The ultrastructure of chicken gizzard vinculin as visualized by high-resolution electron microscopy

OBJECTIVES: A myocardial calcium-independent PLA2 has been described that is activated during myocardial ischemia and this enzyme may modulate ATP-sensitive potassium channels (KATP). The aim of this study was to determine the effect of an inhibitor of this enzyme, a bromoenol lactone, in isolated globally ischemic rat hearts. METHODS: Isolated rat hearts were treated for 10 min with 0.3-6 microM bromoenol lactone and then subjected to 25 min ischemia and 30 min reperfusion. RESULTS: The bromoenol lactone significantly increased coronary flow in nonischemic myocardium, and slightly reduced cardiac function at 6 microM. During global ischemia, time to contracture was significantly increased from vehicle group values in the presence of the bromoenol lactone (EC50 = 1.2 microM). During reperfusion, a concentration-dependent increase in function and a reduction in LDH release were observed for the PLA2 inhibitor. The concentrations of the PLA2 inhibitor which were significantly cardioprotective, inhibited this enzyme in membrane fractions of rat myocardium (IC50 = 0.87 microM). The KATP blocker sodium 5-hydroxydecanoate (5-HD) inhibited the increase in time to contracture observed for the bromoenol lactone. During reperfusion, 5-HD abolished the protective effects of the bromoenol lactone on cardiac function and LDH release. Glyburide had similar effects on the cardioprotective activity of the bromoenol lactone, although it only partially abolished the LDH reducing effect of this agent. CONCLUSIONS: The bromoenol lactone protects ischemic myocardium at concentrations which also inhibit calcium-independent PLA2. This cardioprotection can be attenuated by blockers of KATP, suggesting a potential mechanism for modulation of myocardial KATP.     

Effects of FR167653 on ischemia-reperfusion injury: evaluation through preservation and transplantation in canine hearts

BACKGROUND: Ischemia-reperfusion injury may result in the local release of proinflammatory cytokines. A newly synthesized organic compound, FR167653, has been characterized as a potent suppressant of interleukin-1beta and tumor necrosis factor-alpha. We investigated the effects of FR 167653 on ischemia-reperfusion injury of canine hearts during preservation and transplantation. METHODS: Seventeen pairs of adult mongrel dogs were used. The donor heart was removed, stored in University of Wisconsin solution at 4 degrees C for 12 hours, and then transplanted orthotopically. Recipients were divided into the FR-treated group (FR167653 1 mg/kg/hr, 8 dogs) and the control group (9 dogs). Hemodynamic parameters, including cardiac output, left ventricular pressure (LVP), and the maximum rate of increase of LVP, were assessed after 120 minutes of reperfusion. The heart specimen was then harvested for histopathologic examination. RESULTS: The values of LVP (mm Hg) of the FR-treated and the control groups were 120+/-10 and 79+/-9, respectively. The values of LV dp/dt (mm Hg/sec) in the FR-treated and control groups were 4944+/-414 and 2292+/-380, respectively. There were significant differences in LVP (P < .05) and the maximum rate of increase of LVP (P < .01) between the two groups. The values of cardiac output (L/min) of the FR-treated and control groups were 1.27+/-0.12 and 0.71+/-0.11 of the baseline, respectively, showing a significant difference (P < .05) between the two groups. Histopathologic findings included irregular glycogen distribution in myocardial cells of the control group, although this change was less frequent in the FR-treated group. CONCLUSION: FR 167653 seems to have a protective effect on tissue subjected to ischemia-reperfusion injury during the acute phase after heart transplantation.     

Enflurane and isoflurane, but not halothane, protect against myocardial reperfusion injury after cardioplegic arrest with HTK solution in the isolated rat heart

To investigate the effects of halothane, enflurane, and isoflurane on myocardial reperfusion injury after ischemic protection by cardioplegic arrest, isolated perfused rat hearts were arrested by infusion of cold HTK cardioplegic solution containing 0.015 mmol/L Ca2+ and underwent 30 min of ischemia and a subsequent 60 min of reperfusion. Left ventricular (LV) developed pressure and creatine kinase (CK) release were measured as variables of myocardial function and cellular injury, respectively. In the treatment groups (each n = 9), anesthetics were given during the first 30 min of reperfusion in a concentration equivalent to 1.5 minimum alveolar anesthetic concentration of the rat. Nine hearts underwent the protocol without anesthetics (controls). Seven hearts underwent ischemia and reperfusion without cardioplegia and anesthetics. In a second series of experiments, halothane was tested after cardioplegic arrest with a modified HTK solution containing 0.15 mmol/L Ca2+ to investigate the influence of calcium content on protective actions against reperfusion injury by halothane. LV developed pressure recovered to 59%+/-5% of baseline in controls. In the experiments with HTK solution, isoflurane and enflurane further improved functional recovery to 84% of baseline (P < 0.05), whereas halothane-treated hearts showed a functional recovery similar to that of controls. CK release was significantly reduced during early reperfusion by isoflurane and enflurane, but not by halothane. After cardioplegic arrest with the Ca2+-adjusted HTK solution, halothane significantly reduced CK release but did not further improve myocardial function. Isoflurane and enflurane given during the early reperfusion period after ischemic protection by cardioplegia offer additional protection against myocardial reperfusion injury. The protective actions of halothane depended on the calcium content of the cardioplegic solution. IMPLICATIONS: Enflurane and isoflurane administered in concentrations equivalent to 1.5 minimum alveolar anesthetic concentration in rats during early reperfusion offer additional protection against myocardial reperfusion injury even after prior cardioplegic protection. Protective effects of halothane solely against cellular injury were observed only when cardioplegia contained a higher calcium concentration.     

Detection of subclinical sensory nerve dysfunction in amyotrophic lateral sclerosis--a microneurographic study

AIM: To study the effects of panaxadiol saponins (PDS) on burn rat heart functions and try to find its mechanisms. METHODS: A 35% skin-full-thickness burn was produced by using napalm in Wistar rats. PDS 30 mg kg-1 was injected i.p. to rats immediately after burn and repeated 2 h before examination. Using the isolated perfused working heart and biochemistry methods, heart rate (HR), cardiac output (CO), coronary flow (CF), left ventricular pressure (LVP), aortic pressure (AP), +/- dp/dtmax, and content of malondialdehyde (MDA), activity of superoxide dismutase (SOD) in ventricular myocardium homogenate were examined 8 h after burn. RESULTS: After burn, HR, CO, CF, LVP, AP, +dp/dtmax, -dp/dtmax, and SOD activity decreased from 206 bpm, 92 mL min-1 g-1, 26 mL min-1 g-1, 7 kPa, 5.9 kPa, 149 kPa s-1, 73 kPa s-1, 2.9 NU/mg protein to 162 bpm, 72 mL min-1 g-1, 14 mL min-1 g-1, 4 kPa, 2.2 kPa, 77 kPa s-1, 44 kPa s-1, 1.7 NU/mg protein, respectively, and MDA content raised from 0.77 nmol/mg protein to 1.35 nmol/mg protein (P all < 0.05). But in PDS-treated group, above decreased or increased dates restored to 202 bpm, 91 mL min-1 g-1, 25 mL min-1 g-1, 6 kPa, 4.1 kPa, 112 kPa s-1, 62 kPa s-1, 2.8 NU/mg protein, 0.91 nmol/mg protein, respectively (P all < 0.05 vs burn). CONCLUSION: PDS exerts definite protective effects on the cardiac functions after burn injury possibly through its enhancement of SOD activity and the reduction of both the levels of free radicals and lipid peroxides (LPO) of the myocardium.     

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-alpha), cardiac mRNA for TNF-alpha, cardiac intercellular adhesion molecule-1 (ICAM-1) immunostaining and myocardial contractility (left ventricle dP/dtmax) 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-alpha. Furthermore increased cardiac mRNA for TNF-alpha 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-alpha 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.     

Effect of acetylsalicylic acid on metabolism and contractility in the ischemic reperfused heart

The effect of acetylsalicylic acid (ASA) on high-energy phosphates (adenosine triphosphate: ATP, creatine phosphate: CrP, inorganic phosphate: Pi) and intracellular pH during myocardial ischemia and reperfusion was studied using phosphorus 31-nuclear magnetic resonance (31P-NMR) in the isolated rabbit hearts. Coronary flow, left ventricular systolic developed pressure (LV Dev.P) and left ventricular end-diastolic pressure (LVEDP) were also measured. Langendorff hearts perfused at 37 degrees C with the perfluorochemical emulsion Fluosol-43 were subjected to 15 min and 30 min of zero-flow ischemia and to 15 min of low-flow ischemia (coronary perfusion pressure = 20 mmHg) followed by 65 min of reperfusion (control, Group I). ASA (0.28 mmol/L) was infused either for the entire experimental period from beginning 45 min prior to ischemia (Group II) and infused immediately after reperfusion (Group III). During ischemia, Group II showed a significant suppression of the decrease in the ATP level and pH with both zero-flow and low-flow ischemia compared to those in the other groups, and moreover the increase in Pi and the decrease in CrP in low-flow ischemia were also suppressed. In Group III, the ATP level during reperfusion was significantly higher than that in Group I, but was not significantly different from that in 30 min zero-flow ischemia. In 30 min zero-flow ischemia, Pi, CrP and coronary flow after reperfusion in Group II tended to recover to preischemic values. There were no differences in LV Dev.P among the 3 groups. In conclusion, ASA has a protective effect on myocardial high-energy phosphates during ischemia and reperfusion in rabbit hearts.     

Modulation of adenosine effects in attenuation of ischemia and reperfusion injury in rat heart

We investigated whether xanthine oxidase-derived superoxide radical generation could be modified by interfering with adenosine transport and metabolism in reducing myocardial injury during post-ischemic reperfusion. Isolated rat hearts perfused at constant pressure were subjected to 20 min of pretreatment with test agents, followed by 40 min global ischemia and 30 min reperfusion with or without test agents. In hearts treated with adenosine deaminase inhibitor, erythro 9-(2-hydroxy-3-nonyl) adenine (EHNA), alone or together with a selective nucleoside transport blocker, p-nitrobenzylthioinosine (NBMPR), the accumulated amount of O-2. was significantly reduced [10.2+/-0.97, 11.6+/-2.4, 8.1+/-0.51, respectively, v 31.6+/-2.1 (s. e.) nmol/wet g/30 min in ischemic control, P<0.01]. A positive correlation between O-2. and inosine release was observed in the initial 5 min of reperfusion in hearts treated with either EHNA or NBMPR ( r=0.475, P<0.05). Furthermore, the accumulated amount of LDH release showed positive correlation with that of O-2. among the same groups (r=0.474, P<0.05). Both EHNA and NBMPR had the cardioprotective effect on the recovery of left ventricular end-diastolic pressure (LVEDP), ATP repletion, and build up of endogenous adenosine. This study suggests that : (1) adenosine metabolism can be manipulated towards the formation of O-2. during reperfusion, and it has an important bearing on the cardiac recovery of ischemic myocardium, (2) the generation of O-2. is related to only inosine release during initial reperfusion.     

Energy metabolism after ischemic preconditioning in streptozotocin-induced diabetic rat hearts

OBJECTIVES: The aim of this study was to compare the cardioprotective effects of preconditioning in hearts from streptozotocin-induced diabetic rats with its effects in normal rat hearts. BACKGROUND: The protective effect of ischemic preconditioning against myocardial ischemia may come from improved energy balance. However, it is not known whether preconditioning can also afford protection to diabetic hearts. METHODS: Isolated perfused rat hearts were either subjected (preconditioned group) or not subjected (control group) to preconditioning before 30 min of sustained ischemia and 30 min of reperfusion. Preconditioning was achieved with two cycles of 5 min of ischemia followed by 5 min of reperfusion. RESULTS: In the preconditioned groups of both normal and diabetic rats, left ventricular developed pressure, high energy phosphates, mitochondrial adenosine triphosphatase and adenine nucleotide translocase activities were significantly preserved after ischemia-reperfusion; cumulative creatine kinase release was smaller during reperfusion; and myocardial lactate content was significantly lower after sustained ischemia. However, cumulative creatine kinase release was less in the preconditioned group of diabetic rats than in the preconditioned group of normal rats. Under ischemic conditions, more glycolytic metabolites were produced in the diabetic rats (control group) than in the normal rats, and preconditioning inhibited these metabolic changes to a similar extent in both groups. CONCLUSIONS: The present study demonstrates that in both normal and diabetic rats, preservation of mitochondrial oxidative phosphorylation and inhibition of glycolysis during ischemia can contribute to preconditioning-induced cardioprotection. Furthermore, our data suggest that diabetic myocardium may benefit more from preconditioning than normal myocardium, possibly as a result of the reduced production of glycolytic metabolites during sustained ischemia and the concomitant attenuation of intracellular acidosis.     

Attenuation of myocardial reperfusion injury by reducing intracellular calcium overloading with dihydropyridines

The effects of three different dihydropyridine (DHP) calcium channel antagonists, nisoldipine, nimodipine, and nifedipine, on myocardial ischemic and reperfusion injury were studied using isolated rat hearts subjected to ischemia and reperfusion. Hearts were perfused with Krebs-Henseleit bicarbonate buffer containing 0, 4, 16, 64 and 100 nM concentrations of the above dihydropyridines for 15 min. Global ischemia was then induced by terminating the aortic flow for 30 min at 37 degrees, followed by 30 min of reperfusion. Left ventricular (LV) functional (LV developed pressure, its first derivative and coronary flow) and biochemical parameters (creatine kinase release) were monitored prior to ischemia and during reperfusion. In separate group of hearts, intracellular free Ca2+ ([Ca2+]i) was monitored with an intracellular calcium analyzer using a fluorescent Ca2+ indicator (Fura-2 AM). Tissue Ca2+ was also measured by atomic absorption spectroscopy after perfusing the hearts with ion-free cold buffer to wash out extracellular Ca2+. Significant recovery of the coronary flow was observed in all hearts treated with a high concentration (100 nM) of DHPs compared with the control group (P < 0.05), while a lower dose of nisoldipine (16 nM) and nifedipine (64 nM) also improved the coronary flow effectively. Reduction of myocardial creatine kinase release and improvement of the recovery of LV developed pressure, dp/dtmax, were achieved by DHPs in a concentration-dependent manner. A higher concentration of DHPs also decreased the formation of myocardial thiobarbituric acid reactive substances, although these compounds did not possess direct free radical scavenging effects in vitro. Tissue Ca2+ content was reduced significantly in treated groups. The rise of [Ca2+]i during ischemia and reperfusion appeared to be attenuated by these DHPs. The concentration-response study of the three DHPs showed the effective concentrations for reducing [Ca2+]i to be 16, 64 and 100 nM nisoldipine, nifedipine and nimodipine, respectively, in this experimental setting. The above results indicate that pretreatment with DHPs can attenuate the myocardial reperfusion injury by modulating Ca2+ overloading and decreasing the susceptibility of the membrane to free radical attack.     

In vitro antiarrhythmic effect of prior whole body hyperthermia: implication of catalase

The protective effect of heat stress against mechanical dysfunction and myocardial necrosis after prolonged ischemia is well known. We have investigated whether the protective effect of heat stress extends to reperfusion arrhythmias in the isolated perfused rat heart. Rats were exposed to 20 min of 42 degrees C hyperthermia. Twenty-four h later their hearts were isolated, perfused and subjected to a 5-min period of occlusion of the left coronary artery. The incidence and duration of reperfusion arrhythmias were assessed in the 30-min reperfusion period. Prior heat stress led to a reduction in the incidence (from 100 to 60%, P相似文献   

Blocking of classical complement pathway inhibits endothelial adhesion molecule expression and preserves ischemic myocardium from reperfusion injury

Myocardial injury after ischemia (I) and reperfusion (R) is related to leukocyte activation with subsequent release of cytokines and oxygen-derived free radicals as well as complement activation. In our study, the cardioprotective effects of exogenous C1 esterase inhibitor (C1 INH) were examined in a rat model of myocardial I + R (i.e., 20 min + 24 hr or 48 hr). The C1 INH (10, 50 and 100 U/kg) administered 2 min before reperfusion significantly attenuated myocardial injury after 24 hr of R compared to vehicle treated rats (P < .001). Further, cardiac myeloperoxidase activity (i.e., a marker of PMN [polymorphonuclear leukocyte] accumulation) in the ischemic area was significantly reduced after C1 INH treatment compared to vehicle treated animals (0.81 +/- 0.1, 0.34 +/- 0.13, 0.13 +/- 0.1 vs. 1.44 +/- 0.3 U/100 mg tissue, P < .001). In addition, C1 INH (100 U/kg) significantly attenuated myocardial injury and neutrophil infiltration even after 48 hr of reperfusion compared to vehicle treatment. Immunohistochemical analysis of ischemic-reperfused myocardial tissue demonstrated activation of classical complement pathway by deposition of C1q on cardiac myocytes and cardiac vessels. In addition, expression of the endothelial adhesion molecules P-selectin and intercellular adhesion molecule 1 (ICAM-1) was observed after reperfusion of the ischemic myocardium. In this regard, C1 INH administration abolished expression of P-selectin and ICAM-1 on the cardiac vasculature after myocardial ischemia and reperfusion. Blocking the classical complement pathway by exogenous C1 INH appears to be an effective means to preserve ischemic myocardium from injury after 24 and 48 hr of reperfusion. The mechanisms of this cardioprotective effect appears to be due to blocking of complement activation and reduced endothelial adhesion molecule expression with subsequent reduced PMN-endothelium interaction, resulting in diminished cardiac necrosis.     

Quantitative two-dimensional echocardiographic assessment of regional wall motion during transient ischemia and reperfusion in the rat

Nonlethal myocardial ischemia produces profound and long-lasting effects on regional ventricular function and metabolism (myocardial stunning) and protects against myocardial infarction from subsequent prolonged ischemia (ischemic preconditioning). Two-dimensional echocardiography (2DE) is an essential tool for quantitative analysis of regional and global left ventricular (LV) function during myocardial ischemia and reperfusion and the study of these phenomena. However, the inability to perform 2DE in the open-chest rat heart has seriously limited the use of this model. To investigate the effect of transient coronary occlusion on segmental wall motion and LV geometry, we employed a 20 MHz intravascular ultrasound catheter placed on the epicardial surface of the rat heart (n = 15) to yield 2DE images suitable for quantitative analysis. Three 2-minute left coronary occlusions were made, separated by 5 minutes of reperfusion, with imaging during occlusion and at 5 and 60 minutes of reperfusion. Ischemic and nonischemic wall thicknesses, LV cross-sectional area, estimated LV volume, and the fractional changes of these parameters were measured. In eight animals these values were also compared with necropsy measurements of wall thickness, LV cross-sectional area, and volume. LV and right ventricular structures were well visualized in short-axis cross-sectional images in all animals, and images suitable for quantitative analysis were obtained in 92% of the periods. Coronary occlusion caused immediate, marked LV cavitary expansion, which rapidly returned to normal by 5 minutes of reperfusion. Active systolic thickening of the anterior wall at baseline (47% +/- 3%) became passive thinning during occlusion (-6% +/- 2%) and recovered partially, to 30% +/- 3% at 5 minutes of reperfusion and 42% +/- 4% at 60 minutes (p < 0.0005 at 5 minutes of reperfusion vs baseline; p not significant at 60 minutes). Recovery of thickening after 5 minutes of reperfusion was not different after the first versus third occlusion (23% +/- 4% vs 30% +/- 3%; p = 0.19). Measurements made by 2DE correlated well with those made by necropsy, although wall thickness was slightly thicker by 2DE. We conclude that epicardial echocardiography with an intravascular ultrasound catheter provides quantifiable 2DE images in this model and yields accurate information on segmental wall thickening and ventricular geometry not available by other techniques. Left coronary occlusion in the rat is associated with marked global and segmental LV expansion, which rapidly reverses with reperfusion. Postischemic regional wall motion abnormalities are present after coronary occlusion as brief as 2 minutes and can be measured accurately. The effect of multiple brief occlusions is not cumulative.(ABSTRACT TRUNCATED AT 400 WORDS)     

Protective effect of K(ATP) openers in ischemic rat hearts treated with a potassium cardioplegic solution

ATP-sensitive potassium channel (KATP) openers directly protect ischemic myocardium, which may make them useful for treating patients undergoing cardiopulmonary bypass, but whether high-potassium-containing cardioplegic solutions would inhibit their protective effects is not clear. We determined whether additional protection greater than that provided by cardioplegia could be found for KATP openers. We studied the effect of 10 microM cromakalim or BMS-180448 pretreatment (10 min before cardioplegia) on severity of ischemia in isolated rat hearts given normothermic or cold St. Thomas' cardioplegic solution (16 mM K+). After cardioplegic arrest, the hearts were subjected to 30-min (normothermic) or 150-min (hypothermic) global ischemia, each followed by 30-min reperfusion. The cardioplegic solutions significantly protected the hearts, as measured by increased time to onset of contracture, enhanced recovery of function, and reduced lactate dehydrogenase (LDH) release. Cromakalim and BMS-180448 both further significantly increased time to contracture in both normothermic and hypothermic arrested hearts; this was accompanied by enhanced recovery of reperfusion contractile function and reduced cumulative LDH release. This additional protective effect of the K ATP openers was abolished by glyburide. Because administration of the K ATP openers only with the cardioplegic solution (1 min before global ischemia) was not efficacious, >1-min pretreatment apparently is necessary. K ATP openers provide additional protection to that afforded by cold or normothermic potassium cardioplegia in rat heart, although the timing of treatment may be crucial.     

Carvedilol, a new beta adrenoreceptor blocker and free radical scavenger, attenuates myocardial ischemia-reperfusion injury in hypercholesterolemic rabbits

Oxygen-derived free radicals play a critical role in atherogenesis and reperfusion injury. The present experiment evaluated the effects of carvedilol, a new beta adrenoreceptor blocker with potent free radical-scavenging activity, on myocardial ischemia and reperfusion injury in a hypercholesterolemic rabbit model. New Zealand rabbits were fed a normal diet, a high-cholesterol diet, or a high-cholesterol diet supplemented with 1200 ppm carvedilol or propranolol. Eight weeks later, the rabbits were subjected to 60 min of myocardial ischemia followed by 60 min of reperfusion. The nontreated cholesterol-fed animals experienced greater cardiac damage after ischemia and reperfusion than rabbits fed a normal diet (necrosis 51% +/- 4% vs. 28% +/- 3% in the normal-diet group, P < .01). In addition, nontreated cholesterol-fed rabbits showed a significantly decreased vasorelaxant response to ACh in U-46619-precontracted aortic rings (56% +/- 5% vs 90% +/- 3% in the control group, P < .001). Treatment with propranolol neither preserved endothelial function after cholesterol feeding nor reduced neutrophil accumulation in ischemic-reperfused myocardial tissue. Propranolol treatment did significantly decrease HR, pressure-rate index and infarct size (necrosis 33% +/- 4%). Despite their having essentially identical effects on HR and pressure-rate index, carvedilol exerted more profound cardiac protective effects than propranolol (necrosis 19% +/- 3%). Moreover, carvedilol treatment significantly preserved aortic endothelial function and markedly reduced neutrophil accumulation in ischemic-reperfused myocardial tissue. These results indicate that in addition to its beta blocking activity, the antioxidant and endothelial protective activities of carvedilol contributed significantly to its cardiac protective effects after ischemia and reperfusion.     

The effect of batroxobin on coronary segmental resistance and coronary blood flow in acute myocardial ischemic dogs

To study the effects of batroxobin on coronary circulation and cardiac performance in acute myocardial ischemia, Batroxobin was given intravenously to dogs with experimental coronary stenosis. A dose-dependent increase of coronary blood flow (CBF) was observed. Forty minutes after batroxobin (2 BU.kg-1 at infusion rate 0.1 BU.kg-1.min-1) administration, CBF increased by 12% (P < 0.05), small coronary resistance(RS) decreased from 4.1 +/- 0.5 to 3.2 +/- 0.5 mmHg.min.ml-1 (P < 0.01), while large coronary resistance(RL) changed insignificantly from 3.9 +/- 0.8 to 3.8 +/- 0.7 mmHg.min.ml-1 (P > 0.05). Two hours following drug administration, the changes in CBF, RS and RL still remained and RT decreased by 13% (P < 0.05). The + LV(dp/dt)max and -LV(dp/dt)max increased by 14% and 16% (P < 0.05) respectively compared with those in control group. It is concluded that batroxobin improves the ischemic canine coronary circulation and cardiac performance by way of lowering the small coronary resistance and thus increasing CBF. The data also suggest the benificial effect of batroxobin in acute myocardial ischemia.     

Myocardial ischemia and reperfusion are associated with an increased stiffness of remote nonischemic myocardium

During and after an ischemic injury, maintenance and recovery of cardiac function may critically depend on remote nonischemic myocardium. Graded myocardial ischemia is associated with an approximately 50% increase in stiffness of nonischemic myocardium. We determined whether this increase in stiffness is unique to the ischemic period or persists during reperfusion. Ten anesthetized (isoflurane 1.0% vol/vol) open-chest dogs were instrumented to measure left ventricular pressure and dimensions (sonomicrometry) in ischemic and nonischemic myocardium. Regional chamber stiffness and myocardial stiffness were assessed using the end-diastolic pressure-length relationship which was modified by stepwise infusion and withdrawal of 200 mL of the animals' own blood during baseline, 45 min low flow ischemia (systolic bulge), and 60 min after the onset of reperfusion. In remote nonischemic myocardium, regional myocardial ischemia was associated with a significant (P < 0.05) increase in chamber stiffness (+44%) and myocardial stiffness (+48%). Sixty minutes after the onset of reperfusion, chamber stiffness (+54%, P < 0.05 versus baseline) and myocardial stiffness (+55%, P < 0.05 versus baseline) remained increased. Thus, the ischemia-induced increase in stiffness of remote nonischemic myocardium persists for at least 60 min after reperfusion.     

Renal ischemia/reperfusion remotely improves myocardial energy metabolism during myocardial ischemia via adenosine receptors in rabbits: effects of "remote preconditioning"

OBJECTIVES: This study examined the changes in myocardial energy metabolism during myocardial ischemia after "remote preconditioning" and investigated the involvement of adenosine receptors in the mechanisms of this effect. BACKGROUND: Recent studies have indicated that a brief period of ischemia and reperfusion (ischemic preconditioning, PC) in a remote organ reduces myocardial infarct size (IS) protecting against subsequent sustained myocardial ischemia. However, the mechanisms of "remote PC" remain unclear. We assessed myocardial energy metabolism during sustained myocardial ischemia and reperfusion after renal PC (RPC), in comparison with that after myocardial PC (MPC) in open-chest rabbits. It has been established that adenosine receptors are involved in the mechanisms of MPC. METHODS: Rabbits that had been anesthetized with halothane were divided into six groups. The control (CNT) group underwent 40-min coronary occlusion followed by 120 min reperfusion. Before the procedure, the MPC group underwent an additional protocol of 5 min coronary artery occlusion and 20 min reperfusion, and the RPC group received a 10 min episode of renal artery occlusion and 20 min reperfusion. In additional experimental groups, 8 sulfophenyl-theophylline (SPT, 10 mg/kg), an adenosine receptor inhibitor, was intravenously injected before the 40 min myocardial ischemia (SPT, MPC + SPT and RPC + SPT groups, respectively). Myocardial levels of phosphocreatine (PCr), ATP and intracellular pH (pHi) were measured by 31P-NMR spectroscopy. RESULTS: RPC and MPC delayed the decreases in ATP levels, preserved pHi during 40-min myocardial ischemia and resulted in better recovery of ATP and PCr during 120 min reperfusion compared with the controls. SPT abolished the improvement in myocardial energy metabolism and the reduction in myocardial IS caused by MPC or RPC. Myocardial IS in the CNT (n = 8), MPC (n = 9), RPC (n = 9), SPT (n = 6), MPC + SPT (n = 8) and RPC + SPT (n = 8) groups averaged 42.8+/-3.5%, 18.2+/-1.8%*, 19.6+/-1.3%*, 44.9+/-5.0%, 35.6+/-2.7% and 34.8+/-3.6% of the area at risk (*p < 0.05 vs. CNT), respectively. CONCLUSIONS: PC in a remote organ, similar to MPC, improved myocardial energy metabolism during ischemia and reperfusion and reduced IS in vivo by an adenosine-dependent mechanism in rabbits.     

Nitric oxide signaling in ischemic heart

OBJECTIVE: Several recent studies have implicated a role of endogenous nitric oxide (NO) in the pathophysiology of myocardial ischemic/reperfusion injury. However, the mechanism by which NO exerts its beneficial/detrimental effects remains unknown. This study examined the intracellular signaling of NO by studying the role of the NO-cGMP signaling pathway on the phospho-diesteratic breakdown and turnover of phosphoinositides during myocardial ischemia and reperfusion. METHODS: Isolated working rat hearts were made ischemic for 30 min followed by 30 min of reperfusion. A separate group of hearts were pre-perfused with 3 mM L-arginine for 10 min prior to ischemia. The release of NO was monitored using an on-line amperometric sensor. The aortic flow and developed pressure were examined to determine the effects of L-arginine on ischemic/reperfusion injury. For signal transduction experiments, sarcolemmal membranes were radiolabeled by perfusing the isolated hearts with [3H]myoinositol and [14C]arachidonic acid. Hearts were then perfused for 10 min in the presence or absence of L-arginine via the Langendorff mode. Ischemia was induced for 30 min followed by 30 min of reperfusion. Experiments were terminated before L-arginine and after L-arginine treatment, after ischemia, and during reperfusion. Biopsies were processed to determine the isotopic incorporation into various phosphoinositols as well as phosphatidic acid and diacylglycerol. cGMP was assayed by radioimmunoassay and SOD content was determined by enzymatic analysis. RESULTS: The release of NO was diminished following ischemia and reperfusion and was augmented by L-arginine. L-Arginine reduced ischemic/reperfusion injury as evidenced by the enhanced myocardial functional recovery. cGMP, which remained unaffected by ischemia and reperfusion, was stimulated significantly after L-arginine treatment. The cGMP level persisted up to 10 min of reperfusion and then dropped slightly. Reperfusion of ischemic myocardium resulted in significant accumulation of radiolabeled inositol phosphate, inositol bisphosphate, and inositol triphosphate. Isotopic incorporation of [3H]inositol into phosphatidylinositol, phosphatidylinositol-4-phosphate, and phosphatidylinositol-4,5-bisphosphate was increased significantly during reperfusion. Reperfusion of the ischemic heart prelabeled with [14C]-arachidonic acid resulted in modest increases in [14C]diacylglycerol and [14C]phosphatidic acid. Pretreatment of the heart with L-arginine significantly reversed this enhanced phosphodiesteratic breakdown during ischemia and early reperfusion. However, at the end of the reperfusion the inhibitory effect of L-arginine on the phosphodiesterases seems to be reduced. In L-arginine-treated hearts, SOD activity was progressively decreased with the duration of reperfusion time. CONCLUSIONS: The results suggest for the first time that NO plays a significant role in transmembrane signaling in the ischemic myocardium. The signaling seems to be transmitted via cGMP and opposes the effects of phosphodiesterases by inhibiting the ischemia/reperfusion-induced phosphodiesteratic breakdown. This signaling effect appears to be reduced as reperfusion progresses. These results, when viewed in the light of free radical chemistry of NO, suggest that such on- and off-signaling of NO may be linked to its interaction with the superoxide radical generated during the reperfusion of ischemic myocardium.     

The effect of coenzyme Q10 and cold cristalloid cardioplegia on hypothermic global ischemia

Coenzyme Q10 (CoQ10, ubiquinone) has been shown to be protective against myocardial ischemia/reperfusion induced injury. The purpose of this study was to investigate the effect of CoQ10 added to cold cristalloid cardioplegia on hypothermic ischemia and normothermic reperfusion using an isolated working rat heart. Hearts (n = 6-9/group) from male Wistar rats were aerobically (37 degrees C) perfused (20 min) with bicarbonate buffer. This was followed by a 3-min infusion of St. Thomas' Hospital cardioplegic solution containing various concentrations of CoQ10 (0, 1, 3, 6, 12, and 58 mumol/L). Hearts were then subjected to 180 min of hypothermic (20 degrees C) global ischemia and 35 min of normothermic (37 degrees C) reperfusion (15 min Langendorff, 20 min working). Ventricular fibrillation (Vf) upon reperfusion was irreversible in the 12 and 58 mumol/ L CoQ10 groups (4/6 and 3/6, respectively). In the hearts which Vf upon reperfusion was not irreversible, the percent recovery of aortic flow (%AF) was 43.3 +/- 5.4% (n = 9) in the control group versus 31.6 +/- 7.7% (n = 6), 38.0 +/- 12.0% (n = 6), 27.2 +/- 6.9% (n = 6), 31.3% (n = 2), and 30.4 +/- 14.2% (n = 3) in the 1, 3, 6, 12, and 58 mumol/L CoQ10 groups, respectively. Creatine kinase leakage during Langendorff reperfusion tended to be greater in the 12 and 58 mumol/L CoQ10 groups than in the control group. Thus, CoQ10 in the cold cristalloid cardioplegic solution induced irreversible Vf upon reperfusion and failed to improve functional recoveries following hypothermic global ischemia.     

The clinical picture and diagnosis of diphtheritic carditis in children

During 1992 1996 we observed 122 children with diphtheria, 49 with the toxic form, in the region of Nizhny Novgorod in Russia. Sixty-four patients suffered from diphtheric carditis, 9 died. The clinical picture was characterized by a rapid development of heart and circulatory failure. ECG showed QRS alterations with intraventricular conduction impairment, sinus node dysfunction, ectopic rhythm disturbances and repolarization disturbances in all patients with carditis. Infarction-like ECG changes were typical for the pseudocoronary form with the worst prognosis. Echocardiographically there was left ventricular (LV) dilatation and depressed LV function, whereas LV muscle mass was increased. Myoglobin, LDH and CPK levels were elevated in each patient demonstrating significant differences between the various courses of disease. CONCLUSION: In diphtheria, the extent of hypermyoglobinaemia (> 2000 ng/ml) and an increased LDH1/LDH2 (> 1) ratio are reliable markers for the development of carditis indicating a poor prognosis.