Reperfusion-induced Myocardial Damage Research Articles

Exosomal miR-455-3p from BMMSCs prevents cardiac ischemia-reperfusion injury

Bone marrow mesenchymal stem cells (BMMSCs) exert protective effects against myocardial infarction (MI). Here, we focused on the function and mechanism of miR-455-3p from BMMSCs-derived exosomes (BMMSCs-Exo) in myocardial infarction. BMMSCs were isolated from rat bone marrow, and the exosomes from the culture medium of BMMSCs were separated, and administered to H9C2 cells under hypoxia-reperfusion (H/R) stimulation. MTT and TUNEL staining analyzed cell viability and apoptosis, respectively. RT-qPCR determined miR-455-3p expression. Apoptosis-related proteins, autophagy-associated proteins, and the MEKK1-MKK4-JNK signaling pathway were detected. The interaction between miR-455-3p and MEKK1 was confirmed through dual luciferase activity and RIP assay. An in vivo ischemia reperfusion (I/R) model was established in rats. 2, 3, 5 triphenyltetrazolium chloride (TTC) staining, hematoxylin-eosin (H&E) staining, Masson staining, and TUNEL staining evaluated the infarct volume and histopathological changes. miR-455-3p's expression was down-regulated in BMMSCs-derived exosomes, I/R myocardial tissues, and H/R myocardial cells. miR-455-3p enriched by BMMSC exosomes reduced H/R-mediated cardiomyocyte damage and death-related autophagy. miR-455-3p upregulation suppressed MEKK1-MKK4-JNK. MEKK1 overexpression notably mitigated cell apoptosis, cramped cell viability, suppressed autophagy expansion, and attenuated Exo-miR-455-3p's protection on H/R myocardial cells. In-vivo trials reflected that BMMSC exosomes enriched with miR-455-3p repressed ischemia reperfusion-induced myocardial damage and myocardial cell function. miR-455-3p, shuttled by exosomes from MSCs, targets the MEKK1-MKK4-JNK signaling pathway to guard against myocardial ischemia-reperfusion damage.

Marjoram extract prevents ischemia reperfusion-induced myocardial damage and exerts anti-contractile effects in aorta segments of male wistar rats

Ethnopharmacological relevanceMarjoram (Origanum majorana L.) is an herb traditionally used as a medicine in different countries, as Morocco and Iran, because of its beneficial cardiovascular effects. Some studies suggest that these effects are due, at least in part, to the presence of phenolic compounds such as rosmarinic acid (RA) and luteolin. Aim of the studyTo analyze the possible cardiprotective effects of a marjoram extract (ME) reducing myocardial damage after coronary ischemia-reperfusion (IR) and its possible antihypertensive effects reducing the response of aorta segments to the vasoconstrictors noradrenaline (NA) and endothelin-1 (ET-1). Materials and methodsMale Wistar rats (300g) were used. After sacrifice, the heart was immediately removed and mounted in a perfusion system (Langendorff). The aorta was carefully dissected and cut in 2 mm segments to perform vascular reactivity experiments. ResultsIn the heart, ME perfusion after IR reduced heart rate and prevented IR-induced decrease of cardiac contractility, possibly through vasodilation of coronary arteries and through the upregulation of antioxidant markers in the myocardium that led to reduced apoptosis of cardiomyocytes. In the aorta, ME decreased the vasoconstrictor response to NA and ET-1 and exerted a potent anti-inflammatory and antioxidant effect. Neither RA nor 6-hydroxi-luteolin-O-glucoside, major compounds of this ME, were effective in improving cardiac contractility after IR or attenuating vasoconstriction to NA and ET-1 in aorta segments. ConclusionIn conclusion, ME reduces the myocardial damage induced by IR and the contractile response to vasoconstrictors in the aorta. Thus, it may be useful for the treatment of cardiovascular diseases such as myocardial infarction and hypertension.

Circulating Cytochrome c as Potential Biomarker of Impaired Reperfusion in ST-Segment Elevation Acute Myocardial Infarction

In patients with ST-segment elevation acute myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (pPCI), abrupt reperfusion can induce myocardial injury and apoptotic cell death. Reperfusion-induced myocardial damage, however, cannot be easily evaluated in clinical practice because of the lack of specific biomarkers. Cytochrome c, a mitochondrial protein, is released on reperfusion into the cytosol, where it triggers the apoptotic process. It can reach the external fluid and circulating blood when cell rupture occurs. We measured the cytochrome c circulating levels in patients with STEMI undergoing pPCI, and correlated them with the clinical signs of myocardial necrosis and reperfusion. The plasma creatine kinase-MB mass and serum cytochrome c (enzyme-linked immunosorbent assay method) were serially measured in 55 patients with STEMI undergoing pPCI. The angiographic and electrocardiographic signs of myocardial reperfusion were also assessed. Cytochrome c transiently increased in all patients with STEMI, with a curve that paralleled that of creatine kinase-MB. A significant relation was found between the peak values of the 2 biomarkers (R = 0.35, p = 0.01) and between the areas under the 2 curves (R = 0.33, p = 0.02). The creatine kinase-MB peak value correlated significantly with the clinical features of infarct extension. In contrast, the cytochrome c peak value correlated inversely with the myocardial blush grade. Patients with clinical signs of myocardial reperfusion injury had a significantly greater cytochrome c peak value than patients without reperfusion injury (median 1.65 ng/ml, interquartile range 1.20 to 2.20, vs 1.1 ng/ml, interquartile range 0.65 to 1.55; p = 0.04). In conclusion, serum cytochrome c is detectable in the early phase of STEMI treated with pPCI and is associated with clinical signs of impaired myocardial reperfusion.

Cardioprotective effects of normothermic reperfusion with oxygenated potassium cardioplegia: a possible mechanism☆

Na(+)/K(+) pump activation induced by normothermic reperfusion with high potassium cardioplegia may exert a protective effect on reperfusion-induced myocardial damage. We investigated (1) temperature dependency and extracellular potassium dependency of the Na(+)/K(+) pump current (Ip), (2) effects of high potassium or ouabain during reperfusion on the post-ischemic left ventricular (LV) function. Ip-voltage relation was constructed at 5.0 and 20 mM of KCl (37 degrees C) using a whole-cell clamp technique in guinea pig myocytes. Ip at -40 mV was measured at 37, 27 and 18 degrees C (KCl: 5.0 mM). Isolated rat hearts were Langendorff-perfused and subjected to 20 min of global ischemia (37 degrees C) followed by 35 min of reperfusion (37 degrees C). The post-ischemic recovery of LV developed pressure (%LVDP) was assessed in the four reperfusate groups (4.8 mM KCl, 10 mM KCl, 20 mM KCl, or 4.8 mM KCl plus 50 microM ouabain during the first 10 min of reperfusion). The 4.8 mM KCl and 10.0 mM KCl groups were compared under metabolic inhibition (glucose-free, NaCN, or hypoxia) during reperfusion. The Ip-voltage relation shifted upward when extracellular KCl was increased from 5.0 to 20 mM. Ip was significantly greater at 37 degrees C than at 18 degrees C (114.3+/-17.2 vs. 22.7+/-1.2 pA, respectively). %LVDP was significantly greater at the 10.0 mM KCl group than at the 4.8 mM KCl group (54.9+/-5.5% vs. 34.2+/-5.9%, respectively). Metabolic inhibition abolished the difference between the two groups. Ouabain significantly decreased %LVDP (15.9+/-1.6%). Potassium-induced cardiac arrest during normothermic reperfusion may exert a cardioprotective effect by inducing Na(+)/K(+) pump activation, which may be supported by aerobic metabolism during reoxygenation rather than by energy saving during cardiac arrest.

Oxytocin exerts protective effects on in vitro myocardial injury induced by ischemia and reperfusionThis article is one of a selection of papers from the NATO Advanced Research Workshop on Translational Knowledge for Heart Health (published in part 1 of a 2-part Special Issue).

Among the cardiovascular pathologies, ischemic heart disease is a serious medical problem that can result in cardiac injury and (or) heart failure. The aim of the present study was to test the hypothesis that neuropeptide oxytocin induces cardioprotective effects on ischemia-reperfusion-induced myocardial damage. The functional parameters of isolated Langendorff-perfused rat hearts were recorded before and after global 25 min ischemia and subsequent reperfusion. The infarct size was determined by a computerized planimetric method. The results showed that oxytocin produced negative chronotropic effect even at low concentrations (90-125 nmol/L). Perfusion with oxytocin before ischemia resulted in significant reduction of the infarct size (p<0.01), which was about 66% smaller than that in the control group. To evaluate the functional mechanisms involved, further experiments were performed under conditions of constant heart rate. The lower dose of oxytocin (90 nmol/L), which was ineffective in spontaneously beating hearts, induced a significant decrease of contractility. Elimination of the negative chronotropic effect of oxytocin prevented its cardioprotective action. In conclusion, our results demonstrated an attenuation of the infarct size in oxytocin-treated hearts, indicating a cardioprotective effect of oxytocin. The data suggest that the negative chronotropic action of oxytocin participates in its protective effects on ischemia-reperfusion-induced myocardial injury.

Reduction of ischemia and reperfusion-induced myocardial damage by cytochrome P450 inhibitors.

Ischemia and reperfusion both contribute to tissue damage after myocardial infarction. Although many drugs have been shown to reduce infarct size when administered before ischemia, few have been shown to be effective when administered at reperfusion. Moreover, although it is generally accepted that a burst of reactive oxygen species (ROS) occurs at the onset of reperfusion and contributes to tissue damage, the source of ROS and the mechanism of injury is unclear. We now report the finding that chloramphenicol administered at reperfusion reduced infarct size by 60% in a Langendorff isolated perfused rat heart model, and that ROS production was also substantially reduced. Chloramphenicol is an inhibitor of mitochondrial protein synthesis and is also an inhibitor of a subset of cytochrome P450 monooxygenases (CYPs). We could not detect any effect on mitochondrial encoded proteins or mitochondrial respiration in chloramphenicol-perfused hearts, and hypothesized that the effect was caused by inhibition of CYPs. We tested additional CYP inhibitors and found that cimetidine and sulfaphenazole, two CYP inhibitors that have no effect on mitochondrial protein synthesis, were also able to reduce creatine kinase release and infarct size in the Langendorff model. We also showed that chloramphenicol reduced infarct size in an open chest rabbit model of regional ischemia. Taken together, these findings implicate CYPs in myocardial ischemia/reperfusion injury.

Epigallocatechin, a Green Tea Polyphenol, Attenuates Myocardial Ischemia Reperfusion Injury in Rats

Epigallocatechin-3-gallate (EGCG) is the most prominent catechin in green tea. EGCG has been shown to modulate numerous molecular targets in the setting of inflammation and cancer. These molecular targets have also been demonstrated to be important participants in reperfusion injury, hence this study examines the effects of EGCG in myocardial reperfusion injury. Male Wistar rats were subjected to myocardial ischemia (30 min) and reperfusion (up to 2 h). Rats were treated with EGCG (10 mg/kg intravenously) or with vehicle at the end of the ischemia period followed by a continuous infusion (EGCG 10 mg/kg/h) during the reperfusion period. In vehicle-treated rats, extensive myocardial injury was associated with tissue neutrophil infiltration as evaluated by myeloperoxidase activity, and elevated levels of plasma creatine phosphokinase. Vehicle-treated rats also demonstrated increased plasma levels of interleukin-6. These events were associated with cytosol degradation of inhibitor kappaB-alpha, activation of IkappaB kinase, phosphorylation of c-Jun, and subsequent activation of nuclear factor-kappaB and activator protein-1 in the infarcted heart. In vivo treatment with EGCG reduced myocardial damage and myeloperoxidase activity. Plasma IL-6 and creatine phosphokinase levels were decreased after EGCG administration. This beneficial effect of EGCG was associated with reduction of nuclear factor-kB and activator protein-1 DNA binding. The results of this study suggest that EGCG is beneficial for the treatment of reperfusion-induced myocardial damage by inhibition of the NF-kappaB and AP-1 pathway.

Sesquiterpene lactone parthenolide, an inhibitor of IkappaB kinase complex and nuclear factor-kappaB, exerts beneficial effects in myocardial reperfusion injury.

Sesquiterpene lactones are extracts of common medicinal Asteracae plants used in folk medicine for their anti-inflammatory activity. Recently, in vitro studies have shown that these compounds may interfere with pro-inflammatory gene regulation. This study examines the effects of parthenolide, a sesquiterpene lactone, in experimental myocardial ischemia and reperfusion. Myocardial injury was induced in rats by 30 min occlusion and 120 min reperfusion of the left coronary artery. Parthenolide (250 or 500 microg/kg) or vehicle (0.05% Tween 80, 1 mL/kg) was administered intraperitoneally 10 min before reperfusion. In vehicle-treated rats, ischemia and reperfusion caused myocardial injury, as evaluated by infarct size, serum levels of creatine phosphokinase and by histological examination. Elevated tissue levels of myeloperoxidase activity were indicative of a significant infiltration of neutrophils. This event paralleled the occurrence of oxidative damage, as evaluated by a marked increase in tissue malondialdehyde levels. These inflammatory events were preceded by activation of the IkappaB kinase complex (IKK) and partial disappearance of inhibitor-kappaBalpha (IkappaBalpha) in the cytosol and translocation of the nuclear factor-kappaB (NF-kappaB) to the nucleus, as early as 15 min after reperfusion. Administration of parthenolide ameliorated myocardial injury, lowered serum creatine phosphokinase activity, and reduced neutrophil infiltration and the subsequent oxidative damage. These beneficial effects were associated with inhibition of IKK activity, enhanced stability of IkappaBalpha, and inhibition of nuclear translocation of NF-kappaB. The results of this study suggest that parthenolide may be beneficial for the treatment of reperfusion-induced myocardial damage by inhibition of the IKK/NF-kappaB pathway.

Protective effect of amiloride against reperfusion damage as evidenced by inhibition of accumulation of free fatty acids in working rat hearts.

To examine whether amiloride protects against ischemia-induced or reperfusion-induced damage to the heart, mechanical and metabolic studies were performed in the isolated, working rat heart. Ischemia decreased both mechanical function and the tissue levels of high-energy phosphates and increased the tissue levels of free fatty acids (FFAs). Reperfusion restored the levels of high-energy phosphates but further increased FFA accumulation. For this reason, accumulation of FFAs was used as an indicator of both ischemia-induced and reperfusion-induced damage. Drugs were added to the perfusion solution 5 min before ischemia until the end of ischemia (pre) or until 10 min after reperfusion (pre + post). Diltiazem (1 or 5 mumol/L pre) decreased the mechanical function of the non-ischemic heart and attenuated both ischemia-induced and reperfusion-induced accumulation of FFAs. Amiloride (50 mumol/L pre) did not affect the mechanical function of the non-ischemic heart or attenuate ischemia-induced or reperfusion-induced FFA accumulation effectively. However, amiloride (50 mumol/L pre + post) did markedly attenuate the reperfusion-induced accumulation of FFAs. In conclusion, diltiazem attenuates both ischemia-induced and reperfusion-induced myocardial damage, probably through its energy-sparing effect as a result of a decrease in mechanical function before ischemia. In contrast, amiloride attenuates only the reperfusion-induced myocardial damage through mechanisms other than the energy-sparing effect.

A study on dilazep: I. Mechanism of anti-ischemic action of dilazep is not coronary vasodilation but decreased cardiac mechanical function in the isolated, working rat heart.

In the isolated, perfused working rat heart, ischemia (15 min) decreased the mechanical function and the tissue levels of adenosine triphosphate and creatine phosphate and increased the levels of lactate and free fatty acids. Reperfusion (20 min) did not restore the mechanical function, but restored incompletely the levels of metabolites, with the exception of free fatty acids, which increased further during reperfusion. Dilazep was given 5 min before starting ischemia until the end of ischemia. Dilazep at 5 or 10 microM decreased the cardiac mechanical function, but did not affect coronary flow in the pre-ischemic heart. Dilazep at 5 or 10 microM accelerated the recovery of mechanical function and coronary flow during reperfusion, and it attenuated metabolic changes induced by ischemia and reperfusion. Dilazep at 1 microM neither decreased the pre-ischemic mechanical function nor restored the mechanical function during reperfusion, although it attenuated the accumulation of free fatty acids during reperfusion. These results suggest that dilazep attenuates both ischemia- and reperfusion-induced myocardial damage and that the anti-ischemic action of dilazep is not due to coronary vasodilation but probably due to an energy-sparing effect and other effects that remain to be studied.

Inhibition of platelet-activating factor fails to limit ischemia and reperfusion-induced myocardial damage.

To determine the role of platelet-activating factor (1-O-hexa-decyl-2-acetyl-sn-glyceryl-phosphoryl-choline, PAF) in myocardial ischemic and reperfusion-induced injury, the effects of a PAF receptor antagonist (WEB 2086) were studied in an anesthetized canine model of ischemia (90 min) and reperfusion (6 h). Thirty minutes after onset of ischemia, WEB 2086 was administered as a bolus (20 mg/kg intravenously, i.v.) followed by a continuous 6-h infusion (10 mg/kg/h i.v.). Controls received vehicle alone (0.9% saline). Platelet aggregation was studied at baseline and at 1, 2, 4, and 6 h of drug administration and at the end of the reperfusion period. WEB 2086 treatment did not significantly affect platelet aggregation stimulated by ADP or arachidonic acid (AA). After 1 h of drug infusion, the ex vivo aggregatory response to exogenous (200 nM) PAF was ablated in WEB 2086-treated animals. WEB 2086 administration did not affect heart rate (HR) or mean arterial blood pressure (MAP) during the occlusion or reperfusion phases. During reperfusion of the ischemic tissue, left circumflex coronary artery (LCX) blood flow of WEB 2086-treated animals increased (p < 0.05) above control value. The area of the left ventricle at risk of infarct was not different between control and WEB 2086-treated groups. Infarct size was not significantly reduced in WEB 2086-treated animals. The results of our investigation using a 90-min ischemic period followed by 6-h reperfusion show that pharmacologic antagonism of PAF by WEB 2086 does not protect the heart against ischemia and reperfusion-induced injury.

Complete prevention of myocardial stunning, contracture, low-reflow, and edema after heart transplantation by blocking neutrophil adhesion molecules during reperfusion

This study tested the hypothesis that preventing neutrophil adhesion during reperfusion, by blocking either the neutrophil membrane CD18 integrin complex or its endothelial and myocyte ligand, intercellular adhesion molecule-1 (ICAM-1), would reduce myocardial inflammation and edema and improve reflow and ventricular function after heart preservation and transplantation. After cardioplegia and insertion of a left ventricular balloon, rabbit hearts were heterotopically transplanted into recipient rabbits either immediately (immediate, n = 12) or after preservation in 4 degrees C saline (3 hours of ischemia, n = 33). Forty-five minutes before reperfusion, recipients of preserved hearts received intravenous infusions of either saline (vehicle, n = 13), anti-CD18 monoclonal antibody (Mab) R15.7 (2 mg/kg) (anti-CD18, n = 10), or anti-ICAM-1 Mab R1.1 (2 mg/kg) (anti-ICAM, n = 10). During 3 hours of reperfusion the slope of the peak-systolic pressure-volume relation and its volume-axis intercept, the exponential elastic coefficient of the end-diastolic pressure-volume relation, the unstressed ventricular volume, and the time constant of the exponential left ventricular pressure decay after dP/dtmin were serially measured. Myocardial blood flow was measured with microspheres from which coronary vascular resistance was calculated. After explanation, the degree of myocardial inflammation, estimated by tissue neutrophil sequestration (myeloperoxidase assay) and myocardial water content were determined. Within each group no significant differences in measurements made at 1, 2, and 3 hours of reperfusion were noted. Compared with the immediate transplantation group, the vehicle group demonstrated a significant increase in myeloperoxidase activity (3380 +/- 456 versus 1712 +/- 552 microU/gm, p < 0.05), coronary vascular resistance (115.5 +/- 13.4 versus 70.5 +/- 10.6 U/gm, p < 0.05), and myocardial water content (79.8% +/- 0.4% versus 75.6% +/- 1.3%, p < 0.05), a significant decrease in unstressed ventricular volume (a leftward shift in the end-diastolic pressure-volume relation) (-0.49 +/- 0.24 versus 0.28 +/- 0.21 ml, p < 0.05), and a marked prolongation in exponential left ventricular pressure delay after dP/dtmin (156.64 +/- 3.81 versus 37.25 +/- 3.34 msec, p < 0.01).(ABSTRACT TRUNCATED AT 400 WORDS)

Extracellular-superoxide dismutase type C (EC-SOD C) reduces myocardial damage in rats subjected to coronary occlusion and 24 hours of reperfusion.

Extracellular-superoxide dismutase type C (EC-SOD C) is a secretory SOD isoenzyme which, in contrast to the intracellular CuZn SOD, has affinity to the endothelium and a long vascular half-life. In the present study, the effects of EC-SOD C and CuZn SOD on reperfusion-induced myocardial damage were determined in rats subjected to 10 min of left coronary artery ligation followed by 24 h of reperfusion. Recombinant human EC-SOD C (rh-EC-SOD C) or the corresponding volume of the vehicle was administered after completion of the coronary ligation. CuZn SOD was given in two equal doses, the first dose directly after ligation and the second one 6 h later. At the end of the reperfusion period the myocardial damage was quantified by measuring the creatine kinase concentration (CK) in the reperfused part of the left ventricular free wall (LVFW), and expressed as a percentage of the concentration in the non-ischemic septum. In the group given the vehicle, 47 +/- 10 (mean +/- SD) of the CK remained in the reperfused LVFW. In the rats receiving rh-EC-SOD C the corresponding values for each dose: 1.4, 4.2 and 12.6 mg/kg were 55 +/- 12 (ns), 55 +/- 12 (ns) and 65 +/- 12% (p less than 0.05, vs. vehicle, Dunnett's multiple comparison test), respectively. Administration of CuZn SOD (2 x 10 mg/kg) resulted in 58 +/- 16% (ns) CK remaining in the LVFW.(ABSTRACT TRUNCATED AT 250 WORDS)

Low molecular weight analogs of trolox with potent antioxidant activity in vitro and in vivo

Alpha-tocopherol and its water-soluble derivative, Trolox, are capable of terminating free radical chain reactions and limiting reperfusion-induced cell damage. In the present study, we have quantitated the effects of two relatively potent analogs of alpha-tocopherol/Trolox, WIN 62079 and U-78517F, which attenuated exogenously generated free radical damage in cultured cells and reperfusion injury in vivo. In a cultured rat renal tubular epithelial cell line (NRK-52E), millimolar concentrations of ascorbate or the combination of Trolox plus ascorbate reduced cellular damage (quantitated as lactate dehydrogenase [LDH] release) induced by radicals generated by hypoxanthine/xanthine oxidase. In contrast, WIN 62079 and U-78517F attenuated damage at micromolar concentrations. Similarly, intravenous administration of WIN 62079 (three hourly doses of 3 mg/kg) and U-78517F (10 mg/kg infused over 5 min) reduced reperfusion-induced myocardial damage in rabbit coronary-occulded hearts: Trolox (three hourly doses of 100 mg/kg) was less potent and required ascorbate (three hourly doses of 150 mg/kg) as a cofactor. These data demonstrate that is feasible to design potent, water-soluble analogs of Trolox which are efficacious against free radical-mediated cell death and which do not require ascorbate as a cofactor. Moreover, since U-78517F and WIN 62079 are two to three orders of magnitude more potent than Trolox, and since they contain different amino side chains, these data further support the concept that side chain modifications of the chromane ring nucleus of alpha-tocopherol derivatives significantly affect activity, possibly by providing additional activity or by enhancing availability to the cellular site of action. © 1992 Wiley-Liss, Inc.

Persistent Cardioprotection by Azapropazone in a Canine Model of Coronary Artery Thrombosis and Thrombolysis

Activated neutrophils and possibly xanthine oxidase-derived free radicals are believed to be mediators of ischemia and reperfusion-induced myocardial damage. We studied the cardioprotective effect of the neutrophil stabilizer and xanthine oxidase inhibitor azapropazone in dogs subjected to thrombotic occlusion of the left anterior descending coronary artery (LAD), induced by intracoronary introduction of a copper coil, followed 60 min later by thrombolytic treatment with intracoronary streptokinase and 4-day reperfusion; we then determined infarct size by triphenyltetrazolium stain. Azapropazone [100 mg/kg intravenously (i.v.) followed by a 24-h i.v. infusion of 10 mg/kg/h, n = 8] or vehicle (n = 10) treatments were started immediately before the streptokinase infusion. Steady-state plasma levels of azapropazone ranged from 97 to 163 micrograms/ml during the infusion. Myocardial blood flow and underperfused area at risk were determined using radiolabeled microspheres. Results were as follows (mean +/- SEM): area at risk (percentage of left ventricle) azapropazone 22.7 +/- 3.16 and vehicle 21.8 +/- 4.13; infarct size (percentage of area at risk), azapropazone 45.1 +/- 11.8 and vehicle 75.7 +/- 10.6, p less than 0.03; collateral blood flow (ml/min/g), azapropazone 0.27 +/- 0.02 and vehicle 0.23 +/- 0.02; total ischemic period (min), azapropazone 106 +/- 5.9 and vehicle 91.5 +/- 4.9. Azapropazone had no effects on heart rate (HR), blood pressure (BP), or rate/pressure product (RPP). These dta show that azapropazone limits infarct size in a canine model of coronary thrombosis and long-term reperfusion and that this cardioprotection is independent of cardiovascular parameters.