bluuebunny/crossref_metadata_2025 huggingface dataset:
Renal sodium excretion in sons of hypertensive parents.
Authors: Turner S T , Reilly S L
Published: June 2012

The objective of this study was to evaluate whether renal excretion of sodium is impaired and whether tubular reabsorption of sodium is increased in normotensive white men with a familial predisposition to develop essential hypertension. We compared 11 normotensive sons of two hypertensive parents (SOHT) with 11 normotensive sons of two normotensive parents (SONT); renal sodium handling was assessed after 1 week of low-sodium diet (10 mmol/d) and after 1 week of high-sodium diet (200 mmol/d). The SOHT were on average 5.5 years older than the SONT (46.9 +/- 5.2 [SD] vs 41.4 +/- 4.1, P = .012). On the sixth day of each diet, mean urinary sodium excretion did not differ between the two groups (12.9 +/- 6.3 vs 12.7 +/- 6.7 mmol/d on low-sodium diet, P = .930; 197 +/- 25 vs 200 +/- 27 mmol/d on high-sodium diet, P = .817). On the seventh day of each diet, baseline means for filtered load of sodium, absolute excretion of sodium, fractional excretion of sodium (an index of total tubular sodium reabsorption), and fractional excretion of lithium (an inverse index of proximal tubular sodium reabsorption) also did not differ between the groups. To assess renal sodium handling under non-steady-state conditions, we infused 2 L normal saline intravenously over a 2-hour period. The means for absolute excretion of sodium, fractional excretion of sodium, and fractional excretion of lithium increased from baseline, but the increases did not differ in magnitude between the groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Divergent hemodynamic and hormonal responses to varying salt intake in normotensive subjects.
Authors: Overlack A , Ruppert M , Kolloch R , Göbel B , Kraft K , Diehl J , Schmitt W , Stumpe K O
Published: June 2012

Blood pressure responses to 1 week of low-salt (20 mmol sodium/d) and high-salt (300 mmol sodium/d) intake were investigated in a single-blind randomized study in 163 white, nonobese normotensive subjects (65 women and 98 men; mean age, 38 +/- 1.2 years). The individuals were classified as salt sensitive when mean arterial blood pressure rose by at least 5 mm Hg during high-salt intake, as salt resistant when mean arterial blood pressure changed by less than 5 mm Hg, and as "counterregulator" when mean arterial blood pressure fell by at least 5 mm Hg during the high-salt diet. Reexamination of 31 subjects showed that this approach to the testing of salt sensitivity was reliable and reproducible. Thirty subjects (18.4%) were classified as salt sensitive, 108 (66.3%) as salt resistant, and 25 (15.3%) as counterregulators. Multiple regression analysis revealed that age, body weight, and family history of hypertension contributed significantly to the change in blood pressure after the diets. Salt sensitivity was more frequent in older subjects and in those with a positive family history of hypertension. An increase in blood pressure after salt restriction was more likely in younger individuals and in those with a negative family history of hypertension. Plasma renin activity and plasma aldosterone concentrations were lower in salt-sensitive compared with salt-resistant and counterregulating subjects. The rise in plasma renin activity during salt restriction was most pronounced in counterregulating subjects. Plasma norepinephrine concentrations were not different among the groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Effects of long-term air jet noise and dietary sodium chloride in borderline hypertensive rats.
Authors: Tucker D C , Hunt R A
Published: June 2012

The hypothesis that simultaneous exposure to a high (8%) sodium chloride diet and behavioral stress (air jet noise) would act synergistically to increase blood pressure was investigated in male borderline hypertensive rats. Rats were fed either a 1% or an 8% sodium chloride diet beginning at 6 weeks of age. Rats in the Air Noise condition were restrained and exposed to random blasts of air jet noise for 2 h/d, 5 d/wk, from 7 to 17 weeks of age. Controls either were placed in identical restrainers and test chambers but not exposed to air jet noise (Restrained Control) or were left undisturbed (Maturation Control). Biweekly indirect blood pressure measurements showed that by 17 weeks of age, the high-sodium chloride diet and air jet noise exposure produced additive increases in blood pressure. Direct blood pressure measurements at 18 weeks of age confirmed the higher systolic pressures in borderline hypertensive rats exposed to both an 8% sodium chloride diet and air jet noise. After ganglionic blockade, the blood pressure of rats in the Air Noise group remained higher than that of Restrained and Maturation Controls, suggesting that the increased blood pressure of air jet noise-exposed rats was not maintained by increased autonomic activity. Blood pressure after maximal vasodilation by hydralazine was increased in rats exposed to both an 8% sodium chloride diet and air jet noise compared with other groups. Baroreceptor reflex sensitivity (tested by graded doses of angiotensin II) did not differ among groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Role of nitric oxide synthesis in salt-sensitive hypertension in Dahl/Rapp rats.
Authors: Chen P Y , Sanders P W
Published: June 2012

Nitric oxide is a potent endogenous vasodilator that regulates arterial tone. A family of nitric oxide synthases uses L-arginine and L-homoarginine stereospecifically as substrates for nitric oxide production in vivo. By preventing expression of inducible but not constitutive nitric oxide synthases, glucocorticoids differentiate which enzyme in this family is the predominant source of nitric oxide generation in a given situation. We proposed that defective production of nitric oxide produces salt-sensitive hypertension in the Dahl/Rapp rat. Plasma concentrations of L-arginine, citrulline, and ornithine of salt-sensitive (SS/Jr) and salt-resistant (SR/Jr) rats on 8% sodium chloride chow for 1 week did not differ. However, intravenous infusion of L-arginine and L-homoarginine, but not D-arginine, increased urinary excretion of nitrate, the degradation product of nitric oxide, and simultaneously lowered blood pressure in hypertensive SS/Jr rats. Oral L-arginine also prevented development of hypertension and increased urinary excretion of cyclic GMP and nitrate in these rats. Dexamethasone, in a dose that prevented hypotension from parenteral injection of lipopolysaccharide, completely prevented the increase in excretion of cyclic GMP and nitrate, and hypertension resulted despite concomitant treatment with L-arginine. These studies supported an important role of dexamethasone-suppressible nitric oxide synthesis in the prevention of salt-sensitive hypertension in the Dahl/Rapp rat.
Cardiovascular reactivity, coronary risk factors, and sympathetic activity in young men.
Authors: Rostrup M , Westheim A , Kjeldsen S E , Eide I
Published: June 2012

We have previously demonstrated that awareness of high blood pressure may increase blood pressure, plasma catecholamine levels, and stress responses. In the present study, three groups of 19-year-old men, all unaware of their blood pressure status, were selected from the first (group-1, 62 +/- 2 mm Hg, [mean +/- SEM], n = 15), 50th (group-50, 90 +/- 4 mm Hg, n = 15), and 99th (group-99, 123 +/- 5 mm Hg, n = 14) percentiles in causal mean blood pressure at a screening. They were studied (blinded examiners) with intra-arterial blood pressure recordings and multiple measurements of arterial plasma epinephrine and norepinephrine during a mental arithmetic challenge and cold pressor test. Despite high mean blood pressure at the screening, group-99 did not differ from group-50 either in intra-arterial mean blood pressure after 30 minutes of supine rest (89 +/- 3 versus 86 +/- 2 mm Hg) or in serum lipids and resting plasma epinephrine and norepinephrine. However, in group-99 resting plasma epinephrine showed a positive hyperbolic relation to resting diastolic blood pressure (r = .73, P = .004) and a negative hyperbolic relation to the ratio of high-density lipoprotein cholesterol to total cholesterol (r = -.75, P = .002). None of these correlations were present in the two other groups. Furthermore, the three groups differed in heart rate responses (P < .0005) and systolic (P < .0005) and diastolic (P < .05) blood pressure responses to mental arithmetic challenge, group-99 being hyperreactive compared with the other two groups.(ABSTRACT TRUNCATED AT 250 WORDS)
Endothelial dysfunction augments myogenic arteriolar constriction in hypertension.
Authors: Huang A , Sun D , Koller A
Published: June 2012

To elucidate the underlying reason or reasons for the increased peripheral resistance in hypertension, we investigated the pressure-diameter relation--the myogenic response--of isolated, cannulated arterioles (approximately 50 microns) of cremaster muscle of 12-week-old Wistar-Kyoto (WKY) rats, spontaneously hypertensive rats (SHR), and normal Wistar (NW) rats. All arterioles constricted in response to step increases in perfusion pressure from 20 to 160 mm Hg. This constriction was, however, significantly enhanced from 60 to 160 mm Hg in arterioles of SHR compared with NW or WKY rats. For example, at 80 and 140 mm Hg, respectively, the normalized diameter (expressed as a percentage of the corresponding passive diameter of arterioles of SHR) was 11.8% and 27.6% (P < .05) less compared with those of WKY rats. Endothelium removal eliminated the enhanced pressure-induced tone in SHR. Similarly, indomethacin (10(-5) mol/L, sufficient to block prostaglandin synthesis) or SQ 29,548 (10(-6) mol/L), a thromboxane A2-prostaglandin H2 receptor blocker that inhibited vasoconstriction to the thromboxane agonist U46619, attenuated the enhanced pressure-diameter curve and reversed the blunted dilation to arachidonic acid in SHR. In contrast, the thromboxane A2 synthesis inhibitor CGS 13,080 (5 x 10(-6) mol/L) did not affect the increased pressure-induced tone or the reduced dilation to arachidonic acid in SHR. Thus, the present findings suggest that in early hypertension pressure-induced arteriolar constriction is increased. This seems to be due to an enhanced production of endothelium-derived constrictor factors, primarily prostaglandin H2.
Carvedilol, a new antihypertensive agent, prevents lipid peroxidation and oxidative injury to endothelial cells.
Authors: Yue T L , Mckenna P J , Gu J L , Cheng H Y , Ruffolo R R , Feuerstein G Z
Published: June 2012

The protective effects of carvedilol, a new beta-adrenergic receptor blocker and vasodilating antihypertensive agent, against oxygen free radical-mediated injury were studied in cultured bovine endothelial cells and compared with five other beta-blockers. Carvedilol dose-dependently inhibited oxygen radical-induced lipid peroxidation (50% inhibition at 2.6 mumol/L) and glutathione depletion (50% inhibition at 1.8 mumol/L) in the cells. Under the same conditions, other beta-blockers--propranolol, labetalol, pindolol, atenolol, and celiprolol--had only mild or no effect. Moreover, carvedilol protected against oxygen radical--mediated cell damage, as assessed by cellular lactate dehydrogenase release, with a 50% inhibition at 4.1 mumol/L and increased the cell survival in a dose-dependent manner, whereas other beta-blockers had mild or no effects. Pretreatment of the cells with carvedilol for 7 days significantly enhanced the protective effects of carvedilol. Using 2-methyl-2-nitrosopropane as a trapping agent, the spin adduct in cell lipids was monitored by electron paramagnetic resonance. Carvedilol dose-dependently decreased the intensity of the free radical signals, indicating its free radical-scavenging ability. The prevention of oxidative injury to endothelial cells might potentially contribute to the clinical beneficial effects of carvedilol as an antihypertensive agent.
Correlates of blood pressure in community-dwelling older adults. The Cardiovascular Health Study. Cardiovascular Health Study (CHS) Collaborative Research Group.
Authors: Tell G S , Rutan G H , Kronmal R A , Bild D E , Polak J F , Wong N D , Borhani N O
Published: June 2012

Although elevated blood pressure is an important predictor of cardiovascular disease and stroke in the elderly, little information exists on the distribution and risk factor correlates of blood pressure in this group. As part of the Cardiovascular Health Study, a population-based cohort study of 5201 men and women aged 65 to 101 years, we investigated correlates of systolic and diastolic blood pressure. Multiple regression analyses were conducted for all participants and a subgroup of 2482 without coronary heart disease and not on antihypertensive therapy (the "healthier" subgroup). In the total group, independent predictors of diastolic blood pressure included heart rate, aortic root dimension, creatinine, hematocrit, alcohol use, and black race (positive associations) and internal carotid artery wall thickness, mitral early/late peak flow velocity, white blood cell count, cigarette smoking, and age (negative associations). Positive predictors of systolic blood pressure included mitral late peak flow velocity, left ventricular mass, common carotid artery wall thickness, serum albumin, factor VII, diabetes, alcohol use, and age; negative predictors were coronary heart disease, uric acid, height, and smoking. In the healthier subgroup, positive predictors of diastolic blood pressure included heart rate, hematocrit, serum albumin, creatinine, and body weight, whereas mitral early/late peak flow velocity, serum potassium, smoking, and age inversely related to diastolic pressure. For the same group, common carotid artery wall thickness, left ventricular mass, serum albumin, factor VII, high-density lipoprotein cholesterol, and age were directly related to systolic blood pressure, whereas serum potassium was inversely related. Both systolic and diastolic pressures varied considerably by geographic site.(ABSTRACT TRUNCATED AT 250 WORDS)
Angiotensin converting enzyme inhibition prevents the increase in aortic collagen in rats.
Authors: Albaladejo P , Bouaziz H , Duriez M , Gohlke P , Levy B I , Safar M E , Benetos A
Published: June 2012

Four groups of 4-week-old spontaneously hypertensive rats were treated during 4 months with the angiotensin converting enzyme inhibitor quinapril at 1 mg/kg per day (Q1) or 10 mg/kg per day (Q10), hydralazine at 15 mg/kg per day (H), or placebo (P). In the first set of experiments, blood pressure was measured in conscious rats, and plasma and aortic angiotensin converting enzyme activities were evaluated. In the second set of experiments, histomorphometric parameters of the thoracic aorta were evaluated. Mean blood pressure was lower in the Q10 and H groups (136 +/- 16 and 149 +/- 11 mm Hg) compared with the P group (190 +/- 23 mm Hg) (P < .01). The Q1 group showed mean blood pressure values (171 +/- 15 mm Hg) lower than the P group (P < .05) but significantly higher than the Q10 and H groups (P < .01 and P < .05, respectively). Aortic medial cross-sectional area was significantly lower in the H and Q10 groups (455 +/- 61 and 487 +/- 57 x 10(3) microns 2) than in the P group (636 +/- 72 x 10(3) microns 2) (P < .001).(ABSTRACT TRUNCATED AT 250 WORDS)
Systemic hemodynamics during sleep in young or middle-aged and elderly patients with essential hypertension.
Authors: Minamisawa K , Tochikubo O , Ishii M
Published: June 2012

Age-related changes in cardiovascular regulatory mechanisms may affect blood pressure homeostasis during sleep and in the daytime. This study compared systemic hemodynamics during the daytime and sleep between 12 young or middle-aged patients (young, 42.1 +/- 13.9 years old, mean +/- SD, less than 56 years old) and 12 elderly patients with essential hypertension (old, 65.3 +/- 2.8, 60 to 70 years old). They were all hospitalized and placed on a diet containing approximately 7 g sodium chloride per day. Intra-arterial blood pressure and electrocardiogram were recorded for 24 hours, and electroencephalogram and electroophthalmogram were recorded during the night with a telemetric method. Cardiac output was measured with patients in the supine position by the cuvette method during the daytime and stage 3 or 4 sleep at night. The averaged 24-hour blood pressure was similar in the two groups (140 +/- 2 [SEM]/85 +/- 3 mm Hg in the young group and 144 +/- 4/81 +/- 2 mm Hg in the old group). The reduction in mean blood pressure during sleep was also comparable in both groups (-18 +/- 2 in the young group and -20 +/- 2 mm Hg in the old group). Cardiac index was smaller in the old group than the young group during both the daytime and sleep (daytime, 2.3 +/- 0.1 versus 3.2 +/- 0.2 [L/min]/m2, P < .01; sleep, 2.1 +/- 0.1 versus 2.6 +/- 0.2 [L/min]/m2, P < .01). The reduction in cardiac index during sleep was greater in the young than the old group (P < .05).(ABSTRACT TRUNCATED AT 250 WORDS)
Renal medullary captopril delivery lowers blood pressure in spontaneously hypertensive rats.
Authors: Lu S , Mattson D L , Cowley A W
Published: June 2012

We examined the contribution of renal medullary function to the maintenance of hypertension in spontaneously hypertensive rats by infusing captopril chronically into the renal medullary interstitial space of uninephrectomized rats. Changes in cortical and medullary blood flow were determined using a newly developed optical fiber implantation technique for laser-Doppler flowmetry. Renal medullary interstitial infusion of captopril (5 mg/kg per day) selectively increased medullary blood flow by 40% without altering renal cortical blood flow throughout the 5 days of captopril delivery. In association with the selective increase of medullary perfusion, a significant natriuresis was observed on the second day of the drug infusion, and urine osmolality was significantly reduced during the first 3 days of captopril infusion. Mean arterial pressure was significantly decreased by 20 mm Hg during 5 days of captopril infusion, and the chronic renal function curve was shifted to a lower level of arterial pressure compared with the control values when 0.9% sodium chloride saline vehicle was infused. Intravenously infused captopril at 5 mg/kg per day did not alter mean arterial pressure, excluding the possibility that the hypotensive effect of medullary captopril infusion was due to recirculation. In summary, chronic reduction of the elevated renal medullary vascular tone by medullary interstitial infusion of captopril reset the steady-state renal function curve and lowered arterial pressure in spontaneously hypertensive rats.
Human SA gene locus as a candidate locus for essential hypertension.
Authors: Iwai N , Ohmichi N , Hanai K , Nakamura Y , Kinoshita M
Published: June 2012

We have recently identified a candidate gene for rat genetic hypertension by identifying an mRNA species that shows markedly higher expression in the kidneys of spontaneously hypertensive rats than in those of Wistar-Kyoto rats. By using a restriction fragment length polymorphism, we carried out cosegregation analyses between the genotype of the SA gene and blood pressure in three F2 cohorts and observed significant effects of the SA gene on blood pressure in all of those cohorts. In the present study, we have isolated a human counterpart of the rat SA gene to investigate the possible association between the human SA gene and human essential hypertension. The deduced amino acid sequence from the isolated human SA cDNA consisted of 578 amino acid residues and had slight homology to a bacterial enzyme, acetyl-coenzyme A synthase. The human gene was mapped to the human chromosome 16 with the use of a rodent/human somatic hybrid cell panel. A restriction fragment length polymorphism was found with the restriction enzyme Pst I, and the allele frequencies were compared between hypertensive and control groups. The hypertensive group consisted of 89 individuals, and the Pst I rare allele (A2 allele) frequency in this group was 0.270. The control group consisted of 81 healthy normotensive individuals whose precise clinical data were available; the A2 allele frequency in this group was 0.09. Significant differences in the frequency of the A2 allele were observed between the hypertensive and control groups (P = .0001). The present findings provide favorable evidence that the SA gene is a candidate gene for human essential hypertension and also provide a starting point for future studies.
Angiotensin-converting enzyme inhibition improves cardiac function. Role of bradykinin.
Authors: Gohlke P , Linz W , Schölkens B A , Kuwer I , Bartenbach S , Schnell A , Unger T
Published: June 2012

The effect of chronic low- and high-dose treatment with the angiotensin-converting enzyme (ACE) inhibitor ramipril (0.01 and 1 mg/kg per day) on the development of hypertension and left ventricular hypertrophy as well as on functional and biochemical alterations of the heart was studied in stroke-prone spontaneously hypertensive rats treated prenatally and subsequently up to the age of 20 weeks. The contribution of endogenous bradykinin potentiation to the ACE inhibitor actions was assessed by cotreatment of rats with the bradykinin B2-receptor antagonist Hoe 140 (500 micrograms/kg per day SC) from 6 to 20 weeks of age. High- but not low-dose ACE inhibitor treatment prevented the development of hypertension and left ventricular hypertrophy. Chronic bradykinin receptor blockade did not attenuate the antihypertensive and antihypertrophic actions of ramipril. High-dose ramipril treatment improved cardiac function, as demonstrated by an increase in left ventricular pressure (29.9%), dP/dtmax (34.9%), and coronary flow (22.1%), without a change in heart rate. The activities of lactate dehydrogenase and creatine kinase and lactate concentration in the coronary effluent were reduced by 39.3%, 55.5%, and 66.7%, respectively. Myocardial tissue concentrations of glycogen and the energy-rich phosphates ATP and creatine phosphate were increased by 31.3%, 39.9%, and 73.7%, respectively, whereas lactate was decreased by 20.8%. Chronic low-dose ACE inhibitor treatment led to a pattern of changes in cardiodynamics and cardiac metabolism similar to that observed with the high dose. All ACE inhibitor-induced effects on cardiac function and metabolism were abolished by chronic bradykinin receptor blockade.(ABSTRACT TRUNCATED AT 250 WORDS)
Effect of potassium on vasodilation to acetylcholine in essential hypertension.
Authors: Taddei S , Mattei P , Virdis A , Sudano I , Ghiadoni L , Salvetti A
Published: June 2012

Patients with essential hypertension show impaired endothelium-dependent vasodilation induced by acetylcholine. Because dietary potassium supplementation increases endothelium-dependent relaxations to acetylcholine in hypertensive rats, we designed the present study to investigate whether potassium increases endothelium-dependent vasodilation in essential hypertensive patients. Therefore, in patients with essential hypertension (n = 13) and in normotensive control subjects (n = 13) we evaluated the effect of intrabrachial potassium chloride (0.2 mmol/min) on forearm blood flow (strain-gauge plethysmography) modifications induced by intrabrachial acetylcholine (0.15, 0.45, 1.5, 4.5, and 15 micrograms/100 mL forearm tissue per minute). In both groups of patients, potassium chloride infusion augmented local plasma potassium concentrations. Furthermore, in essential hypertensive patients but not in normotensive subjects it increased the vasodilating effect of the first three infusion rates of acetylcholine. In contrast, in seven adjunctive essential hypertensive patients, potassium chloride did not alter intrabrachial sodium nitroprusside-induced forearm vasodilation (1, 2, and 4 micrograms/100 mL forearm tissue per minute). Finally, to evaluate the role of nitric oxide on potassium-dependent facilitation of acetylcholine-induced vasodilation in essential hypertension, we studied the effect of intrabrachial NG-monomethyl L-arginine (100 micrograms/100 mL per minute) in another group of seven hypertensive patients. Vasodilation to acetylcholine was again increased by potassium chloride; NG-monomethyl L-arginine slightly blunted the vasorelaxing effect of acetylcholine but abolished the potentiating effect of potassium.(ABSTRACT TRUNCATED AT 250 WORDS)
Oxidized lipoproteins inhibit endothelium-dependent vasodilation. Effects of pressure and high-density lipoprotein.
Authors: Galle J , Ochslen M , Schollmeyer P , Wanner C
Published: June 2012

Hypertension and atherogenic low-density lipoproteins cause attenuation of endothelium-dependent dilations in vivo. We investigated a potential interference of high transmural pressure with the effects of low-density lipoproteins on endothelium-dependent dilation in vitro. Furthermore, we determined whether high-density lipoproteins preserve endothelial function. Endothelium-intact rabbit renal arteries were isolated, placed in an organ bath, perfused intraluminally with Tyrode's solution, and exposed to different degrees of transmural pressure and native or oxidized low-density lipoproteins. In preconstricted arteries perfused under low-pressure conditions (30 mm Hg), acetylcholine dose dependently elicited endothelium-dependent dilations that were not altered by increasing the perfusion pressure to 100 mm Hg for 90 minutes (high-pressure conditions). Incubation of the arteries with native or oxidized low-density lipoproteins (0.2 and 1 mg/mL for 60 minutes, respectively) under low-pressure conditions did not attenuate acetylcholine-induced dilations. However, under high-pressure conditions dilations were dose dependently attenuated by oxidized but not by native low-density lipoproteins. Endothelium-independent dilations to glyceroltrinitrate (0.001 to 3 mumol/L) were not affected. Preincubation of the segments with high-density lipoproteins (0.5 mg/mL, 30 minutes) prevented attenuation of dilator responses. The attenuation of endothelium-dependent dilations by oxidized low-density lipoproteins under high-pressure conditions was accompanied by a transmural, dose-dependent infiltration of the vessel wall with lipoprotein, as detected by light microscopy of cryostat sections stained with Sudan III. This infiltration was prevented by high-density lipoprotein. Under low-pressure conditions no lipoprotein infiltration was visible. In segments incubated with native low-density lipoprotein, no lipoprotein infiltration was detectable.(ABSTRACT TRUNCATED AT 250 WORDS)
Gene expression of 11 beta-hydroxysteroid dehydrogenase in the mesenteric arteries of genetically hypertensive rats.
Authors: Takeda Y , Miyamori I , Yoneda T , Iki K , Hatakeyama H , Takeda R
Published: June 2012

11 beta-Hydroxysteroid dehydrogenase (11 beta-HSD) modulates the access of corticosteroids to their receptors and plays an important role in controlling blood pressure. We determined 11 beta-HSD activity and mRNA levels in the mesenteric arteries of genetically hypertensive rats, the Dahl salt-sensitive hypertensive rat, and compared them with Dahl salt-resistant and Sprague-Dawley rats. 11 beta-HSD activity was expressed as the percent conversion of [3H]corticosterone to [3H]11-dehydrocorticosterone. 11 beta-HSD activity was significantly decreased in the mesenteric arteries of 8-week-old Dahl salt-sensitive hypertensive rats (11.4 +/- 1.4%) compared with Dahl salt-resistant rats (17.4 +/- 1.4%) or Sprague-Dawley rats (18.0 +/- 1.5%) of the same age (P < .05). There were no significant differences in 11 beta-HSD activity between 4-week-old Dahl salt-sensitive hypertensive and Dahl salt-resistant rats of the same age (15.3 +/- 1.3% and 15.1 +/- 1.9%, respectively). The concentration of 11 beta-HSD mRNA in the mesenteric arteries of 8-week-old Dahl salt-sensitive hypertensive rats was significantly lower than in Dahl salt-resistant or Sprague-Dawley rats of the same age (P < .05). There were no significant differences in the concentration of 11 beta-HSD mRNA in the mesenteric arteries of 4-week-old Dahl salt-sensitive hypertensive rats, Dahl salt-resistant rats, and Sprague-Dawley rats. These results indicate that 11 beta-HSD in the vascular wall may play a role in the pathogenesis of hypertension in this rat model.
Endothelin receptor antagonists inhibit endothelin in human skin microcirculation.
Authors: Wenzel R R , Noll G , Lüscher T F
Published: June 2012

Endothelin is a potent vasoconstrictor peptide produced by endothelial cells, but its role in physiology and disease is uncertain. We investigated the influence of the endothelin-A-selective receptor antagonist PD 147953 and the nonselective endothelin receptor antagonist PD 145065 on the effects of endothelin-1 and endothelin-3 in the skin microcirculation of healthy volunteers, using laser Doppler flowmetry. A double injection model was developed, allowing simultaneous injection of two substances, ie, agonist and antagonist or saline. The injection of saline led to a well-defined vasodilation at the injection site (maximum increase, from 19 +/- 2 to 97 +/- 15 perfusion units at 6 minutes; P < .001; n = 10). Endothelin-1 (10(-12) mol) decreased blood flow (difference from saline control, -79 +/- 14 perfusion units; P < .001; n = 11) within the injection wheal (diameter, 4 to 5 mm), while endothelin-3 had no effect. In the surrounding area (at 8 mm from the injection site), both endothelin-1 (+116 +/- 32 perfusion units; P < .001; n = 11) and endothelin-3 (+59 +/- 16 perfusion units; P < .001; n = 11) markedly increased blood flow. Both endothelin receptor antagonists slightly increased blood flow (maximum difference from control, +56 +/- 18 [PD 147953] and +31 +/- 10 [PD 145065] perfusion units; P < .05; n = 8) and inhibited endothelin-1-induced (P < .01) vasoconstriction. The vasoconstriction to norepinephrine was not affected by the endothelin antagonist PD 147953. Endothelin-1- and endothelin-3-induced vasodilation in the surrounding area were also inhibited by both endothelin antagonists or by lidocaine.(ABSTRACT TRUNCATED AT 250 WORDS)
Angiotensin receptor regulates cardiac hypertrophy and transforming growth factor-beta 1 expression.
Authors: Everett A D , Tufro-McReddie A , Fisher A , Gomez R A
Published: June 2012

The role of angiotensin II via the angiotensin type 1 or type 2 receptor in the development of cardiac hypertrophy was determined in adult male Sprague-Dawley rats subjected to coarctation of the abdominal aorta. Five groups of animals were studied: coarctation, coarctation plus DuP 753, coarctation plus PD 123319, sham plus DuP 753, or sham operation. Type 1 receptor blockade was accomplished with DuP 753 given in the drinking water and type 2 blockade with PD 123319 delivered by osmotic minipumps beginning with the day of surgery until 72 hours after aortic coarctation. Mean carotid blood pressures and the carotid-femoral artery blood pressure gradients were not different among coarctation, coarctation plus DuP 753, and coarctation plus PD 123319 animals. However, ratios of heart weight to body weight were higher in coarctation (4.95 +/- 0.8) or coarctation plus PD 123319 (4.52 +/- 0.5) than in sham animals (3.6 +/- 0.4; P < .005 and .05, respectively). In coarctation plus DuP 753-treated animals heart weight-body weight ratios were not different from sham or sham plus DuP 753 animals (3.9 +/- 0.4 versus 3.6 +/- 0.4 or 3.3 +/- 0.08, respectively). Type 1 receptor mRNA levels were significantly increased in the coarctation group, with the highest levels in the coarctation plus DuP 753 and sham plus DuP 753 groups. To determine whether growth factors were involved in the hypertrophic process, we measured transforming growth factor-beta 1 mRNA levels. Northern analysis demonstrated a twofold increase in coarctation animals compared with sham or coarctation plus DuP 753-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)
Dietary magnesium prevents fructose-induced insulin insensitivity in rats.
Authors: Balon T W , Jasman A , Scott S , Meehan W P , Rude R K , Nadler J L
Published: June 2012

Increased dietary fructose may produce insulin insensitivity and elevate blood pressure in rats. It is possible that the reduced magnesium content of the high-fructose commercial diet used in some studies may play a role in these abnormalities because it is known that magnesium deficiency can produce insulin insensitivity and increased angiotensin II action in humans. To study this, we maintained rats for 9 weeks on either a normal control diet, a standard high-fructose diet, or the same high-fructose diet supplemented with magnesium. Glucose uptake was assessed using a perfused rat hindquarter preparation sequentially with 0, 900, and 120,000 pmol/L of added insulin. Basal serum glucose, plasma insulin, and basal glucose uptake in the absence of insulin were similar among all three groups. However, insulin sensitivity, defined as glucose uptake in the presence of 900 pmol/L insulin minus basal, was depressed in the high-fructose compared with the control group (1.02 +/- 0.38 to 1.77 +/- 0.57 mumol/g per hour, P < .05). In contrast, the high-fructose group supplemented with normal magnesium had similar insulin sensitivity as the control group (2.09 +/- 0.69 mumol/g per hour). Total serum magnesium was reduced in the high-fructose group compared with control or high-fructose plus magnesium-supplemented groups. Blood pressure and fasting insulin levels were also lower in the magnesium-supplemented group. These results suggest that magnesium deficiency and not fructose ingestion per se leads to insulin insensitivity in skeletal muscle and changes in blood pressure.
Evidence against a role of insulin in hypertension in spontaneously hypertensive rats. CS-045 does not lower blood pressure despite improvement of insulin resistance.
Authors: Katayama S , Abe M , Kashiwabara H , Kosegawa I , Ishii J
Published: June 2012

Hyperinsulinemia resulting from peripheral insulin resistance has been demonstrated both in spontaneously hypertensive rats (SHR) and in humans with essential hypertension. A new class of antidiabetic drugs, thiazolidinediones, which can improve insulin resistance, may be able to lower not only blood glucose levels but also blood pressure. The present study was therefore designed to clarify the proportion of SHR that are glucose intolerant and to observe the effect on blood pressure of CS-045 (troglitazone) administered at 70 mg/kg per day for 2 weeks to male SHR (n = 13). Among 67 male 8-week-old SHR, 74.6% were glucose intolerant and hyperinsulinemic. Systolic blood pressure did not correlate with plasma glucose or insulin levels before or after glucose loading. Treatment with CS-045 improved insulin resistance, as evidenced by a smaller area under the curve of plasma glucose and insulin levels in response to glucose loading. However, systolic blood pressure was not altered. When the data were reanalyzed according to the presence or absence of glucose intolerance before the treatment, blood pressure in the treated group was the same as in controls despite significant improvement in steady-state plasma glucose levels. These results suggest that hyperinsulinemia and/or insulin resistance may not be involved in the development or maintenance of hypertension in SHR, which is in contrast to models of hypertension such as obese Zucker rats or fructose-fed rats.
Cardiac and arterial hypertrophy and atherosclerosis in hypertension.
Authors: Devereux R B , Roman M J , Ganau A , de Simone G , Okin P M , Kligfield P
Published: June 2012

Clinical evaluation of the hypertensive patient has traditionally relied on physician measurement of blood pressure and assessment of target-organ involvement by simple laboratory tests. However, this approach is limited in its ability to identify individual patients at high or low risk of complications. In recent years, noninvasive methods have been developed to identify pathological transformations of the heart and arteries that collectively comprise "preclinical hypertensive disease." Measurements by echocardiogram or other methods of left ventricular mass and relative wall thickness identify a spectrum of cardiac adaptations to hypertension, including concentric and eccentric hypertrophy, the recently described pattern of "concentric left ventricular remodeling" (normal mass but increased relative wall thickness), and normal ventricular geometry. In clinical studies, each anatomic pattern is associated with a distinct profile of resting hemodynamics, ambulatory blood pressure, myocardial contractility, and risk of adverse outcomes. Ultrasonic imaging of the carotid or other arteries makes it possible to detect increased arterial wall thickness and discrete atheromas noninvasively. Carotid wall thickness and lumen diameter parallel similar ventricular dimensions in normotensive and hypertensive humans, indicating the presence of integrated patterns of cardiac and vascular adaptation to hypertension. Furthermore, peripheral atherosclerosis is associated with higher ventricular mass and a more adverse 24-hour blood pressure profile. In summary, noninvasive visualization of the heart and blood vessels reveals a spectrum of patterns of anatomic and functional adaptations that are related to the pathophysiology and prognosis of hypertension.
Angiotensin II alters aortic fibronectin independently of hypertension.
Authors: Himeno H , Crawford D C , Hosoi M , Chobanian A V , Brecher P
Published: June 2012

We performed these studies to assess the potential role of hemodynamic forces in mediating the changes in aortic fibronectin mRNA expression that occur in the rat in response to angiotensin II administration. With the use of an acute hypertensive model involving a 3-day infusion with a pressor dose of angiotensin II given by osmotic minipump, a selective increase in fibronectin mRNA expression but not of several other extracellular matrix genes was documented. This change was inhibited by losartan, indicating the importance of angiotensin receptors in the response. Prazosin, hydralazine, or L-arginine added to the drinking water all lowered the angiotensin II-induced increase in blood pressure but did not attenuate the increase in fibronectin mRNA expression. Angiotensin-converting enzyme inhibition using trandolapril did reduce fibronectin mRNA in the angiotensin II-infusion model, despite an inability to reduce blood pressure, whereas when angiotensin I was infused, quinapril lowered both blood pressure and fibronectin expression even at doses that did not completely normalize blood pressure. These studies suggest that angiotensin II induced an increase in aortic fibronectin mRNA that was not dependent solely on blood pressure.
Effects of angiotensin receptor subtype inhibitors on plasma angiotensin clearance.
Authors: Vernace M A , Mento P F , Maita M E , Wilkes B M
Published: June 2012

The aim of this study was to determine whether angiotensin receptor subtypes play a role in angiotensin clearance from plasma. Angiotensin metabolic clearance rate was measured in rats by the constant infusion method. Increasing doses of angiotensin II were infused for 15 minutes, and blood was sampled for angiotensin II. The type 1 angiotensin II receptor antagonist losartan decreased the apparent metabolic clearance rate by > 50% at low-dose infusion, suggesting that type 1 angiotensin II receptors are involved in angiotensin II clearance from plasma. At higher angiotensin infusion rates, the-metabolic clearance rate of angiotensin was unaffected. To dissect the contribution of renin-generated angiotensin, additional experiments were performed in nephrectomized rats. In anephric rats, angiotensin clearance was unaffected by type 1 angiotensin II receptor inhibition. In contrast, the type 2 angiotensin II receptor ligand PD123319 in intact rats caused a > 50% increase in metabolic clearance rate of angiotensin at higher infusion rates (P < .05). In anephric rats, the type 2 angiotensin II receptor ligand alone or combined with type 1 receptor inhibition was without effect on the metabolic clearance rate or the T1/2 for angiotensin disappearance. These data argue against a role for type 1 or 2 angiotensin II receptors as clearance receptors. Increased clearance of angiotensin by type 2 receptor blockade in the presence but not the absence of kidneys suggests an alternative renal mechanism by which selective type 2 ligands may alter angiotensin effects.
Carotid artery distensibility and distending pressure in hypertensive humans.
Authors: Laurent S , Caviezel B , Beck L , Girerd X , Billaud E , Boutouyrie P , Hoeks A , Safar M
Published: June 2012

Whether the decrease in large-artery distensibility observed in hypertensive patients is due primarily to an increase in distending pressure or to hypertension-induced changes in structural properties has been much debated. We determined noninvasively the diameter-pressure curve of the common carotid artery over the systolic-diastolic range by continuously recording both the pulsatile changes in internal diameter (high-resolution echo-tracking system) and, simultaneously on the contralateral artery, the pressure waveform (high-fidelity applanation tonometry). We then derived the distensibility/pressure curve and compared arterial distensibility in 14 normotensive subjects and 15 age- and sex-matched hypertensive subjects at their respective mean arterial pressures (MAP) and at a common distending pressure: 100 mm Hg. Distensibility decreased as blood pressure increased, and distensibility at MAP was significantly lower in hypertensive than in normotensive subjects (7.8 +/- 0.7 versus 11.7 +/- 1.7 kPa-1.10(-3), mean +/- SEM; P < .05). In hypertensive subjects, the distensibility-pressure curve was shifted toward higher levels of blood pressure, and a large part of the curve overlapped that of normotensive subjects. No significant downward shift of the distensibility-pressure curve was observed in hypertensive subjects, and distensibility at 100 mm Hg was not significantly different from that of normotensive subjects (10.0 +/- 1.0 versus 9.0 +/- 1.1 kPa-1.10(-3)). Distensibility at 100 mm Hg decreased with aging (P < .05) and was not reduced in hypertensive subjects compared with normotensive subjects after adjustment for age.(ABSTRACT TRUNCATED AT 250 WORDS)
Sympathetic baroreceptor responses after chronic NG-nitro-L-arginine methyl ester treatment in conscious rats.
Authors: Scrogin K E , Veelken R , Luft F C
Published: June 2012

Blood pressure elevations after nitric oxide inhibition may result in part from increased sympathetic tone. In this study arterial baroreceptor reflex control of heart rate, renal sympathetic nerve activity (RSNA), and adrenal sympathetic nerve activity (ASNA) were compared in rats given normal tap water or a 3.7 nmol/L (10 mg%) solution of NG-nitro-L-arginine methyl ester (L-NAME) for 1 or 5 weeks. L-NAME raised blood pressure after 5 weeks of treatment (153 +/- 3 versus 130 +/- 3 and 124 +/- 2 mm Hg, 5 weeks versus 1 week and control). The sensitivity of arterial baroreceptor reflex control of RSNA was reduced after both 1 and 5 weeks of treatment (-5.05 +/- 0.63% and -4.46 +/- 0.2% versus -6.43 +/- 0.39% baseline activity per millimeters of mercury). Set point gain of ASNA was attenuated after 5 weeks of treatment compared with controls (-1.7 +/- 3% versus -3.3 +/- 3% baseline activity per millimeters of mercury). Maximal inhibition of ASNA was attenuated in groups treated 1 and 5 weeks (60 +/- 3% and 66 +/- 3% versus 34 +/- 4% baseline activity). The maximal increase in both RSNA and ASNA was elevated in rats treated 5 weeks (RSNA: control, 263 +/- 19%; 1 week, 224 +/- 17%; 5 weeks, 324 +/- 20%; ASNA: control, 272 +/- 29%; 1 week, 252 +/- 31%; 5 weeks, 361 +/- 28% baseline activity). The data indicate that chronic L-NAME treatment alters arterial baroreceptor reflexes in part before the onset of hypertension.
Blunted natriuretic response to a high-sodium meal in obese dogs. Role of renal nerves.
Authors: Kassab S , Patterson S , Wilkins F C , Mizelle H L , Reinhart G A , Granger J P
Published: June 2012

Although the relation between body weight and arterial pressure is well established, the mechanisms involved in the pathogenesis of obesity-related hypertension are unclear. However, recent studies suggest that abnormalities in renal function may be involved. The purpose of this study was to test the hypothesis that obese animals have a reduced ability to excrete a sodium load as a result of abnormal renal nerve function. To quantify the role of renal nerves, we examined changes in renal hemodynamics and sodium excretion in response to a high-sodium meal (200 mmol Na) in separate innervated and denervated kidneys simultaneously within the same conscious dog. Two surgically designed hemibladders with indwelling catheters were used to collect urine from innervated and denervated kidneys of the same dog. Body weight averaged 19.9 +/- 1.0 kg in the control lean dogs and 25.1 +/- 1.1 kg in the obese dogs. Arterial pressure averaged 101 +/- 4 mm Hg in the obese dogs and 90 +/- 4 mm Hg in the lean dogs. In response to the high-sodium meal in lean dogs, urinary sodium excretion increased from 20.8 +/- 4.2 to 189.7 +/- 21.2 mumol/min in the innervated kidneys and from 25.3 +/- 5.9 to 194.8 +/- 26.9 mumol/min in the denervated kidneys. In contrast, urinary sodium excretion in obese dogs increased from 9.6 +/- 1.4 to 129.9 +/- 34.3 mumol/min in the innervated kidneys and from 18.4 +/- 3.7 to 125.2 +/- 30.5 mumol/min in the denervated kidneys.(ABSTRACT TRUNCATED AT 250 WORDS)
Diurnal blood pressure variation and dietary salt in spontaneously hypertensive rats.
Authors: Calhoun D A , Zhu S , Wyss J M , Oparil S
Published: June 2012

We have previously reported that high dietary salt exposure significantly increases daytime mean arterial pressure in spontaneously hypertensive rats (SHR) but not in normotensive Wistar-Kyoto (WKY) controls. In the present study, we used a telemetry monitoring system to evaluate the effects of high dietary salt exposure on diurnal variation of mean arterial pressure and heart rate in SHR and WKY rats. After implantation of a radio frequency transducer, SHR and WKY rats were maintained on either high (8%) or basal (1%) salt diets. Hemodynamic values were then analyzed for diurnal variation with the use of a nonlinear data-fitting program. After 2 weeks of dietary exposure, high salt-fed SHR had significantly greater 24-hour mean arterial pressure (156 +/- 3 mmHg) than SHR receiving basal (135 +/- 2 mmHg) and WKY rats receiving high (100 +/- 2 mmHg) or basal (100 +/- 1 mmHg) salt diets. Rhythm analysis indicated significant increases in both daytime and nighttime mean arterial pressure during high salt exposure in SHR. In WKY rats, high salt exposure increased nighttime but not daytime mean arterial pressure, with no net effect on 24-hour mean arterial pressure. High dietary salt exposure significantly decreased heart rate in both SHR and WKY rats, and it did not significantly alter the pattern of diurnal blood pressure or heart rate variation. These results indicate that WKY rats manifest an acute sensitivity to salt ingestion but have compensatory mechanisms sufficient to prevent sustained increases in mean arterial pressure; such mechanisms are lacking in SHR.