Reduction of myocardial damage and polymorphonuclear leukocyte accumulation following coronary artery occlusion and reperfusion by the thromboxane receptor antagonist BM 13.505

This study was designed to assess the effect of the thromboxane receptor antagonist, BM 13.505, in limiting myocardial damage and polymorphonuclear leukocyte accumulation in rats subjected to coronary artery occlusion for 30 min with reperfusion for 24 h (MI/R). Myocardial injury and polymorphonuclear leukocyte infiltration were determined by measuring creatine phosphokinase (CPK) specific activity and myeloperoxidase (MPO) activity, respectively, in the left ventricular free wall (LVFW). Myocardial CPK levels were 8.24 +/- 0.33 U/mg protein in sham MI/R-vehicle-treated animals (n = 18), and were significantly decreased to 6.51 +/- 0.44 U/mg protein in MI/R-vehicle animals (n = 22). Myocardial MPO values were 2.4 +/- 0.5 U/g LVFW in sham MI/R animals, and significantly increased to 10.9 +/- 1.3 U/g LVFW in MI/R-vehicle animals. Administration of BM 13.505 (30 mg/kg, i.p.) 1 min prior to coronary occlusion resulted in CPK values of 7.83 +/- 0.45 U/mg protein and MPO levels of 6.1 +/- 0.9 U/g LVFW (p less than 0.05, compared to the MI/R-vehicle group). The survival rate in the MI/R-BM 13.505 group was 74 and 65% at 2 and 24 h, respectively, and was not different from the MI/R-vehicle group. There were no significant differences in mean arterial blood pressure or heart rate between the MI/R-vehicle and MI/R-BM 13.505 groups, indicating that changes in myocardial oxygen demand do not explain the protective effects. A lower dose did not reduce myocardial injury, indicating that the effects of BM 13.505 were dose dependent.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cardioprotective effects of the vasodilator/beta-adrenoceptor blocker, carvedilol, in two models of myocardial infarction in the rat.

The purpose of this study was to evaluate the cardioprotective effects of carvedilol, a beta-adrenergic blocker and vasodilator, in two models of ischemic myocardial damage in the rat. Following coronary artery occlusion for 0.5 h and reperfusion for 24 h (MI/R group), left ventricular (LV) injury was determined by planimetric analysis of triphenyltetrazolium chloride-stained tissue, and polymorphonuclear leukocyte infiltration was assessed by measuring myeloperoxidase (MPO) activity. In the vehicle-treated MI/R group, infarct size was 14.2 +/- 1.3% of the LV (n = 16), and MPO activity was increased to 2.8 +/- 0.7 from 0.14 +/- 0.03 U/g tissue in the vehicle-treated sham-occluded group (p less than 0.01). Carvedilol (1 mg/kg i.v., 15 min prior to coronary artery occlusion and at 3.5 h following reperfusion) reduced myocardial infarct size to 7.5 +/- 1.2% of the LV (n = 14; p less than 0.01) and attenuated the increase in MPO activity to 1.4 +/- 0.4 U/g tissue (p less than 0.05). A lower dose of carvedilol (i.e. 0.3 mg/kg i.v.) did not limit myocardial infarct size or the increase in MPO activity. In a model of permanent coronary artery occlusion, 24-hour survival was reduced from 85% in sham-occluded animals (n = 38) to 44% in the vehicle-treated MI group (n = 84; p less than 0.01). In comparison to the vehicle-treated MI group, carvedilol (0.3 mg/kg i.v., 15 min prior to coronary artery occlusion and 1 mg/kg 4 h after occlusion) improved survival by 55% (n = 64; p less than 0.05, compared to the vehicle-treated MI group), whereas the same dose of propranolol (n = 42) had no significant effect on survival. These results indicate that carvedilol reduces myocardial ischemia/reperfusion injury, and significantly improves survival in a permanent coronary artery occlusion model of myocardial infarction.     

Proteasome inhibitor lactacystin ablates liver injury induced by intestinal ischaemia-reperfusion

1. The aim of the present study was to investigate the role of proteasome in the pathogenesis of liver injury induced by intestinal ischaemia-reperfusion (I/R) and the effect of the proteasome inhibitor lactacystin on neutrophil infiltration, intracellular adhesion molecule (ICAM)-1 and nuclear factor (NF)-kappaB expression in the liver tissues of rats. 2. Thirty-two Wistar rats were randomly divided into four groups (n = 8 in each group) as follows: (i) a control, sham-operated group; (ii) an I/R group subjected to 1 h intestinal ischaemia and 4 h reperfusion; (iii) a group pretreated with 0.2 mg/kg lactacystin 1 h before intestinal I/R; and (iv) a group pretreated with 0.6 mg/kg lactacystin 1 h before intestinal I/R. Liver and intestine histology were observed. Serum levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT) and lactate dehydrogenase (LDH), as well as 20S proteasome activity in circulating white blood cells, were measured. Myeloperoxidase (MPO) activity in liver tissues and the immunohistochemical expression of liver NF-kappaB and ICAM-1 were assayed. In addition, a western blot of liver NF-kappaB was performed. 3. Compared with the sham-operated control group, liver and intestine injury was induced by intestinal I/R, characterized as histological damage including oedema, haemorrhage and infiltration by inflammatory cells, as well as a significant increase in serum AST (365 +/- 121 vs 546 +/- 297 IU/L, respectively; P < 0.05), ALT (65 +/- 23 vs 175 +/- 54 IU/L, respectively; P < 0.01) and LDH levels (733 +/- 383 vs 1434 +/- 890 IU/L, respectively; P < 0.05). Compared with the control group, MPO activity in the liver tissues increased significantly in the I/R group (2.05 +/- 0.69 vs 3.42 +/- 1.11 U/g, respectively; P < 0.05). Strong positive expression of liver ICAM-1 and NF-kappaB p65 was observed. 4. Compared with the intestinal I/R group, administration of 0.6 mg/kg lactacystin markedly reduced 20S proteasome activity in circulating white blood cells (15.47 +/- 4.00 vs 2.07 +/- 2.00 pmol 7-amino-4-methylcoumarin (AMC)/s per mg, respectively; P < 0.01) and ameliorated liver injury, which was demonstrated by decreased levels of serum AST (546 +/- 297 vs 367 +/- 86 IU/L, respectively; P < 0.05), ALT (175 +/- 54 vs 135 +/- 26 IU/L, respectively; P < 0.05) and LDH (1434 +/- 890 vs 742 +/- 218 IU/L, respectively; P < 0.05) and a reduced liver pathological score (2.13 +/- 0.64 vs 1.25 +/- 0.46, respectively; P < 0.01). Compared with the intestinal I/R group, MPO activity in liver tissues decreased significantly following lactacystin pretreatment (3.42 +/- 1.11 vs 2.58 +/- 0.61 U/g, respectively; P < 0.05) and the expression of liver NF-kappaB and ICAM-1 was markedly ameliorated. 5. The present study reveals that the proteasome inhibitor lactacystin ablates liver injury induced by intestinal I/R. One possible mechanism responsible for this effect is the inhibition of enhanced ICAM-1 and neutrophil infiltration by inhibition of NF-kappaB activity. The results suggest the feasibility of using proteasome inhibitor clinically in the treatment of intestinal I/R.     

Reduction of infarct size and infiltration of polymorphonuclear leukocytes by a thromboxane synthetase inhibitor. Studies in a rabbit ischemic heart model.

The effect of sodium 6-(2-(1-(1H)-imidazolyl)methyl-4,5-dihydrobenzo(b) thiophene)carboxylate (RS-5186), a potent and long acting thromboxane synthetase inhibitor in vitro and in vivo, on infarct size and on the infiltration of polymorphonuclear leukocytes (PMNs), was studied in a rabbit coronary artery occlusion (1 h)--reperfusion (0.5 h or 3 h) model. The infarcted region was stained with triphenyltetrazolium, and the ratio of infarcted area/left ventricular area was calculated. The infiltration of PMNs into the infarcted region was determined by measuring the PMNs specific enzyme, myeloperoxidase (MPO) activity. In the vehicle treated group, infarct size and MPO activity were increased with increased reperfusion time from 0.5 h to 3 h (infarct size: 15.3 +/- 2.7 to 25.2 +/- 3.2%; MPO activity: 255 +/- 51 to 825.3 +/- 169.4 units/g wet weight). There was also a significant correlation (r = 0.90, p less than 0.01) between the infarct size and MPO activity. In contrast, in the RS-5186 treated group (2 mg/kg i.v.), both infarct size and MPO activity did not increase with prolongation of the reperfusion period (infarct size: 12.8 +/- 5.5 to 10.3 +/- 3.6%; MPO activity: 318.8 +/- 36.7 to 381.2 +/- 72.6 units/g wet weight). In 0.5 h reperfused samples, there was no significant difference in infarct size or in MPO activity between the vehicle treated group and RS-5186 treated group.(ABSTRACT TRUNCATED AT 250 WORDS)     

Anti-inflammatory actions of aprotinin provide dose-dependent cardioprotection from reperfusion injury

BACKGROUND AND PURPOSE: Myocardial injury following ischaemia and reperfusion has been attributed to activation and transmigration of polymorphonuclear leukocytes (PMNs) with release of mediators including oxygen-derived radicals and proteases causing damage. EXPERIMENTAL APPROACH: We studied the serine protease inhibitor aprotinin in an in vivo rabbit model of 1 h of myocardial ischaemia followed by 3 h of reperfusion (MI+R). Aprotinin (10,000 Ukg(-1)) or its vehicle were injected 5 min prior to the start of reperfusion. KEY RESULTS: Myocardial injury was significantly reduced with aprotinin treatment as indicated by a reduced necrotic area (11+/-2.7% necrosis as percentage of area at risk after aprotinin; 24+/-3.1% after vehicle; P<0.05) and plasma creatine kinase activity (12.2+/-1.5 and 17.3+/-2.3 IU g(-1) protein in aprotinin and vehicle groups, respectively, P<0.05). PMN infiltration (assessed by myeloperoxidase activity) was significantly decreased in aprotinin-treated animals compared to vehicle (P<0.01). Histological analysis also revealed a substantial increase in PMN infiltration following MI+R and this was significantly reduced by aprotinin therapy (44+/-15 vs 102+/-2 PMN mm2 in aprotinin vs vehicle-treated animals, P<0.05). In parallel in vitro experiments, aprotinin inhibited neutrophil-endothelium interaction by reducing PMN adhesion on isolated, activated aortic endothelium. Finally, immunohistochemical analysis illustrated aprotinin significantly reduced myocardial apoptosis following MI+R. CONCLUSIONS AND IMPLICATIONS: Inhibition of serine proteases by aprotinin inhibits an inflammatory cascade initiated by MI+R. The cardioprotective effect appears to be at least partly due to reduced PMN adhesion and infiltration with subsequently reduced myocardial necrosis and apoptosis.     

Protective actions of S-nitroso-N-acetylpenicillamine (SNAP) in a rat model of hemorrhagic shock.

The anti-shock effects of an organic nitric oxide donor, S-nitroso-N-acetylpenicillamine (SNAP), were tested in a rat model of hemorrhagic shock. Administration of SNAP at a dose of 10 mcg/kg injection followed by 10 mcg/kg/h infusion neither significantly decreased mean arterial blood pressure (MABP) nor significantly altered bleedout volumes in hemorrhagic rats, indicating that SNAP did not modify the severity of the shock protocol. However, hemorrhaged rats treated with SNAP maintained post-reinfusion MABP at significantly higher values than hemorrhaged rats receiving 0.9% NaCl (final MABP 81 +/- 3.0 mmHg vs. 54 +/- 1.1 mmHg, respectively; p < 0.001). SNAP also significantly increased survival times following hemorrhagic shock (113 +/- 4 min in SNAP treated rats compared with 70 +/- 4.5 min in vehicle treated rats, p < 0.001). The overall survival rates were 87.5% when treated with SNAP and 0% with 0.9% NaCl (p < 0.01). In hemorrhagic shock rats receiving only vehicle, a significant accumulation of neutrophils in intestinal tissue occurred as indicated by a higher MPO activity in intestinal tissue (MPO activity, 1.26 +/- 0.31 vs. 0.14 +/- 0.05U/100 mg in sham hemorrhagic shock rats, p < 0.02). Administration of SNAP significantly attenuated the neutrophil accumulation in the intestinal tissue (MPO activity, 0.42 +/- 0.09U/100 mg, p < 0.05 compared with hemorrhagic rats receiving only the vehicle). Moreover, endothelial dysfunction of superior mesenteric artery rings occurred in hemorrhagic shock rats given only 0.9% NaCl.(ABSTRACT TRUNCATED AT 250 WORDS)     

Cyclosporin-A reduces leukocyte accumulation and protects against myocardial ischaemia reperfusion injury in rats

The present study was designed to evaluate the effect of cyclosporin A in a rat model of myocardial ischaemia reperfusion injury (MI/R). Anaesthetized rats were subjected to total occlusion (20 min) of the left main coronary artery followed by 5 h reperfusion (MI/R). Sham myocardial ischaemia-reperfusion rats (Sham MI/R) were used as controls. Myocardial necrosis, myocardial myeloperoxidase activity (MPO), serum creatinine phosphokinase activity (CPK), serum tumor necrosis factor (TNF-α), cardiac mRNA for TNF-α, cardiac intercellular adhesion molecule-1 (ICAM-1) immunostaining and myocardial contractility (left ventricle dP/dt_max) were evaluated. Myocardial ischaemia plus reperfusion in untreated rats produced marked myocardial necrosis, increased serum CPK activity and myeloperoxidase activity (a marker of leukocyte accumulation) both in the area-at-risk and in the necrotic area, reduced myocardial contractility and induced a marked increase in the serum levels of the TNF-α. Furthermore increased cardiac mRNA for TNF-α was measurable within 10 to 20 min of left main coronary artery occlusion in the area-at-risk and increased levels were generally sustained for 0.5 h. Finally, myocardial ischaemia-reperfusion injury increased ICAM-1 staining in the myocardium. Administration of cyclosporin A (0.25, 0.5 and 1 mg/kg as an i.v. infusion 5 min after coronary artery occlusion) lowered myocardial necrosis and myeloperoxidase activity in the area-at-risk and in the necrotic area, decreased serum CPK activity, increased myocardial contractility, reduced serum levels of TNF-α and the cardiac cytokine mRNA levels, and blunted ICAM-1 immunostaining in the injured myocardium. The data suggest that cyclosporin A suppresses leukocyte accumulation and protects against myocardial ischaemia-reperfusion injury.     

Protective effects of a novel nonglucocorticoid 21-aminosteroid (U74006F) during traumatic shock in rats.

The purpose of this study was to investigate the effect of the nonglucocorticoid steroid U74006F in the pathogenesis of a murine traumatic shock model. Pentobarbital-anesthetized (40 mg/kg) rats were subjected to Noble-Collip drum trauma and developed a lethal shock state characterized by a decreased mean arterial blood pressure (MABP) to 67 +/- 2 mm Hg and survival time (1.5 +/- 0.2 h). In contrast, sham trauma rats exhibited a MABP of 122 +/- 4 mm Hg at 5 h postanesthesia. Administration of U74006F at doses of 22.5 mg/kg at 15 to 20 min following trauma significantly maintained a higher MABP and prolonged survival compared to those trauma rats receiving only the vehicle for U74006F (0.002 N HCl). U74006F at 15 and 22.5 mg/kg prolonged survival time to 2.6 +/- 0.3 (p less than 0.05) and 3.1 +/- 0.6 h (p less than 0.02), respectively. U74006F also significantly attenuated the plasma accumulation of cathepsin D (p less than 0.02 to p less than 0.01) and free amino-nitrogen compounds (p less than 0.01) compared to the rats receiving only vehicle. Additionally, U74006F at 15 and 22.5 mg/kg blunted the production of the cardiotoxic peptide, myocardial depressant factor (MDF) (p less than 0.01 to p less than 0.001). Moreover, U74006F is a steroid without significant glucocorticoid or mineralocorticoid activity. These results suggest that U74006F may be useful as a therapeutic agent in traumatic shock.     

Effects of two nonsulfhydryl angiotensin-converting enzyme inhibitors, CGS 14831 and CGS 16617, on myocardial damage and left-ventricular hypertrophy following coronary artery occlusion in the rat

The present study was designed to examine the effects of two new angiotensin-converting enzyme (ACE) inhibitors, CGS 14831 and CGS 16617 (3 mg/kg i. v. 1 min prior to occlusion and 4 and 24 h after occlusion), on myocardial ischemic (MI) damage and left-ventricular hypertrophy in rats. Administration of CGS 14831 or CGS 16617 inhibited angio-tensin-I-induced pressor responses by 40-100% for 4 h after each dose. Myocardial creatine phosphokinase (CK) levels were 10.6 +/- 0.6 U/mg protein in sham-MI animals, and following coronary artery occlusion for 48 h were decreased to 4.1 +/- 0.2 U/mg protein in MI + vehicle animals (p less than 0.01). CGS 14831 and CGS 16617 attenuated the decrease in CK content and resulted in 47 and 40% sparing, respectively, of the left-ventricular free wall. Neither agent attenuated the left-ventricular hypertrophy which developed following coronary artery occlusion. These data indicate that the nonsulfhydryl ACE inhibitors CGS 14831 and CGS 16617 have a significant cardioprotective effect in rats surviving 48 h, and suggest a potential therapeutic usefulness of these agents for the treatment of ischemia-induced heart failure.     

Effect of propranolol on ischemic myocardial damage and left ventricular hypertrophy following permanent coronary artery occlusion or occlusion followed by reperfusion

This study was designed to assess the effect of propranolol for limiting myocardial damage and hypertrophy in rats with permanent coronary artery occlusion or occlusion followed by reperfusion. Rats were subjected to occlusion of the left main coronary artery for 48 h (MI) or 0.5 h of occlusion followed by reperfusion for 47.5 h (MI/R). Myocardial injury was determined by measuring the depletion of creatine phosphokinase (CK) levels from the left ventricular free wall. In comparison to sham-occluded animals, myocardial CK levels were significantly decreased by 40% in MI + vehicle animals and 30% in MI/R + vehicle animals. Propranolol (0.3 mg/kg 1 min before occlusion followed by 1 mg/kg at 4 and 24 h after occlusion) significantly reduced the loss of myocardial CK-specific activity in MI animals, but failed to prevent the loss of CK-specific activity in animals subjected to coronary artery reperfusion. Left ventricular hypertrophy developed to a similar extent in both vehicle-treated MI and MI/R groups. Propranolol had no effect on the myocardial hypertrophy in MI or MI/R animals. Likewise, in MI/R animals no diminution of polymorphonuclear leukocyte infiltration was seen with propranolol. These data indicate that propranolol had a significant cardioprotective effect in rats with permanent coronary artery occlusion but failed to salvage ischemic tissue, reduce myocardial hypertrophy or mitigate neutrophil infiltration in animals with early reperfusion of the ischemic myocardium. These results suggest that propranolol may afford a significant protection of the ischemic myocardium, but the combination of reperfusion and propranolol may not result in any greater reduction in infarct size than reperfusion alone.     

阿魏酸钠保护大鼠心肌缺血再灌注损伤的作用机制研究

目的 探讨阿魏酸钠(SF)对心肌缺血再灌注(MI/R)损伤大鼠的保护作用及其机制.方法 40只SD大鼠随机分为假手术组、模型组、SF高剂量组(40 mg/kg)、SF低剂量组(20 mg/kg),每组10只.采用结扎左冠状动脉前降支30 min再灌注2 h的方法 复制MI/R损伤大鼠模型,造模成功后取心脏测定心肌梗死面积、心肌组织细胞间黏附分子-1(ICAM-1)和核因子-κB(NF-κB)表达情况及髓过氧化物酶(MPO)的活力.结果 SF高、低剂量组心肌梗死面积小于模型组(P<0.05,P<0.01).模型组心肌MPO活力和ICAM-1、NF-κB阳性表达率高于假手术组,SF高、低剂量组均低于模型组(P<0.05,P<0.01).结论 SF对心肌MI/R损伤的保护作用是通过抑制中性粒细胞浸润,下调NF-κB和ICAM-1的表达,抑制炎性反应等途径实现的.     

Pterostilbene protects against myocardial ischemia/reperfusion injury via suppressing oxidative/nitrative stress and inflammatory response

Recent studies have shown that pterostilbene (Pte) confers protection against myocardial ischemia/reperfusion injury. The oxidative/nitrative stress and inflammation induce injury after myocardial ischemia/reperfusion. The present study was designed to evaluate whether treatment with Pte attenuates oxidative/nitrative stress and inflammation in myocardial ischemia/reperfusion (MI/R). Rats were subjected to 30 min of myocardial ischemia and 3 h of reperfusion, and the rats were administered with vehicle or Pte. The results showed that Pte (10 mg/kg) dramatically improved cardiac function and reduced myocardial infarction and myocardial apoptosis following MI/R. As an indicator of oxidative/nitrative stress, myocardial ONOO⁻ content was markedly reduced after Pte treatment. And, Pte led to a dramatic decrease in superoxide generation and malondialdehyde (MDA) content and a dramatic increase in superoxide dismutase (SOD) activity. In addition, Pte treatment significantly reduced p38 MAPK activation and the expression of iNOS and gp91^phox and increased phosphorylated eNOS expression. Pte treatment dramatically decreased myocardial TNF-α, and IL-1β levels and myeloperoxidase (MPO) activity. Furthermore, ONOO⁻ suppression by either Pte or uric acid (UA), an ONOO⁻ scavenger, reduced myocardial injury. In conclusion, Pte exerts a protective effect against MI/R injury by suppressing oxidative/nitrative stress. These results provide evidence that Pte might be a therapeutic approach for the treatment of MI/R injury.     

Role of cytochrome P4502E1 in retinol's attenuation of carbon tetrachloride-induced hepatotoxicity in the Swiss Webster mouse.

In the mouse, retinol administration attenuates carbon tetrachloride (CCl4)-induced hepatic injury. We have investigated the role of cytochrome P4502E1 (CYP2E1) in this interaction. Male Swiss Webster mice were administered retinol (75 mg/kg/d) or vehicle for 3 days prior to CCl4 (30 microl/kg, ip). Hepatotoxicity produced by CCl4 was assessed by plasma alanine aminotransferase (ALT) activity and light microscopy (ALT activity of 1391+/-430 vs. 274+/-92 IU/L for vehicle + CCl4 and retinol + CCl4 treatments respectively, p < 0.05). Retinol's attenuation of liver injury was maintained when CCl4 was administered 48 h after the conclusion of the retinol pretreatment. Aniline hydroxylation activity, an indicator of CYP2E1 catalytic activity, determined on day 4 was 33.8% of untreated control in vehicle + CCl4 treatments while the retinol + CCl4 treatment group was 94.2% of untreated control. Additionally, CYP2E1 immunoreactive protein was 78% lower in vehicle + CCl4 vs. retinol + CCl4 treatment groups. Attenuation of potentiated hepatotoxicity was also observed when CYP2E1 was induced by acetone (ALT activity of 3119+/-1066 vs. 247+/-77 IU/L for vehicle and retinol treatments respectively, p < 0.05). In the mouse, retinol itself does not alter constitutive or inducible CYP2E1 expression. However, in combination with CCl4 retinol does reduce the amount of CCl4 bioactivated to its toxic metabolite. We conclude that retinol attenuates CCl4-induced hepatotoxicity by causing a decrease in CCl4 bioactivation but does not cause a decrease in CYP2E1 expression.     

Cardioprotection from ischemia and reperfusion injury by an endothelin A-receptor antagonist in relation to nitric oxide production

It has previously been shown that endothelin (ET)-receptor antagonists protect the myocardium from ischemia and reperfusion (I/R) injury. The mechanism behind this effect is unclear. The aim of this study was to elucidate the possible interaction between ET(A)-receptor antagonism and nitric oxide (NO) during I/R. Anesthetized pigs were subjected to 45-min ligation of the left anterior descending coronary artery (LAD) followed by 4 h of reperfusion. Vehicle (n = 7), the ET(A)-receptor antagonist LU 135252 (LU; 0.1 mg/kg, n = 7), the combination of LU and the NO precursor L-arginine (15 mg/kg, n = 7; LU + L-arg), the NO synthase inhibitor N(G)-monomethyl-L-arginine (L-NMMA; 0.2 mg/kg, n = 6), or the combination of LU and L-NMMA (LU + L-NMMA; n = 6) were injected into the LAD during the last 10 min of ischemia and the first 5 min of reperfusion. There were no significant differences in coronary flow, pulmonary capillary wedge pressure, mean arterial pressure, or heart rate between the groups before ischemia or at the end of reperfusion. The area at risk was similar in all five groups. The infarct size of the vehicle group was 79 +/- 6% of the area at risk. LU and LU + L-arginine (L-arg) reduced the infarct size to 39 +/- 6% and 35 +/- 8%, respectively (p < 0.001 vs. vehicle). L-NMMA completely prevented the infarct-limiting effect of LU. Thus the infarct size in the LU + L-NMMA group was 83 +/- 4% (p < 0.001 vs. LU alone); L-NMMA did not affect infarct size per se (79 +/- 4%). ET immunoreactivity increased threefold in the I/R myocardium of the vehicle group. The increase in ET immunoreactivity was significantly attenuated in the LU and LU + L-arg groups (p < 0.001), but not in the groups given L-NMMA or LU + L-NMMA. In conclusion, ET(A)-receptor blockade results in cardioprotection and attenuation of the increase in myocardial ET levels after I/R. Both effects were inhibited by NO synthase blockade, suggesting that they are dependent on maintained production of NO.     

Effects of combined thromboxane synthetase inhibition/thromboxane receptor antagonism in two models of sudden cardiac death in the canine: limited role for thromboxane.

The effects of combined thromboxane synthetase inhibition and thromboxane receptor antagonism (TSI/TRA) were studied in conscious and in anesthetized canine models of sudden cardiac death. Administration of the TSI/TRA, R68070 10 mg/kg intravenously (i.v.), decreased thrombin-stimulated thromboxane synthesis and significantly antagonized platelet aggregation in response to the thromboxane-mimetic U46,619. In the conscious canine model, R68070 did not change ventricular refractoriness, did not prevent induction of ventricular arrhythmias by programmed electrical stimulation, and failed to prevent development of spontaneous ventricular fibrillation (VF) in response to ischemia produced at a site remote from the area of previous myocardial infarction (R68070 mortality = 70%, vehicle = 100%, p = NS). In the anesthetized canine model, R68070 prevented development of ischemia in 7 of 11 animals and reduced mortality significantly (R68070 27% and vehicle 73%; p = 0.038). R68070 inhibited thrombus formation in both models (R68070 conscious 7.0 +/- 2.6 mg and vehicle conscious 15 +/- 7.6 mg, p = NS; R68070 anesthetized 5.9 +/- 1.9 mg and vehicle anesthetized 17.7 +/- 4.3 mg; p less than 0.05). The results suggest that inhibition of thromboxane-dependent activity during acute recovery from infarction was able to protect the myocardium from developing ischemia in response to current-mediated intimal damage in a noninfarct-related artery. In the subacute phase of recovery from infarction, when the underlying myocardial substrate is susceptible to electrical derangement induced by transient ischemia, thromboxane inhibition in itself was unable to prevent ischemia-induced sudden cardiac death. Although R68070 may delay onset of ischemia due to thrombotic occlusion of the coronary artery, there does not appear to be an antiarrhythmic/antifibrillatory action to be derived from interfering with the synthesis or receptor-mediated action of thromboxane. Furthermore, R68070 does not alter the electrophysiologic properties of the heart which would result in an antiarrhythmic or antifibrillatory action.     

Effect of cloricromene during ischemia and reperfusion of rabbit hindlimb: evidence for an involvement of leukocytes in reperfusion-mediated tissue and vascular injury.

The involvement of polymorphonuclear leukocytes (PMN) in reperfusion-mediated vascular injury was studied in a model of ischemia and reperfusion in rabbit hindlimb. Ischemia was induced by 4-h occlusion of the left iliac artery followed by 4-h reperfusion. Plasma creatine kinase (CK) and lactate dehydrogenase (LDH) activities, hindlimb vascular resistance (HVR), and myeloperoxidase (MPO) activity in the postischemic extensor digitorum longus (EDL) muscle were measured to evaluate the extent of vascular and skeletal muscle injury. In addition, the ischemia/reperfusion-induced injury of the hindlimb vasculature was evaluated by electron microscopy. Ischemia and reperfusion (n = 10) was associated with an increase in CK (6,380 +/- 1,346 U/L, p < 0.05) and LDH (552 +/- 76 U/L, p < 0.05) activities which were significantly greater than those observed in sham-operated control animals (CK 1,651 +/- 207 U/L, LDH 246 +/- 14 U/L; n = 6). HVR in sham-operated animals decreased by 20 +/- 3%, but increased in the ischaemic group by 56 +/- 16% (p < 0.05). MPO activity of EDL muscle increased from 7.3 +/- 3.9 U per muscle (sham) to 28.0 +/- 5.9 U per muscle (p < 0.05) after ischemia and reperfusion. Morphologic analysis did not show any alteration in the microvascular bed of the hindlimb. Moreover, 1 mg/kg/h intravenous (i.v.) cloricromene, an antithrombotic drug that inhibits superoxide anion production as well as PMN adhesion to endothelium, reduced the increase in plasma CK and LDH and the increase in MPO and HVR observed in animals subjected to hindlimb ischemia.(ABSTRACT TRUNCATED AT 250 WORDS)     

心肌缺血再灌注中TNF动态变化及药物干预

目的探讨肿瘤坏死因子(TNF)、髓过氧化物酶(MPO)在心肌缺血再灌注(MI/R)中的动态变化的临床意义及卡托普利的干预作用。方法将实验兔54只分为MI/R组、卡托普利治疗组及假手术对照组,分别测缺血前、缺血0.5h,再灌注0.5、1.5、6h5个时相点外周血TNF,以及后4个时相点心肌组织TNF、MPO含量,对照组心肌指标只检测最后一个时相点。结果再灌注0.5h外周血TNF即开始升高(P<0.05),再灌注6h更高(P<0.01),心肌组织TNF、MPO含量则于再灌注1.5h升高并持续至再灌注6h,卡托普利干预后上述指标均有明显改善。结论TNF参与再灌注损伤,是再灌注后导致内皮功能紊乱的重要因素之一。卡托普利通过保护内皮,减少致伤因素而减轻再灌注损伤。     

Effects of U74006F, a novel inhibitor of lipid peroxidation, in stunned reperfused canine myocardium.

U74006F, a novel 21-amino steroid is a potent inhibitor of iron-mediated lipid peroxidation and has been shown to be of therapeutic benefit in central nervous system ischemia. As oxygen radicals have been implicated in the development of postischemic myocardial dysfunction, we examined the efficacy of U74006F to enhance the recovery of function in a canine model of stunned, reperfused myocardium. Twenty-six dogs were randomized to either a vehicle (n = 11), U74006F (n = 10), or U74006F-paced group (n = 5). U74006F (6 mg/kg i.v.) was administered 15 min prior to coronary artery occlusion. Myocardial blood flows were measured by the microsphere technique, and function data were obtained by sonomicrometry. Both U74006F-treated groups demonstrated a significant increase in posterior wall thickening as compared to the vehicle treatment (U74006F-paced, 27.0 +/- 12.8%; U74006F, 22.4 +/- 11%; vehicle, -13.5 +/- 9.9%, p less than 0.001 following 3 h of reperfusion). Enhanced function recovery was accompanied by lower heart rates in the U74006F-treated group following reperfusion (treated versus vehicle, 109 +/- 6.7 versus 131 +/- 8.8 beats/min, p = 0.004). The U74006F-paced group was maintained at the same rate as the vehicle group, with no diminution in function recovery compared to the unpaced group. No effects in systemic hemodynamics or nutrient blood flow were evident as a function of drug treatment. We conclude that pretreatment with U74006F enhances the recovery of function in stunned canine myocardium via the inhibition of oxygen radicals and lipid peroxidation products. This activity suggests that this compound represents a new therapeutic adjunct in reperfusion and recanalization therapies.     

槲皮素对心肌缺血再灌注损伤的保护作用及机制研究

目的探讨槲皮素(QU)对心肌缺血再灌注(MI/R)损伤的保护作用及其作用机制。方法采用结扎左冠脉前降支30 min再灌注2 h的方法复制MI/R损伤大鼠模型,随机分为假手术组、模型组、QU组(25、50、100 mg/kg),每组10只,各组于术前1周开始灌胃给药,1次/d。再灌注后取心脏,染色法测定心肌梗死面积;免疫组化法测定心肌组织NF-κB和ICAM-1表达情况;取心肌匀浆,髓过氧化物酶(MPO)法测定中性粒细胞浸润情况。结果QU高、中剂量可分别缩小心肌梗死面积至25.00%、25.31%,与模型组(32.55%)比较差异有统计学意义(P<0.05);QU各剂量组心肌MPO活力分别降低至185.70、190.66、210.03 U/g,与模型组(311.72 U/g)比较差异均有统计学意义(P<0.05,P<0.01);QU各剂量组心肌组织ICAM-1阳性区面积百分比分别降至32.08%、32.65%、36.42%,与模型组(42.67%)比较差异有统计学意义(P<0.05,P<0.01);QU高、中剂量可使心肌NF-κB的表达水平分别降低至55.23%、54.90%,与模型组(61.05%)比较差异有统计学意义(P<0.05)。结论QU预处理可保护MI/R所致心肌损伤,其机制与抑制中性粒细胞浸润、下调NF-κB和ICAM-1的表达等有关。