scholarly journals AT1 receptor participates in the cardiac hypertrophy induced by resistance training in rats

2008 ◽  
Vol 295 (2) ◽  
pp. R381-R387 ◽  
Author(s):  
Valerio G. Barauna ◽  
Flávio C. Magalhaes ◽  
Jose E. Krieger ◽  
Edilamar M. Oliveira
Keyword(s):  
Resistance Training ◽  
Left Ventricle ◽  
Cardiac Hypertrophy ◽  
Receptor Gene ◽  
Weight Ratio ◽  
High Salt ◽  
Receptor Expression ◽  
Ang Ii ◽  
High Salt Diet ◽  
Salt Diet

Resistance training is accompanied by cardiac hypertrophy, but the role of the renin-angiotensin system (RAS) in this response is elusive. We evaluated this question in 36 male Wistar rats divided into six groups: control ( n = 6); trained ( n = 6); control + losartan (10 mg·kg−1·day−1, n = 6); trained + losartan ( n = 6); control + high-salt diet (1%, n = 6); and trained + high-salt diet (1%, n = 6). High salt was used to inhibit the systemic RAS and losartan to block the AT1 receptor. The exercise protocol consisted of: 4 × 12 bouts, 5×/wk during 8 wk, with 65–75% of one repetition maximum. Left ventricle weight-to-body weight ratio increased only in trained and trained + high-salt diet groups (8.5% and 10.6%, P < 0.05) compared with control. Also, none of the pathological cardiac hypertrophy markers, atrial natriuretic peptide, and αMHC (α-myosin heavy chain)-to-βMHC ratio, were changed. ACE activity was analyzed by fluorometric assay (systemic and cardiac) and plasma renin activity (PRA) by RIA and remained unchanged upon resistance training, whereas PRA decreased significantly with the high-salt diet. Interestingly, using Western blot analysis and RT-PRC, no changes were observed in cardiac AT2 receptor levels, whereas the AT1 receptor gene (56%, P < 0.05) and protein (31%, P < 0.05) expressions were upregulated in the trained group. Also, cardiac ANG II concentration evaluated by ELISA remained unchanged (23.27 ± 2.4 vs. 22.01 ± 0.8 pg/mg, P > 0.05). Administration of a subhypotensive dose of losartan prevented left ventricle hypertrophy in response to the resistance training. Altogether, we provide evidence that resistance training-induced cardiac hypertrophy is accompanied by induction of AT1 receptor expression with no changes in cardiac ANG II, which suggests a local activation of the RAS consistent with the hypertrophic response.

Renal endothelin in chronic angiotensin II hypertension

2002 ◽  
Vol 283 (1) ◽  
pp. R243-R248 ◽  
Author(s):  
Jennifer M. Sasser ◽  
Jennifer S. Pollock ◽  
David M. Pollock
Keyword(s):  
Sodium Intake ◽  
Renal Tissue ◽  
High Salt ◽  
Ang Ii ◽  
Sprague Dawley ◽  
Outer Medulla ◽  
High Salt Diet ◽  
Salt Diet ◽  
Sprague Dawley Rats ◽  
Saline Vehicle

To determine the influence of chronic ANG II infusion on urinary, plasma, and renal tissue levels of immunoreactive endothelin (ET), ANG II (65 ng/min) or saline vehicle was delivered via osmotic minipump in male Sprague-Dawley rats given either a high-salt diet (10% NaCl) or normal-salt diet (0.8% NaCl). High-salt diet alone caused a slight but not statistically significant increase (7 ± 1%) in mean arterial pressure (MAP). MAP was significantly increased in ANG II-infused rats (41 ± 10%), and the increase in MAP was significantly greater in ANG II rats given a high-salt diet (59 ± 1%) compared with the increase observed in rats given a high-salt diet alone or ANG II infusion and normal-salt diet. After a 2-wk treatment, urinary excretion of immunoreactive ET was significantly increased by ∼50% in ANG II-infused animals and by over 250% in rats on high-salt diet, with or without ANG II infusion. ANG II infusion combined with high-salt diet significantly increased immunoreactive ET content in the cortex and outer medulla, but this effect was not observed in other groups. In contrast, high-salt diet, with or without ANG II infusion, significantly decreased immunoreactive ET content within the inner medulla. These data indicate that chronic elevations in ANG II levels and sodium intake differentially affect ET levels within the kidney and provide further support for the hypothesis that the hypertensive effects of ANG II may be due to interaction with the renal ET system.

scholarly journals Discharge of RVLM vasomotor neurons is not increased in anesthetized angiotensin II-salt hypertensive rats

2013 ◽  
Vol 305 (12) ◽  
pp. H1781-H1789 ◽  
Author(s):  
Gustavo R. Pedrino ◽  
Alfredo S. Calderon ◽  
Mary Ann Andrade ◽  
Sergio L. Cravo ◽  
Glenn M. Toney
Keyword(s):  
Sympathetic Nerve Activity ◽  
High Salt ◽  
Ventrolateral Medulla ◽  
Ang Ii ◽  
Hypertensive Rats ◽  
Nerve Activity ◽  
High Salt Diet ◽  
Salt Diet ◽  
Salt Hypertension ◽  
Single Unit Recordings

Neurons of the rostral ventrolateral medulla (RVLM) are critical for generating and regulating sympathetic nerve activity (SNA). Systemic administration of ANG II combined with a high-salt diet induces hypertension that is postulated to involve elevated SNA. However, a functional role for RVLM vasomotor neurons in ANG II-salt hypertension has not been established. Here we tested the hypothesis that RVLM vasomotor neurons have exaggerated resting discharge in rats with ANG II-salt hypertension. Rats in the hypertensive (HT) group consumed a high-salt (2% NaCl) diet and received an infusion of ANG II (150 ng·kg−1·min−1 sc) for 14 days. Rats in the normotensive (NT) group consumed a normal salt (0.4% NaCl) diet and were infused with normal saline. Telemetric recordings in conscious rats revealed that mean arterial pressure (MAP) was significantly increased in HT compared with NT rats ( P < 0.001). Under anesthesia (urethane/chloralose), MAP remained elevated in HT compared with NT rats ( P < 0.01). Extracellular single unit recordings in HT ( n = 28) and NT ( n = 22) rats revealed that barosensitive RVLM neurons in both groups (HT, 23 cells; NT, 34 cells) had similar cardiac rhythmicity and resting discharge. However, a greater ( P < 0.01) increase of MAP was needed to silence discharge of neurons in HT (17 cells, 44 ± 5 mmHg) than in NT (28 cells, 29 ± 3 mmHg) rats. Maximum firing rates during arterial baroreceptor unloading were similar across groups. We conclude that heightened resting discharge of sympathoexcitatory RVLM neurons is not required for maintenance of neurogenic ANG II-salt hypertension.

scholarly journals Effects of Aqueous Extract of Persea americana (Mill.) Leaf on the Myocardium of Left Ventricle of High Salt Fed Adult Wistar Rat

2018 ◽  
Vol 35 (01) ◽  
pp. 31-36
Author(s):  
I.O. Ayoola ◽  
O.A. Komolafe ◽  
O.S. Saka ◽  
R.A. Bejide ◽  
S.O.A. Odukoya
Keyword(s):  
Left Ventricle ◽  
Wistar Rats ◽  
Wistar Rat ◽  
Persea Americana ◽  
High Salt ◽  
High Salt Diet ◽  
Salt Diet ◽  
Morphological Alterations ◽  
Ketamine Anesthesia ◽  
Group B

Introduction This study was designed to show that Persea americana extract possess the ability to protect the myocardium of left ventricle against injury caused by high salt diet in adult Wistar rats. Method Forty healthy Wistar rats of both sexes weighing 120–150 g were randomly assigned into 8 groups of 5 rats each (Groups A, B, C, D, E, F, G and H). Rats in groups A, F, G and H were fed with standard laboratory pellets, while groups B, C, D and E were fed on the high-salt diet for four weeks. Concomitantly, daily administration of 50 mg kg-1, 100 mg kg-1 and 150 mg kg-1 of the Persea americana extract were given orally to groups C&F, D&G and E&H respectively while rats in groups A and B were administered distilled water. The rats were sacrificed under ketamine anesthesia (30mg/kg i.m). The left ventricle of the heart was excised, processed in paraffin wax and stained with haematoxylin and eosin and Verhoeff-Van Gieson stains. One-way ANOVA was used to analyze data, followed by Student Newman-keuls (SNK) test for multiple comparison. Result Results revealed that there was statistically significant (p < 0.05) difference in body weight change across all experimental groups; which was significantly lower in high salt fed groups. It was revealed that there were morphological alterations in the myocardium of left ventricle in group B while Persea americana protected myocardium in other experimental groups. Conclusion In conclusion, high salt diet induced myocardium alterations which were significantly protected by oral administration of Persea americana extract.

scholarly journals Time course of decompensation after angiotensin II and high-salt diet in Balb/CJ mice suggests pulmonary hypertension-induced cardiorenal syndrome

2019 ◽  
Vol 316 (5) ◽  
pp. R563-R570 ◽  
Author(s):  
Mediha Becirovic-Agic ◽  
Sofia Jönsson ◽  
Maria K. Tveitarås ◽  
Trude Skogstrand ◽  
Tine V. Karlsen ◽  
...  
Keyword(s):  
Cardiac Output ◽  
Angiotensin Ii ◽  
Cardiac Function ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
High Salt ◽  
Ang Ii ◽  
Salt Treatment ◽  
High Salt Diet ◽  
Salt Diet

The genetic background of a mouse strain determines its susceptibility to disease. C57BL/6J and Balb/CJ are two widely used inbred mouse strains that we found react dramatically differently to angiotensin II and high-salt diet (ANG II + Salt). Balb/CJ show increased mortality associated with anuria and edema formation while C57BL/6J develop arterial hypertension but do not decompensate and die. Clinical symptoms of heart failure in Balb/CJ mice gave the hypothesis that ANG II + Salt impairs cardiac function and induces cardiac remodeling in male Balb/CJ but not in male C57BL/6J mice. To test this hypothesis, we measured cardiac function using echocardiography before treatment and every day for 7 days during treatment with ANG II + Salt. Interestingly, pulsed wave Doppler of pulmonary artery flow indicated increased pulmonary vascular resistance and right ventricle systolic pressure in Balb/CJ mice, already 24 h after ANG II + Salt treatment was started. In addition, Balb/CJ mice showed abnormal diastolic filling indicated by reduced early and late filling and increased isovolumic relaxation time. Furthermore, Balb/CJ exhibited lower cardiac output compared with C57BL/6J even though they retained more sodium and water, as assessed using metabolic cages. Left posterior wall thickness increased during ANG II + Salt treatment but did not differ between the strains. In conclusion, ANG II + Salt treatment causes early restriction of pulmonary flow and reduced left ventricular filling and cardiac output in Balb/CJ, which results in fluid retention and peripheral edema. This makes Balb/CJ a potential model to study the adaptive capacity of the heart for identifying new disease mechanisms and drug targets.

scholarly journals Salt-sensitive hypertension and cardiac hypertrophy in mice deficient in the ubiquitin ligase Nedd4-2

2008 ◽  
Vol 295 (2) ◽  
pp. F462-F470 ◽  
Author(s):  
Peijun P. Shi ◽  
Xiao R. Cao ◽  
Eileen M. Sweezer ◽  
Thomas S. Kinney ◽  
Nathan R. Williams ◽  
...  
Keyword(s):  
Cardiac Hypertrophy ◽  
Critical Role ◽  
Specific Inhibitor ◽  
Normal Diet ◽  
High Salt ◽  
High Salt Diet ◽  
Salt Diet ◽  
Ww Domains ◽  
Salt Sensitive Hypertension

Nedd4-2 has been proposed to play a critical role in regulating epithelial Na+ channel (ENaC) activity. Biochemical and overexpression experiments suggest that Nedd4-2 binds to the PY motifs of ENaC subunits via its WW domains, ubiquitinates them, and decreases their expression on the apical membrane. Phosphorylation of Nedd4-2 (for example by Sgk1) may regulate its binding to ENaC, and thus ENaC ubiquitination. These results suggest that the interaction between Nedd4-2 and ENaC may play a crucial role in Na+ homeostasis and blood pressure (BP) regulation. To test these predictions in vivo, we generated Nedd4-2 null mice. The knockout mice had higher BP on a normal diet and a further increase in BP when on a high-salt diet. The hypertension was probably mediated by ENaC overactivity because 1) Nedd4-2 null mice had higher expression levels of all three ENaC subunits in kidney, but not of other Na+ transporters; 2) the downregulation of ENaC function in colon was impaired; and 3) NaCl-sensitive hypertension was substantially reduced in the presence of amiloride, a specific inhibitor of ENaC. Nedd4-2 null mice on a chronic high-salt diet showed cardiac hypertrophy and markedly depressed cardiac function. Overall, our results demonstrate that in vivo Nedd4-2 is a critical regulator of ENaC activity and BP. The absence of this gene is sufficient to produce salt-sensitive hypertension. This model provides an opportunity to further investigate mechanisms and consequences of this common disorder.

scholarly journals Renal Urotensin II System Plays Roles in the Regulation of Blood Pressure in Dahl Salt-Resistant Rat

2016 ◽  
Vol 2016 ◽  
pp. 1-11
Author(s):  
Fei Wu ◽  
Guanjong Chen ◽  
Aihua Zhang ◽  
Yang Yu ◽  
Minhua Fan ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Animal Models ◽  
Receptor Gene ◽  
Urinary Sodium Excretion ◽  
High Salt ◽  
Sodium Absorption ◽  
Urotensin Ii ◽  
High Salt Diet ◽  
Salt Diet ◽  
Regulation Of Blood Pressure

Introduction. Dahl salt-resistant (SR) animal models are similar to peritoneal dialysis patients with fluid volumes overload with normal blood pressure in hemodynamic profiles. We will verify the roles of UII in the regulation of blood pressure in these animal models.Methodology. The Dahl salt-sensitive (SS) and SR rats and UII receptor gene knocked out (KO) mice were placed on a high-salt diet. Renal tissues were performed for the expression of UII in Dahl groups.Results. After high-salt diet for 6 weeks, the systolic blood pressure (SBP) in SR group was significantly lower, accompanied with higher urinary UII levels, higher 24-hour urinary sodium excretion, and higher urinary creatinine clearance in the SR rats in comparison to SS group. The expressions of UII and UT were both upregulated in the kidney tissues of SR group in comparison to SS group (P<0.05). After high-salt diet for 8 weeks, the SBP of the KO group is significantly higher than that of the wild type group.Conclusion. We first demonstrate that renal UII system can play important roles in the regulation of blood pressure in Dahl SR rats which can be highly correlated to its effect on renal tubular sodium absorption.

Salt-sensitive hypertension develops after transient induction of ANG II-dependent hypertension in Cyp1a1-Ren2 transgenic rats

2005 ◽  
Vol 288 (4) ◽  
pp. F810-F815 ◽  
Author(s):  
Laura L. Howard ◽  
Matthew E. Patterson ◽  
John J. Mullins ◽  
Kenneth D. Mitchell
Keyword(s):  
Blood Pressure ◽  
Renal Plasma Flow ◽  
Systolic Pressure ◽  
High Salt ◽  
Ang Ii ◽  
Transgenic Rats ◽  
High Salt Diet ◽  
Blood Pressure Elevation ◽  
Salt Diet ◽  
Salt Sensitive Hypertension

Transient exposure to ANG II results in the development of salt-sensitive hypertension in rats. This study was performed to determine whether a transient hypertensive episode can induce salt-sensitive hypertension in transgenic rats with inducible expression of the mouse Ren2 renin gene [strain name TGR(Cyp1a1-Ren2)]. Systolic blood pressures were measured in conscious male Cyp1a1-Ren2 rats ( n = 6) during control conditions and during dietary administration of indole-3-carbinol (I3C; 0.15%, wt/wt), for 14 days. Systolic pressure increased from 135 ± 5 to 233 ± 7 mmHg by day 14. I3C administration was terminated and blood pressure returned to normal levels (137 ± 5 mmHg) within 10 days. Subsequently, the rats were placed on a high-salt diet (8% NaCl) for 10 days. Systolic pressure increased by 34 ± 2 mmHg throughout 10 days of the high-salt diet. Neither glomerular filtration rate nor renal plasma flow was altered in Cyp1a1-Ren2 rats with salt-sensitive hypertension. In a separate group of male Cyp1a1-Ren2 rats ( n = 6) transiently induced with 0.15% I3C for 14 days, administration of the superoxide dismutase mimetic tempol (4-hydroxy-2,2,6,6-tetramethyl piperidinoxyl, 2 mM) attenuated the increase in systolic pressure induced by high salt. Systolic pressure increased by only 11 ± 1 mmHg throughout 8 days of a high-salt diet and tempol administration. Thus transient induction of ANG II-dependent hypertension via activation of the Cyp1a1-Ren2 transgene induces salt-sensitive hypertension in these transgenic rats. The attenuation by tempol of the high salt-induced blood pressure elevation indicates that ANG II-induced production of superoxide anion contributes to the development of salt-sensitive hypertension after transient induction of ANG II-dependent hypertension.

Renal endosomes contain angiotensin peptides, converting enzyme, and AT1A receptors

1999 ◽  
Vol 277 (2) ◽  
pp. F303-F311 ◽  
Author(s):  
John D. Imig ◽  
Gabriel L. Navar ◽  
Li-Xian Zou ◽  
Katie C. O’Reilly ◽  
Patricia L. Allen ◽  
...  
Keyword(s):  
High Salt ◽  
Dietary Sodium ◽  
Kidney Cortex ◽  
Ang Ii ◽  
Converting Enzyme ◽  
High Salt Diet ◽  
Salt Diet ◽  
Angiotensin Peptides ◽  
Low Salt ◽  
Ace Activity

Kidney cortex and proximal tubular angiotensin II (ANG II) levels are greater than can be explained on the basis of circulating ANG II, suggesting intrarenal compartmentalization of these peptides. One possible site of intracellular accumulation is the endosomes. In the present study, we tested for endosomal ANG I, ANG II, angiotensin type 1A receptor (AT1A), and angiotensin converting enzyme (ACE) activity and determined whether these levels are regulated by salt intake. Male Sprague-Dawley rats were fed chow containing either high or low dietary sodium for 10–14 days. Blood and kidneys were harvested and processed for measurement of plasma, kidney, and renal intermicrovillar cleft and endosomal angiotensin levels. Kidney ANG I averaged 179 ± 20 fmol/g and ANG II averaged 258 ± 36 fmol/g in rats fed a high-sodium diet and were significantly higher, averaging 347 ± 58 fmol/g and 386 ± 55 fmol/g, respectively, in rats fed a low-salt diet. Renal intermicrovillar clefts and endosomes contained ANG I and ANG II. Intermicrovillar cleft ANG I and ANG II levels averaged 8.4 ± 2.6 and 74 ± 26 fmol/mg, respectively, in rats fed a high-salt diet and 7.6 ± 1.7 and 70 ± 25 fmol/mg in rats fed a low-salt diet. Endosomal ANG I and ANG II levels averaged 12.3 ± 4.4 and 43 ± 19 fmol/mg, respectively, in rats fed a high-salt diet, and these levels were similar to those observed in rats fed a low-salt diet. Renal endosomes from rats fed a low-salt diet demonstrated significantly more AT1A receptor binding compared with rats fed a high-salt diet. ACE activity was detectable in renal intermicrovillar clefts and was 2.5-fold higher than the levels observed in renal endosomes. Acute enalaprilat treatment decreased ACE activity in renal intermicrovillar clefts by 90% and in renal endosomes by 84%. Likewise, intermicrovillar cleft and endosomal ANG II levels decreased by 61% and 52%, respectively, in enalaprilat-treated animals. These data demonstrate the presence of intact angiotensin peptides and ACE activity in renal intermicrovillar clefts and endosomes, indicating that intact angiotensin peptides are formed and/or trafficked through intracellular endosomal compartments and are dependent on ACE activity.

Alterations in apoptosis regulatory factors during hypertrophy and heart failure

2004 ◽  
Vol 287 (1) ◽  
pp. H72-H80 ◽  
Author(s):  
Peter M. Kang ◽  
Patrick Yue ◽  
Zhilin Liu ◽  
Oleg Tarnavski ◽  
Natalya Bodyak ◽  
...  
Keyword(s):  
Heart Failure ◽  
Cardiac Hypertrophy ◽  
Primary Cultures ◽  
High Salt ◽  
Terminal Deoxynucleotidyl Transferase ◽  
High Salt Diet ◽  
Salt Diet ◽  
Pathological Hypertrophy ◽  
Increased Sensitivity ◽  
Physiological Hypertrophy

Cardiac hypertrophy from pathological stimuli often proceeds to heart failure, whereas cardiac hypertrophy from physiological stimuli does not. In this study, physiological hypertrophy was created by a daily exercise regimen and pathological hypertrophy was created from a high-salt diet in Dahl salt-sensitive rats. The rats continued on a high-salt diet progressed to heart failure associated with an increased rate of terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling-positive cardiomyocytes. We analyzed primary cultures of these hearts and found that only cardiomyocytes made hypertrophic by a pathological stimulus show increased sensitivity to apoptosis. Examination of the molecular changes associated with these distinct types of hypertrophy revealed changes in Bcl-2 family members and caspases favoring survival during physiological hypertrophy. However, in pathological hypertrophy, there were more diffuse proapoptotic changes, including changes in Fas, the Bcl-2 protein family, and caspases. Therefore, we speculate that this increased sensitivity to apoptotic stimulation along with proapoptotic changes in the apoptosis program may contribute to the development of heart failure seen in pathological cardiac hypertrophy.

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