bluuebunny/crossref_metadata_2025 huggingface dataset:
Cathepsin B Is a Prorenin Processing Enzyme
Authors: Neves Francisco A.R. , Duncan Keith G. , Baxter John D.
Published: June 2012

Abstract
Conversion of prorenin to renin results from proteolytic cleavage of a 43-amino-acid prorenin prosegment in renal juxtaglomerular cells. The enzyme that performs this processing is not known. Of several enzymes proposed, cathepsin B is a candidate because it colocalizes with renin in juxtaglomerular cell secretory granules and accurately cleaves the prosegment of human prorenin in vitro. It is not known whether cathepsin B can perform this function in the cell. We examined this using secretory granule–containing rat GH4C1 cells transfected with a human preprorenin expression vector. When treated with secretagogue (KCl 50 mmol/L+forskolin 10 μmol/L), these cells secrete 95% prorenin and 5% active renin into the medium, indicating little prorenin processing activity. In contrast, when the cells are cotransfected with a vector that expresses human preprocathepsin B or mouse prohormone convertase 1, secretagogue-induced secretion of active renin increased to 12% and 16.5%, respectively. With antisera that recognize the prosegment and renin, prorenin and renin were identified as proteins of 47 and 43 kD, respectively, and an antibody specific to the prosegment precipitated only the 47-kD species. These results do not address whether cathepsin B is the authentic renal prorenin processing enzyme. However, the results do demonstrate that cathepsin B can localize to the appropriate subcellular compartment and process prorenin to renin in GH4C1 cells and are consistent with a role for this enzyme in prorenin processing.
Angiotensin-(1-7) Dilates Canine Coronary Arteries Through Kinins and Nitric Oxide
Authors: Brosnihan K. Bridget , Li Ping , Ferrario Carlos M.
Published: June 2012

Abstract
Angiotensin-(1-7) [Ang-(1-7)] was recently recognized to have novel biological functions that are distinct from those of Ang II. In these studies, we determined the vasoactive effects of Ang-(1-7) together with the endothelium-dependent mediator(s) of these responses in canine coronary arteries. Isometric tension was measured in intact canine coronary artery rings suspended in organ chambers perfused with 95% O
2
/5% CO
2
at 37°C. Ang-(1-7) caused significant concentration-dependent vascular relaxation (2.73±0.58 μmol/L, EC
50
) of rings precontracted with the thromboxane A
2
analogue U46,619. Pretreatment with the nitric oxide synthase inhibitor
N
ω
-nitro-
l
-arginine (1 mol/L) abolished the vasodilator response to Ang-(1-7), whereas treatment with the cyclooxygenase inhibitor indomethacin (10 μmol/L) was without effect. The vasodilator response produced by Ang-(1-7) was blocked by 75% with the bradykinin B
2
receptor antagonist Hoe 140 (1 μmol/L) or by 80% with the nonselective Ang II antagonist [Sar
1
,Thr
8
]-Ang II (1 μmol/L). In contrast, the selective AT
1
or AT
2
Ang II antagonists CV 11974 (1 μmol/L) and PD 123319 (1 μmol/L), respectively, were ineffective in inhibiting the Ang-(1-7)–elicited vasodilation. Furthermore, pretreatment of the coronary rings with 2 μmol/L Ang-(1-7) markedly potentiated the bradykinin response. These results suggest that Ang-(1-7) elicits coronary vasodilation that is specifically mediated by the endothelium-dependent release of nitric oxide. These responses involve a B
2
bradykinin receptor and a non-AT
1
, non-AT
2
angiotensin receptor. These data suggest that increases in circulating levels of Ang-(1-7) accompanying long-term administration of converting enzyme inhibitors or Ang II receptor blockers may contribute to the cardioprotective actions of these drugs.
Genetic Characterization of the ‘New’ Harlan Sprague Dawley Dahl Salt-Sensitive Rats
Authors: Walder Roxanne Y. , Morgan Donald A. , Haynes William G. , Sigmund Rita D. , McClain Ann M. , Stokes John B. , Mark Allyn L.
Published: June 2012

Abstract
In 1994, it was reported that Dahl salt-sensitive SS/Jr rats supplied by Harlan Sprague Dawley were genetically contaminated and resistant to the pressor effects of a high salt diet. Harlan Sprague Dawley subsequently developed new pedigree expansion and production colonies from their foundation colony to supply new, purportedly inbred, Harlan Sprague Dawley SS/Jr (S
HSD
). To evaluate the genetic integrity and salt sensitivity of these new S
HSD
, we performed genotyping (microsatellite DNA markers) and phenotyping (radiotelemetric arterial pressure) of 12 S
HSD
, 16 “authentic” SS/Jr from the inbred colony of John Rapp (S
Rapp
), 9 Harlan Sprague Dawley salt-resistant SR/Jr (R
HSD
), and (genotyping only) 6 known “contaminated” Harlan Sprague Dawley Dahl SS/Jr (S*). In the genotyping studies, 20 of 22 markers revealed polymorphisms between S
Rapp
and S* and 18 were polymorphic between S
Rapp
and R
Rapp
, but none of the 22 markers revealed polymorphisms between S
Rapp
and the new S
HSD
. The phenotyping studies showed that during an ultra–low salt diet, mean arterial pressure was higher (
P
<.05) in both authentic S
Rapp
(129±2 mm Hg; mean±SE) and new S
HSD
(120±2 mm Hg) than in R
HSD
(93±1 mm Hg). A high salt diet increased mean arterial pressure in every S
HSD
and S
Rapp
. Increases in mean arterial pressure after 4 weeks of a high salt diet were significantly (
P
<.05) greater in authentic S
Rapp
(+51±3 mm Hg) than in new S
HSD
(+39±3 mm Hg). In addition, salt-induced mortality was significantly greater in S
Rapp
(62.5%) than S
HSD
(8.3%) after 8 weeks (
P
<.01). S
HSD
were genotypically indistinguishable from S
Rapp
, had an elevated arterial pressure on a low salt diet, and had a pressor response to salt. Thus, the new S
HSD
supplied to us had several characteristics of inbred Dahl SS/Jr and did not have evidence of the previously detected genetic contamination. However, phenotypic characteristics such as body weight, salt-induced hypertension, and mortality were significantly different in S
HSD
compared with S
Rapp
. This may reflect genetic differences between these two strains or differences in environmental factors and suggests that the S
HSD
and S
Rapp
may now constitute distinct substrains of Dahl SS/Jr.
Bradykinin and Protein Kinase C Activation Fail to Stimulate Renal Sensory Neurons in Hypertensive Rats
Authors: Kopp Ulla C. , Smith Lori A.
Published: June 2012

Abstract
In normotensive rats, renal sensory receptor activation by increased ureteral pressure results in increased ipsilateral afferent renal nerve activity, decreased contralateral efferent renal nerve activity, and contralateral diuresis and natriuresis, a contralateral inhibitory renorenal reflex response. In spontaneously hypertensive rats (SHR), increasing ureteral pressure fails to increase afferent renal nerve activity. The nature of the inhibitory renorenal reflexes indicates that an impairment of the renorenal reflexes would contribute to the increased efferent renal nerve activity in SHR. We therefore examined whether there was a general decrease in the responsiveness of renal sensory receptors in SHR by comparing the afferent renal nerve activity responses to bradykinin in SHR and Wistar-Kyoto rats (WKY). In WKY, renal pelvic perfusion with bradykinin at 4, 19, 95, and 475 μmol/L increased afferent renal nerve activity by 1066±704, 2127±1121, 3517±1225, and 4476±1631%·second (area under the curve of afferent renal nerve activity versus time). In SHR, bradykinin at 4 to 95 μmol/L failed to increase afferent renal nerve activity. Bradykinin at 475 μmol/L increased afferent renal nerve activity in only 6 of 10 SHR. In WKY, renal pelvic perfusion with the phorbol ester 4β-phorbol 12,13-dibutyrate, known to activate protein kinase C, resulted in a peak afferent renal nerve activity response of 24±4%. However, 4β-phorbol 12,13-dibutyrate failed to increase afferent renal nerve activity in SHR. These findings demonstrate decreased responsiveness of renal pelvic sensory receptors to bradykinin in SHR. The impaired afferent renal nerve activity responses to bradykinin in SHR may be due to a lack of protein kinase C activation or a defect in the intracellular signaling mechanisms distal to protein kinase C activation.
Influence of Dietary Sodium Intake on Renal Medullary Nitric Oxide Synthase
Authors: Mattson David L. , Higgins Daniel J.
Published: June 2012

Abstract
We previously reported that chronic systemic treatment of rats with a nitric oxide synthase inhibitor leads to a selective decrease in renal medullary blood flow, retention of sodium, and the development of hypertension. In the present studies, we used protein blotting techniques to determine the whole tissue distribution and relative quantitation of the different nitric oxide synthase isoforms in the renal cortex and medulla of Sprague-Dawley rats maintained on a low (0.4% NaCl) or high (4.0% NaCl) dietary salt intake. Neural, endothelial, and inducible nitric oxide synthase were readily detectable in homogenized renal inner and outer medullas. Only endothelial nitric oxide synthase was detectable in the renal cortex. Densitometric comparison of Western blots from equal amounts of total inner medullary tissue protein indicated that endothelial, inducible, and neural nitric oxide synthase were increased by 145%, 49%, and 119%, respectively, in rats maintained on a high NaCl diet compared with rats on a low NaCl diet. No significant differences in nitric oxide synthase levels were detected in the outer medulla, renal cortex, or aorta of rats maintained on low and high NaCl diets. In separate studies, continuous intravenous infusion of
N
G
-nitro-
l
-arginine methyl ester (8.6 mg/kg per day) for 11 days in chronically instrumented rats increased mean arterial pressure 32±3 mm Hg in rats on a high NaCl diet (n=5) but only increased pressure 17±3 mm Hg in rats on a low NaCl diet (n=6). These data indicate that increased levels of renal medullary nitric oxide synthase may be important in the chronic adaptation to increased sodium intake.
Mechanisms of Interleukin-1β Regulation of Nitric Oxide Synthase in Cardiac Myocytes
Authors: LaPointe Margot C. , Sitkins Jodi R.
Published: June 2012

Abstract
Cytokines and endotoxin stimulate inducible NO synthase (iNOS) in different types of cells; however, little is known about regulatory mechanisms. Using the Griess reagent for nitrite levels, Western blots for iNOS protein, Northern blots for iNOS mRNA, and transient transfection studies to monitor transcription, we determined potential mechanisms involved in interleukin-1β stimulation of iNOS in cultured neonatal ventricular myocytes. When myocytes were treated with interleukin-1β (5 ng/mL), nitrite levels increased, and this effect was inhibited 80% by the specific iNOS inhibitor aminoguanidine. Neither interferon gamma nor tumor necrosis factor–α alone stimulated nitrite production. Bacterial endotoxin alone stimulated nitrites and potentiated the effect of interleukin. To determine whether a tyrosine kinase–mediated signaling pathway was involved in interleukin action, we used the inhibitor genistein, which blocked interleukin-stimulated nitrites, iNOS protein, and iNOS mRNA. To determine the effect of activation of protein kinase C, we treated cells with the phorbol ester phorbol 12-myristate 13-acetate (PMA). PMA decreased both interleukin-stimulated nitrites and iNOS protein by 40%. To determine the involvement of cyclic nucleotides, cells were treated with either dibutyryl cAMP or cGMP. cAMP (1 mmol/L) stimulated iNOS mRNA, protein, and nitrite production, whereas cGMP had no effect. To test for a direct effect of interleukin on transcription of the iNOS gene, we transfected the full-length mouse iNOS 5′ regulatory sequences (−1592 to +160) coupled to a luciferase reporter gene (−1592iNOSLuc). Interleukin stimulated luciferase activity 1.8±0.2-fold. To determine whether interleukin also affects iNOS mRNA stability, interleukin-stimulated iNOS mRNA was allowed to decay in the presence of the transcription inhibitor actinomycin D. iNOS mRNA t
1/2
(≈1 hour) was not affected by interleukin. Thus, our data suggest that (1) interleukin-1β is the primary cytokine in myocyte iNOS regulation and acts predominantly at the transcriptional level; (2) interleukin stimulation of iNOS mRNA and protein is coupled to a tyrosine kinase–mediated signaling pathway; and (3) protein kinase C and cAMP can modify interleukin signaling by decreasing and increasing iNOS, respectively.
Poor Glycemic Control Induces Hypertension in Diabetes Mellitus
Authors: Brands Michael W. , Hopkins Timothy E.
Published: June 2012

Abstract
We conducted this study to test the hypothesis that hypertension is a primary consequence of poor glycemic control per se very early in insulin-dependent diabetes mellitus. Sprague-Dawley rats (n=15) were instrumented with artery and vein catheters, placed in metabolic cages, and sodium intake was clamped throughout the study. Mean arterial pressure was measured 24 h/d. After a precontrol period, streptozotocin (70 mg/kg IV) was administered, and 15 hours later a continuous intravenous insulin infusion was begun at 4 U/rat per day. The insulin infusion was titrated on an individual rat basis to maintain good glycemic control, and after this 7-day control period, blood glucose, urinary sodium excretion, and mean arterial pressure were not different from precontrol values, averaging 8.8±0.6 mmol/L, 2.8±0.2 mmol/d, and 103±2 mm Hg, respectively, for control days 5 through 7. Subsequently, a 4-day period of poor glycemic control was initiated by reducing the insulin infusion rate. Blood glucose, urinary sodium excretion, and mean arterial pressure began to increase on day 1; for diabetes days 3 and 4, they averaged 23.4±1.0 mmol/L, 3.6±0.1 mmol/d, and 110±2 mm Hg, respectively. All were significantly elevated. When insulin treatment was restored, all variables returned to control levels during the next 4 days. A second 4-day diabetic period yielded similar results. These results indicate that elevated blood pressure is a primary consequence of poor glycemic control in insulin-dependent diabetes, occurring before renal injury has had time to develop, and therefore, may be a factor contributing to the initiation of end-organ injury.
Smooth Muscle Cell–Derived Adenosine Inhibits Cell Growth
Authors: Dubey Raghvendra K. , Gillespie Delbert G. , Mi Zaichuan , Suzuki Fumio , Jackson Edwin K.
Published: June 2012

Abstract
Several endogenous factors generated within the vessel wall have been implicated in contributing to the vascular remodeling process associated with hypertension and atherosclerosis. Furthermore, substances generated by smooth muscle cells (SMCs) are known to regulate SMC proliferation in an autocrine fashion. Adenosine is a vasodilator synthesized by SMCs, and exogenous adenosine inhibits SMC proliferation. However, whether adenosine produced endogenously has antimitogenic effects is not known. Hence, we evaluated the effects of SMC-derived adenosine on 2.5% fetal calf serum–induced proliferation of rat aortic SMCs. SMC proliferation was assayed by measurement of DNA synthesis ([
3
H]thymidine incorporation) and cell counting. To determine the effects of endogenous adenosine on SMC proliferation, we stimulated growth-arrested SMCs with 2.5% fetal calf serum in the presence and absence of modulators of adenosine levels, including (1) erythro-9-(2-hydroxy-3-nonyl)adenine hydrochloride (EHNA; inhibits adenosine deaminase), (2) dipyridamole (blocks adenosine transport and inhibits phosphodiesterase), (3) dipyridamole plus EHNA, and (4) adenosine with or without EHNA. [
3
H]Thymidine incorporation and cell number were measured after 24 and 96 hours, respectively. EHNA and dipyridamole inhibited both FCS-induced DNA synthesis and cell proliferation in a concentration-dependent manner. Furthermore, extracellular (in medium) adenosine levels were significantly increased when cultured cells were treated with EHNA, and the inhibitory effects of dipyridamole as well as exogenous adenosine were enhanced in the presence of EHNA. Additionally, the inhibitory effects of dipyridamole and EHNA on DNA synthesis were significantly reduced in the presence of KF17837, an A
2
adenosine receptor antagonist. These results indicate that SMC-derived adenosine can inhibit SMC proliferation. Hence, it is possible that a defect in localized adenosine synthesis within the vessel wall could contribute to vascular thickening and neointima formation.
Adenosine Inhibits Growth of Rat Aortic Smooth Muscle Cells
Authors: Dubey Raghvendra K. , Gillespie Delbert G. , Osaka Kazuhiro , Suzuki Fumio , Jackson Edwin K.
Published: June 2012

Abstract
Abnormal growth of vascular smooth muscle cells (SMC) is frequently associated with hypertension and atherosclerosis, and homeostasis within a normal vessel is maintained by the balanced generation of both vasoconstrictors and vasodilators. Moreover, several endogenous vasoconstricting factors induce SMC growth, whereas several vasodilators inhibit SMC growth. Inasmuch as adenosine is a potent vasodilator, it is possible that it too could inhibit SMC growth. Hence, the effects of adenosine (10
−8
to 10
−3
mol/L), 2-chloroadenosine (a stable analogue of adenosine; 10
−8
to 10
−3
mol/L), and 8-bromo-cAMP (10
−8
to 10
−3
mol/L) on fetal calf serum (FCS; 2.5%)–induced growth of rat aortic SMC were evaluated. Growth was analyzed by assaying DNA synthesis (thymidine incorporation in SMC pulsed for 4 hours with 1 μCi/mL [
3
H]thymidine) and cell proliferation (change in cell number). Growth-arrested SMC were treated with 2.5% FCS in the presence and absence of adenosine, 2-chloroadenosine, or 8-bromo-cAMP for 24 hours for DNA synthesis or 4 days for cell proliferation. All three substances inhibited DNA synthesis and cell proliferation in a concentration-dependent manner. Compared with adenosine, 2-chloroadenosine was more potent in inhibiting growth. The inhibitory effects of 2-chloroadenosine were reversed by KF17837 (a specific A
2
receptor antagonist) but not by DPCPX (a specific A
1
receptor antagonist). Furthermore, the inhibitory effects of 2-chloroadenosine were not mimicked by
CGS21680
(an A
2a
receptor agonist), and the effects of
N
6
-cyclopentyladenosine (CPA; an A
1
receptor agonist) were not markedly more potent than those of 2-chloroadenosine, suggesting that the inhibitory effects of adenosine are possibly mediated via A
2b
receptors. These studies provide evidence that adenosine inhibits SMC growth and suggest that a decrease in local levels of adenosine may initiate SMC growth and contribute to the vascular remodeling process observed in hypertension and atherosclerosis.
Remodeling of the Radial Artery in Response to a Chronic Increase in Shear Stress
Authors: Girerd Xavier , London Gérard , Boutouyrie Pierre , Mourad Jean-Jacques , Safar Michel , Laurent Stéphane
Published: June 2012

Abstract
Chronic changes in large artery blood flow rates induce corresponding adjustments in arterial diameter, but little is known about structural adaptations of the vessel wall in humans. We used a high-resolution echo-tracking system to measure radial artery internal diameter, wall thickness, and mean blood flow on both arms of 11 patients with end-stage renal disease. Measurements were performed on the wrist side of the arteriovenous fistula. The contralateral radial artery was investigated as control. Wall cross-sectional area, circumferential wall stress, and mean wall shear stress were calculated. Results indicate a sixfold increase in blood flow on the side of the arteriovenous fistula compared with the control side, with a 1.4-fold increase in internal diameter. The diameter enlargement was sufficient to normalize wall shear stress. Changes in diameter were not associated with arterial wall hypertrophy because wall cross-sectional area was not increased and rather suggest a “remodeling” of the arterial wall. For the same level of blood pressure, circumferential wall stress was increased on the side of the arteriovenous fistula. These results suggest that the structural adaptations of the arterial wall to a chronic increase in blood flow normalize wall shear stress and overcome stretch-induced changes in the particular circumstance of arteriovenous fistula.
Improvement of Coronary Flow Reserve After Long-term Therapy With Enalapril
Authors: Motz Wolfgang , Strauer Bodo E.
Published: June 2012

Abstract
To date, no clinical study shows an improvement in coronary flow reserve due to long-term antihypertensive therapy. In view of the contribution of the renin-angiotensin system to the process of hypertensive remodeling of the heart and coronary circulation, angiotensin-converting enzyme (ACE) inhibitors might act as cardioreparative drugs in arterial hypertension. Accordingly, our objective in this investigation was to examine under clinical conditions to what extent long-term antihypertensive treatment with an angiotensin-converting enzyme inhibitor improved the diminished coronary flow reserve in hypertensive patients with microvascular angina pectoris. For the purpose of comparison, we also treated a normotensive control group of 6 patients with hypertrophic nonobstructive cardiomyopathy. Fifteen hypertensive individuals (10 men, 5 women; age, 58±6 years) were treated with enalapril (10 to 20 mg/d; mean, 16.7±4.9 mg/d) for 11 to 13 months. At the end of the treatment period, systolic pressure decreased from 178±14 to 137±12 mm Hg and diastolic pressure from 102±11 to 86±4 mm Hg under ambulatory conditions. Left ventricular muscle mass index decreased by 8%, from 149±32 to 137±28 g/m
2
(
P
<.05). Maximal coronary blood flow after dipyridamole was increased by 43%, from 181±69 to 258±116 mL/min per 100 g (
P
<.001), and minimal coronary vascular resistance was diminished by 29%, from 0.66±0.23 to 0.47±0.24 mm Hg·min·100 g·mL
−1
(
P
<.001) after enalapril treatment. Consequently, the calculated coronary reserve increased from 2.2±0.6 to 3.3±1.2 (
P
<.001). After enalapril therapy, the functional class of angina pectoris according to the Canadian classification system had changed from 2.5±0.6 to 1.5±0.6 (
P
<.01). The maximal working capacity had increased from 23.775±3.970 to 26.255±4.598 J (mean±SE,
P
<.05). The maximal ST-segment depression at maximal workload was reduced from 0.18±0.02 to 0.06±0.02 mV (mean±SE,
P
<.01). In summary, long-term therapy with the angiotensin-converting enzyme inhibitor enalapril must be considered a cardioreparative treatment with respect to the coronary microcirculation in hypertensive heart disease.
Prospective Study of Nutritional Factors, Blood Pressure, and Hypertension Among US Women
Authors: Ascherio Alberto , Hennekens Charles , Willett Walter C. , Sacks Frank , Rosner Bernard , Manson JoAnn , Witteman Jacqueline , Stampfer Meir J.
Published: June 2012

Abstract
We examined prospectively the relation of nutritional factors with hypertension and blood pressure levels among 41 541 predominantly white US female nurses, aged 38 to 63 years, who completed a detailed semiquantitative food frequency questionnaire in 1984 and were without diagnosed hypertension, cancer, or cardiovascular disease. During 4 years of follow-up, from 1984 to 1988, 2526 women reported a diagnosis of hypertension. Age, relative weight, and alcohol consumption were the strongest predictors for the development of hypertension. Dietary calcium, magnesium, potassium, and fiber were not significantly associated with risk of hypertension, after adjusting for age, body mass index, alcohol, and energy intake. Among women who did not report hypertension during the follow-up period, calcium, magnesium, potassium, and fiber were each significantly inversely associated with self-reported systolic and diastolic pressures, after adjusting for age, body mass index, alcohol consumption, and energy intake. When the four nutrients were added simultaneously to the regression model, only fiber and magnesium intakes retained significant inverse associations with systolic and diastolic pressures. In analyses of food groups, intakes of fruit and vegetables were inversely associated with systolic and diastolic pressures, and intakes of cereals and meat were directly associated with systolic pressure. These results support hypotheses that age, body weight, and alcohol consumption are strong determinants of risk of hypertension in middle-aged women. They are compatible with the possibilities that magnesium and fiber as well as a diet richer in fruits and vegetables may reduce blood pressure levels.
Role of Nitric Oxide in Short-term and Prolonged Effects of Angiotensin II on Renal Hemodynamics
Authors: Deng Xiaolin , Welch William J. , Wilcox Christopher S.
Published: June 2012

Abstract
Short-term infusions of angiotensin II (Ang II) increase renal vascular resistance and thereby endothelial shear stress and nitric oxide (NO) release. Prolonged stimulation of Ang II can decrease the expression of NO synthase isoforms in the macula densa, but prolonged increases in shear stress can increase transcription of endothelial NO synthase. Therefore, we designed these studies to test the hypothesis that Ang II exerts time-dependent effects on renal NO generation as assessed from renal excretion of nitrate and nitrite, percent increases in renal vascular resistance during inhibition of NO synthase with intravenous
N
G
-nitro-
l
-arginine methyl ester (L-NAME), or decreases in renal vascular resistance during stimulation of endothelial NO synthase with intravenous acetylcholine. Rats were tested during graded short-term (30 to 90 minutes intravenous) or prolonged (5 to 6 days subcutaneous) Ang II infusions that led to dose-dependent increases in blood pressure and renal vascular resistance and reductions in renal blood flow. Captopril was administered for 3 to 4 days to suppress Ang II generation. The renal excretion of nitrate and nitrite was increased during short-term Ang II infusions (from 205±22 to 331±58 pmol·min
−1
,
P
<.05) but was unchanged during prolonged Ang II infusion (control group, 197±33 versus Ang II, 245±42 pmol·min
−1
,
P
=NS). The percent increase in renal vascular resistance with L-NAME was potentiated dose dependently by short-term but not long-term Ang II infusions. The increase in renal vascular resistance with L-NAME in control rats without Ang II infusions was +150±13%. At an Ang II infusion of 200 ng·kg
−1
·min
−1
, the L-NAME–induced percent increase in renal vascular resistance was significantly (
P
<.01) increased compared with controls in short-term Ang II–infused rats (+369±70%) but was not significantly different in prolonged infused rats (+190±33%). Intravenous acetylcholine caused dose-dependent renal vasodilation that was not significantly changed in rats receiving short-term intravenous Ang II but was significantly (
P
<.005) potentiated in those receiving prolonged Ang II infusions (change in renal vascular resistance with acetylcholine at 10 μg·kg
−1
·min
−1
versus control, −21.5±5.0%; with short-term Ang II, −24.9±4.5%; with long-term Ang II, −52.1±7.2%). In conclusion, short- and long-term Ang II infusions caused equivalent changes in blood pressure and renal blood flow and hence presumably equivalent increases in endothelial shear stress. However, only short-term Ang II infusions increased NO generation and the dependence of the renal circulation on NO, whereas acetylcholine-induced NO release was enhanced selectively during long-term Ang II infusions. This suggests that during long-term Ang II, renal NO release may become uncoupled from shear stress yet remains highly responsive to receptor-mediated stimulation.
Association of Hypertension with β
2
- and α
2c10
-Adrenergic Receptor Genotype
Authors: Svetkey Laura P. , Timmons Phillip Z. , Emovon Osemwegie , Anderson Norman B. , Preis Lisa , Chen Yuan-Tsong
Published: June 2012

Abstract
The adrenergic receptors have been implicated in the pathogenesis of essential hypertension. We hypothesized that hypertension is associated with variants at the β
2
-adrenergic receptor locus and at one of the α
2
-adrenergic receptor loci. In unrelated individuals, we measured untreated blood pressure and characterized each subject as hypertensive or normotensive. We then used genomic DNA to identify β
2
- and α
2c10
-adrenergic receptor restriction fragment length polymorphisms. In 175 subjects (49% with hypertension, 55% black), both hypertension and race were associated with genotype at the β
2
locus (χ
2
for hypertension=11,
P
=.004; χ
2
for race=8.8,
P
=.012). The association with hypertension persisted in each race group separately (blacks only: χ
2
=9.6,
P
=.008; whites only: χ
2
=14.2,
P
=.001). This association persisted in a logistic model that controlled for race (
P
=.01). Genotype was also significantly associated with baseline systolic, diastolic, and mean arterial blood pressures (
P
=.05, .01, and .02, respectively). These data suggest that the β
2
-adrenergic receptor gene is a candidate gene for hypertension in blacks and whites. We also genotyped subjects at the α
2
-adrenergic receptor coded on chromosome 10. There was no association between hypertension and genotype at the α
2c10
locus in the total group or in blacks, but there was significant association in whites (χ
2
=6.7,
P
=.03). These data suggest that the β
2
- and α
2c10
-adrenergic receptor genes may contribute, in a race-specific manner, to the inheritance of essential hypertension. Linkage studies in related individuals are needed to confirm these findings.
Changes in the Baroreflex Control of Heart Rate Produced by Central Infusion of Selective Angiotensin Antagonists in Hypertensive Rats
Authors: Oliveira Djenane R. , Santos Robson A.S. , Santos Gláucia F.P. , Khosla Mahesh C. , Campagnole-Santos Maria J.
Published: June 2012

Abstract
We have recently shown that an angiotensin-(1-7) [Ang-(1-7)] analogue,
d
-Ala
7
-Ang-(1-7) (A-779), is a selective Ang-(1-7) antagonist with no significant action on angiotensin type 1 or type 2 receptors. The availability of selective angiotensin antagonists prompted us to evaluate the role of Ang-(1-7) and Ang II on central modulation of the baroreflex control of heart rate in normotensive Wistar rats and spontaneously hypertensive rats (SHR). Blood pressure recording and reflex changes in heart rate elicited by intravenous bolus injections of phenylephrine were made before and within 1 and 3 hours of intracerebroventricular (ICV, lateral ventricle) infusion of saline (8 μL/h), A-779 (4 μg/h), DuP 753 (100 μg/h), or CGP 42112A (50 μg/h) in conscious rats. The slope of the relationship between changes in pulse interval versus changes in mean arterial pressure was used as an index of the baroreflex control of heart rate. ICV infusion of saline or any of the antagonists did not significantly change basal levels of mean arterial pressure and heart rate in SHR (170±6 mm Hg and 360±9 beats per minute, respectively; n=29) or Wistar rats (108±2 mm Hg and 377±6 beats per minute, respectively; n=29). Three hours of ICV infusion of A-779 markedly decreased baroreflex sensitivity in Wistar rats (from a basal slope of 1.09±0.3). In contrast, A-779 did not significantly alter the depressed baroreflex sensitivity of SHR (0.61±0.1). ICV infusion of DuP 753 produced a significant increase (60%) in baroreflex control of heart rate in both Wistar rats and SHR. Saline or CGP 42112A infusions did not significantly alter baroreflex control of heart rate. These results suggest that endogenous Ang II and Ang-(1-7) are differentially affecting central baroreflex modulation, acting probably through distinct receptor subtypes. Although the central Ang II inhibitory effect is mediated by the type 1 receptor subtype, the facilitatory effect of Ang-(1-7) might be mediated by a different, unidentified receptor.
Inhibition of Aldosterone Production by Adrenomedullin, a Hypotensive Peptide, in the Rat
Authors: Yamaguchi Tatsuyuki , Baba Koreaki , Doi Yutaka , Yano Katsusuke , Kitamura Kazuo , Eto Tanenao
Published: June 2012

Recently, we conducted in vitro studies and reported that adrenomedullin, a novel hypotensive peptide, inhibits aldosterone secretion by dispersed rat adrenal zona glomerulosa cells. To assess the physiological role of this inhibitory effect, we investigated the effect of adrenomedullin on aldosterone production in vivo. Male Sprague-Dawley rats were fed a normal sodium diet before the experiments. To begin the experimental procedure, we stimulated aldosterone production with a sodium-deficient diet or bilateral nephrectomy. After 3 days of sodium depletion or immediately after nephrectomy, we injected synthetic human adrenomedullin (2.5 nmol/kg SC) and repeated the injection three times at 6-hour intervals. Two hours after the last injection, the rats were decapitated and adrenal capsular tissue was collected. Adrenomedullin had no effect on plasma and adrenal aldosterone concentrations in the rats fed a normal sodium diet. Rats fed a sodium-deficient diet had significantly increased aldosterone concentrations in both plasma (4770.1±364.3 pmol/L) and adrenal gland (57.34±3.27 pmol per adrenal). Subsequently, injection of adrenomedullin significantly inhibited increases in concentrations (plasma, 2648.9±313.2 pmol/L; adrenal, 44.28±4.94 pmol per adrenal). In nephrectomized rats, increased aldosterone concentrations in plasma and adrenal gland were also significantly inhibited by adrenomedullin. In the second part of the study, plasma renin concentration, adrenal renin activity, plasma corticosterone concentration, serum potassium concentration, and plasma immunoreactive adrenomedullin concentration were examined for adrenomedullin effects. The first four were unaffected, and the last, plasma immunoreactive adrenomedullin, was elevated 15% to 30%. These in vivo results, together with our in vitro data, suggest that adrenomedullin may indeed play a physiological role in the control of blood pressure and electrolyte balance.
Tissue-Specific Regulation of Type 1 Angiotensin II Receptor mRNA Levels in the Rat
Authors: Sechi Leonardo A. , Griffin Chandi A. , Giacchetti Gilberta , Valentin Jean-Pierre , Llorens-Cortes Catherine , Corvol Pierre , Schambelan Morris
Published: June 2012

Most of the biological effects of the renin-angiotensin system are mediated by the binding of angiotensin II (Ang II) to the type 1 Ang II (AT
1
) receptor, the predominant receptor subtype present after fetal life. To study tissue-specific regulation of the expression of the AT
1
receptor in the rat, we altered activity of the renin-angiotensin system by feeding rats a low (0.07% NaCl), normal (0.3% NaCl), or high (7.5% NaCl) salt chow for 14 days; infusing Ang II (200 ng/kg per minute IP) or vehicle for 7 days; and administering an angiotensin-converting enzyme inhibitor (captopril, 100 mg/dL in the drinking water) or vehicle for 7 days. Renin, angiotensinogen, and total AT
1
receptor mRNA levels were measured by slot-blot hybridization with cRNA probes, and AT
1
receptor subtypes (A and B) were measured by reverse transcription–polymerase chain reaction in the presence of a cRNA internal standard. Plasma renin concentration and renal renin, renal and hepatic angiotensinogen, and hepatic AT
1
receptor mRNA levels were all inversely related to salt intake; in contrast, renal AT
1
receptor mRNA levels were significantly lower in rats fed low salt, a difference that was exclusively due to a decrease in the AT
1A
subtype. This difference did not appear to be mediated by a change in the circulating levels of Ang II, because Ang II infusion reduced plasma renin concentration and renal renin mRNA with no effect on either angiotensinogen or AT
1
receptor mRNA levels in kidney or liver; renal Ang II receptor density (determined by in situ autoradiography) decreased, presumably via a posttranscriptional mechanism. Similarly, inhibition of Ang II generation with captopril increased plasma renin concentration and renal renin mRNA levels without altering renal or hepatic angiotensinogen mRNA or renal AT
1
receptor mRNA levels. Thus, AT
1
receptor gene expression is regulated in a tissue-specific manner that is distinct from other components of systemic and local renin-angiotensin systems and that appears to be mediated by a mechanism other than through changes in the circulating levels of Ang II.
A New Classification Scheme for Hypertension Based on Relative and Absolute Risk With Implications for Treatment and Reimbursement
Authors: Black Henry R. , Yi Jong-Yoon
Published: June 2012

Classification schemes for hypertension are necessary. They provide us with definitions for when hypertension begins and help us to assess risk, determine prognosis, and guide management. Systems in current use rely on either the level of blood pressure (diastolic, systolic, or both) and classify patients based on the level of relative risk (the proportional likelihood of cardiovascular events occurring as blood pressure rises), absolute risk (the actual odds that a patient or a population will develop an event), or both. Absolute risk reflects the sum of all the factors that contribute to the likelihood that a patient will experience cardiovascular disease. The system we propose stages hypertensive individuals on the basis of blood pressure level (as does the Fifth Joint National Committee report on the detection, evaluation, and treatment of high blood pressure [JNC-V] and the World Health Organization/International Society of Hypertension guidelines) but uses different levels for each stage than do the previous systems and then modifies the numerical stage with the subscript “c” for complicated (when target-organ damage and/or other cardiovascular risk factors are present) or “u” for uncomplicated (when they are absent). The data obtained from a complete medical history and physical examination and a few inexpensive laboratory tests provide the information a provider needs to classify an individual as being complicated or uncomplicated. This system also provides a guide to treatment, as drug therapy would be used sooner in individuals with complicated hypertension, and we propose that compensation for providers be higher when they are caring for a patient with complicated rather than uncomplicated hypertension.
Heritability of Salt Sensitivity in Black Americans
Authors: Svetkey Laura P. , McKeown Sean P. , Wilson Alexander F.
Published: June 2012

Salt sensitivity is defined as a change in blood pressure in response to changes in salt and water homeostasis. Found in 73% of hypertensive and 36% of normotensive blacks, it is generally considered a hallmark of hypertension in blacks. The higher prevalence of salt sensitivity in blacks compared with whites suggests a genetic influence on this trait, but there is little direct evidence of heritability. We determined the extent to which salt sensitivity is correlated in black families and estimated the heritability of this phenotype. Black families were recruited through a hypertensive proband. Both hypertensive and normotensive adults were phenotyped with respect to salt sensitivity with an intravenous sodium-loading, furosemide volume-depletion protocol. Salt sensitivity was defined as the difference between sodium-loaded and volume-depleted blood pressure. We enrolled 20 families, comprising 30 parent-offspring pairs and 115 adult sibling pairs. Age-adjusted familial correlations ranged from .33 to .44, .19 to .37, and .12 to .21 for mean arterial and systolic and diastolic pressure responses to the salt sensitivity maneuver, respectively. Corresponding heritability estimates were 0.26 to 0.84, 0.26 to 0.74, and 0.004 to 0.24, respectively. These data strongly suggest a heritable component of salt sensitivity.
Vascular Gap Junctional Communication Is Increased in Mineralocorticoid-Salt Hypertension
Authors: Watts Stephanie W. , Webb R. Clinton
Published: June 2012

Cells rely on gap junctions for intercellular communication, which is important for growth and contractility. For example, gap junctional communication in the uterus increases near parturition, with a concomitant increase in oscillatory contractions. Because arterial responsiveness to contractile agonists is increased in hypertension, we tested the hypothesis that gap junctional communication is increased in hypertension. We examined thoracic aortas from deoxycorticosterone acetate (DOCA)–salt hypertensive and sham normotensive rats using isolated tissue baths and Western blotting techniques. The concentration of 5-hydroxytryptamine necessary to produce a threshold response was significantly lower in aortas from DOCA-salt (4 nmol/L) compared with sham (100 nmol/L) rats; this was also true for norepinephrine and KCl. In these same aortas, the appearance of spontaneous oscillatory contractions, which are sensitive to the gap junctional inhibitor heptanol (0.3 mmol/L), was more frequent in DOCA-salt arteries (93% versus 14% in sham). Heptanol (1 mmol/L) normalized the DOCA-salt aortic contraction to 5-hydroxytryptamine to levels similar to those of the response of the sham aorta in the presence of heptanol. Western analyses revealed that the density of connexin43 immunoreactivity, the connexin being a constituent of gap junctions, was found to be threefold more abundant in aortic homogenates of DOCA-salt rats compared with that of sham rats. This finding supports the hypothesis that gap junctional communication is increased in hypertension, at least at the protein level. We speculate that this increase results in a portion of the increased vascular reactivity and appearance of contractile oscillations in vascular smooth muscle.
Angiotensin II Type 2 Receptor Inhibits Cell Proliferation and Activates Tyrosine Phosphatase
Authors: Tsuzuki Satoshi , Matoba Teruyoshi , Eguchi Satoru , Inagami Tadashi
Published: June 2012

The angiotensin II type 2 (AT
2
) receptor inhibits basic fibroblast growth factor–induced proliferation of R3T3 fibroblast cells and transiently stimulates a vanadate-sensitive phosphotyrosine phosphatase, strongly suggesting that AT
2
is a mitogen inhibitor. We generated AT
2
gene–null mice that showed increased blood pressure, indicating the hypotensive action of AT
2
. However, inhibition of renomedullary AT
2
by selective antagonists, as reported by Sassard and associates, show that AT
2
suppresses pressure natriuresis. Thus, both AT
1
and AT
2
work in the direction of sodium retention, suggesting a unique role for angiotensin II in the kidney in terms of blood pressure regulation and sodium metabolism.
Angiotensin II Induction of Osteopontin Expression and DNA Replication in Rat Arteries
Authors: deBlois Denis , Lombardi Donna M. , Su Enming J. , Clowes Alexander W. , Schwartz Stephen M. , Giachelli Cecilia M.
Published: June 2012

We recently identified the adhesive protein osteopontin as a novel smooth muscle cell product overexpressed in rat developing neointima and human atheroma. Although osteopontin is a candidate stimulant for intimal lesion progression because of its chemotactic and calcium binding functions, factors controlling osteopontin expression in arteries remain poorly defined. In vitro, smooth muscle cell expression of osteopontin is associated with cell cycle transit or alterations in cell phenotype, and it is increased by angiotensin II (Ang II) stimulation. In the present studies, we investigated both osteopontin expression and DNA replication in the arterial wall in response to chronic Ang II infusion in vivo. Rat carotid arteries with or without intimal thickening (induced by balloon catheterization) were examined. Ang II (250 ng/kg per minute) or vehicle was coinfused with bromodeoxyuridine (to label replicating DNA in vivo) for 2 weeks beginning 4 weeks after injury. With Ang II, smooth muscle cells overexpressed osteopontin as shown by protein immunohistochemistry, in situ hybridization, and Northern blot analyses. Osteopontin mRNA levels were increased markedly (approximately fivefold) in the normal artery media and injured artery neointima, but levels remained low in the injured artery media, in positive correlation (
R
2
=0.88,
P
<.001) with DNA replication in the smooth muscle layers, further suggesting that osteopontin may be a growth-associated, phenotype-dependent gene for smooth muscle cells. However, osteopontin expression in neointima was not restricted to areas showing DNA replication, suggesting a nonobligatory association. Ang II induced severe hypertension. Arterial osteopontin expression was increased also by chronic catecholamine infusion, a model of vascular growth stimulation showing labile pressure elevations. Osteopontin induction in smooth muscle cells may contribute to Ang II–dependent intimal lesion progression and vascular remodeling events associated with renovascular diseases or hyperadrenergic disorders.
Models of Experimental Hypertension in Mice
Authors: Johns Conrado , Gavras Irene , Handy Diane E. , Salomao Abrahao , Gavras Haralambos
Published: June 2012

Experimental models of hypertension in various animals are useful in the research of vasoactive mechanisms. Recombinant DNA technology has produced genetically engineered animals, mostly mice, useful in hypertension research. However, the development of hypertensive models in mice is fraught with technical difficulties. We describe here the successful development in mice of two common types of experimental hypertension: the renovascular two-kidney, one clip and mineralocorticoid deoxycorticosterone-salt models. By adapting technology previously used in rats, we succeeded in developing hypertension (defined as systolic pressures higher than 140 mm Hg) in more than 50% of mice so treated. We also adapted the methodology for indirect tail-cuff blood pressure measurements as well as for direct intra-arterial monitoring of blood pressure in conscious, freely moving mice. Application of these techniques in transgenic or gene knockout mice with altered vasoactive hormones or receptors should allow elucidation of the role of the target gene products in various types of hypertension.
Targeted Inactivation of the
Ren-2
Gene in Mice
Authors: Sharp Matthew G.F. , Fettes David , Brooker Gillian , Clark Allan F. , Peters Jörg , Fleming Stewart , Mullins John J.
Published: June 2012

Several recent studies have demonstrated that ablation of genes of the renin-angiotensin system can have wide-ranging and sometimes unexpected effects. Renin is directly involved in blood pressure regulation and is encoded by a single gene in most mammals. Wild mouse strains and some inbred laboratory strains have a duplicated renin gene (
Ren-2
), the physiological significance of which is unclear. Significant differences exist in the structure and expression of these renin genes, but as yet, no distinct biological function that distinguishes these genes has been defined. We have used gene targeting to discover the effects of inactivating the duplicated (
Ren-2
) gene in strain 129 mice, and we show that mice lacking the
Ren-2
gene are viable and healthy. There appear to be no histopathological differences in renin-expressing tissues between
Ren-2
–null mice and their controls. Studies of our
Ren-2
–null mice allow, for the first time, a direct evaluation of the ability of the

Ren-1
d

gene to regulate blood pressure in the absence of expression of the
Ren-2
enzyme. We observed no alteration to blood pressure in adult mice homozygous for the mutated
Ren-2
gene, even though the concentration of active renin is increased and of prorenin is decreased in plasma of these mice.

Ren-1
d

is therefore capable of regulating normal blood pressure and despite a different tissue expression profile, is functionally equivalent to

Ren-1
c

.