Effects of dobutamine and arbutamine on regional myocardial function in a porcine model of myocardial ischemia

AbstractObjectives. The present study was performed to determine the mechanisms for catecholamine-induced wall motion abnormalities and to compare the diagnostic efficacy of two catecholamines: arbutamine and dobutamine.Background. Catecholamine stress echocardiography is used to induce regional wall motion abnormalities for the detection of coronary artery disease, but the mechanism by which these abnormalities occur is unknown.Methods. Ten pigs were instrumented with left circumflex coronary artery ameroid constrictors, sonomicrometers to measure transmural wall thickening in the left circumflex (ischemic) and left anterior descending (control) coronary artery beds and a pressure gauge to measure left ventricular pressure and its first derivative (dP/dt). Myocardial blood flow was measured by microspheres.Results. At 38 ± 6 days (mean ± SEM) after surgery, percent wall thickening was normal at rest in both beds but abnormal in the left circumflex coronary artery bed during atrial pacing. These findings were associated with reduced myocardial blood flow in the ischemic bed during atrial pacing. Dobutamine infusion increased percent wall thickening, with no differences between the two beds (p = 0.63). In contrast, arbutamine infusion increased percent wall thickening only in the nonischemic bed, with no effect on percent wall thickening in the ischemic bed (p s 0.03). Although the endocardial/epicardial blood flow ratio tended to be reduced in the left circumflex artery bed during catecholamine infusion (p = 0.07), both agents were similar in this effect. Despite differences in function between the beds, there was no difference in transmural myocardial blood flow between the two beds during catecholamine infusion. When examined at matched metabolic demands, arbutamine elicited greater differences in percent wall thickening than dobutamine between the two beds (p < 0.01).Conclusions. Arbutamine was able to provoke regional differences in fonction in a manner superior to dobutamine. This occurred independently of altered transmural myocardial blood flow or differences in hemodynamic effects between the agents. Differences in their inotropic properties may be important in explaining their different effects on ischemic myocardium

Metabolomic analysis of serum and myocardium in compensated heart failure after myocardial infarction

AIMS:To determine the metabolic adaptations to compensated heart failure using a reproducible model of myocardial infarction and an unbiased metabolic screen. To address the limitations in sample availability and model variability observed in preclinical and clinical metabolic investigations of heart failure. MAIN METHODS:Metabolomic analysis was performed on serum and myocardial tissue from rabbits after myocardial infarction (MI) was induced by cryo-injury of the left ventricular free wall. Rabbits followed for 12 weeks after MI exhibited left ventricular dilation and depressed systolic function as determined by echocardiography. Serum and tissue from the viable left ventricular free wall, interventricular septum and right ventricle were analyzed using a gas chromatography time of flight mass spectrometry-based untargeted metabolomics assay for primary metabolites. KEY FINDINGS:Unique results included: a two- three-fold increase in taurine levels in all three ventricular regions of MI rabbits and similarly, the three regions had increased inosine levels compared to sham controls. Reduced myocardial levels of myo-inositol in the myocardium of MI animals point to altered phospholipid metabolism and membrane receptor function in heart failure. Metabolite profiles also provide evidence for responses to oxidative stress and an impairment in TCA cycle energy production in the failing heart. SIGNIFICANCE:Our results revealed metabolic changes during compensated cardiac dysfunction and suggest potential targets for altering the progression of heart failure

Impact of blood factors on endothelial cell metabolism and function in two diverse heart failure models.

Role of blood-based factors in development and progression of heart failure (HF) is poorly characterized. Blood contains factors released during pathophysiological states that may impact cellular function and provide mechanistic insights to HF management. We tested effects of blood from two distinct HF models on cardiac metabolism and identified possible cellular targets of the effects. Blood plasma was obtained from daunorubicin- and myocardial infarction-induced HF rabbits (Dauno-HF and MI-HF) and their controls (Dauno-Control and MI-Control). Effects of plasma on bioenergetics of myocardial tissue from healthy mice and cellular cardiac components were assessed using high-resolution respirometry and Seahorse flux analyzer. Since endothelial cell respiration was profoundly affected by HF plasma, effects of plasma on endothelial cell barrier function and death were further evaluated. Western-blotting and electron microscopy were performed to evaluate mitochondrial proteins and morphology. Brief exposure to HF plasma decreased cardiac tissue respiration. Endothelial cell respiration was most impacted by exposure to HF plasma. Endothelial cell monolayer integrity was decreased by incubation with Dauno-HF plasma. Apoptosis and necrosis were increased in cells incubated with Dauno-HF plasma for 24 h. Down-regulation of voltage-dependent anion-selective channel (VDAC)-1, translocase of outer membrane 20 (Tom20), and mitochondrial fission factor (MFF) in cells exposed to Dauno-HF plasma and mitochondrial signal transducer and activator of transcription 3 (Stat3) and MFF in cells exposed to MI-HF plasma were observed. Mitochondrial structure was disrupted in cells exposed to HF plasma. These findings indicate that endothelial cells and mitochondrial structure and function may be primary target where HF pathology manifests and accelerates. High-throughput blood-based screening of HF may provide innovative ways to advance disease diagnosis and management

Modulation of caveolins, integrins and plasma membrane repair proteins in anthracycline-induced heart failure in rabbits

<div><p>Anthracyclines are chemotherapeutic drugs known to induce heart failure in a dose-dependent manner. Mechanisms involved in anthracycline cardiotoxicity are an area of relevant investigation. Caveolins bind, organize and regulate receptors and signaling molecules within cell membranes. Caveolin-3 (Cav-3), integrins and related membrane repair proteins can function as cardioprotective proteins. Expression of these proteins in anthracycline-induced heart failure has not been evaluated. We tested the hypothesis that daunorubicin alters cardioprotective protein expression in the heart. Rabbits were administered daunorubicin (3 mg/kg, IV) weekly, for three weeks or nine weeks. Nine weeks but not three weeks of daunorubicin resulted in progressive reduced left ventricular function. Cav-3 expression in the heart was unchanged at three weeks of daunorubicin and increased in nine week treated rabbits when compared to control hearts. Electron microscopy showed caveolae in the heart were increased and mitochondrial number and size were decreased after nine weeks of daunorubicin. Activated beta-1 (β1) integrin and the membrane repair protein MG53 were increased after nine weeks of daunorubicin vs. controls with no change at the three week time point. The results suggest a potential pathophysiological role for Cav3, integrins and membrane repair in daunorubicin-induced heart failure.</p></div

Expression of caveolin in the control heart.

<p>(A) Western Blot for caveolin-1 (Cav-1) and caveolin-3 (Cav-3) in rabbit left ventricle (LV), intraventricular septum (IVS) and right ventricle (RV). (B) Quantification of Cav-1 and Cav-3, n = 6, respectively. **<i>p</i><0.01. GAPDH, Glyceraldehyde 3-phosphate dehydrogenase; NS, not significant.</p

Expression of caveolin in the Dau-treated heart.

<p>(A) Western blot of Cav-1 and Cav-3 in control and Dau-treated left ventricle (LV). (B) Quantification of Cav-1 and Cav-3 in the LV, n = 6, respectively. (C) Western blot of Cav-1 and Cav-3 in control and Dau-treated intraventricular septum (IVS). (D) Quantification of Cav-1 and Cav-3 in the IVS, n = 6, respectively. (E) Western blot of Cav-1 and Cav-3 in control and Dau-treated right ventricle (RV). (F) Quantification of Cav-1 and Cav-3 in the RV, n = 6, respectively. (G) Representative images of immunostaining for Cav-3 in the control rabbit LV and Dau-treated rabbit hearts. Scale bar; 20 μm *<i>p</i><0.05, **<i>p</i><0.01, ***<i>p</i><0.001. GAPDH, Glyceraldehyde 3-phosphate dehydrogenase; NS, not significant.</p

Caveolae number in cardiac myocyte from Dau-treated and control hearts.

<p>(A-B) Excised control and Dau-treated hearts underwent sucrose density fractionation. Fractions were probed for Caveolin-1 (Cav-1) and Caveolin-3 (Cav-3). Cav-3, but not Cav-1, was increased in BFs in 9w Dau-treated heart (representative immunoblots are shown) and confirmed by densitometry normalized to whole tissue lysate. (C-D) Quantification of (A) and (B). n = 4, respectively (E-F) Protein and cholesterol concentration in each fraction. n = 4, (G) 9w Dau treatment increased the number of caveolae. Electron microscopy showed an increase in number of caveolae in 9w Dau-treated vs. control hearts. Arrow indicates caveolae. Scale bar; 500 nm, (H) Caveolae number in Dau-treated and control left ventricle. (n = 10–13, respectively) *<i>p</i><0.05, **<i>p</i><0.01, NS, not significant; BF, buoyant fraction; non BF, non-buoyant fraction.</p