Effects of adrenomedullin on load and myocardial performance in normal and heart-failure dogs

2000 ◽  
Vol 279 (3) ◽  
pp. H1000-H1006 ◽  
Author(s):  
John G. Lainchbury ◽  
Donna M. Meyer ◽  
Michihisa Jougasaki ◽  
John C. Burnett ◽  
Margaret M. Redfield
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Diastolic Pressure ◽  
Ex Vivo ◽  
Systolic Pressure ◽  
Atrial Pacing ◽  
Arterial Elastance ◽  
Systolic Volume ◽  
Before And After

Myocardial actions of the vasodilator peptide adrenomedullin (ADM) in the intact animal are unknown. Negative and positive inotropic actions have been reported in ex vivo experiments. Myocardial and load-altering actions of ADM in dogs before and after development of heart failure were studied. With controlled heart rate (atrial pacing) and after β-blockade, ADM was administered to five normal dogs in doses of 20 ng · kg−1 · min−1 iv, 100 ng · kg−1 · min−1 iv, and 200 ng · kg−1 · min−1 into the left ventricle (LV). LV peak systolic pressure and end-systolic volume decreased with each dose of ADM. End-systolic pressure decreased with the two higher doses. At the highest dose, arterial elastance and the time constant of LV isovolumic relaxation (τ) decreased, and LV end-systolic elastance ( E es) increased. LV end-diastolic pressure and volume were unchanged. In five additional normal dogs receiving only the highest dose of ADM (200 ng · kg−1 · min−1 intra-LV), to control for increased heart rate and sympathetic activation observed with the cumulative infusion, ADM produced arterial vasodilation but no change in E es or τ. In four dogs with pacing-induced heart failure, ADM (200 ng · kg−1 · min−1 intra-LV) was without effect on τ, E es, and systolic or diastolic pressure and volume. In vivo, ADM appears to be a selective arterial dilator without inotropic or lusitropic effects. The vasodilatory actions are attenuated in heart failure.

Abstract 13421: Ventricular and Arterial Elastance During Isometric Handgrip Exercise and Post-exercise Circulatory Arrest in Heart Failure With and Without Preserved Ejection Fraction

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Naoki Fujimoto ◽  
Keishi Moriwaki ◽  
Issei Kameda ◽  
Masaki Ishiyama ◽  
Taku Omori ◽  
...  
Keyword(s):  
Heart Failure ◽  
Blood Pressure ◽  
Heart Rate ◽  
Ejection Fraction ◽  
Circulatory Arrest ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Isometric Handgrip ◽  
Arterial Elastance ◽  
Post Exercise

Introduction: Isometric handgrip (IHG) training at 30% maximal voluntary contraction (MVC) lowers blood pressure in hypertensive patients. Impacts of IHG exercise and post-exercise circulatory arrest (PECA), which isolates metaboreflex control, have been unclear in heart failure (HF). Purpose: To investigate the impacts of IHG exercise and PECA on ventricular-arterial stiffness and left ventricular (LV) relaxation in HF with preserved (HFpEF) and reduced ejection fraction (HFrEF). Methods: We invasively obtained LV pressure-volume (PV) loops in 20 patients (10 HFpEF, 10 HFrEF) using conductance catheter with microtip-manometer during 3 minutes of IHG at 30%MVC and 3 minutes of PECA. Hemodynamics and LV-arterial function including LV end-systolic elastance (Ees) by the single-beat method, effective arterial elastance (Ea), and time constant of LV relaxation (Tau) were evaluated every minute. Results: At rest, HFpEF had higher LV end-systolic pressure (ESP) and lower heart rate than HFrEF with similar LV end-diastolic pressure (EDP). The coupling ratio (Ees/Ea) was greater in HFpEF than HFrEF (1.0±0.3 vs. 0.6±0.3, p<0.01). IHG for 3minutes similarly increased heart rate in HFpEF (by 10±8 bpm) and HFrEF (by 14±6 bpm). IHG also increased end-diastolic and LVESP (134±21 vs. 158±30 mmHg and 113±25 vs. 139±25 mmHg) in both groups (groupхtime effect p≥0.25). In HFpEF, Ees, Ea and Ees/Ea (1.0±0.3 vs. 1.1±0.4) were unaffected during IHG. In HFrEF, IHG induced variable increases in Ea. LV end-systolic volume and the ESPV volume-axis intercept were larger, and Ees at IHG 3 rd min was greater (1.30±0.7 vs. 3.1±2.1 mmHg/ml, p<0.01) than baseline, resulting in unchanged Ees/Ea at IHG 3 rd min (0.6±0.3 vs. 0.8±0.4, p≥0.37). Tau was prolonged only in HFrEF during IHG and was returned to the baseline value during PECA. During the first 2 minutes of PECA, LVESP was lower than that at IHG 3 rd min only in HFpEF, suggesting less metaboreflex control of blood pressure in HFpEF during IHG. Conclusions: IHG exercise at 30%MVC induced modest increases in LV end-systolic and end-diastolic pressures in HFpEF and HFrEF. Although the prolongation of LV relaxation was observed only in HFrEF, the ventricular and arterial coupling was maintained throughout the IHG exercise in both groups.

scholarly journals Electromechanical and structural alterations in the aging rabbit heart and aorta

2012 ◽  
Vol 302 (8) ◽  
pp. H1625-H1635 ◽  
Author(s):  
Leroy L. Cooper ◽  
Katja E. Odening ◽  
Min-Sig Hwang ◽  
Leonard Chaves ◽  
Lorraine Schofield ◽  
...  
Keyword(s):  
Conduction Velocity ◽  
Structural Changes ◽  
Optical Mapping ◽  
Diastolic Pressure ◽  
Ex Vivo ◽  
Rabbit Model ◽  
Systolic Pressure ◽  
Age Related ◽  
Sheet Structure

Aging increases the risk for arrhythmias and sudden cardiac death (SCD). We aimed at elucidating aging-related electrical, functional, and structural changes in the heart and vasculature that account for this heightened arrhythmogenic risk. Young (5–9 mo) and old (3.5–6 yr) female New Zealand White (NZW) rabbits were subjected to in vivo hemodynamic, electrophysiological, and echocardiographic studies as well as ex vivo optical mapping, high-field magnetic resonance imaging (MRI), and histochemical experiments. Aging increased aortic stiffness (baseline pulse wave velocity: young, 3.54 ± 0.36 vs. old, 4.35 ± 0.28 m/s, P < 0.002) and diastolic (end diastolic pressure-volume relations: 3.28 ± 0.5 vs. 4.95 ± 1.5 mmHg/ml, P < 0.05) and systolic (end systolic pressure-volume relations: 20.56 ± 4.2 vs. 33.14 ± 8.4 mmHg/ml, P < 0.01) myocardial elastances in old rabbits. Electrophysiological and optical mapping studies revealed age-related slowing of ventricular and His-Purkinje conduction (His-to-ventricle interval: 23 ± 2.5 vs. 31.9 ± 2.9 ms, P < 0.0001), altered conduction anisotropy, and a greater inducibility of ventricular fibrillation (VF, 3/12 vs. 7/9, P < 0.05) in old rabbits. Histochemical studies confirmed an aging-related increased fibrosis in the ventricles. MRI showed a deterioration of the free-running Purkinje fiber network in ventricular and septal walls in old hearts as well as aging-related alterations of the myofibrillar orientation and myocardial sheet structure that may account for this slowed conduction velocity. Aging leads to parallel stiffening of the aorta and the heart, including an increase in systolic stiffness and contractility and diastolic stiffness. Increasingly, anisotropic conduction velocity due to fibrosis and altered myofibrillar orientation and myocardial sheet structure may contribute to the pathogenesis of VF in old hearts. The aging rabbit model represents a useful tool for elucidating age-related changes that predispose the aging heart to arrhythmias and SCD.

Abstract 2474: Dynamic Change in LV Twist Mechanics in a Canine Model of Pacing-Induced Heart Failure

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Jianwen Wang ◽  
Sherif F Nagueh ◽  
Nilesh Mathuria ◽  
April L Gilbert ◽  
Daryl G Schulz ◽  
...  
Keyword(s):  
Heart Failure ◽  
Diastolic Pressure ◽  
Dynamic Change ◽  
Time Derivative ◽  
Systolic Pressure ◽  
Canine Model ◽  
Systolic Volume ◽  
Relaxation Period ◽  
End Diastolic Volume ◽  
The Difference

Background : LV twist may reflect LV contractility under different conditions. This study investigated LV twist dynamics and its determinants in a canine model of congestive heart failure (CHF). Methods : Pacemakers and percutaneous leads were implanted in 8 adult hound dogs (mean weight, 38 kg), and continuous chronic RV pacing was applied at 230–250 bpm until CHF induction. Subsequently, pacing was turned off to allow the heart to recover. Echocardiography and LV catheterization were performed simultaneously at baseline, during CHF while pacing was temporarily switched off, and during recovery from CHF after pacing was stopped. CHF induction by pacing was repeated in 4 dogs. Apical and basal rotations were measured using 2D speckle tracking, and LV twist was calculated as the difference between apical and basal rotations. Untwisting rate was calculated as the peak diastolic time derivative of LV twist. Results : CHF developed after 2–4 wks of pacing with LV end-diastolic volume (LVEDV), end-systolic volume (LVESV), end-diastolic pressure (LVEDP), and time constant of LV relaxation during isovolumic relaxation period (tau) all increasing significantly compared to baseline (Table ), and recovering to baseline levels 2–4 wks after pacing was stopped. LV twist and untwisting rate decreased with CHF compared to baseline, and improved during recovery from CHF although the change in untwisting rate between CHF and baseline was not significant. In pooled data, LV twist was significantly related to LVEDV (r=-0.60, P<0.001), LVESV (r=-0.59, P=0.001), LVEF (r=0.81, P<0.001), LVEDP (r=0.41, P=0.03) and +dp/dt (r=0.71, P<0.001), but not with end-systolic pressure (r=0.06, P=0.77). In multiple analysis, +dp/dt was the only independent predictor of twist (P < 0.001). Conclusions : LV twist dynamics can reflect the presence of pacing-induced CHF and its recovery. LV contractility appears to be the only determinant of LV twist in CHF.

Trabecular cutting: a novel surgical therapy to increase diastolic compliance

2019 ◽  
Vol 127 (2) ◽  
pp. 457-463
Author(s):  
Meagan Oglesby ◽  
Danny Escobedo ◽  
Gladys Patricia Escobar ◽  
Fatemeh Fatemifar ◽  
Edward Y. Sako ◽  
...  
Keyword(s):  
Heart Failure ◽  
Left Ventricle ◽  
Diastolic Pressure ◽  
Ex Vivo ◽  
Systolic Function ◽  
Wall Stress ◽  
Rabbit Heart ◽  
Left Ventricular ◽  
Before And After ◽  
Diastolic Compliance

Heart failure with preserved ejection fraction (HFpEF) is a common cause of hospital admission in patients over 65 yr old and has high mortality. HFpEF is characterized by left ventricular (LV) hypertrophy that reduces compliance. Current HFpEF therapies control symptoms, but no existing medications or therapies can sustainably increase LV compliance. LV trabeculae develop hypertrophy and fibrosis that contribute to reduced LV compliance. This study expands our previous results in ex vivo human hearts to show that severing LV trabeculae increases diastolic compliance in an ex vivo working rabbit heart model. Trabecular cutting was performed in ex vivo rabbit hearts set up in a working heart perfusion system perfused with oxygenated Krebs-Henseleit buffer. A hook was inserted in the LV to cut trabeculae. End-systolic and end-diastolic pressure-volume relationships during transient preload reduction were recorded using an admittance catheter in the following three groups: control (no cutting; n = 9), mild cutting (15 cuts; n = 5), and aggressive cutting (30 cuts; n = 5). In a second experiment, each heart served as its own control. Hemodynamic data were recorded before and after trabecular cutting ( n = 10) or sham cutting ( n = 5) within the same heart. In the first experiments, trabecular cutting did not affect systolic function ( P > 0.05) but significantly increased overall diastolic compliance ( P = 0.009). Greater compliance was seen as trabecular cutting increased ( P = 0.002, r2 = 0.435). In the second experiment, significant increases in systolic function ( P = 0.048) and diastolic compliance ( P = 0.002) were seen after trabecular cutting compared with baseline. In conclusion, trabecular cutting significantly increases diastolic compliance without reducing systolic function. NEW & NOTEWORTHY We postulate that, in mammalian hearts, free-running trabeculae carneae exist to provide tensile support to the left ventricle and minimize diastolic wall stress. Because of hypertrophy and fibrosis of trabeculae in patients with left ventricular hypertrophy, this supportive role can become pathologic, worsening diastolic compliance. We demonstrate a novel operation involving cutting trabeculae as a method to acutely increase diastolic compliance in patients presenting with heart failure and diastolic dysfunction to improve their left ventricle compliance.

scholarly journals Muscle metaboreflex-induced increases in effective arterial elastance: effect of heart failure

2020 ◽  
Vol 319 (1) ◽  
pp. R1-R10 ◽  
Author(s):  
Joseph Mannozzi ◽  
Jasdeep Kaur ◽  
Marty D. Spranger ◽  
Mohamed-Hussein Al-Hassan ◽  
Beruk Lessanework ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Dynamic Exercise ◽  
Stroke Work ◽  
Arterial Elastance ◽  
Muscle Metaboreflex ◽  
Effective Arterial Elastance

Dynamic exercise elicits robust increases in sympathetic activity in part due to muscle metaboreflex activation (MMA), a pressor response triggered by activation of skeletal muscle afferents. MMA during dynamic exercise increases arterial pressure by increasing cardiac output via increases in heart rate, ventricular contractility, and central blood volume mobilization. In heart failure, ventricular function is compromised, and MMA elicits peripheral vasoconstriction. Ventricular-vascular coupling reflects the efficiency of energy transfer from the left ventricle to the systemic circulation and is calculated as the ratio of effective arterial elastance ( Ea) to left ventricular maximal elastance ( Emax). The effect of MMA on Ea in normal subjects is unknown. Furthermore, whether muscle metaboreflex control of Ea is altered in heart failure has not been investigated. We utilized two previously published methods of evaluating Ea [end-systolic pressure/stroke volume ( EaPV)] and [heart rate × vascular resistance ( EaZ)] during rest, mild treadmill exercise, and MMA (induced via partial reductions in hindlimb blood flow imposed during exercise) in chronically instrumented conscious canines before and after induction of heart failure via rapid ventricular pacing. In healthy animals, MMA elicits significant increases in effective arterial elastance and stroke work that likely maintains ventricular-vascular coupling. In heart failure, Ea is high, and MMA-induced increases are exaggerated, which further exacerbates the already uncoupled ventricular-vascular relationship, which likely contributes to the impaired ability to raise stroke work and cardiac output during exercise in heart failure.

Myocardial adrenergic changes at two stages of heart failure due to adriamycin treatment in rats

1991 ◽  
Vol 260 (3) ◽  
pp. H909-H916 ◽  
Author(s):  
J. Tong ◽  
P. K. Ganguly ◽  
P. K. Singal
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Structural Changes ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Ventricular Systolic Pressure ◽  
Two Stages

Changes in myocardial norepinephrine (NE) levels, turnover, uptake, and release in rats were examined at two stages of cardiac dysfunction induced by adriamycin (ADR) given intraperitoneally in six equal doses over a period of 2 wk for a cumulative dose of 15 mg/kg. At 3 wk posttreatment, ADR-treated animals showed no changes in left ventricular systolic pressure (LVSP), aortic systolic pressure (ASP), and aortic diastolic pressure (ADP) but left ventricular end-diastolic pressure (LVEDP) was significantly higher. At 6 wk posttreatment, LVSP, ASP, and ADP were significantly lower and LVEDP remained elevated. Animals in both ADR-treated groups showed signs of congestive heart failure as indicated by ascites, congestive liver, and elevated LVEDP. Structural changes typical of ADR cardiomyopathy were more pronounced in the 6-wk group. In vivo hemodynamic as well as in vitro muscle function response to different concentrations of epinephrine was depressed in its duration as well as extent in both 3- and 6-wk ADR-treated groups. Myocardial NE levels were increased in the 3-wk group but were depressed in the 6-wk group. NE turnover was faster in both 3- and 6-wk ADR groups, uptake was increased only in the 6-wk group, and release was unchanged. These data show increased cardiac sympathetic tone at both stages of ADR-induced congestive heart failure.

Spontaneous baroreflex control of heart rate versus cardiac output: altered coupling in heart failure

2008 ◽  
Vol 294 (3) ◽  
pp. H1304-H1309 ◽  
Author(s):  
Javier A. Sala-Mercado ◽  
Masashi Ichinose ◽  
Robert L. Hammond ◽  
Matthew Coutsos ◽  
Tomoko Ichinose ◽  
...  
Keyword(s):  
Heart Failure ◽  
Heart Rate ◽  
Cardiac Output ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Baroreflex Control ◽  
Ventricular Systolic Pressure ◽  
Linear Relationships ◽  
Before And After ◽  
Spontaneous Baroreflex

Dynamic cardiac baroreflex responses are frequently investigated by analyzing the spontaneous reciprocal changes in arterial pressure and heart rate (HR). However, whether the spontaneous baroreflex-induced changes in HR translate into changes in cardiac output (CO) is unknown. In addition, this linkage between changes in HR and changes in CO may be different in subjects with heart failure (HF). We examined these questions using conscious dogs before and after pacing-induced HF. Spontaneous baroreflex sensitivity in the control of HR and CO was evaluated as the slopes of the linear relationships between HR or CO and left ventricular systolic pressure (LVSP) during spontaneous sequences of greater or equal to three consecutive beats when HR or CO changed inversely versus pressure. Furthermore, the translation of baroreflex HR responses into CO responses (HR-CO translation) was examined by computing the overlap between HR and CO sequences. In normal resting conditions, 44.0 ± 4.4% of HR sequences overlapped with CO sequences, suggesting that only around half of the baroreflex HR responses cause CO responses. In HF, HR-LVSP, CO-LVSP, and the HR-CO translation significantly decreased compared with the normal condition (−2.29 ± 0.5 vs. −5.78 ± 0.7 beats·min−1·mmHg−1; −70.95 ± 11.8 vs. −229.89 ± 29.6 ml·min−1·mmHg−1; and 19.66 ± 4.9 vs. 44.0 ± 4.4%, respectively). We conclude that spontaneous baroreflex HR responses do not always cause changes in CO. In addition, HF significantly decreases HR-LVSP, CO-LVSP, and HR-CO translation.

Inhibition of NO production increases myocardial blood flow and oxygen consumption in congestive heart failure

2002 ◽  
Vol 282 (6) ◽  
pp. H2278-H2283 ◽  
Author(s):  
Jay H. Traverse ◽  
Yingjie Chen ◽  
Mingxiao Hou ◽  
Robert J. Bache
Keyword(s):  
Heart Failure ◽  
Congestive Heart Failure ◽  
Blood Flow ◽  
Oxygen Consumption ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
No Production ◽  
Before And After ◽  
Rapid Ventricular Pacing

Coronary blood flow (CBF) and myocardial oxygen consumption (MV˙o 2) are reduced in dogs with pacing-induced congestive heart failure (CHF), which suggests that energy metabolism is downregulated. Because nitric oxide (NO) can inhibit mitochondrial respiration, we examined the effects of NO inhibition on CBF and MV˙o 2 in dogs with CHF. CBF and MV˙o 2 were measured at rest and during treadmill exercise in 10 dogs with CHF produced by rapid ventricular pacing before and after inhibition of NO production with N G-nitro-l-arginine (l-NNA, 10 mg/kg iv). The development of CHF was accompanied by decreases in aortic and left ventricular (LV) systolic pressure and an increase in LV end-diastolic pressure (25 ± 2 mmHg). l-NNA increased MV˙o 2 at rest (from 3.07 ± 0.61 to 4.15 ± 0.80 ml/min) and during exercise; this was accompanied by an increase in CBF at rest (from 31 ± 2 to 40 ± 4 ml/min) and during exercise (both P < 0.05). Althoughl-NNA significantly increased LV systolic pressure, similar increases in pressure produced by phenylephrine did not increase MV˙o 2. The findings suggest that NO exerts tonic inhibition on respiration in the failing heart.

Abstract 12583: C-Type Natriuretic Peptide Improves Left Ventricular Systolic and Diastolic Functional Performance at Rest and During Exercise After Heart Failure

Circulation ◽  
2014 ◽  
Vol 130 (suppl_2) ◽  
Author(s):  
Che Ping Cheng ◽  
Hiroshi Hasegawa ◽  
Atsushi Morimoto ◽  
Heng-Jie Cheng ◽  
William C Little
Keyword(s):  
Heart Failure ◽  
Natriuretic Peptide ◽  
Functional Performance ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Diastolic Filling ◽  
Arterial Elastance ◽  
Beneficial Effects ◽  
Mitral Flow

Background: In heart failure (HF), the impaired left ventricular (LV) arterial coupling and diastolic dysfunction present at rest are exacerbated during exercise (Ex). C-type natriuretic peptide (CNP), the third member of the natriuretic peptide family produced by the vascular endothelium and heart is elevated in HF. However, its functional effects are unclear. We tested the hypotheses that CNP with vasodilating, natriuretic, and lusitropic actions may prevent this abnormal Ex response after HF. Methods: We assessed the effects of CNP on LV functional performance at rest and during submaximum Ex (3.5-5.5 mph for 6-8 min) in 10 instrumented dogs with pacing-induced HF. Since CNP mediated its biological actions via cGMP, we also measured plasma cGMP levels in response to CNP infusion at rest before and after HF. Results: CNP (2 μg/kg plus 0.4 μg/kg/min, iv, 20 min) caused a similar increase in cGMP levels before (7.2±3.8 to 24.7±4.9 pmol/ml) and after HF (20.2±4.4 to 71.6±5.0 pmol/ml). After HF, at rest, CNP reduced LV end-systolic pressure (P ES , CNP: 93 vs Baseline: 104 mmHg), arterial elastance (E A , 8.3 vs 11.7 mmHg/ml) and end-diastolic pressure (P ED , 37.2 vs 42.4 mmHg) (p<0.05). The peak mitral flow (dV/dt max , 201±51 vs 160±34ml/sec) was also increased due to decreased minimum LVP (LVP min , 17.1 vs 23.8 mmHg) and the time constant of LV relaxation (t, 40±4 vs 48±6 msec) (p<0.05). In addition, the slope of LV end-systolic pressure-volume relations (E ES ) was increased (5.6±0.7 vs 4.2±0.9 mmHg/ml). The LV-arterial coupling, quantified as E ES /E A , was improved (0.69±0.22 vs 0.48±0.16) (p<0.05). The beneficial effects persisted during Ex. At matched levels of Ex, treatment with CNP, Ex-induced significantly less increases in P ES (ΔP= 3.4±0.5 vs 7.4±0.8 mmHg), mean LAP (ΔP= -3.1±2.2 vs 3.6±2.9 mmHg), and LVP min (ΔP= -3.6±1.4 vs 1.4±1.2 mmHg) (p<0.05). With CNP, t was much shortened (Δ= -0.8±4.0 vs 2.8±3.2 ms), and the peak mitral flow was further augmented (ΔdV/dt max , 75±20 vs 43±12 ml/sec) (p<0.05). Conclusion: After HF, the generation of cGMP in response to CNP is not blunted. CNP produces arterial vasodilatation and augments LV contraction, relaxation, diastolic filling and LV arterial coupling, thus improving LV performance, both at rest and during Ex after HF.

Ventricular-specific expression of angiotensin II type 2 receptors causes dilated cardiomyopathy and heart failure in transgenic mice

2003 ◽  
Vol 285 (5) ◽  
pp. H2179-H2187 ◽  
Author(s):  
Xinhua Yan ◽  
Robert L. Price ◽  
Masaharu Nakayama ◽  
Kenta Ito ◽  
Adam J. T. Schuldt ◽  
...  
Keyword(s):  
Heart Failure ◽  
Angiotensin Ii ◽  
Dilated Cardiomyopathy ◽  
Diastolic Pressure ◽  
Systolic Pressure ◽  
Left Ventricular ◽  
Specific Expression ◽  
Protein Levels

The angiotensin II type 2 (AT2) receptor is upregulated in the left ventricle in heart failure, but its pathophysiological roles in vivo are not understood. In the present study, AT2 receptors were expressed in transgenic (TG) mice using the ventricular-specific myosin light-chain (MLC-2v) promoter. In TG compared with nontransgenic (NTG) mice, in vivo left ventricular (LV) systolic pressure and peak +dP/d t were depressed while LV diastolic pressure was elevated ( P < 0.05). Echocardiography showed severely depressed LV fractional shortening, increased systolic and diastolic dimensions, and wall thinning ( P < 0.05). Confocal and electron microscopy studies revealed an increase in the size of myocytes and interstitial spaces as well as an increase in interstitial collagen, disruption of the Z-band, and changes in cytochrome c localization. The changes were most prominent in the highest-expressing TG line, which implies a dose-response relationship. AT2 overexpression was also directly associated with the increase of phosphorylated protein levels of PKC-α, PKC-β, and p70S6 kinase. These data demonstrate that ventricular myocyte-specific expression of AT2 receptors promotes the development of dilated cardiomyopathy and heart failure in vivo.

Sign in / Sign up

Export Citation Format

Share Document