Effects of pre-, peri-, and postmyocardial infarction treatment with losartan in rats: effect of dose on survival, ventricular arrhythmias, function, and remodeling

2005 ◽  
Vol 288 (4) ◽  
pp. H1997-H2005 ◽  
Author(s):  
Ali Pourdjabbar ◽  
Thomas G. Parker ◽  
Quang Trinh Nguyen ◽  
Jean-Francois Desjardins ◽  
Nathalie Lapointe ◽  
...  
Keyword(s):  
Gene Expression ◽  
Ventricular Arrhythmias ◽  
Angiotensin Receptor Blockers ◽  
Ischemia Reperfusion ◽  
Left Ventricular ◽  
Lv Function ◽  
High Dose ◽  
Postmyocardial Infarction ◽  
Lv Remodeling ◽  
Cardiac Hemodynamics

Angiotensin receptor blockers (ARBs) reduce adverse left ventricular (LV) remodeling and improve LV function and survival when started postmyocardial infarction (MI). ARBs also reduce ventricular arrhythmias during ischemia-reperfusion injury when started pre-MI. No information exists regarding their efficacy and safety when started pre-MI and continued peri- and post-MI. We evaluated whether the ARB losartan improves the outcome when started pre-MI and continued peri- and post-MI. Male Wistar rats ( n = 502) were treated for 7 days pre-MI with losartan at a high dose (30 mg·kg−1·day−1), progressively increasing dose (3 mg·kg−1·day−1 increased to 10 mg·kg−1·day−1 10 days and 30 mg·kg−1·day−1 20 days post-MI), or no treatment. Ambulatory systolic blood pressure and Holter monitoring were performed for 24 h post-MI. Echocardiography was done 30 days post-MI, and LV remodeling, cardiac hemodynamics, and fetal gene expression were assessed 38 days post-MI. High-dose losartan reduced 24-h post-MI survival compared with the progressive dose and control (21.9% vs. 36.6% and 38.1%, P = 0.033 and P = 0.009, respectively). This was associated with greater hypotension in the high dose and no change in ventricular arrhythmias in all groups. In 24-h post-MI survivors, the progressive dose group had reduced mortality from 24 h to 38 days (8.5% vs. 28.6% for control vs. 38.9% for high dose, P = 0.032 and P = 0.01, respectively). Survivors of both losartan groups demonstrated improved LV remodeling, cardiac hemodynamics, preserved GLUT-4, and reduced cardiac fetal gene expression. Pretreatment with ARBs does not reduce 24-h post-MI ventricular arrhythmias or survival, and high doses increase mortality by causing excessive hypotension. In 24-h post-MI survivors, progressively increasing doses of losartan have multiple beneficial effects, including improved survival.

Effects of pre-, peri-, and postmyocardial infarction treatment with omapatrilat in rats: survival, arrhythmias, ventricular function, and remodeling

2003 ◽  
Vol 285 (1) ◽  
pp. H398-H405 ◽  
Author(s):  
Nathalie Lapointe ◽  
Quang Trinh Nguyen ◽  
Jean-François Desjardins ◽  
Francois Marcotte ◽  
Ali Pourdjabbar ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Ventricular Arrhythmias ◽  
Left Ventricular ◽  
Treatment Control ◽  
Postmyocardial Infarction ◽  
Vasopeptidase Inhibitor ◽  
Lv Remodeling ◽  
Cardiac Hemodynamics ◽  
The Subject ◽  
Early Benefit

We showed previously that the vasopeptidase inhibitor (VPI) omapatrilat improves peri-myocardial infarction (MI) survival, but the mechanisms involved and whether these effects are sustained remained to be determined, and are the subject of this study. Rats ( n = 272) received omapatrilat (20 mg · kg-1 · day-1) starting 7 days before MI and continued peri- and post-MI, or no treatment (control). One group of rats had continuous ambulatory ECG and blood pressure recordings started 6 h before MI and continued until 24 h after MI, when survival was evaluated, and the rats were killed, and MI size was evaluated. A second group had left ventricular (LV) remodeling evaluated by echocardiography at 30 days and, at 38 days, had cardiac hemodynamics and morphology done and survival evaluated. Survival 24 h after MI ( n = 255) improved with omapatrilat (60% vs. 46% for control; P = 0.0378). Over the next 37 days, there was no further improvement with omapatrilat but the early benefit was sustained. Omapatrilat reduced MI size 24 h after MI (36 ± 2 vs. 42 ± 2 mm2 for controls; P = 0.034). Omapatrilat reduced ventricular arrhythmia score 1–12 h after MI. Omapatrilat decreased blood pressure, but not during the first 24 h after MI. Omapatrilat reduced LV diastolic and systolic dimensions and LV and right ventricular weights compared with control large MI, indicating a decrease in reactive hypertrophy. Improvement in cardiac remodeling was accompanied by improved cardiac hemodynamics. Thus this study indicates that pre-, peri-, and post-MI treatment with the VPI omapatrilat is beneficial in survival, ventricular arrhythmias, LV remodeling, and cardiac function.

scholarly journals High-fat, low-carbohydrate diet promotes arrhythmic death and increases myocardial ischemia-reperfusion injury in rats

2014 ◽  
Vol 307 (4) ◽  
pp. H598-H608 ◽  
Author(s):  
Jian Liu ◽  
Peipei Wang ◽  
Luyun Zou ◽  
Jing Qu ◽  
Silvio Litovsky ◽  
...  
Keyword(s):  
Myocardial Ischemia ◽  
Ventricular Arrhythmias ◽  
Ischemia Reperfusion ◽  
Left Ventricular ◽  
Lv Function ◽  
High Fat ◽  
Carbohydrate Diet ◽  
Low Carbohydrate ◽  
Myocardial Ischemia Reperfusion

High-fat, low-carbohydrate diets (HFLCD) are often eaten by humans for a variety of reasons, but the effects of such diets on the heart are incompletely understood. We evaluated the impact of HFLCD on myocardial ischemia/reperfusion (I/R) using an in vivo model of left anterior descending coronary artery ligation. Sprague-Dawley rats (300 g) were fed HFLCD (60% calories fat, 30% protein, 10% carbohydrate) or control (CONT; 16% fat, 19% protein, 65% carbohydrate) diet for 2 wk and then underwent open chest I/R. At baseline (preischemia), diet did not affect left ventricular (LV) systolic and diastolic function. Oil red O staining revealed presence of lipid in the heart with HFLCD but not in CONT. Following I/R, recovery of LV function was decreased in HFLCD. HFLCD hearts exhibited decreased ATP synthase and increased uncoupling protein-3 gene and protein expression. HFLCD downregulated mitochondrial fusion proteins and upregulated fission proteins and store-operated Ca2+ channel proteins. HFLCD led to increased death during I/R; 6 of 22 CONT rats and 16 of 26 HFLCD rats died due to ventricular arrhythmias and hemodynamic shock. In surviving rats, HFLCD led to larger infarct size. We concluded that in vivo HFLCD does not affect nonischemic LV function but leads to greater myocardial injury during I/R, with increased risk of death by pump failure and ventricular arrhythmias, which might be associated with altered cardiac energetics, mitochondrial fission/fusion dynamics, and store-operated Ca2+ channel expression.

Cardioprotection of electroacupuncture against myocardial ischemia-reperfusion injury by modulation of cardiac norepinephrine release

2012 ◽  
Vol 302 (9) ◽  
pp. H1818-H1825 ◽  
Author(s):  
Wei Zhou ◽  
Yoshihiro Ko ◽  
Peyman Benharash ◽  
Kentaro Yamakawa ◽  
Sunny Patel ◽  
...  
Keyword(s):  
Myocardial Ischemia ◽  
Infarct Size ◽  
Ventricular Arrhythmias ◽  
Ischemia Reperfusion Injury ◽  
Ischemia Reperfusion ◽  
Sham Acupuncture ◽  
Left Ventricular ◽  
Lv Function ◽  
Cardioprotective Effects ◽  
Myocardial Ischemia Reperfusion

Augmentation of cardiac sympathetic tone during myocardial ischemia has been shown to increase myocardial O2 demand and infarct size as well as induce arrhythmias. We have previously demonstrated that electroacupuncture (EA) inhibits the visceral sympathoexcitatory cardiovascular reflex. The purpose of this study was to determine the effects of EA on left ventricular (LV) function, O2 demand, infarct size, arrhythmogenesis, and in vivo cardiac norepinephrine (NE) release in a myocardial ischemia-reperfusion model. Anesthetized rabbits ( n = 36) underwent 30 min of left anterior descending coronary artery occlusion followed by 90 min of reperfusion. We evaluated myocardial O2 demand, infarct size, ventricular arrhythmias, and myocardial NE release using microdialysis under the following experimental conditions: 1) untreated, 2) EA at P5–6 acupoints, 3) sham acupuncture, 4) EA with pretreatment with naloxone (a nonselective opioid receptor antagonist), 5) EA with pretreatment with chelerythrine (a nonselective PKC inhibitor), and 6) EA with pretreatment with both naloxone and chelerythrine. Compared with the untreated and sham acupuncture groups, EA resulted in decreased O2 demand, myocardial NE concentration, and infarct size. Furthermore, the degree of ST segment elevation and severity of LV dysfunction and ventricular arrhythmias were all significantly decreased ( P < 0.05). The cardioprotective effects of EA were partially blocked by pretreatment with naloxone or chelerythrine alone and completely blocked by pretreatment with both naloxone and chelerythrine. These results suggest that the cardioprotective effects of EA against myocardial ischemia-reperfusion are mediated through inhibition of the cardiac sympathetic nervous system as well as opioid and PKC-dependent pathways.

Abstract 2415: Long-Term Baroreflex Activation Therapy Increases the Threshold for the Induction of Lethal Ventricular Arrhythmias in Dogs with Chronic Advanced Heart Failure

Circulation ◽  
2008 ◽  
Vol 118 (suppl_18) ◽  
Author(s):  
Mengjun Wang ◽  
Valerio Zaca ◽  
Alice Jiang ◽  
Itamar Ilsar ◽  
Matthew Ebinger ◽  
...  
Keyword(s):  
Heart Failure ◽  
Sudden Cardiac Death ◽  
Cardiac Death ◽  
Ventricular Arrhythmias ◽  
Lv Function ◽  
Baroreflex Activation Therapy ◽  
Increased Risk ◽  
Lv Remodeling ◽  
Activation Therapy

Heart failure (HF) is associated with a high incidence of ventricular tachycardia (VT) and fibrillation (VF). Patients with HF in whom these lethal arrhythmias can be induced by electrophysiological (EP) testing carry a high risk of sudden cardiac death. We showed that chronic electrical carotid baroreflex activation therapy (BAT) with the Rheos® System (CVRx, Inc.) improves LV function, attenuates LV remodeling and restores autonomic sympathetic-parasympathetic balance in dogs with HF. This study examined the effects of long-term therapy with BAT on the induction of VT or VF in dogs with coronary microembolization-induced HF (LV ejection fraction ~20%). Eleven dogs with HF underwent EP testing at baseline prior to therapy and after 3 and 6 months of therapy with BAT and again 6 weeks after withdrawal of BAT therapy (n = 7) or no therapy at all (Control, n = 4). Programmed ventricular stimulation was performed from the right ventricular apex and included delivery of up to 4 extrastimuli at progressively shorter coupling intervals (in steps of 10 msec). The extrastimuli were delivered following 8 ventricular paced beats with a drive cycle length between 600 and 200 msec. If a sustained monomorphic VT or VF could not be induced, isoproterenol infusion was initiated to increase the sinus rate by ~30% and the EP stimulation protocol was repeated. At baseline, a sustained VT or VF was induced in all 11 dogs (100%). After 3 and 6 months of follow-up, all Control dogs (100%) were induced into sustained VT or VF. After 3 months of BAT, only 3 of 7 dogs (43%) were induced into sustained VT or VF. After 6 months of BAT, only 2 of 7 dogs (29%) were induced into sustained VT or VF. Finally after withdrawal of BAT therapy, all dogs (100%) were again induced into systained VT or VF. In addition to improving LV function and attenuating LV remodeling, long-term monotherapy with BAT markedly increases the threshold for lethal ventricular arrhythmias in dogs with chronic HF. This is a marked improvement over inducibility of lethal arrhythmias seen in historical untreated controls. This benefit of BAT supports the continued exploration of this device as a therapeutic modality for treating patients with chronic HF and increased risk of sudden cardiac death.

Cardiac contractile injury after intestinal ischemia-reperfusion

1991 ◽  
Vol 261 (4) ◽  
pp. H1164-H1170 ◽  
Author(s):  
J. W. Horton ◽  
D. J. White
Keyword(s):  
Intestinal Ischemia ◽  
Ischemia Reperfusion ◽  
Multiorgan Failure ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
In Vivo Studies ◽  
Lv Function ◽  
Acid Base Balance ◽  
Cardiac Contractile ◽  
Sequence Of Events

Experimental and clinical data suggest that even a brief period of intestinal ischemia followed by reperfusion initiates a sequence of events that include release of inflammatory mediators and multiorgan failure. In this study, 41 rats were subjected to occlusion of the superior mesenteric artery (SMA) for 20 min and collateral arcade ligation. Twelve rats were sham operated and served as controls (group 1). Groups of rats with SMA occlusion were killed at several time intervals after reperfusion (group 2, 2-3 h; group 3, 4-5 h; group 4, 12-16 h). In group 5, rats were pretreated with enterally administered allopurinol (10 mg.kg-1.day-1) for 4 days before the intestinal ischemia episode and were studied 2-3 h after reperfusion. In vivo studies confirmed that 20 min of intestinal ischemia produced a transient bradycardia (P less than 0.05) and no change in systemic blood pressure, acid-base balance, or hematocrit. In vitro studies showed marked cardiac contractile depression as early as 2 h after ischemia-reperfusion as indicated by a fall in left ventricular pressure (LVP; from 77 +/- 3 to 63 +/- 4 mmHg, P = 0.01) and +dP/dtmax (from 1,827 +/- 59 to 1,557 +/- 99 mmHg/s, P less than 0.02) and -dP/dtmax (from 1,267 +/- 57 to 953 +/- 67 mmHg/s, P = 0.02), a rightward shift in LV function curves, and a decreased responsiveness to perfusate Ca2+. Allopurinol pretreatment prevented ischemia-reperfusion-mediated deficits in cardiac contraction and relaxation.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Systolic Time Interval (STI) in Hypothyroid Patients Receiving High Dose L-Thyroxine

2020 ◽  
Vol 18 (2) ◽  
Author(s):  
Nurul Aulia Zakaria ◽  
Hafizah Pasi ◽  
Mohammad Arif Shahar
Keyword(s):  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Lv Function ◽  
High Dose ◽  
Time Interval ◽  
Ejection Time ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time ◽  
Significant Increment

Introduction: Systolic Time Interval (STI) is a simple,noninvasive and precise technique to assess left ventricular (LV) function. It measures aortic Pre-Ejection Period (PEP) over Left Ventricular Ejection Time (LVET) from echocardiogram. Thyrotoxicosis will enhance LV function and cause reduction of STI.  This study was perform to measure the changes of STI after administration of high dose L-thyroxine and to determine the correlation between high dose L-thyroxine administration and STI. Materials and Method: A Total of 22 patients were screened. Those with cardiac diseases and high Framingham risk score were excluded. Nine patients were started on high dose L-thyroxine (7x their usual dose) once a week during the month of Ramadan.Thyroid hormones ( T3,T4,TSH)  and STI (PEP/LVET) were measured at baseline and within 24 hrs after high dose L-thyroxine ingestion. Results: All patients have normal thyroid hormones level and normal cardiac function at baseline. The median dose (mcg) of L-thyroxine was 600 (437.5,700) while the median level of fT4 (pmol/L) was 17.43(12.38,20.8). Despite the significant increment of fT4 after Lthyroxine ingestion [baseline 13.21(8.19,14.63) vs high dose 17.43(12.38,22.55) p; 0.011] there was no significant change in STI [baseline 0.3(0.2,0.4) vs high dose 0.28(0.26,0.45) p; 0.513]. There was no correlation found between the dose of Lthyroxine and STI (r=0.244 , p;0.526).  Conclusion: Administration of high dose Lthyroxine did not significantly alter STI despite significant increment of fT4 level unlike the naturally occurring thyrotoxicosis.Therefore ‘exogenous’ administration of high dose L-thyroxine is cardiac safe.

scholarly journals Inhibition of class I histone deacetylase activity represses matrix metalloproteinase-2 and -9 expression and preserves LV function postmyocardial infarction

2015 ◽  
Vol 308 (11) ◽  
pp. H1391-H1401 ◽  
Author(s):  
Santhosh K. Mani ◽  
Christine B. Kern ◽  
Denise Kimbrough ◽  
Benjamin Addy ◽  
Harinath Kasiganesan ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Hdac Inhibitor ◽  
Histone Deacetylases ◽  
Left Ventricular ◽  
Class I ◽  
Matrix Metalloproteinase 2 ◽  
Lv Function ◽  
Extracellular Matrix Remodeling ◽  
Matrix Remodeling ◽  
Lv Remodeling

Left ventricular (LV) remodeling, after myocardial infarction (MI), can result in LV dilation and LV pump dysfunction. Post-MI induction of matrix metalloproteinases (MMPs), particularly MMP-2 and MMP-9, have been implicated as causing deleterious effects on LV and extracellular matrix remodeling in the MI region and within the initially unaffected remote zone. Histone deacetylases (HDACs) are a class of enzymes that affect the transcriptional regulation of genes during pathological conditions. We assessed the efficacy of both class I/IIb- and class I-selective HDAC inhibitors on MMP-2 and MMP-9 abundance and determined if treatment resulted in the attenuation of adverse LV and extracellular matrix remodeling and improved LV pump function post-MI. MI was surgically induced in MMP-9 promoter reporter mice and randomized for treatment with a class I/IIb HDAC inhibitor for 7 days post-MI. After MI, LV dilation, LV pump dysfunction, and activation of the MMP-9 gene promoter were significantly attenuated in mice treated with either the class I/IIb HDAC inhibitor tichostatin A or suberanilohydroxamic acid (voronistat) compared with MI-only mice. Immunohistological staining and zymographic levels of MMP-2 and MMP-9 were reduced with either tichostatin A or suberanilohydroxamic acid treatment. Class I HDAC activity was dramatically increased post-MI. Treatment with the selective class I HDAC inhibitor PD-106 reduced post-MI levels of both MMP-2 and MMP-9 and attenuated LV dilation and LV pump dysfunction post-MI, similar to class I/IIb HDAC inhibition. Taken together, these unique findings demonstrate that selective inhibition of class I HDACs may provide a novel therapeutic means to attenuate adverse LV remodeling post-MI.

scholarly journals Liraglutide protects cardiac function in diabetic rats through the PPARα pathway

2018 ◽  
Vol 38 (2) ◽  
Author(s):  
Qian Zhang ◽  
Xinhua Xiao ◽  
Jia Zheng ◽  
Ming Li ◽  
Miao Yu ◽  
...  
Keyword(s):  
Oxidative Stress ◽  
Insulin Resistance ◽  
Cardiac Dysfunction ◽  
Diabetic Rats ◽  
Left Ventricular ◽  
Serum Adiponectin ◽  
Diabetic Rat ◽  
Lv Function ◽  
High Dose ◽  
And Oxidative Stress

Increasing evidence shows that diabetes causes cardiac dysfunction. We hypothesized that a glucagon-like peptide-1 (GLP-1) analog, liraglutide, would attenuate cardiac dysfunction in diabetic rats. A total of 24 Sprague–Dawley (SD) rats were divided into two groups fed either a normal diet (normal, n=6) or a high-fat diet (HFD, n=18) for 4 weeks. Then, the HFD rats were injected with streptozotocin (STZ) to create a diabetic rat model. Diabetic rats were divided into three subgroups receiving vehicle (diabetic, n=6), a low dose of liraglutide (Llirag, 0.2 mg/kg/day, n=6), or a high dose of liraglutide (Hlirag, 0.4 mg/kg/day, n=6). Metabolic parameters, systolic blood pressure (SBP), heart rate (HR), left ventricular (LV) function, and whole genome expression of the heart were determined. Diabetic rats developed insulin resistance, increased blood lipid levels and oxidative stress, and impaired LV function, serum adiponectin, nitric oxide (NO). Liraglutide improved insulin resistance, serum adiponectin, NO, HR, and LV function and reduced blood triglyceride (TG), total cholesterol (TC) levels, and oxidative stress. Moreover, liraglutide increased heart nuclear receptor subfamily 1, group H, member 3 (Nr1h3), peroxisome proliferator activated receptor (Ppar) α (Pparα), and Srebp expression and reduced diacylglycerol O-acyltransferase 1 (Dgat) and angiopoietin-like 3 (Angptl3) expression. Liraglutide prevented cardiac dysfunction by activating the PPARα pathway to inhibit Dgat expression and oxidative stress in diabetic rats.

Abstract 405: Inhibition of Class I Histone Deacetylases at Reperfusion Attenuates Ischemia-reperfusion Injury and Modifies Mitochondrial Acetylation

2015 ◽  
Vol 117 (suppl_1) ◽  
Author(s):  
Daniel J Herr ◽  
Sverre E Aune ◽  
Donald R Menick
Keyword(s):  
Ischemia Reperfusion Injury ◽  
Contractile Function ◽  
Ischemia Reperfusion ◽  
Left Ventricular ◽  
Class I ◽  
Mass Spectrometry Analysis ◽  
Rate Pressure Product ◽  
Lv Function ◽  
Mitochondrial Enzymes ◽  
Reperfusion Phase

Although rapid reperfusion of ischemic tissue is the treatment of choice for myocardial infarction, much of the resultant damage occurs as a consequence of reperfusion itself. Previously, we have shown that pretreatment with MS-275, a selective class I histone deacetylase (HDAC) inhibitor, preserves left-ventricular (LV) function and substantially reduces the area of infarcted tissue in isolated rat hearts subjected to ischemia-reperfusion (IR) injury. Here, we tested the hypothesis that MS-275 treatment at reperfusion reduces LV tissue damage and improves post-ischemic LV contractile function. To do this, hearts from male Sprague-Dawley rats were isolated and perfused ex vivo on a Langendorff perfusion apparatus. A saline-filled balloon was inserted into the left ventricle of the heart to monitor ventricular pressure development throughout the experiment. Hearts were subjected to 30 minutes of ischemia, followed by 60 minutes of reperfusion. MS-275 was administered during the entire reperfusion phase, and resultant functional data were compared to untreated hearts. There was no difference in any metric of pre-ischemic contractile function between groups. 10nM MS-275 administered at reperfusion significantly improved multiple measures of LV function, including dP/dtmax, -dP/dtmax, developed pressure and rate pressure product. We also observed a significant reduction in infarct area of treated hearts compared to control, as measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining. Unexpectedly, mass spectrometry analysis revealed significant changes in acetylation state of multiple mitochondrial enzymes. Administration of MS-275 during the reperfusion phase of IR is sufficient to partially rescue LV function from reperfusion-induced damage. This study emphasizes the importance of exploring class I HDAC inhibitors for protection against ischemia-reperfusion.

Abstract 3295: De-induction of the Maladaptive Fetal Gene Program During Chronic Monotherapy with Metoprolol Succinate is Retained Following Withdrawal of Therapy in Dogs with Chronic Heart Failure

Circulation ◽  
2007 ◽  
Vol 116 (suppl_16) ◽  
Author(s):  
Rasha Bazari ◽  
Sharad Rastogi ◽  
Valerio Zaca ◽  
Sidney Goldstein ◽  
Hani N Sabbah
Keyword(s):  
Heart Failure ◽  
Chronic Heart Failure ◽  
Mrna Expression ◽  
Natriuretic Peptide ◽  
Left Ventricular ◽  
Lv Function ◽  
Metoprolol Succinate ◽  
Myosin Heavy Chain Isoform ◽  
Chronic Therapy ◽  
Lv Remodeling

Background: Chronic therapy with extended release metoprolol succinate (MET), a selective β1 adrenergic receptor blocker, improves left ventricular (LV) function and attenuates global LV remodeling in dogs with chronic heart failure (HF). We previously showed that chronic therapy with β-blockade results in de-induction of the fetal gene program (FGP) in LV myocardium of dogs with HF. In this study, we tested the hypothesis that in dogs with HF withdrawal of chronic MET does not lead to re-induction of FGP. Methods: Studies were performed in 17 intracoronary microembolization-induced HF dogs randomized to 3 months oral therapy with MET (100 mg, once daily, n=11) or no therapy at all (Controls, n=6). In dogs randomized to MET, 6 were sacrificed after 3 months of therapy and in the remaining 5, MET was withdrawn after 3 months of therapy and dogs were observed for 6 weeks after withdrawal of MET (MET-W) and then sacrificed. LV tissue was also obtained from 6 normal (NL) dogs for comparison. mRNA expression of the FGP genes namely, atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), sarcoplasmic reticulum calcium ATPase (CAA), cardiac β-1 adren-ergic receptor (AR) and α-myosin heavy chain isoform (α-MHC) was measured using reverse transcriptase polymerase chain reaction (RT-PCR) and bands were quantified in densitometric units (du). Results: In Controls, mRNA expression of ANP and BNP increased and expression of CAA, β 1-AR and α-MHC decreased. Treatment with MET decreased expression of ANP and BNP and increased expression of CAA, β 1-AR and α-MHC. Except for α-MHC, the improvement in FGP seen during MET treatment was preserved in MET-W dogs. Conclusions: Withdrawal of MET is associated with sustained de-induction of the FGP in LV myocardium of dogs with HF. This observation supports the concept that chronic β-blockade therapy in HF confers lasting reversal of LV remodeling and molecular recovery of the failing myocardium.

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