ANG II receptor blockade prevents ventricular hypertrophy and ANF gene expression with pressure overload in mice

1994 ◽  
Vol 266 (6) ◽  
pp. H2468-H2475 ◽  
Author(s):  
H. A. Rockman ◽  
S. P. Wachhorst ◽  
L. Mao ◽  
J. Ross
Keyword(s):  
Body Weight ◽  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Ventricular Hypertrophy ◽  
Systolic Pressure ◽  
Weight Ratio ◽  
Pressure Overload ◽  
Heart Weight ◽  
Receptor Blockade ◽  
Body Weight Ratio

There is increasing evidence that the renin-angiotensin system may play a important role in cardiac hypertrophy. To assess the role of angiotensin II in the induction of cardiac hypertrophy, three groups of adult mice were subjected to left ventricular pressure overload by transverse aortic constriction (TAC). For the next 7 days the groups received either the specific angiotensin II subtype 1 receptor (AT1) antagonist (losartan, 1.05 g/l; n = 17), an angiotensin enzyme inhibitor (captopril, 2 g/l; n = 17), or no treatment (n = 22) administered in the drinking water and compared with three similarly treated sham-operated groups (n = 7 each). TAC resulted in a significant increase in heart weight-to-body weight ratio (0.634 +/- 0.087 vs. 0.525 +/- 0.039, g/g x 100, P < 0.05), which was prevented by losartan (0.506 +/- 0.069, g/g x 100, P < 0.0001) despite similar hemodynamic load (proximal systolic pressure 146 +/- 31 vs. 136 +/- 32 mmHg, untreated vs. losartan, P = NS). Proximal systolic pressure was positively correlated with the development of ventricular hypertrophy. In the presence of AT1-receptor blockade, the increase in heart weight-to-body weight ratio at any given systolic pressure was significantly attenuated compared with untreated TAC mice. The increase in heart weight-to-body weight ratio was also significantly attenuated by captopril compared with untreated banded controls (0.542 +/- 0.091, g/g x 100, P = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Lansoprazole alleviates pressure overload-induced cardiac hypertrophy and heart failure in mice by blocking the activation of β-catenin

2019 ◽  
Vol 116 (1) ◽  
pp. 101-113 ◽  
Author(s):  
Hairuo Lin ◽  
Yang Li ◽  
Hailin Zhu ◽  
Qiancheng Wang ◽  
Zhenhuan Chen ◽  
...  
Keyword(s):  
Heart Failure ◽  
Body Weight ◽  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Weight Ratio ◽  
Left Ventricular ◽  
Neonatal Rat ◽  
Cardiac Remodelling ◽  
Heart Weight ◽  
Body Weight Ratio

Abstract Aims Proton pump inhibitors (PPIs) are widely used in patients receiving percutaneous coronary intervention to prevent gastric bleeding, but whether PPIs are beneficial for the heart is controversial. Here, we investigated the effects of lansoprazole on cardiac hypertrophy and heart failure, as well as the underlying mechanisms. Methods and results Adult male C57 mice were subjected to transverse aortic constriction (TAC) or sham surgery and then were treated with lansoprazole or vehicle for 5 weeks. In addition, cultured neonatal rat ventricular cardiomyocytes and fibroblasts were exposed to angiotensin II in the presence or absence of lansoprazole. At 5 weeks after TAC, the heart weight/body weight ratio was lower in lansoprazole-treated mice than in untreated mice, as was the lung weight/body weight ratio, while left ventricular (LV) fractional shortening and the maximum and minimum rates of change of the LV pressure were higher in lansoprazole-treated mice, along with less cardiac fibrosis. In cultured cardiomyocytes, lansoprazole inhibited angiotensin II-induced protein synthesis and hypertrophy, as well as inhibiting proliferation of fibroblasts. Lansoprazole decreased myocardial levels of phosphorylated Akt, phosphorylated glycogen synthase kinase 3β, and active β-catenin in TAC mice and in angiotensin II-stimulated cardiomyocytes. After overexpression of active β-catenin or knockdown of H+/K+-ATPase α-subunit, lansoprazole still significantly attenuated myocyte hypertrophy. Conclusion Lansoprazole inhibits cardiac remodelling by suppressing activation of the Akt/GSK3β/β-catenin pathway independent of H+/K+-ATPase inhibition, and these findings may provide a novel insight into the pharmacological effects of PPIs with regard to alleviation of cardiac remodelling.

scholarly journals A Reduction in ADAM17 Expression Is Involved in the Protective Effect of the PPAR-α Activator Fenofibrate on Pressure Overload-Induced Cardiac Hypertrophy

PPAR Research ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Si-Yu Zeng ◽  
Hui-Qin Lu ◽  
Qiu-Jiang Yan ◽  
Jian Zou
Keyword(s):  
Body Weight ◽  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Wall Thickness ◽  
Protective Action ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Heart Weight ◽  
Hypertensive Rats ◽  
Protein Levels

The peroxisome proliferator-activated receptor-α (PPAR-α) agonist fenofibrate ameliorates cardiac hypertrophy; however, its mechanism of action has not been completely determined. Our previous study indicated that a disintegrin and metalloproteinase-17 (ADAM17) is required for angiotensin II-induced cardiac hypertrophy. This study aimed to determine whether ADAM17 is involved in the protective action of fenofibrate against cardiac hypertrophy. Abdominal artery constriction- (AAC-) induced hypertensive rats were used to observe the effects of fenofibrate on cardiac hypertrophy and ADAM17 expression. Primary cardiomyocytes were pretreated with fenofibrate (10 μM) for 1 hour before being stimulated with angiotensin II (100 nM) for another 24 hours. Fenofibrate reduced the ratios of left ventricular weight to body weight (LVW/BW) and heart weight to body weight (HW/BW), left ventricular anterior wall thickness (LVAW), left ventricular posterior wall thickness (LVPW), and ADAM17 mRNA and protein levels in left ventricle in AAC-induced hypertensive rats. Similarly, in vitro experiments showed that fenofibrate significantly attenuated angiotensin II-induced cardiac hypertrophy and diminished ADAM17 mRNA and protein levels in primary cardiomyocytes stimulated with angiotensin II. In summary, a reduction in ADAM17 expression is associated with the protective action of PPAR-α agonists against pressure overload-induced cardiac hypertrophy.

Abstract 16205: MKP-5 Deficiency Attenuates Pressure Overload-induced Cardiac Hypertrophy

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Kisuk Min ◽  
Yan Huang ◽  
Frank J Giordano ◽  
Sudip Bajpeyi ◽  
Anton M Bennett
Keyword(s):  
Heart Failure ◽  
Body Weight ◽  
Cardiac Hypertrophy ◽  
Cardiac Muscle ◽  
Molecular Mechanisms ◽  
Weight Ratio ◽  
Pressure Overload ◽  
Body Weight Ratio ◽  
Pathological Cardiac Hypertrophy

Introduction: Cardiac remodeling occurs in response to pathological stimuli including chronic pressure overload, subsequently leading to heart failure. Despite considerable research efforts, the molecular mechanisms responsible for heart failure have yet to be fully elucidated. One of the prominent signaling pathways involved in the development of pathological cardiac hypertrophy is the mitogen-activated protein kinases (MAPKs) pathways. The MAPKs are inactivated by the MAPK phosphatases (MKPs) through direct dephosphorylation. Growing evidence suggests the importance of MKP-5 signaling mechanisms in physiological and pathological processes. However, the role of MKP-5 has not been explored in cardiac muscle. The objective of this study is to investigate how MKP-5-mediated MAPK activity contributes to mechanisms responsible for pressure overload-induced cardiac hypertrophy. Hypothesis: We tested the hypothesis that MKP-5 serves as a central regulator of MAPKs in pressure overload-induced cardiac hypertrophy. Methods: To investigate the role of MKP-5 in cardiac muscle, we caused pressure overload-induced cardiac hypertrophy in wild type (mkp-5 +/+ ) mice and MKP-5 deficient mice (mkp-5 -/- ) through transverse aortic constriction (TAC). Cardiac function was evaluated by echocardiographic analysis at 4 weeks after TAC. Cardiac hypertrophy was measured by heart-to-body weight ratio. Interstitial myocardial fibrosis was evaluated by Sirius red stains and expression of fibrogenic genes was determined by quantitative PCR. Results: Echocardiographic analysis showed that the ejection fraction and fractional shortening of mkp-5 +/+ mice significantly decreased by at 4 weeks after TAC. Heart-to-body weight ratio increased in mkp-5 +/+ mice. However, MKP-5-deficient heart was protected from cardiac dysfunction and cardiac hypertrophy induced by TAC. Importantly, the fibrogenic genes were markedly reduced in mkp-5 -/- mice as compared with mkp-5 +/+ mice at 4 weeks after TAC. Conclusions: Collectively, our study demonstrates that MKP-5 deficiency prevents the heart from pressure overload-induced cardiac hypertrophy and suggests that MKP-5 may serve as a novel therapeutic target for treatment of heart disease.

scholarly journals Bawei Chenxiang Wan Ameliorates Cardiac Hypertrophy by Activating AMPK/PPAR-α Signaling Pathway Improving Energy Metabolism

2021 ◽  
Vol 12 ◽  
Author(s):  
Xiaoying Zhang ◽  
Zhiying Zhang ◽  
Pengxiang Wang ◽  
Yiwei Han ◽  
Lijun Liu ◽  
...  
Keyword(s):  
Body Weight ◽  
Energy Metabolism ◽  
Cardiac Hypertrophy ◽  
Heart Function ◽  
Weight Ratio ◽  
Tibetan Medicine ◽  
Heart Weight ◽  
Cardiomyocyte Hypertrophy ◽  
Body Weight Ratio ◽  
Cross Sectional

Bawei Chenxiang Wan (BCW), a well-known traditional Chinese Tibetan medicine formula, is effective for the treatment of acute and chronic cardiovascular diseases. In the present study, we investigated the effect of BCW in cardiac hypertrophy and underlying mechanisms. The dose of 0.2, 0.4, and 0.8 g/kg BCW treated cardiac hypertrophy in SD rat model induced by isoprenaline (ISO). Our results showed that BCW (0.4 g/kg) could repress cardiac hypertrophy, indicated by macro morphology, heart weight to body weight ratio (HW/BW), left ventricle heart weight to body weight ratio (LVW/BW), hypertrophy markers, heart function, pathological structure, cross-sectional area (CSA) of myocardial cells, and the myocardial enzymes. Furthermore, we declared the mechanism of BCW anti-hypertrophy effect was associated with activating adenosine 5'-monophosphate (AMP)-activated protein kinase (AMPK)/peroxisome proliferator–activated receptor-α (PPAR-α) signals, which regulate carnitine palmitoyltransferase1β (CPT-1β) and glucose transport-4 (GLUT-4) to ameliorate glycolipid metabolism. Moreover, BCW also elevated mitochondrial DNA-encoded genes of NADH dehydrogenase subunit 1(ND1), cytochrome b (Cytb), and mitochondrially encoded cytochrome coxidase I (mt-co1) expression, which was associated with mitochondria function and oxidative phosphorylation. Subsequently, knocking down AMPK by siRNA significantly can reverse the anti-hypertrophy effect of BCW indicated by hypertrophy markers and cell surface of cardiomyocytes. In conclusion, BCW prevents ISO-induced cardiomyocyte hypertrophy by activating AMPK/PPAR-α to alleviate the disturbance in energy metabolism. Therefore, BCW can be used as an alternative drug for the treatment of cardiac hypertrophy.

Evaluation of right and left ventricular size in SHR-Wistar hybrids

1988 ◽  
Vol 255 (3) ◽  
pp. H587-H591
Author(s):  
A. O. Grassi de Gende
Keyword(s):  
Body Weight ◽  
Growth Factor ◽  
Arterial Pressure ◽  
Cardiac Hypertrophy ◽  
Ventricular Hypertrophy ◽  
Systolic Pressure ◽  
Pressure Overload ◽  
Left Ventricular ◽  
Ventricular Size ◽  
Spontaneously Hypertensive

The relative right and left ventricular sizes were evaluated in hybrid rats obtained by crossing spontaneously hypertensive (SHR) and pure Wistar strains to detect cardiac hypertrophy dissociated from the hypertension genetically transmitted by the SHR strain. In female hybrids of the the F1, F2, and F3 generations, both ventricles were found to have bigger size in relation to body weight than in the pure Wistar, whereas only the F3 group was hypertensive. All generations of male hybrids had arterial pressure values in the hypertensive range, which were not consistently accompanied by increases in the ventricle mass. The correlation between arterial pressure and indexes of ventricular size was assessed in sex-age matched groups. In a range of systolic pressure values of 100– 200 mmHg, the variables showed no correlation or poor positive correlation (correlation coefficient values from -0.3641 to 0.6153). The correlation was not improved in the F3 generation as would be expected, because these hybrids underwent higher left pressure load than the preceding generations. The results indicate that increased ventricular size in SHR-Wistar hybrids may be independent from the hypertension genetically transmitted by the SHR strain and suggest that some of the previously proposed factors, i.e., cardioadrenergic activity or the growth factor isolated from SHR hearts, may be playing a role in the ventricular hypertrophy process in this strain. If this characteristic of hybrids is a constant in pure SHR strain, its validity as a model of cardiac hypertrophy due to left pressure overload would be questioned.

P0875INFLUENCE OF CHRONIC KIDNEY DISEASE AND LEFT VENTRICULAR HYPERTROPHY ON CHANGE IN FGF23 AND RENIN-ANGIOTENSIN-ALDOSTERONE-SYSTEM

2020 ◽  
Vol 35 (Supplement_3) ◽  
Author(s):  
Kohei Okamoto ◽  
Hideki Fujii ◽  
Shunsuke Goto ◽  
Keiji Kono ◽  
Kentaro Watanabe ◽  
...  
Keyword(s):  
Chronic Kidney Disease ◽  
Body Weight ◽  
Mrna Expression ◽  
Ventricular Hypertrophy ◽  
Weight Ratio ◽  
Left Ventricular ◽  
Heart Weight ◽  
Control Group ◽  
Body Weight Ratio ◽  
Related Factors

Abstract Background and Aims Left ventricular hypertrophy (LVH) is a clinically important risk factor for mortality and often observed in patients with chronic kidney disease (CKD). Serum FGF23 levels are elevated in CKD patients, and the relationship between elevated FGF23 and LVH has been reported in the previous studies. However, whether elevated FGF23 is a cause or result of LVH and whether FGF23 directly or indirectly affects LVH remain unclear. Therefore, we investigated changes in heart weight, CKD-mineral and bone disorder (MBD) parameters, including FGF23, and renin-angiotensin-aldosterone system (RAAS) related-factors in the setting of LVH and CKD using a mouse model. Method In the present study, twenty-four C57BL/6J mice were used and divided into 4 groups; control group (N=6), CKD group (N=6), LVH group (N=6), and LVH+CKD group (N=6). The mice in the CKD group underwent left 2/3 nephrectomy at 11 weeks of age and right nephrectomy at 12 weeks of age. Those in the LVH group underwent transverse aortic constriction (TAC) at 10 weeks of age. Those in the LVH+CKD group, TAC at 10 weeks of age, and left 2/3 nephrectomy at 11 weeks of age, and right nephrectomy at 12 weeks of age were performed. At 16 weeks of age, echocardiography was performed for all the mice, and they were sacrificed for blood and urine analysis, histopathological analysis and evaluating mRNA expressions of CKD-MBD- and RAAS-related factors in the heart. Results The systolic blood pressure was significantly higher in the LVH+CKD group and the CKD group than in the control group. The heart weight/body weight ratio in the LVH+CKD group was the highest, and that in the LVH was higher than that in the CKD group. Although serum creatinine and phosphate levels increased in CKD condition, those were comparable between the CKD and LVH+CKD groups. The urinary albumin excretion also increased in the CKD and LVH+CKD groups compared to the LVH and control groups. Serum FGF23 levels increased in the LVH and CKD group compared to the control group, and those in the LVH+CKD group were the highest among all the study groups. The cardiac mRNA expressions of FGF23, angiotensinogen (ANG), angiotensin type 1 receptor (AT1R), and angiotensin-converting enzyme (ACE) were also increased by induction of LVH and CKD, and those in the LVH+CKD group significantly increased compared to other groups. Heart weight/body weight ratio was significantly correlated with serum FGF23 levels and mRNA expression of FGF23, ANG, AT1R, ACE. In addition, significant correlations of serum FGF23 levels and cardiac mRNA expression of FGF23 with cardiac mRNA expressions of RAAS-related factors were observed. Conclusion Our results suggest that serum FGF23 levels and cardiac mRNA expression of FGF23 increase with the development of LVH and CKD and the changes is possibly enhanced through the colocalized activation of RAAS.

Abstract 3551: Cyclophilin a Promotes Angiotensin II-Induced Inflammation and Cardiovascular Hypertrophy in Mice

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Kimio Satoh ◽  
Liam Casey ◽  
Michael R O’Dell ◽  
Patrizia Nigro ◽  
Amy Mohan ◽  
...  
Keyword(s):  
Body Weight ◽  
Angiotensin Ii ◽  
Cardiac Hypertrophy ◽  
Rhode Island ◽  
Bone Marrow Cells ◽  
Weight Ratio ◽  
Cyclophilin A ◽  
Ros Production ◽  
Body Weight Ratio ◽  
Cardiovascular Hypertrophy

Background - Cyclophilin A (CyPA) is a chaperone protein secreted from vascular smooth muscle cells (VSMC) in response to reactive oxygen species (ROS). We have recently demonstrated that extracellular CyPA stimulates at least 3 signaling pathways (ERK1/2, Akt and JAK) and mediates numerous cellular effects of ROS. Angiotensin II (Ang II) induces ROS through NADPH oxidases and activates matrix metalloproteinase (MMP) in VSMC. ROS and MMPs have been demonstrated to mediate cardiac hypertrophy and remodeling. We hypothesized that VSMC-derived CyPA contributes to AngII-induced cardiovascular hypertrophy in vivo due to its proinflammatory properties. Methods and Results - ApoE −/− and ApoE −/− CyPA −/− mice were treated with AngII (1000 ng/min/kg for 4 weeks) to induce cardiac hypertrophy. Long-term infusion of AngII significantly increased heart/body weight ratio in ApoE −/− mice, which was significantly less in ApoE −/− CyPA −/− mice (6.6±1.0 vs. 4.8±0.7, P <0.01). Echocar-diography confirmed a significantly greater increase in LV mass in ApoE −/− mice compared to ApoE −/− CyPA −/− mice (112% vs. 47%). Perivascular accumulation of inflammatory cells and cardiac myofibroblasts in ApoE −/− mice was significantly greater than in ApoE −/− CyPA −/− mice. Consequently, coronary artery ROS production (DHE fluorescence) and MMP activation (in situ zymography) were markedly increased by AngII in ApoE −/− mice compared to ApoE −/− CyPA −/− mice. To determine the source of CyPA, bone marrow cells (BMCs) transplantation was performed. The heart/body weight ratio was still higher in ApoE −/− mice compared with ApoE −/− CyPA −/− mice after reconstitution with GFP + CyPA +/+ BMCs (6.7±0.6 vs. 5.6±0.9, P <0.01). Recruitment of GFP + BMCs to the heart in chimeric ApoE −/− mice was significantly greater than the chimeric ApoE −/− CyPA −/− mice (count/area; 218±63 vs. 109±43, P <0.01). To prove a vascular source of CyPA was essential, VSMC-specific CyPA overexpressing mice were generated. In these mice there was a significant increase in cardiac MMP activity after AngII infusion (VSMC-Tg > WT > CyPA −/− ). Conclusion - CyPA is a novel mediator of AngII-induced cardiac hypertrophy by stimulating vascular ROS production, MMP activation, and inflammatory cell recruitment. This research has received full or partial funding support from the American Heart Association, AHA Founders Affiliate (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Rhode Island, Vermont).

scholarly journals PO-148 Effect of Aerobic Exercise on the Expression of CaMKIIδ/MEF2 in Hypertensive and Physiological Cardiac Hypertrophy

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Man Zhu ◽  
Lijun Shi
Keyword(s):  
Body Weight ◽  
Cardiac Hypertrophy ◽  
Aerobic Exercise ◽  
Weight Ratio ◽  
Exercise Group ◽  
The Body ◽  
Expression Level ◽  
Heart Weight ◽  
Control Group ◽  
Body Weight Ratio

Objective The type II calcium/calmodulin-dependent protein kinase IIδ (CaMKIIδ) signal plays a key role in the development of cardiac hypertrophy. This study used CaMKIIδ as an entry point to investigate the mechanism of moderate-intensity aerobic exercise affecting myocardial function. Methods Male spontaneously hypertensive rats (SHRs) and Wistar-Kyoto rats (WKYs), 12 weeks age, were randomly divided into aerobic exercise group (SHR-EX/WKY-EX) and sedentary control group (SHR-SED/WKY-SED), with 12 rats in each group. The aerobic exercise group conducted an 8-week treadmill exercise training with a slope of 0°, 20m/min (about 55-65% of maximal aerobic velocity), 60min/day, and 5d/wk. The control group did not exercise. The body weight of each group of rats was measured weekly and the blood pressure of the rats was measured non-invasively. After 8 weeks, the hearts of SHR-EX group, WKY-EX group, SHR-SED group and WKY-SED group were weighed, and then myocardial tissue sections were taken for HE staining to observe the thickness of the ventricular wall and the morphology of myocardial cells. The expression of CaMKIIδ and MEF2 in each group was determined by Western blotting. Results (1) The body weight of SHR-SED group was significantly higher than that of SHR-EX group (p<0.01), and the heart weight of rats in exercise group changed significantly. The WKY-EX group had greater heart weight than the WKY-SED group, and the SHR-SED group was heavier than the SHR-EX group (p<0.05). The heart weight/body weight ratio of the WKY-EX group was significantly higher than that of the WKY-SED group (p<0.01). The heart weight/body weight ratio of SHR-EX group and SHR-SED group was higher than that of WKY-EX group and WKY-SED group (p<0.01). (2) Compared with the WKY-SED group, the SHR-SED group had loose interstitial cells and increased single cell area. The SHR-EX group is more compact than the SHR-SED group, and the cell cross-sectional area is reduced. (3) The expression of CaMKIIδ protein in SHR-EX group was significantly lower than that in SHR-SED group (p<0.01), but the expression level of CaMKIIδ in WKY-EX group was significantly higher than that in WKY-SED group (p<0.01). The expression level of CaMKIIδ was significantly higher in the SHR-SED group than in the WKY-SED group. In addition, the expression of MEF2 protein in SHR-EX group and WKY-SED group was significantly lower than that in SHR-SED group (p<0.01), while the MEF2 expression level in WKY-EX group was higher than WKY-SED group and SHR-EX group (p<0.05). Conclusions There is an interaction between aerobic exercise and hypertension. Aerobic exercise can effectively delay the development of hypertensive cardiac hypertrophy by regulating the expression of CaMKIIδ and MEF2 protein in the myocardium, but it can also cause cardiac hypertrophy in normal heart. It is one of the important mechanisms affecting the myocardial morphology and function.    

scholarly journals Cardiac hypertrophy associated with impaired regulation of cardiac ryanodine receptor by calmodulin and S100A1

2013 ◽  
Vol 305 (1) ◽  
pp. H86-H94 ◽  
Author(s):  
Naohiro Yamaguchi ◽  
Asima Chakraborty ◽  
Tai-Qin Huang ◽  
Le Xu ◽  
Angela C. Gomez ◽  
...  
Keyword(s):  
Body Weight ◽  
Amino Acid ◽  
Atrial Natriuretic Peptide ◽  
Cardiac Hypertrophy ◽  
Cardiac Function ◽  
Ryanodine Receptor ◽  
Weight Ratio ◽  
Heart Weight ◽  
Mrna Levels ◽  
Body Weight Ratio

The cardiac ryanodine receptor (RyR2) is inhibited by calmodulin (CaM) and S100A1. Simultaneous substitution of three amino acid residues (W3587A, L3591D, F3603A; RyR2ADA) in the CaM binding domain of RyR2 results in loss of CaM inhibition at submicromolar (diastolic) and micromolar (systolic) Ca2+, cardiac hypertrophy, and heart failure in Ryr2 ADA/ADA mice. To address whether cardiac hypertrophy results from the elimination of CaM and S100A1 inhibition at diastolic or systolic Ca2+, a mutant mouse was generated with a single RyR2 amino acid substitution (L3591D; RyR2D). Here we report that in single-channel measurements RyR2-L3591D isolated from Ryr2 D/D hearts lost CaM inhibition at diastolic Ca2+ only, whereas S100A1 regulation was eliminated at both diastolic and systolic Ca2+. In contrast to the ∼2-wk life span of Ryr2 ADA/ADA mice, Ryr2 D/D mice lived longer than 1 yr. Six-month-old Ryr2 D/D mice showed a 9% increase in heart weight-to-body weight ratio, modest changes in cardiac morphology, and a twofold increase in atrial natriuretic peptide mRNA levels compared with wild type. After 4-wk pressure overload with transverse aortic constriction, heart weight-to-body weight ratio and atrial natriuretic peptide mRNA levels increased and echocardiography showed changes in heart morphology of Ryr2 D/D mice compared with sham-operated mice. Collectively, the findings indicate that the single RyR2-L3591D mutation, which distinguishes the effects of diastolic and systolic Ca2+, alters heart size and cardiac function to a lesser extent in Ryr2 D/D mice than the triple mutation in Ryr2 ADA/ADA mice. They further suggest that CaM inhibition of RyR2 at systolic Ca2+ is important for maintaining normal cardiac function.

Dissociation of Direct and Indirect Effects of Angiotensin II on the Heart

Hypertension ◽  
2000 ◽  
Vol 36 (suppl_1) ◽  
pp. 683-684
Author(s):  
Jorge P van Kats ◽  
David W Silversides ◽  
Timothy L Reudelhuber
Keyword(s):  
Heart Rate ◽  
Angiotensin Ii ◽  
Systolic Pressure ◽  
Weight Ratio ◽  
Renin Angiotensin System ◽  
Cardiac Cells ◽  
Heart Weight ◽  
Ang Ii ◽  
Direct Stimulation ◽  
Beneficial Effects

33 Cardiac angiotensin II (Ang II), either derived from the circulation or locally synthesized, is often suggested to be involved in the structural adaptations occurring in the heart in hypertension and following myocardial infarction. However, it is debated whether the proven beneficial effects of renin-angiotensin system blockade in these pathologies are related to an inhibition of the direct cardiac actions of the peptide. The objective of the present study was to investigate which of the effects of cardiac Ang II are due to direct stimulation of cardiac cells by Ang II. To test for cardiac specific functions of Ang II, transgenic mice were developed that express an Ang II-releasing fusion protein (J Biol Chem 1997;272:12994-99) exclusively in cardiomyocytes. Blood pressure, heart rate, cardiac and plasma Ang II content, Ang II receptor binding and organ morphology were monitored in transgenic (TG) and non-transgenic littermate mice (control). Cardiac Ang II levels in TG mice were 20-40 fold higher than in hearts of control mice (15±3 pg/100 mg ww). In 3 independent founder lines of TG mice, plasma Ang II concentration was not altered as compared to control (119±20 vs. 127±20 pg/mL). The heart weight to body weight ratio in TG mice (4.0±0.1 mg/g) was not different from controls (3.8±0.1 mg/g), neither was systolic pressure (137±4 and 138±7 mm Hg respectively) or heart rate (618±13 and 662±15 bpm respectively). Microscopic inspection of TG hearts did not reveal any differences with control regarding size and number of cardiomyocytes and organization of extracellular matrix proteins. TG mice had not become less sensitive for Ang II signaling since Ang II receptor number was not altered in TG mice (Bmax = 23±3 fmol/mg protein) as compared to control (22±2 fmol/mg protein). Our data show that very high Ang II levels in hearts of TG mice do not lead to myocardial enlargement or affect cardiovascular physiology. We conclude that elevated Ang II in the heart has no direct effects on cardiac cells and we hypothesize that effects of cardiac Ang II become apparent upon altered hemodynamic loading.

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