Myocardial Creatine Kinase Activity Research Articles

Synergistic effect on cardiac energetics by targeting the creatine kinase system: in vivo application of high-resolution 31P-CMRS in the mouse

BackgroundPhosphorus cardiovascular magnetic resonance spectroscopy (31P-CMRS) has emerged as an important tool for the preclinical assessment of myocardial energetics in vivo. However, the high rate and diminutive size of the mouse heart is a challenge, resulting in low resolution and poor signal-to-noise. Here we describe a refined high-resolution 31P-CMRS technique and apply it to a novel double transgenic mouse (dTg) with elevated myocardial creatine and creatine kinase (CK) activity. We hypothesised a synergistic effect to augment energetic status, evidenced by an increase in the ratio of phosphocreatine-to-adenosine-triphosphate (PCr/ATP). Methods and resultsSingle transgenic Creatine Transporter overexpressing (CrT-OE, n = 7) and dTg mice (CrT-OE and CK, n = 6) mice were anaesthetised with isoflurane to acquire 31P-CMRS measurements of the left ventricle (LV) utilising a two-dimensional (2D), threefold under-sampled density-weighted chemical shift imaging (2D-CSI) sequence, which provided high-resolution data with nominal voxel size of 8.5 µl within 70 min. (1H-) cine-CMR data for cardiac function assessment were obtained in the same imaging session. Under a separate examination, mice received invasive haemodynamic assessment, after which tissue was collected for biochemical analysis. Myocardial creatine levels were elevated in all mouse hearts, but only dTg exhibited significantly elevated CK activity, resulting in a 51% higher PCr/ATP ratio in heart (3.01 ± 0.96 vs. 2.04 ± 0.57—mean ± SD; dTg vs. CrT-OE), that was absent from adjacent skeletal muscle. No significant differences were observed for any parameters of LV structure and function, confirming that augmentation of CK activity does not have unforeseen consequences for the heart. ConclusionsWe have developed an improved 31P-CMRS methodology for the in vivo assessment of energetics in the murine heart which enabled high-resolution imaging within acceptable scan times. Mice over-expressing both creatine and CK in the heart exhibited a synergistic elevation in PCr/ATP that can now be tested for therapeutic potential in models of chronic heart failure.

Nootkatone, a Dietary Fragrant Bioactive Compound, Attenuates Dyslipidemia and Intramyocardial Lipid Accumulation and Favorably Alters Lipid Metabolism in a Rat Model of Myocardial Injury: An In Vivo and In Vitro Study.

In the present study, we assessed whether nootkatone (NKT), a sesquiterpene in edible plants, can provide protection against dyslipidemia, intramyocardial lipid accumulation, and altered lipid metabolism in a rat model of myocardial infarction (MI) induced by subcutaneous injections of isoproterenol (ISO, 85 mg/kg) on days 9 and 10. The rats were pre- and co-treated with NKT (10 mg/kg, p.o.) administered daily for 11 days. A significant reduction in the activities of myocardial creatine kinase and lactate dehydrogenase, as well as non-enzymatic antioxidants, and alterations in lipids and lipoproteins, along with a rise in plasma lipid peroxidation and intramyocardial lipid accumulation, were observed in ISO-treated rats. ISO administration induced alterations in the activities of enzymes/expressions that played a significant role in altering lipid metabolism. However, NKT treatment favorably modulated all biochemical and molecular parameters altered by ISO and showed protective effects against oxidative stress, dyslipidemia, and altered lipid metabolism, attributed to its free-radical-scavenging and antihyperlipidemic activities in rats with ISO-induced MI. Additionally, NKT decreased the accumulation of lipids in the myocardium as evidenced from Oil red O staining. Furthermore, the in vitro observations demonstrate the potent antioxidant property of NKT. The present study findings are suggestive of the protective effects of NKT on dyslipidemia and the underlying mechanisms. Based on our findings, it can be suggested that NKT or plants rich in NKT can be promising for use as a phytopharmaceutical or nutraceutical in protecting the heart and correcting lipid abnormalities and dyslipidemia, which are risk factors for ischemic heart diseases.

Loss of Rubicon ameliorates doxorubicin-induced cardiotoxicity through enhancement of mitochondrial quality

BackgroundThe therapeutic potential of doxorubicin (DOX) is limited by cardiotoxicity. Rubicon is an inhibitory interacting partner of autophagy protein UVRAG. Currently, the role of Rubicon in DOX-induced cardiotoxicity is unknown. In this study, we test the hypothesis that loss of Rubicon attenuates DOX-induced cardiotoxicity. MethodsA mouse model of acute DOX-induced cardiotoxicity was established by a single intraperitoneal injection of DOX at a dose of 20 mg/kg. Rubicon expression was detected by Western blot. Cardiac damage was determined by measuring activities of lactate dehydrogenase and myocardial muscle creatine kinase in the serum, cytoplasmic vacuolization, collagen deposition, ROS levels, ATP content and mitochondrial damage in the heart. Cardiac morphometry and function were assessed by echocardiography. Markers for autophagy, mitophagy and mitochondrial dynamics were evaluated by Western blot and real time reverse transcription polymerase chain reaction. ResultsRubicon expression was reduced in the heart 16 h after DOX treatment. DOX induced accumulation of cytoplasmic vacuolization and collagen, increased serum activities of lactate dehydrogenase and myocardial muscle creatine kinase, enhanced ROS levels, reduced ATP content, pronounced mitochondrial damage and greater left ventricular wall thickness in wild type mice, which were mitigated by Rubicon deficiency. Mechanistically, loss of Rubicon improved DOX-induced impairment of autophagic flux, Parkin-mediated mitophagy and mitochondrial fission and fusion in the heart. ConclusionsLoss of Rubicon ameliorates DOX-induced cardiotoxicity through enhancement of mitochondrial quality by improving autophagic flux, mitophagy and mitochondrial dynamics. Rubicon is a potential molecular target for prevention and therapy of DOX cardiotoxicity.

Localized rest and stress human cardiac creatine kinase reaction kinetics at 3T.

Changes in the kinetics of the creatine kinase (CK) shuttle are sensitive markers of cardiac energetics but are typically measured at rest and in the prone position. This study aims to measure CK kinetics during pharmacological stress at 3 T, with measurement in the supine position. A shorter “stressed saturation transfer” (StreST) extension to the triple repetition time saturation transfer (TRiST) method is proposed. We assess scanning in a supine position and validate the MR measurement against biopsy assay of CK activity. We report normal ranges of stress CK forward rate (kf CK) for healthy volunteers and obese patients.TRiST measures kf CK in 40 min at 3 T. StreST extends the previously developed TRiST to also make a further kf CK measurement during <20 min of dobutamine stress. We test our TRiST implementation in skeletal muscle and myocardium in both prone and supine positions. We evaluate StreST in the myocardium of six healthy volunteers and 34 obese subjects. We validated MR‐measured kf CK against biopsy assays of CK activity.TRiST kf CK values matched literature values in skeletal muscle (kf CK = 0.25 ± 0.03 s−1 vs 0.27 ± 0.03 s−1) and myocardium when measured in the prone position (0.32 ± 0.15 s−1), but a significant difference was found for TRiST kf CK measured supine (0.24 ± 0.12 s−1). This difference was because of different respiratory‐ and cardiac‐motion‐induced B0 changes in the two positions. Using supine TRiST, cardiac kf CK values for normal‐weight subjects were 0.15 ± 0.09 s−1 at rest and 0.17 ± 0.15 s−1 during stress. For obese subjects, kf CK was 0.16 ± 0.07 s−1 at rest and 0.17 ± 0.10 s−1 during stress. Rest myocardial kf CK and CK activity from LV biopsies of the same subjects correlated (R = 0.43, p = 0.03).We present an independent implementation of TRiST on the Siemens platform using a commercially available coil. Our extended StreST protocol enables cardiac kf CK to be measured during dobutamine‐induced stress in the supine position.

Isoquercetin ameliorates myocardial infarction through anti-inflammation and anti-apoptosis factor and regulating TLR4-NF-κB signal pathway.

The aim of the present study was to investigate the protective mechanisms and identify the effects of isoquercetin on myocardial infarction in a rat model of acute myocardial infarction (AMI). Isoquercetin ameliorated myocardial infarct size, creatine kinase (CK), CK‑MB and lactic dehydrogenase activity and inhibited inflammation, oxidative stress and heart cell apoptosis in a rat with AMI. Isoquercetin increased endothelial nitric oxide synthase, reduced inducible nitric oxide synthase levels and suppressed the Toll-like receptor 4‑nuclear factor (TLR4‑NF)‑κB signaling pathway in a rat with AMI. Overall, isoquercetin ameliorated AMI through anti‑inflammatory and anti‑apoptotic factors, and regulation of the TLR4‑NF‑κB signaling pathway. Isoquercetin may therefore potentially exert a protective effect against AMI or other heart diseases.

UVRAG Deficiency Exacerbates Doxorubicin-Induced Cardiotoxicity

Doxorubicin (DOX) is an effective chemotherapeutic drug in the treatment of various types of cancers. However, its clinical application has been largely limited by potential development of cardiotoxicity. Previously we have shown that ultra-violet radiation resistance-associated gene (UVRAG), an autophagy-related protein, is essential for the maintenance of autophagic flux in the heart under physiological conditions. Here, we sought to determine the role of UVRAG-mediated autophagy in DOX-induced cardiotoxicity. Mouse models of acute or chronic DOX-induced cardiotoxicity were established. UVRAG deficiency exacerbated DOX-induced mortality and cardiotoxicity manifested by increased cytoplasmic vacuolization, enhanced collagen accumulation, elevated serum activities of lactate dehydrogenase and myocardial muscle creatine kinase, higher ROS levels, aggravated apoptosis and more depressed cardiac function. Autophagic flux was impaired in DOX-induced cardiotoxicity. UVRAG deficiency aggravated impaired autophagic flux in DOX-induced cardiotoxicity. Intermittent fasting restored autophagy and ameliorated pathological alterations of DOX-induced cardiotoxicity. Collectively, our data suggest that UVRAG deficiency exacerbates DOX-induced cardiotoxicity, at least in part, through aggravation of DOX-induced impaired autophagic flux. Intermittent fasting, which restores blunted autophagic flux and ameliorates pathology in the mouse models of DOX-induced cardiotoxicity, may be used as a potential preventive or therapeutic approach for DOX cardiotoxicity.

Mitochondrial ATP-sensitive K+ channels mediate the antioxidative influence of diosgenin on myocardial reperfusion injury in rat hearts.

The contribution of reactive oxygen species and oxidative stress in the pathogenesis of ischemia-reperfusion (I/R) injury has been supported by many studies. The effect of diosgenin on oxidative stress induced by I/R injury was evaluated in this study. Rat hearts were subjected to 30 minutes of global ischemia followed by 90 minutes of reperfusion. 5-hydroxydecanoate (5-HD) was used before administration of diosgenin and before ischemia. The activities of myocardial creatine kinase (CK), malondialdehyde (MDA), superoxide dismutase (SOD) and glutathione peroxidase (GPX) were measured. Administration of diosgenin before ischemia significantly lowered CK and MDA levels as compared with control group (p < 0.05) and increased GPX (p < 0.05) and SOD (p < 0.01) activities in comparison with control group. Pre-administration of 5-HD significantly attenuated the protective effects of diosgenin. In conclusion, opening of mitochondrial ATP-sensitive K(+) channels and attenuating of oxidative stress can be suggested as underlying mechanisms for cardioprotective effect of diosgenin in I/R injury.

Seamless networks of myocardial bioenergetics

Seamless networks of myocardial bioenergetics

Cardioprotective effect of MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one) during acute ischemia-reperfusion injury in rats

MCI-186 (3-methyl-1-phenyl-2-pyrazolin-5-one), a free radical scavenger, has the ability to stimulate prostacyclin release and to inhibit the lipoxygenase pathway in the arachidonic acid cascade. The authors investigated the cytoprotective effect of MCI-86 in a reperfusion model of myocardial ischemia. Rats were subjected to occlusion of the left coronary artery for ten minutes followed by reperfusion for twenty-four hours. The loss of myocardial creatine kinase activity (CK) from the left ventricular free wall (LVFW) twenty-four hours after the induction of myocardial ischemia was used as an index of ischemic damage. Administration of MCI-186 (3 mg/kg IV) significantly blunted the depletion of LVFW-CK activity when compared with vehicle (MCI-186 vs vehicle, 31.5 ± 1.1 vs 26.5 ± 1.2 U/mg protein, respectively,p<0.01). In another group of rats that underwent coronary artery occlusion—reperfusion, infarct size was measured by planimetry on histologic sections of serial slices of the left ventricle and was found to be 20.0 ± 1.3% of the left ventricle in vehicle-treated rats and 10.7 ± 1.3% in MCI-186 (3 mg/kg)-treated rats (p<0.01). These results indicate the potential usefulness of MCI-186 in myocardial ischemia-reperfusion injury.

Prognostic Impact of Early ST-Segment Resolution and Biochemical Markers in Patients With ST-Elevation Myocardial Infarction

Refer to the page 372-378 Considerable variability exists for the reported mortality risk among patients with ST-elevation myocardial infarction (STEMI) and who are treated with primary percutaneous coronary intervention (PCI). The diversity in the clinical out comes for these patients challenges the physician at each step: risk stratification, planning the treatment and monitoring the response to PCI. In this regard, the current guidelines for the treatment of patients with acute coronary syndrome (ACS) recommend risk stratification using a variety of clinical vari ables. Clinical variables such as biomarkers, electrocardiography (ECG), and the imaging modalities have been studied for whether these variables may improve the risk assessment and clinical care. The standard 12-lead ECG has been used as the single most important diagnostic tool for the evaluation of ACS. Measurement via ECG is very useful and informative for determining the quality of reperfusion in patients with acute STEMI. The degree of ST segment deviation also confers prognostic information. 1) Since it was first documented in 1971 in an animal study that the magnitude of ST segment elevation was well correlated well with depressed myocardial creatine kinase activity as well as myocardial necrosis, 2) the degree of ST segment elevation has been used as an

Effects of different concentrations of nitroglycerin on ischemia-reperfusion injury in isolated rat hearts

Objective To investigate the effects of different concentrations of nitroglycerin on ischemia-reperfusion (IR) injury in the isolated rat hearts. Methods Healthy adult male SD rats 7 weeks old weighing 220-330 g were anesthetized with intraperitoneal pentobarbital 50 mg/kg. Their hearts were excised and perfused in a Langendorff apparatus. Thirty isolated hearts were randomly divided into 3 groups (n = 10 each) : group 1R, low-concentration nitroglycerin group (group LN) and high-concentration nitroglycerin group (group HN). The hearts in group IR were perfnsed with plain modified K-H solution. The hearts in group LN were perfused with K-H solution containing nitroglycerin 2.5 μg/L. The hearts in group HN were perfnsed with K-H solution containing nitroglycerin 25 μg/L. After 15 min of post-preparation equilibration, IR was induced by 20 min suspension of perfusion followed by 60 min reperfusion. HR, left ventricular end-diastolic pressure (LVEDP), coronary flow (CF), left ventricular developed pressure (LVDP), + dp/dtmax, and - dp/dtmax were measured at 10, 20, 30, 40, 50 and 60 min of reperfusion. To determine the activities of myocardial lactate dehydrogenase (LDH) and creatine kinase (CK), 1.5 ml of coronary effluent was collected at the end of equilibration, and at 5, 30 and 60 min of reperfusion. At 60 min of reperfusion, myocardial tissues were obtained to determine myocardial infarct size (IS) (by Trc staining) and assess the apoptosis rate (by TUNAL technique) .Results Compared with group IR, HR, CF, LVDP, + dp/dtmax and - dp/dtmax were significantly increased in group LN, while significantly decreased in group HN, and LVEDP, activities of CK and LDH in the coronary effluent, myocardial IS and apoptosis rate were significantly decreased in group LN, while significantly increased in group HN (P < 0.05). Compared with group LN, HR, CF, LVDP, + dp/dtmax and - dp/dtmax were significantly decreased, and LVEDP, activities of CK and LDH in the coronary effluent, myocardial IS and apoptosis rate significantly increased in group HN (P < 0. 05). Conclusion Low-concentration nitroglycerin can attenuate myocardial IR injury in isolated rat hearts, but high-concentration nitroglycerin can exacerbate the injury. Key words: Nitroglycerin; Myocardial reperfusion injury

Increased myocardial energy reservation by creatine supplementation and estrogen replacement in exercise-trained ovariectomized hamsters

Background: Menopause in elder women may induce various dysfunctions in the cardiovascular system. Previous studies show that creatine (Cr) supplementation, estrogen (E₂) replacement, or exercise training are effective for cardiac performance. Objective: To examine the combined effect of Cr and/or E₂ with exercise training on myocardial energy reservation, using ovariectomized female hamsters. Materials and methods: Female Golden Syrian hamsters were used for this study. A hundred ovariectomized hamsters were divided into no-exercise and exercise-trained groups, in which each group was separated into control (n=10), Cr depletion (Cr-; n=10), Cr supplementation (Cr+; n=10), E₂ replacement (E₂; n=10) and Cr supplementation combined with E₂ replacement (Cr+E₂; n=10). In the exercise-trained group, wheel-running exercise (10 min. a day, 5 days a week) was imposed for 9 weeks, and the exercise metabolic rate (EMR) was measured. After the animals were sacrificed, the right ventricles were cut and weighed, which were rapidly frozen in liquid nitrogen for storage at -70°C. The contents of Cr, phosphocreatine (PCr), total Cr (TCr) and creatine kinase (CK) activities were measured, using the spectrophotometric method. Creatine transporter protein (CrT) was measured by Western blotting. Results: Cr+ or E₂ combined with exercise training yielded greater accumulation of all myocardial metabolic phosphate contents, CK activity and CrT protein than Cr+ or E₂ alone. All parameters regulating myocardial Cr metabolism improved greatly in Cr+ plus E₂ combined with exercise training. Conclusion: Creatine supplementation and estrogen replacement, when combined with exercise training, become more effective for myocardial energy reservation via in estrogen-deficient hamsters.

Sildenafil citrate increases myocardial cGMP content in rat heart, decreases its hypertrophic response to isoproterenol and decreases myocardial leak of creatine kinase and troponin T

BackgroundCardiac hypertrophy is a major risk factor for morbidity and mortality in a number of cardiovascular diseases. Consequently, the signaling pathways that inhibit cardiac hypertrophy are currently receiving much interest. Among them, nitric oxide (NO), signaling via cGMP and cGMP-dependent protein kinase I, has been recognized as a negative regulator of cardiac hypertrophy. The present study investigated the in-vivo effect of sildenafil as a phosphodiestrase-5A (PDE-5A) inhibitor on the hypertrophic response of rat heart to isoproterenol and the relation of this effect to the level of myocardial cGMP and integrity of the constitutive nitric oxide synthase (cNOS) activity.ResultsThe results showed that daily intraperitoneal administration of sildenafil per se for 10 days was without noticeable adverse effects on survival or myocardium. Conversely, daily subcutaneous administration of isoproterenol for 10 days caused significant myocardial hypertrophy, cell injury and decline in survival. When sildenafil was injected daily, one hour before isoproterenol, survival was significantly improved and the myocardium didn't show significant hypertrophy or cell injury. Interestingly, sildenafil was accompanied by significant rise in myocardial cGMP level, a parameter which was found in the present study to possess a significant negative correlation with cardiac hypertrophy and leak of cardiac troponin T into serum. At the same time, cGMP was found to possess a positive correlation with myocardial creatine kinase activity that reflects the efficiency of the energy utilization processes in the myocardium. However, in rats given Nω-nitro-L-arginine (L-NNA) as a competitive inhibitor of cNOS, sildenafil failed to show any favorable effect on survival or the myocardial injury parameters used to assess isoproterenol-induced injury.ConclusionThe present study suggests that increased cardiac cGMP level by sildenafil have a cardioprotective effect probably through acting as a post-receptor negative regulator of cardiac sympathetic responsiveness. Integrity of NOS function was an essential prerequisite for sildenafil's mediated cardioprotection encountered in the present study.

Myocardial creatine kinase expression after left ventricular assist device support

ObjectivesWe examined whether unloading of the left ventricle with a ventricular assist device (LVAD) can result in normalization of the creatine kinase (CK) abnormalities in the failing human heart. BackgroundLeft ventricular failure is associated with a decrease of myocardial total CK activity and a fetal shift in CK isoform expression that results in an increase in the cytosolic brain type homodimeric-creatine kinase (CK-B) subunit and decreases of the cytosolic muscle-creatine kinase (CK-M) and CK-mitochondrial (CK-Mt) isoforms. The mechanisms of this abnormality are not known. MethodsTotal CK activity and CK protein isoform expression (Western blotting) were examined in 11 patients with end-stage cardiomyopathy. In 7 patients, myocardial tissue was also obtained after 4.1 ± 1.1 months of left ventricular assist device (LVAD) support. ResultsLeft ventricular unloading produced by LVAD implantation resulted in a 270% ± 114% increase in total CK activity (p < 0.01) that was associated with a 69% ± 18% increase in CK-M protein expression (p < 0.01) and a 121% ± 69% increase in CK-Mt protein expression (p < 0.01), but no significant change in CK-B expression. ConclusionsSystolic and diastolic unloading provided by the LVAD resulted in increases of total CK activity as well as CK-Mt and CK-M protein expression. The failure of CK-B expression to decrease suggests that abnormalities other than increased loading are responsible for the increase in CK-B expression in the failing heart.

Exercise training increases creatine kinase capacity in canine myocardium.

The creatine kinase (CK) energy shuttle of cardiomyocytes channels metabolic energy from the mitochondria to sites of energy utilization at contracting myofibrils and sarcolemmal and sarcoplasmic reticular ion pumps. Although plasticity of the myocardial CK system in response to hemodynamic overload has been repeatedly demonstrated, the effects of aerobic exercise training on myocardial CK are less well understood. This investigation tested the hypothesis that aerobic exercise training increases the capacity of the CK system in canine myocardium. Mongrel dogs were conditioned by a 9-wk treadmill running program or cage-rested for 4 wk. Total CK activity was measured colorimetrically; CK(MB) was separated from other CK isoforms and measured by electrophoresis. Relative to sedentary controls, training increased left ventricular total CK activity 46% (P < 0.05) but did not alter total CK activity in right ventricular myocardium. Also in left ventricular myocardium, training increased CK(MB) isoenzyme activity 4.5-fold and the CK(MB) fraction of total CK threefold from 1.1+/-0.4 to 3.4+/-0.8% (P < 0.05). In contrast to left ventricle, CK(MB) activity and its fraction of total CK activity were not altered by training in right ventricular myocardium. Aerobic exercise training increases total myocardial CK activity and CK(MB) content in canine left ventricular myocardium, although CK(MB) remains a minor component of the myocardial CK system. The right ventricular CK system was not affected by training.

Elucidation of a tripartite mechanism underlying the improvement in cardiac tolerance to ischemia by coenzyme Q 10 pretreatment

Coenzyme Q 10 , which is involved in mitochondrial adenosine triphosphate production, is also a powerful antioxidant. We hypothesize that coenzyme Q 10 pretreatment protects myocardium from ischemia reperfusion injury both by its ability to increase aerobic energy production and by protecting creatine kinase from oxidative inactivation during reperfusion. Isolated hearts (six per group) from rats pretreated with either coenzyme Q 10 , 20 mg/kg intramuscularly and 10 mg/kg intraperitoneally (treatment) or vehicle only (control) 24 and 2 hours before the experiment were subjected to 15 minutes of equilibration, 25 minutes of ischemia, and 40 minutes of reperfusion. Developed pressure, contractility, compliance, myocardial oxygen consumption, and myocardial aerobic efficiency were measured. Phosphorus 31 nuclear magnetic resonance ( 31 P-NMR) spectroscopy was used to determine adenosine triphosphate and phosphocreatine concentrations as a percentage of a methylene diphosphonic acid standard. Hearts were assayed for myocardial coenzyme Q 10 and myocardial creatine kinase activity at end equilibration and at reperfusion. Treated hearts showed higher myocardial coenzyme Q 10 levels (133 ± 5 μg/gm ventricle versus 117 ± 4 μg/gm ventricle, p < 0.05). Developed pressure at end reperfusion was 62% ± 2% of equilibration in treatment group versus 37% ± 2% in control group, p < 0.005. Preischemic myocardial aerobic efficiency was preserved during reperfusion in treatment group (0.84 ± 0.08 mm Hg/(μl O 2 /min/gm ventricle) vs 1.00 ± 0.08 mm Hg/(μl O 2 /min/gm ventricle) at equilibration, p = not significant), whereas in the control group it fell to 0.62 ± 0.07 mm Hg/(μl O 2 /min/gm ventricle, p < 0.05 vs equilibration and vs the treatment group at reperfusion. Treated hearts showed higher adenosine triphosphate and phosphocreatine levels during both equilibration (adenosine triphosphate 49% ± 2% for the treatment group vs 33% ± 3% in the control group, p < 0.005; phosphocreatine 49% ± 3% in the treatment group vs 35% ± 3% in the control group, p < 0.005) and reperfusion (adenosine triphosphate 18% ± 3% in the treatment group vs 11% ± 2% in the control group, CTRL p < 0.05; phosphocreatine 45% ± 2% in the treatment group vs 23% ± 3% in the control group, p < 0.005). Creatine kinase activity in treated hearts at end reperfusion was 74% ± 3% of equilibration activity vs 65% ± 2% in the control group, p < 0.05). Coenzyme Q 10 pretreatment improves myocardial function after ischemia and reperfusion. This results from a tripartite effect: (1) higher concentration of adenosine triphosphate and phosphocreatine, initially and during reperfusion, (2) improved myocardial aerobic efficiency during reperfusion, and (3) protection of creatine kinase from oxidative inactivation during reperfusion. (J T HORAC C ARDIOVASC S URG 1996;111:443-50)

New collateral flow increasing early after coronary occlusion prevented myocardial necrosis in dogs.

Increases in regional myocardial blood flow (Qm) developing soon after myocardial infarction may minimize myocardial necrosis. To test this hypothesis, Qm in the area surrounding an acutely occluded coronary artery was determined successively over 4 weeks in 11 dogs. Non-radioactive colored microspheres were injected into the left atrium 5 s (Qm at this time is referred to as Q1), 3 h (Q2), 12 h (Q3), and 4 weeks (Q4) after occlusion of the coronary artery. After termination of the experiment, the heart was removed, and Qm and three indices of myocardial necrosis i.e., myocardial creatine kinase activity (CK), infarct size determined by triphenyl tetrazolium chloride stain (TTC), and myocardial fibrosis visualized by Azan-Mallory stain, were determined. Each Qm was expressed as a percentage of normal: Qm (% of normal) = [Q/Qc] ischemic area/[Q'/Qc']non-ischemic area x 100, where Qc indicates Qm determined before coronary occlusion. In the ischemic area of the left ventricle, Q1, Q2, Q3, and Q4 were 25 +/- 3%, 30 +/- 3%, 31 +/- 3%, and 42 +/- 3% of normal, respectively, in the inner layer, and 31 +/- 3%, 52 +/- 4%, 52 +/- 4%, and 77 +/- 6% of normal, respectively, in the outer layers. During the 4-week period, the increase of Qm in the outer layer was greater than that in the inner layer. The inner layer showed a small increase of flow from Q3 to Q4 (9 +/- 2%), but in the outer layer there were greater flow increases from Q1 to Q2 (21 +/- 3%) and from Q3 to Q4 (24 +/- 6%).(ABSTRACT TRUNCATED AT 250 WORDS)

The Cumulative Nature of Pyruvate's Dual Mechanism for Myocardial Protection

Pyruvate (PYR) supplementation protects myocardium from ischemia reperfusion injury. This study was designed to characterize and quantify the mechanism underlying this protection: specifically whether this ability resides in PYR's metabolic effect or in its antioxidant effect. Isolated perfused rat hearts ( n = 6/group) were subjected to 15 min of equilibration (EQ), 25 min of ischemia, and 10 min of reperfusion (RP). Glucose was the sole metabolic substrate (Control) or was supplemented with PYR (5 m M) during (a) EQ only (PYR EQ group), (b) RP only (PYR RP group), or (c) EQ and RP (PYR EQ-RP group). Left ventricular developed pressure (DP) and ± dP/dt were recorded throughout the experiment. ATP concentrations and intracellular pH were determined by 31P NMR spectroscopy. Myocardial creatine kinase (CK) activity was assayed at end EQ and end RP. In vitro, purified CK was assayed and, after exposure to H 2O 2 (200 μ M) and increasing concentrations of PYR (0-6 m M) for 10 min, reassayed to determine the antioxidant effect of PYR. In all cases PYR improved recovery of mechanical function at end RP (DP: Control, 11 ± 1%; PYR RP, 23 ± 6%; PYR EQ, 34 ± 8%; PYR EQ&RP, 53 ± 7%; P < 0.05 between all groups and Control). Ischemic contracture was delayed in hearts that received PYR during EQ (PYR EQ and PYR EQ&RP: 17.8 ± 0.2 vs 12.5 ± 0.3 min, P < 0.001). PYR during EQ (PYR EQ and PYR EQ&RP) led to higher end ischemic ATP levels (32 ± 4% vs 14 ± 3%, P < 0.001) and a more acidic end ischemic pH (5.92 ± 0.02 vs 5.98 ± 0.03 in Control and PYR RP, P < 0.05). PYR EQ&RP showed the highest end reperfusion ATP levels (55 ± 7% vs 38 ± 4 %, P < 0.05 vs other groups). PYR during reperfusion (PYR EQ&RP and PYR RP) showed more end reperfusion CK activity (501 ± 9 IU/gV vs 446 ± 13 IU/gV, P < 0.001). In vitro, CK exposure to H 2O 2 abolished 65 ± 6% of its activity, while in the presence of PYR 6 mM abolished only 9 ± 2% ( P < 0.001). We conclude that PYR given during EQ stimulates anaerobic glycolysis during ischemia as seen by the lower pH and higher end ischemic ATP with a correlative delay in onset of contracture and improvement in DP at end RP. PYR during RP protects CK from hydrogen peroxide-induced inactivation and improves recovery of function. PYR given during EQ and RP has a cumulative effect leading to an even greater recovery of function. PYR must be present both prior to ischemia and during reperfusion for best utilization of its metabolic and antioxidant effects.

The effect of radiofrequency catheter ablation on myocardial creatine kinase activity.

The primary mechanism of myocardial injury during radiofrequency (RF) catheter ablation in the heart is presumed to be thermal. Creatine kinase has been measured in serum to assess the volume of myocardial injury after ablation. However, its thermal inactivation by RF ablation could lead to underestimation of the true volume of injury. Serial RF lesions were created in 10 canine left ventricles in vivo, and serial serum creatine kinase activities were measured and compared to lesion volume. To assess the stability of myocardial creatine kinase during RF catheter ablation, 29 RF ablations were made on the epicardial surface of porcine left ventricle in vivo and a 2-mm core biopsy was rapidly removed. The cores were rapidly frozen, sectioned longitudinally in 1-mm slices, and homogenized in 0.3 M Tris buffer solution containing EDTA and dithiothreitol for subsequent analysis of creatine kinase activity. An additional 19 tissue cores from RF lesions were stained and used to determine mean lesion depth. Normal tissue biopsies were exposed to 60 seconds of hyperthermia (37 degrees to 85 degrees C, n = 190), or high-density RF current at 50 degrees C (0 to 100 mA/mm2, n = 50), and tissue creatine kinase activity was measured. There was no evidence of creatine kinase washout within the first 2 hours, and peak values were measured 5 to 7 hours postablation. Tissue creatine kinase activity in the first mm depth of RF lesions averaged 10% of control values and increased over the first 5 mm of lesion depth. The mean creatine kinase activity within the hemisphere of ablated myocardium was calculated to be 31% of control. Creatine kinase activity declined significantly at temperatures above 65 degrees C, but no difference in tissue creatine kinase activity was observed among differing levels of RF current exposure in the absence of significant heating. Creatine kinase activity in myocardial tissue is significantly diminished within the RF lesion. Creatine kinase activity is not stable at temperatures above 65 degrees C, which are routinely achieved within the central zone of RF ablation, and is unaffected by RF current in the absence of hyperthermia. Measurements of serum creatine kinase activity after RF catheter ablation may significantly underestimate the volume of myocardial injury.

Platelet-Derived Adenosine Contributes to the Cardioprotective Effects of Platelets Against Ischemia-Reperfusion Injury in Isolated Rat Heart

Platelets have been shown to protect isolated perfused rat hearts from injury and dysfunction after ischemia and reperfusion. We examined the role of platelet-derived adenosine in the cardioprotective effects of platelets against reperfusion injury. Isolated perfused rat hearts were subjected to 40-min global ischemia followed by 30-min reperfusion. The buffer-perfused hearts developed dysfunction, as indicated by 40 +/- 4% decrease in force of cardiac contraction (FCC) and 24 +/- 3% increase in coronary perfusion pressure (CPP). Creatine kinase (CK) was released in coronary effluent during reperfusion, indicating myocardial injury. At the end of reperfusion, myocardial CK content and superoxide dismutase (SOD) activity were lower than in sham ischemia-reperfused hearts. Perfusion of hearts with washed platelets resulted in protection against myocardial dysfunction and injury after ischemia and reperfusion, indicated by preservation of FCC (-2 +/- 5%) and CPP (-3 +/- 2%) (both p < 0.01 vs. buffer-perfused hearts). Myocardial CK and SOD activity were also preserved, and release of CK in the coronary effluent was minimal (all p < 0.05 vs. buffer-perfused hearts). The cardioprotective effects of platelets were attenuated by preincubation of platelets with adenosine deaminase. Perfusion with adenosine or the adenosine2 receptor agonist N6-[2-(3,5-dimethoxyphenyl)-2-(2- methylphenyl)-ethyl]adenosine (DPMA) also protected heart from myocardial dysfunction and injury after ischemia and reperfusion. Both adenosine and DPMA had salutary effects on indexes of cardiac injury. Platelet-derived adenosine contributes at least in part to the cardioprotective effects of platelets against ischemia and reperfusion in isolated rat heart.