Preischemic and postischemic administration of AEOL10113 reduces infarct size in a rat model of myocardial ischemia and reperfusion

Reactive oxygen species (ROS) have been implicated as important mediators of cellular damage during ischemia/reperfusion. AEOL10113 is a low-molecular-weight superoxide dismutase mimetic that has dismutase activity against ROS. The objective of this study was to test the cardioprotective efficacy of postischemic administration of AEOL10113 in a rat model of left ventricular ischemia and reperfusion. Left ventricular infarction was produced by 25 min of left coronary artery occlusion followed by 3 h of reperfusion. Infarct size (IS) is reported as IS/area at risk (AAR). The control group had an IS/AAR of 67.5 +/- 2.6%. Postischemic administration of AEOL10113 beginning 5 min prior to reperfusion at doses of 0.03, 0.1, and 0.3 mg/kg resulted in an IS/AAR of 69.3 +/- 3.4%, 57.8 +/- 3.3% (P < 0.05), and 55.0 +/- 2.9% (P < 0.05), respectively. Preischemic administration of AEOL10113 beginning 5 min prior to occlusion at a dose of 0.3 mg/kg resulted in an IS/AAR of 44.2 +/- 5.9% (P < 0.0125). AAR as a percentage of the left ventricle and rate-pressure product were unaffected by any dose tested. The data from this study demonstrate that pre- and postischemic administration of AEOL10113 reduces IS in a rat model of myocardial ischemia and reperfusion.     

Defibrotide reduces infarct size in a rabbit model of experimental myocardial ischaemia and reperfusion.

1. Defibrotide, a single-stranded polydeoxyribonucleotide obtained from bovine lungs, has significant anti-thrombotic, pro-fibrinolytic and prostacyclin-stimulating properties. 2. The present study was designed to evaluate the effects of defibrotide on infarct size and regional myocardial blood flow in a rabbit model of myocardial ischaemia and reperfusion. 3. Defibrotide (32 mg kg-1 bolus + 32 mg kg-1 h-1, i.v.) either with or without co-administration of indomethacin (5 mg kg-1 x 2, i.v.) was administered 5 min after occlusion of the left anterior-lateral coronary artery and continued during the 60 min occlusion and subsequent 3 h reperfusion periods. 4. Defibrotide significantly attenuated the ischaemia-induced ST-segment elevation and abolished the reperfusion-related changes (R-wave reduction and Q-wave development) in the electrocardiogram. In addition, defibrotide significantly improved myocardial blood flow in normal and in ischaemic, but not in infarcted sections of the heart. The improvement in blood flow in normal perfused myocardium, but not in the ischaemic area was prevented by indomethacin. 5. Although the area at risk was similar in all animal groups studied, defibrotide treatment resulted in a 51% reduction of infarct size. Indomethacin treatment abolished the reduction of infarct size seen with defibrotide alone. 6. The data demonstrate a considerable cardioprotective effect of defibrotide in the reperfused ischaemic rabbit myocardium. This effect may be related, at least in part, to a stimulation of endogenous prostaglandin formation. Other possible mechanisms are discussed.     

Opioid receptor agonist Eribis peptide 94 reduces infarct size in different porcine models for myocardial ischaemia and reperfusion

Eribis peptide 94 (EP 94) is a novel enkephalin analog, thought to interact with the μ- and δ-opioid receptors. The purpose of the present study was to examine the cardioprotective potential of EP 94 in two clinically relevant porcine models of myocardial ischaemia and reperfusion, and to investigate if such an effect is associated with an increased expression of endothelial nitric oxide synthase (eNOS). Forty-one anesthetized pigs underwent 40min of coronary occlusion followed by 4h of reperfusion. In Protocol I, balloon occlusion of the left anterior descending artery was performed with concurrent intravenous administration of (A) vehicle (n=7), (B) EP 94 (1ug/kg) after 5, 12, 19 and 26min of ischaemia (n=4) or (C) EP 94 (1ug/kg) after 26, 33, 40min of ischaemia (n=6). In Protocol II, open-chest pigs were administered (D) vehicle (n=6) or (E) 0.2ug/kg/min of EP 94 (n=6) through an intracoronary infusion into the jeopardized myocardium, started after 30min of ischaemia and maintained for 15min. The hearts were stained and the protein content of eNOS measured. EP 94 reduces infarct size when administered both early and late during ischaemia compared with vehicle (infarct size group A 61.6±2%, group B 50.2±3% and group C 49.2±2%, respectively, P<0.05), as well as when infused intracoronary (infarct size group D 82.2±3.9% and group E 61.2±2.5% respectively, P<0.01). Phosphorylated eNOS Ser(1177) in relation to total eNOS was significantly increased in the group administered EP 94, indicating activation of nitric oxide production.     

Magnolol reduces myocardial ischemia/reperfusion injury via neutrophil inhibition in rats.

The accumulation of oxygen-free radicals and activation of neutrophils are strongly implicated as important pathophysiological mechanisms mediating myocardial ischemia/reperfusion injury. It has been proven that various antioxidants have cardioprotective effects. Magnolol, an active component extracted from the Chinese medicinal herb Magnolia officinalis, possesses potent antioxidant and free radical scavenging activities. In this study, the cardioprotective activity of magnolol was evaluated in an open-chest anesthetized rat model of myocardial ischemia/reperfusion injury. The results demonstrated that pretreatment with magnolol (0.2 and 0.5 microg/kg, i.v. bolus) at 10 min before 45 min of left coronary artery occlusion, significantly suppressed the incidence of ventricular fibrillation and mortality when compared with the control group. Magnolol (0.2 and 0.5 microg/kg) also significantly reduced the total duration of ventricular tachycardia and ventricular fibrillation. After 1 h of reperfusion, pretreatment with magnolol (0.2 and 0.5 microg/kg) caused a significant reduction in infarct size. In addition, magnolol (0.2 microg/kg) significantly reduced superoxide anion production and myeloperoxidase activity, an index of neutrophil infiltration in the ischemic myocardium. In addition, pretreatment with magnolol (0.2 and 0.5 microg/kg) suppressed ventricular arrhythmias elicited by reperfusion following 5 min of ischemia. In vitro studies of magnolol (5, 20 and 50 microM) significantly suppressed N-formylmethionyl-leucyl-phenylalanine (fMLP; 25 nM)-activated human neutrophil migration in a concentration-dependent manner. It is concluded that magnolol suppresses ischemia- and reperfusion-induced ventricular arrhythmias and reduces the size of the infarct resulting from ischemia/reperfusion injury. This pronounced cardioprotective activity of magnolol may be mediated by its antioxidant activity and by its capacity for neutrophil inhibition in myocardial ischemia/reperfusion.     

Effects of cariporide (HOE642) on myocardial infarct size and ventricular arrhythmias in a rat ischemia/reperfusion model: comparison with other drugs

The effects of pretreatment with cariporide on myocardial infarction and ventricular arrhythmias in a rat model of ischemia/reperfusion were compared with those of nicorandil, propranolol, and nifedipine. Each drug was administered intravenously before coronary occlusion. Cariporide at 0.1, 0.3, and 1 mg/kg significantly reduced the infarct size (infarct mass/risk mass) from 28 +/- 4% (vehicle control value) to 9 +/- 3, 9 +/- 3, and 5 +/- 2%, respectively. Propranolol at 2.5 mg/kg also significantly reduced the infarct size to 11 +/- 1%. Neither nicorandil nor nifedipine was effective when given at 0.1 mg/kg. Cariporide dose dependently decreased the number of ischemia-induced ventricular premature beats (VPB), incidence and duration of ventricular tachycardia, and the number of reperfusion-induced VPB. Nicorandil was effective against only VPB after reperfusion, and propranolol reduced only postischemic arrhythmias, but nifedipine had no effect on either type of arrhythmia. In summary, cariporide reduced the infarct size and dose dependently suppressed arrhythmias induced by ischemia/reperfusion in rats. In contrast, in the present rat model, the doses of the other three drugs used in this study did not show comparable effects.     

Edaravone reduces myocardial infarct size and improves cardiac function and remodelling in rabbits

1. In the present study, we investigated the effect of 3-methyl-1-phenyl-2-pyrazolin-5-one (edaravone), a free radical scavenger, on myocardial infarct (MI) size and cardiac function in an in vivo model of MI in rabbits. We further investigated the contribution of hydroxyl radicals, superoxide and nitric oxide (NO) to its effects. 2. Anaesthetized open-chest Japanese white male rabbits were subjected to 30 min coronary occlusion and 48 h reperfusion. The control group (n = 10) was injected with saline 10 min before reperfusion. The edaravone group (n = 10) was injected with a bolus of 3 mg/kg edaravone 10 min before reperfusion. The edaravone + N(G)-nitro-L-arginine methyl ester (L-NAME) group (n = 5) was given 10 mg/kg, i.v., L-NAME 10 min before the administration of 3 mg/kg edaravone. The L-NAME group (n = 5) was given 10 mg/kg, i.v., L-NAME 20 min before reperfusion. Infarct size was measured using the triphenyl tetrazolium chloride method and is expressed as a percentage of area at risk. Cardiac function was assessed by echocardiography 14 days after infarction. 3. In another series of experiments, rabbits were subjected to 30 min coronary occlusion and 30 min reperfusion and myocardial interstitial 2,3-dihydroxybenzoic acid (DHBA) and 2,5-DHBA levels, indicators of hydroxyl radical, were measured using a microdialysis technique. 4. Infarct size in the edaravone group was significantly reduced compared with that in the control group (27.4 +/- 6.8 vs 43.4 +/- 6.8%, respectively; P < 0.05). The edaravone-induced reduction of infarct size was abolished by pretreatment with L-NAME. Myocardial interstitial levels of 2,3-DHBA and 2,5-DHBA increased 20 and 30 min after ischaemia and peaked at 10 min reperfusion in the control group. Edaravone significantly inhibited the increase in 2,3-DHBA and 2,5-DHBA levels seen during reperfusion. Dihydroethidium staining showing in situ detection of superoxide was less intense in ischaemic myocardium in the edaravone-treated group compared with the control group. Edaravone improved cardiac function and left ventricular remodelling 14 days after infarction. 5. In conclusion, edaravone significantly reduces MI size and improves cardiac function and LV remodelling by decreasing hydroxyl radicals and superoxide in the myocardium and increasing the production of NO during reperfusion in rabbits.     

Non-specific caspase inhibition reduces infarct size and improves post-ischaemic recovery in isolated ischaemic/reperfused rat hearts

Myocardial ischaemia and reperfusion lead to myocardial cell death due, at least in part, to apoptotic mechanisms. Although cysteinyl aspartate-specific proteinase (caspase) activation is a major event and the most-cited culprit in the development of apoptosis, its potential contribution to ischaemic myocardial cell death is largely unknown. To study the role of caspase activation, isolated rat hearts (n=6 per group) were subjected to 30 min coronary artery occlusion followed by 120 min reperfusion. A non-selective [0.1 or 0.5 microM acetyl-Tyr-Val-Ala-Asp chloromethylketone (YVAD-cmk)] or selective caspase inhibitors [0.07 or 0.2 microM acetyl-Asp-Glu-Val-Asp-cmk (Ac-DEVD-cmk, caspase-3 inhibitor); 0.07 or 0.2 microM benzoxycarbonyl-Leu-Glu-OMe-His-Asp(OMe)-fluoromethylketone (z-LEHD-fmk, caspase-9 inhibitor)] were added to the perfusate at the start of reperfusion. Non-selective caspase inhibition with 0.1 or 0.5 microM YVAD-cmk limited infarct size: (21 +/- 4%, P<0.05; 17 +/- 3%, P<0.05, respectively) compared with the ischaemic/reperfused control (32 +/- 5%). In hearts treated with 0.1 or 0.5 microM caspase II non-selective inhibitor, the fraction of terminal-deoxynucleotidyl-transferase deoxyuridine nick end labelling (TUNEL)-positive myocyte nuclei in the infarcted zone was reduced from the ischaemic/reperfused non-treated control of 11.2 +/- 2.1% to 6.2 +/- 1.6% (P<0.05) and 1.2 +/- 0.2% (P<0.05), respectively. The recovery of post-ischaemic cardiac function (coronary flow, aortic flow and left-ventricular developed pressure) improved significantly with the application of the non-selective caspase inhibitor as well. In hearts perfused with specific caspase inhibitors (caspase-3 and caspase-9) there was no significant reduction in the infarct size, no improvement in post-ischaemic cardiac function and no reduction of apoptotic cell death. We conclude that non-specific inhibition of caspases may be therapeutically beneficial in myocardial ischaemia/reperfusion-induced damage, while selective caspase inhibitors may fail to prevent such reperfusion-induced injury in our model system.     

Uridine-5'-triphosphate (UTP) reduces infarct size and improves rat heart function after myocardial infarct

We have previously found that uridine 5'-triphosphate (UTP) significantly reduced cardiomyocyte death induced by hypoxia via activating P2Y(2) receptors. To explore the effect of UTP following myocardial infarction (MI) in vivo we studied four groups: sham with or without LAD ligation, injected with UTP (0.44microg/kg i.v.) 30min before MI, and UTP injection (4.4microg/kg i.v.) 24h prior to MI. Left ventricular end diastolic area (LVEDA), end systolic area (LVESA) fractional shortening (FS), and changes in posterior wall (PW) thickness were performed by echocardiography before and 24h after MI. In addition, we measured different biochemical markers of damage and infarct size using Evans blue and TTC staining. The increase in LVEDA and LVESA of the treated animals was significantly smaller when compared to the MI rats (p<0.01). Concomitantly, FS was higher in groups pretreated with UTP 30min or 24h (56+/-14.3 and 36.7+/-8.2%, p<0.01, respectively). Ratio of infarct size to area at risk was smaller in the UTP pretreated hearts than MI rats (22.9+/-6.6, 23.1+/-9.1%, versus 45.4+/-7.6%, respectively, p<0.001). Troponin T and ATP measurements, demonstrated reduced myocardial damage. Using Rhod-2-AM loaded cardiomyocytes, we found that UTP reduced mitochondrial calcium levels following hypoxia. In conclusion, early or late UTP preconditioning is effective, demonstrating reduced infarct size and superior myocardial function. The resulting cardioprotection following UTP treatment post ischemia demonstrates a reduction in mitochondrial calcium overload, which can explain the beneficial effect of UTP.     

NCX4016 (NO-aspirin) reduces infarct size and suppresses arrhythmias following myocardial ischaemia/reperfusion in pigs

1. The effect of the nitro-derivative of aspirin, NCX4016, was assessed on ischaemic ventricular arrhythmias and myocardial infarct size in anaesthetized pigs in comparison to native aspirin. 2. Pigs were given aspirin (10 mg kg(-1); n=6), low dose NCX4016 (18.4 mg kg(-1); n=6) or high dose NCX4016 (60 mg kg(-1); n=7) orally for 5 days prior to coronary occlusion and reperfusion. None of the interventions had any effect on baseline haemodynamics prior to coronary occlusion in comparison to control pigs (n=9). Aspirin and high dose NCX4016 both prevented the generation of thromboxane A(2) from platelets activated ex vivo with A23187 (30 microM), whereas all three interventions markedly attenuated platelet aggregation in response to collagen in whole blood in comparison to controls. 3. None of the drug interventions had any effect on the incidence of ventricular fibrillation (VF) during myocardial ischaemia (100% in all groups). However, 60 mg kg(-1) NCX4016 significantly attenuated the total number of premature ventricular beats (PVB's) (62+/-16 vs 273+/-40 in control pigs; P<0.05) during the first 30 min of occlusion. The higher dose of NCX4016 also significantly reduced myocardial infarct size (22.6+/-3.7% of area at risk vs 53.0+/-2.8% of area at risk in control pigs; P<0.05). 4. These results suggest that the nitro-derivative of aspirin, NCX4016, is an effective antiplatelet agent, which unlike aspirin also reduces the extent of myocardial injury following ischaemia and reperfusion.     

The pathway-selective estrogen receptor ligand WAY-169916 reduces infarct size after myocardial ischemia and reperfusion by an estrogen receptor dependent mechanism

Previous studies have shown that estrogen treatment protects the heart from reperfusion injury. The adverse effects of long-term estrogen treatment limit its clinical use and emphasize the need for the development of specific pharmacological interventions such as pathway-selective estrogen receptor (ER) ligands. Pathway-selective ER ligands are compounds that retain estrogen's anti-inflammatory ability, but they are devoid of conventional estrogenic action. In the present study, the pathway-selective ER ligand WAY-169916 was assessed for its cardioprotective potential in an in vivo model of ischemia-reperfusion injury. Anesthetized, ovariectomized rabbits were administered WAY-169916 (1 mg/kg), 17beta-estradiol (E2; 20 microg/rabbit), or vehicle intravenously 30 minutes before a 30-minute occlusion and 4 hours of reperfusion. Acute treatment with either WAY-169916 or E2 resulted in a decrease in infarct size, expressed as a percent of area at risk (WAY-169916, 21.2 +/- 3.3; P < 0.001 and E2, 18.8 +/- 1.7; P < 0.001) compared with vehicle 59.4 +/- 5.4). Pretreatment with estrogen receptor antagonist ICI 182,780 significantly limited the infarct size sparing effect of both WAY-169916 and E2 when expressed as a percent of the risk region (WAY 169916, 47.4 +/- 4.4; E2, 53.01 +/- 5.0). The results demonstrate that WAY-169916 protects the heart against ischemia-reperfusion injury through an ER-dependent mechanism.     

UTP reduces infarct size and improves mice heart function after myocardial infarct via P2Y2 receptor

Pyrimidine nucleotides are signaling molecules, which activate G protein-coupled membrane receptors of the P2Y family. P2Y₂ and P2Y₄ receptors are part of the P2Y family, which is composed of 8 subtypes that have been cloned and functionally defined. We have previously found that uridine-5′-triphosphate (UTP) reduces infarct size and improves cardiac function following myocardial infarct (MI). The aim of the present study was to determine the role of P2Y₂ receptor in cardiac protection following MI using knockout (KO) mice, in vivo and wild type (WT) for controls. In both experimental groups used (WT and P2Y₂^−/− receptor KO mice) there were 3 subgroups: sham, MI, and MI + UTP. 24 h post MI we performed echocardiography and measured infarct size using triphenyl tetrazolium chloride (TTC) staining on all mice. Fractional shortening (FS) was higher in WT UTP-treated mice than the MI group (44.7 ± 4.08% vs. 33.5 ± 2.7% respectively, p < 0.001). However, the FS of P2Y₂^−/− receptor KO mice were not affected by UTP treatment (34.7 ± 5.3% vs. 35.9 ± 2.9%). Similar results were obtained with TTC and hematoxylin and eosin stainings. Moreover, troponin T measurements demonstrated reduced myocardial damage in WT mice pretreated with UTP vs. untreated mice (8.8 ± 4.6 vs. 12 ± 3.1 p < 0.05). In contrast, P2Y₂^−/− receptor KO mice pretreated with UTP did not demonstrate reduced myocardial damage. These results indicate that the P2Y₂ receptor mediates UTP cardioprotection, in vivo.     

Caspase inhibition and limitation of myocardial infarct size: protection against lethal reperfusion injury

Ischaemia-reperfusion injury causes cell death by both necrosis and apoptosis. Caspase activation is a major event in apoptosis. We therefore examined the effect of caspase inhibitors during reperfusion upon myocardial infarction. Rat isolated hearts were subjected to 35 min coronary occlusion and 120 min reperfusion. Treatment groups were perfused with caspase inhibitors during early reperfusion. We assessed a non-selective caspase inhibitor (Z-VAD. fmk, 0.1 microM), a caspase-8 inhibitor (Z-IETD.fmk, 0.07 microM), a caspase-9 inhibitor (Z-LEHD.fmk, 0.07 microM) and a caspase-3 inhibitor (Ac-DEVD.cmk, 0.07 microM). All caspase inhibitors limited infarct size (infarct-risk ratio per cent: control 38.5+/-2.6; Z-VAD. fmk 24.6+/-3.4; Z-LEHD.fmk 19.3+/-2.4; Z-IETD.fmk 23.0+/-5.4; Ac-DEVD.cmk 27.8+/-3.3; P<0.05 when compared with control value, 1-way ANOVA). We conclude that caspase inhibition during early reperfusion protects myocardium against lethal reperfusion injury.     

Reduction of myocardial infarct size after ischemia and reperfusion by the glycosaminoglycan pentosan polysulfate.

Activation of the complement system contributes to the tissue destruction associated with myocardial ischemia/reperfusion. Pentosan polysulfate (PPS), a negatively charged sulfated glycosaminoglycan (GAG) and an effective inhibitor of complement activation, was studied for its potential to decrease infarct size in an experimental model of myocardial ischemia/reperfusion injury. Open-chest rabbits were subjected to 30-min occlusion of the left coronary artery followed by 5 h of reperfusion. Vehicle (saline) or PPS (30 mg/kg/h) was administered intravenously immediately before the onset of reperfusion and every hour during the reperfusion period. Treatment with PPS significantly (p < 0.05) reduced infarct size as compared with vehicle-treated animals (27.5+/-2.9% vs. 13.34+/-2.6%). Analysis of tissue demonstrated decreased deposition of membrane-attack complex and neutrophil accumulation in the area at risk. The results indicate that, like heparin and related GAGs, PPS possesses the ability to decrease infarct size after an acute period of myocardial ischemia and reperfusion. The observations are consistent with the suggestion that PPS may mediate its cytoprotective effect through modulation of the complement cascade.     

Calpain inhibitor-1 reduces infarct size and DNA fragmentation of myocardium in ischemic/reperfused rat heart

Myocardial ischemia/reperfusion activates a calcium-dependent protease, calpain, in the ischemic myocytes. It is not known whether calpain is involved in the mechanism of ischemia/reperfusion injury in hearts. Thus the purpose of this study was to clarify the effect of a selective calpain inhibitor (CAI) on infarct size and the extent of DNA damage in ischemic/reperfused rat hearts. Rats were divided in four groups (n = 7 each). In saline group, 0.3 ml of saline was administered (i.v.) 10 min before 30-min coronary occlusion followed by 6-h reperfusion. In vehicle group, 0.3 ml of 10% dimethyl sulfoxide (DMSO) was administered 10 min before the 30-min ischemia. CAI (0.5 mg/kg) was administered 10 min before the 30-min ischemia (CAI-A group) and 10 min before the 6-h reperfusion period (CAI-B group). Infarct size was detected with triphenyl tetrazolium chloride, and DNA fragmentation was detected by agarose gel electrophoresis and by in situ nick end labeling (ISEL). Infarct size was significantly smaller in the CAI-A group compared with the vehicle group (13+/-9% vs. 48+/-12%; p < 0.01), and the incidence of ISEL-positive myocyte nuclei in the subendocardial region was significantly reduced in the CAI-A group compared with the vehicle group (26+/-3% vs. 59+/-6%; p < 0.01). However, the effects of CAI in CAI-B group were not significant. Activation of calpain is involved in the mechanism of ischemia/reperfusion injury, and the preischemic administration of CAI was effective in reducing myocardial infarct size and the DNA damage of the myocytes in ischemic/reperfused rat heart.     

Beneficial effects of streptokinase on left ventricular function after myocardial reoxygenation and reperfusion following global ischemia in the isolated rabbit heart

To determine the effect of streptokinase on the ischemic myocardium independent of its effects on the occluding thrombus, the isolated rabbit heart, perfused with Krebs-Henseleit solution, was subjected to a 45-min period of ischemia--83% reduction in myocardial (perfusion) flow--plus anoxia (95% N2 and 5% CO2), followed by restoration of perfusion and reoxygenation. Streptokinase, 75 or 150 IU/min, was infused starting 15 min before reperfusion and continuing for 30 min after reperfusion. Compared with the control group, streptokinase was associated during reperfusion with a significant dose-dependent greater restoration or smaller depression of ventricular function, dP/dt, and developed pressure. To determine if streptokinase effects were mediated during the ischemic or reperfusion phase, the high streptokinase dose was administered in either the last 30 min of the ischemia or the first 30 min of reperfusion. The improvement in recovery of left ventricular function was primarily in the group having streptokinase administered only during the ischemic period. Thus, streptokinase affects the ischemic myocardium so that there is an acceleration in the recovery of ventricular function or a reduction of the impairment in ventricular function during myocardial reperfusion.     

Mildronate, a novel fatty acid oxidation inhibitor and antianginal agent, reduces myocardial infarct size without affecting hemodynamics

Mildronate is a fatty acid oxidation inhibitor approved as an antianginal drug in parts of Europe. We carried out the first study to determine whether a 10-day course of mildronate could reduce myocardial infarct size (IS) during acute myocardial ischemia. Sprague Dawley rats received 200 mg/kg/d of mildronate (treated group, n = 16) or sterile water (control group, n = 14) subcutaneously for 10 days before ischemia-reperfusion. Rats were then subjected to 45 minutes of left coronary artery occlusion and 2 hours of reperfusion. The 2 groups had identical areas at risk: treated 38 +/- 3%; controls 38 +/- 2%. The amount of necrosis was smaller in the mildronate group at 16 +/- 2% of the left ventricle versus controls, 22 +/- 2% (P = 0.05); and for any amount of risk >25%, necrosis was smaller in the treated group (P = 0.0035). Myocardial IS (% of risk zone) was 43+/-3% in the mildronate-treated rats, and 57+/-4% in controls (P = 0.004). During occlusion, there were no differences between the 2 groups in heart rate (216 +/- 12 bpm, mildronate and 210 +/- 9 bpm, control), in mean arterial pressure (60 +/- 2 mm Hg, mildronate and 64 +/- 3 mm Hg, control) or in the frequency of arrhythmias. Our study for the first time demonstrated that a 10-day treatment with mildronate reduced myocardial IS in an experimental model of acute myocardial ischemia, without any effect on hemodynamics.     

3',4'-Dihydroxyflavonol reduces infarct size and injury associated with myocardial ischaemia and reperfusion in sheep

1 The antioxidant properties of flavonols in vivo and their potential benefits in myocardial ischaemia/reperfusion (I/R) injury have been little investigated. We evaluated the ability of a synthetic flavonol, 3',4'-dihydroxyflavonol (DiOHF) to scavenge superoxide in post-I/R myocardium and to prevent myocardial I/R injury. 2 Anaesthetized sheep were studied in four groups (n=5-6): control, ischaemic preconditioning (IPC), vehicle and DiOHF (before reperfusion, 5 mg kg(-1), i.v.). The left anterior descending coronary artery was occluded distal to the second diagonal branch for 1 h followed by 2 h of reperfusion. Infarct size, myocardial function, NADPH-activated superoxide generation and biochemical markers of injury were measured. 3 DiOHF (10(-8)-10(-4) m) incubated in vitro with post-I/R myocardium from the vehicle group suppressed superoxide production dose-dependently. 4 DiOHF administered in vivo also significantly reduced superoxide generation in vitro. DiOHF and IPC markedly reduced infarct size, which was 73+/-2% of the area at risk in vehicle, 50+/-4% in DiOHF, 75+/-5% in control and 44+/-4% in IPC. Post-I/R segment shortening within the ischaemic zone was greater in DiOHF (2.3+/-0.7%; P<0.01) and IPC (1.7+/-0.5%; P<0.01) than those in corresponding controls (-1.7+/-0.4; -2.1+/-0.4%). 5 DiOHF and IPC improved coronary blood flow to the ischaemic area and preserved higher levels of nitric oxide metabolites in the venous outflow from the ischaemic zone. 6 DiOHF attenuated superoxide production in post-I/R myocardium, and significantly reduced infarct size and injury following I/R in anaesthetized sheep. The extent of protection by DiOHF is comparable to that afforded by IPC. Thus, DiOHF has clinical potential for improving recovery from acute myocardial infarction and other ischaemic syndromes.     

Postischemic administration of CGX-1051, a peptide from cone snail venom, reduces infarct size in both rat and dog models of myocardial ischemia and reperfusion

CGX-1051 is a synthetic version of a peptide originally isolated from the venom of cone snails. In the present studies, we tested the potential cardioprotective effect of CGX-1051 in a rat and dog model of myocardial ischemia/reperfusion. CGX-1051 was administered 5 minutes before reperfusion as intravenous bolus doses of 30, 100, and 300 microg/kg. Infarct size (IS) is reported as IS/area at risk (AAR). In the rat, the vehicle control group had an IS/AAR of 59.8+/-2.1%. Postischemic administration of CGX-1051 at doses of 30, 100, and 300 microg/kg resulted in an IS/AAR of 52.6+/-4.2%, 34.6+/-5.6% (P<0.05), and 40.8+/-5.2% (P<0.05), respectively. In the dog, the vehicle control group had an IS/AAR of 18.8+/-1.7%. Postischemic administration of CGX-1051 at doses of 30, 100, and 300 microg/kg resulted in an IS/AAR of 16.9+/-2.5%, 8.4+/-2.9% (P<0.05) and 9.9+/-2.4% (P<0.05), respectively. These results demonstrate that administration of CGX-1051 at a clinically relevant time point results in a dose-dependent reduction in IS in both rats and dogs.     

Carvedilol (Kredex) reduces infarct size in a canine model of acute myocardial infarction.

Carvedilol (Kredex) is a multiple action, antihypertensive agent that may also prove to be useful in the treatment of angina and congestive heart failure. Carvedilol combines in one molecule both beta-adrenoceptor blocking and vasodilating activities. Inasmuch as beta-adrenoceptor blocking agents are known to be cardioprotective and thereby reduce infarct size, it is logical to assume that carvedilol, likewise, would possess this desirable activity. Furthermore, the additional vasodilating activity of carvedilol could contribute to further reductions in infarct size by reducing myocardial work (and therefore myocardial oxygen demand) through reductions in both afterload and myocardial wall tension. As such, we have investigated the ability of carvedilol to reduce infarct size in a canine model of acute myocardial infarction. Carvedilol (1 mg/kg i.v.) or its vehicle, dimethylformamide, were administered 15 min before left circumflex coronary artery (LCX) occlusion. Following 1 h of LCX occlusion, dogs were reperfused through a critical stenosis and then allowed to recover for 24 h. Carvedilol-treated animals exhibited a 78% reduction in infarct size compared to vehicle controls, such that the percentage of the left ventricle infarcted was reduced significantly from 16.2 +/- 4.1% in control animals to 3.6 +/- 1.3% in animals treated with carvedilol (p = 0.017, n = 6). Stained tissue sections of the left ventricle were photographed, digitized and color-enhanced using an Image Analysis Computer System, and three-dimensional reconstruction of the left ventricle, including the infarcted areas, was performed.(ABSTRACT TRUNCATED AT 250 WORDS)     

Platelet depletion and infarct size in an occlusion-reperfusion model of myocardial ischemia in anesthetized dogs

The formation of platelet aggregates and release of platelet-derived vasoactive mediators have been suggested to aggravate ischemic myocardium. The contribution of platelets to myocardial damage induced by 90-min occlusion and 5-h reperfusion in chloralose-anesthetized dogs was assessed after depletion of platelets with specific antidog platelet antiserum. Dogs treated with antiplatelet antiserum showed greater than 90% reduction in circulating platelets and serum TxB2 levels, but showed no reduction in infarct size (58 +/- 3 vs. 51 +/- 3% of risk area for control and thrombocytopenic dogs, respectively). Platelet depletion had no hemodynamic effect during the occlusion or reperfusion phases, nor reduced the incidence of arrhythmias. These results indicate that platelet aggregates or platelet-derived mediators do not contribute directly to the extent of damage in this occlusion-reperfusion model of myocardial ischemia.