heistad Donald D.
Published: June 2012

Abstract
—Angiotensin II stimulates vascular NADPH oxidase to produce superoxide, which can react with nitric oxide and impair vasomotor function. We tested the hypothesis that the overexpression of endothelial nitric oxide synthase (eNOS) or superoxide dismutase (SOD) would correct angiotensin II–induced endothelial dysfunction. We examined the effects of the gene transfer of eNOS or 2 isoforms of SOD to the aorta in angiotensin II–treated rabbits on vasomotor function. New Zealand White rabbits were treated for 1 week with angiotensin II (100 ng · kg
−1
· min
−1
) or saline by osmotic minipumps. In angiotensin II–treated rabbits, mean blood pressure was 107±8 mm Hg; it was 67±5 mm Hg in saline-infused rabbits (
P
<0.05). In aortas from angiotensin II–treated rabbits, lucigenin-enhanced chemiluminescence demonstrated a 2.5-fold increase in superoxide levels, and the oxidative fluorescent probe hydroethidine indicated increased superoxide levels throughout the vascular wall, especially in the endothelium and adventitia. Maximal relaxation to acetylcholine was less in aortas from rabbits treated with angiotensin II (72±5% versus 87±4% in saline-treated rabbits;
P
<0.01), but responses to sodium nitroprusside were similar. Segments of the thoracic aorta were incubated in vitro with an adenoviral vector that expressed eNOS, copper zinc SOD (CuZnSOD), extracellular SOD (ECSOD), or β-galactosidase. β-Gal treatment with adenovirus containing the gene for eNOS (AdeNOS) but not adenovirus containing the gene for β-gal (Adβ-gal) (control virus) restored responses to acetylcholine (82±3% after AdeNOS and 67±4% after Adβ-gal). Gene transfer of CuZnSOD or ECSOD did not improve the endothelium-dependent relaxation of the aorta in rabbits that received angiotensin II. Thus, gene transfer of eNOS, but not SOD, effectively restores vasomotor function in angiotensin II–infused rabbits.
Vasopressin Does not Effect Hypertension Caused by Long-Term Nitric Oxide Inhibition
Authors: Loichot Cécile , Cazaubon Catherine , Grima Michèle , De Jong Wybren , Nisato Dino , Imbs Jean-Louis , Barthelmebs Mariette
Published: June 2012

Abstract
—Nitric oxide attenuates both vasopressin-induced vasoconstriction and vasopressin release. We tested whether hypertension and renal dysfunction elicited by chronic inhibition of nitric oxide (NO) synthesis using
N
G
-nitro-
l
-arginine (L-NNA) could be mediated in part by vasopressin V
1A
receptors. Male rats were treated orally for 6 weeks with L-NNA (15 mg/kg per day), a nonpeptide V
1A
receptor antagonist (2
S
)-1-[(2
R
,3
S
)-5-chloro-3-(2-chlorophenyl)-1-(3,4-dimethoxybenzene-sulfonyl)-3-hydroxy-2,3-dihydro-1
H
-indole-2-carbonyl]-pyrrolidine-2-carboxamide (SR 49059, 30 mg/kg per day), or a combination of SR 49059 and L-NNA (same doses), or they received no treatment. Both drugs were added to the food. Measurements were performed in conscious rats (urine collection in metabolic cages, tail-cuff arterial pressure) and at the end of the study in anesthetized rats (clearance measurements). L-NNA produced sustained hypertension, decreased glomerular filtration rate, and increased renal vascular resistance, plasma renin activity, and urinary albumin excretion. SR 49059 had no effect per se on these parameters and also did not attenuate the hypertension and renal dysfunction induced by L-NNA. Surprisingly, SR 49059 potentiated L-NNA–induced hypertension at the end of the 6-week treatment. However, the blood pressure response and the renal and mesenteric vasoconstriction elicited by exogenous vasopressin were attenuated in rats treated with SR 49059. L-NNA did not change plasma vasopressin concentration or 24-hour urinary vasopressin excretion. Our findings suggest that activation of vasopressin V
1A
receptors does not contribute to the hypertension and renal dysfunction induced by chronic NO synthesis inhibition. They also document unchanged plasma vasopressin concentration in NO-deficient hypertension.