Metabolism of extracellular phosphocreatine during changes in the ionic composition of the medium in the perfused rat heart]

Perfusion of isolated rat hearts with a phosphocreatine (10(-4) M) containing solution to which strophanthin or KCl had been added up to a concentration of 27 mM as well as Ca2+ depletion decreased phosphocreatine concentration in the perfusate with a simultaneous increase in creatine and phosphocreatine concentrations in the myocardium. Neither high extracellular concentrations of Na+ (200 mM), nor phosphocreatine increased creatine and phosphocreatine levels in the myocardium. The effect of high sodium perfusion media was completely reversed by strophanthin. Phosphocreatine decreased the lactate content in the perfusate. Strophanthin or potassium chloride enhanced the effect of phosphocreatine on the lactate release. Conversely, creatine augmented the lactate content in the perfusate. A high specificity of the phosphocreatine effect on the myocardium independently of the ionic composition of the perfusate was postulated. A mechanism of protective effects of phosphocreatine and high sodium perfusion media on "calcium paradox" is proposed.     

Some mechanisms of nonspecific antiarrhythmic action of phosphocreatine in acute myocardial ischemia

Using isotope-labeled microspheres (diameter 15 microns) it was shown that phosphocreatine at a dose of 300 mg/kg does not affect the myocardial blood flow in the ischemic zone during acute occlusion (5 min) of the left anterior descending coronary artery (LAD) in dogs. Intravenous administration of NaCl hypertonic solution which contained the same amount of Na+ as 300 mg/kg of phosphocreatinine disodium salt prevented the development of ventricular fibrillation during acute LAD occlusion in dogs. Under these conditions excitation conduction velocity significantly increased. Experiments in isolated intraventricular rabbit septum have showed that the addition of phosphocreatine or phosphocreatinine to the perfusion medium at a concentration of 10 mmole/liter increased excitation conduction velocity in ischemic myocardium. However, when changes in perfusate Na+ and Ca2+ concentration produced by addition of phosphocreatine or phosphocreatinine were compensated, these compounds do not affect excitation conduction velocity. On the other hand, the alterations similar to those produced by the addition of phosphocreatine or phosphocreatinine led to the same increase of excitation conduction velocity. The results obtained indicate an important role of the changes of blood plasma ionic composition on intravenous administration of phosphocreatine in electrophysiological and antiarrhythmic effects of this substance during acute myocardial ischemia.     

Prevention of myocardial reperfusion injury by increasing artificial trans-membrane sodium gradient in "calcium paradox" and post-ischemic reperfusion

An effect of the high sodium gradient during "calcium paradox" and postischemic reperfusion has been studied. A decrease of Na/Ca exchange by high sodium gradient (200 mM NaCl in the perfusion solution) resulted in the reduction of myoglobin release from the heart during "calcium paradox". High sodium concentration solution (200 mM) increased protective effect of ATP during "calcium paradox". Exogenous phosphocreatine (100 mumol/mol) increased myoglobin release from the heart. During perfusion of the heart by high sodium concentration, phosphocreatine efficiently decreased myoglobin release from the heart during "calcium paradox". Exogenous ATP (as Na-pump activator) and high Na+ concentration solution (180 mM) prevented the LDH release from the myocardium, decreased ATP hydrolysis, inhibited Ca influx, maintained total adenine nucleotides, phosphate potential, energy charge of the cardiomyocytes.     

含血停搏液镁离子浓度对未成熟心肌保护的影响

目的 采用幼兔离体心脏模型。模拟临床上可能出现的含血停搏液Ca^2 浓度变化,探讨适宜于未成熟心肌保护的Mg^2 浓度。方法 3-4周龄长耳白兔,依照含血停搏液不同Mg^2 浓度（0.6mmol/L,4.0mmol/L,8.0mmol/L,120mmol/L,16.0mmol/L）随机分为5组,建立Langendorff离体心脏灌注模型。采用Ca^2 浓度1.2-1.5mmol/L的含血停搏液,运用温血停搏液诱导停搏,冷血停搏液间断灌注,低温保护,终末温血停搏液控制性再灌注技术,观察以下指标：1、血流动力学指标;实验前后恢复率;心率,主动脉流量,冠脉流量,心排量,左室收缩压和左室舒张末压;2、心肌含水量;3、冠脉流出液乳酸盐含量;4、心肌肌酸激酶和乳酸脱氢酶漏出率;5、心肌细胞内Na^2 ,Ca^2 含量;6、心肌组织ATP含量;7、心肌组织SOD活性,MDA含量;8、心肌超微结构。结果 1、心率恢复率,主动脉流量恢复率及左室收缩压恢复率组间总体差异无显著性。而冠脉流量恢复率,心排量恢复率和左室舒张末压恢复率以Mg^2 浓度8.0mmol/L和12.0mmol/L为优,0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳酸盐含量0.4mmol/L组,8.0mmol/L和12.0mmol/L组高于欺科2组。4、心肌乳本能部氢酶漏出率以8.0mmol/L组最低,而肌酸激酶漏出率以8.0mmol/L和12.0mmol/L组为最低。5、心肌细胞内Na^ 、Ca^2 含量;6、心肌组织ATP含量;7、心肌组织SOD活性,MDA含量;8、心肌超微结构。结果：1、心率恢复率,主动脉流量恢复率及左室收缩压恢复率组间总体差异无显著性。而冠脉流量恢复率,心排量恢复率和左室舒张末压恢复率以Mg^2 浓度8.0mmol/L和12.0mmol/L为优,0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳酸盐含量0.4mmol/L组最差。2、心肌含水量以Mg^2 浓度8.0mmol/L和12.0mmol/L为最低。3、冠脉流出液乳桎卤含量0.4mmol/L组,8.0mmol/L和12.0mmol/L组高于其余2组。4、心肌乳酸脱氢酶漏出率以8.0mmol/L组最低,而肌酸激酶漏出率以8.0mmol/L和12.0mmol/L组为最低。5、心肌细胞内Na^2 含量以8.0mmol/L和12.0mmol/L组为最低,而心肌细胞内Ca^2 含量以8.0mmol/L组最低。6、心肌组织ATP含量以12.0mmol/L组为最高。7、心肌组织SOD活性以8.0mmol/L和12.0mmol/L组库最高,而MDA含量各组间总体差异无显著性。8、心肌超微结构;8.0mmol/L和12.0mmol/L组表现为基本正常未成熟心肌超微结构,而0.4mmol/L组超微结构有明显损伤表现。结论 对于未成熟心肌,当采用温血停搏液诱导停搏,冷血停搏液间断灌注,低温保护,温血停搏液终末控制性再灌注技术时,为避免含血停搏液Ca^2 浓度偏高对未成熟心肌的不利影响。应维持含血停搏液中Mg^2 浓度在8-12mmol/L。     

Dependence of the protective effect of the elevated sodium level on the type of oxidative substrate in the isolated heart during "calcium paradox"

Isolated guinea pig heart were perfused with the Tyrode solution followed in 15 min. by a 10-min. Ca(2+)-free solution with subsequent return to the normal Ca(2+)-containing Tyrode solution. Sarcolemma damage was measured by myoglobin release. The perfusion resulted in damage of the myocardium cells. The data obtained show that elevation of the extracellular pressure during reperfusion with the Ca(2+)-containing medium is more important than the absolute value of the osmotic pressure.     

Real-time monitoring of nitric oxide in ischemic myocardium using an NO-selective electrode calibrated by electron spin resonance

Using a Langendorff-perfused rat heart preparation and selective electrodes, we determined nitric oxide (NO) and oxygen levels in cardiac tissue. An NO-selective electrode that was calibrated by electron spin resonance (ESR) spectroscopy was inserted into the middle of the myocardium in the left ventricle. Simultaneously, we used an O2-selective electrode to measure the partial pressure of oxygen (pO2) in the perfusate, Krebs-Henseleit (K-H) solution, that was ejected from the heart. After 30 min of aerobic control perfusion, hearts were subjected to 30 min of global ischemia followed by 30 min of reperfusion. Under ischemic conditions, with a gradually decreasing pO2, NO detected by an NO-sensitive electrode within the myocardium was gradually increased. The maximum concentration increases in NO and decreases in pO2 during global ischemia were +10.200 +/- 1.223 microM and -58.608 +/- 4.123 mmHg, respectively. NO and pO2 levels both recovered to pre-ischemia baseline values when perfusion was restarted after global ischemia (reperfusion). The presence of Nomega-nitro-L-arginine methyl ester (L-NAME, 10 mM), a NOS inhibitor, prevented ischemia/reperfusion-induced changes in NO. This study shows that an NO-selective electrode that is calibrated by ESR can provide accurate, real-time monitoring of cardiac NO in normal and ischemic myocardium.     

Effects of Ca2+ deficiency, collagenase, and mechanical dispersion on the ultrastructure of cardiac myocytes of adult rats

A new perfusion medium for isolating cardiac myocytes from adult rats was developed, thereby yielding numerous viable cells with few morphological changes. The main factors in the isolation procedure are Ca2+ deficiency, collagenase, and mechanical dispersion. Their effects on the ultrastructure of cardiac myocytes were separately tested. In isolated hearts, perfusion with a medium containing a physiological Ca2+ concentration (2.5 mM, controls) preserved the cellular fine structure well, whereas perfusion with a medium containing 2.5 mM Ca2+ plus 0.05% collagenase caused swelling and disruption of most cells. Perfusion with a Ca2+-deficient medium followed by a medium with a low Ca2+ concentration (25 microM) either containing or lacking collagenase resulted in widening of the T-tubules, reduced electron density of the external lamina and occasional separation, or even dissolution of this layer. Some cells were damaged and hypercontracted. These appeared more numerous in suspensions, that means after mechanical dispersion of the myocardium. However, most of the isolated cells were regularly shaped (up to 30-60 min as shown in another study) and their ultrastructure was only slightly altered. This corresponds to an adequate preservation of the cell membranes proven in earlier membrane transfer studies.     

Significance of extracellular concentration of sodium ions in the protective effect during the "calcium paradox"]

Increasing of extracellular sodium concentration up to 200 mM diminishes heart damage under "calcium paradox". Phosphocreatine (10(-4) M) potentiates the effect of high sodium perfusion media; in this case myoglobin release from the myocardium is minimal (5-9% of control). An the same time, ATP and phosphocreatine concentrations and oxidation to phosphorylation coupling in mitochondria remain at a sufficiently high level. Elevation of osmotic pressure by the effect of 120 mM sucrose enhances heart damage under "calcium paradox" both in the presence and absence of phosphocreatine. The protective effects of superhigh (200 mM) sodium concentrations and phosphocreatine are completely reversed by strophanthin or decreasing K+ concentration down to 0.5 mM.     

Allopurinol-Enhanced Postischemic Recovery in the Isolated Pat Heart Involves Repletion of High-Energy Phosphates

The effects of allopurinol (AP) on functional and metabolic recovery of the isolated rat heart after global ischemia were studied. Hearts were subjected to aerobic perfusion (30 min), cardioplegic infusion (5 min), normothermic ischemia (37 min), and reperfusion (50 min) which was started with secondary cardioplegic infusion (10 min). AP was injected into rats (44 mg/kg body wt ip 2 h before heart excision) and added to cardioplegic solution (2 mM) prior and after ischemia. AP treatment significantly improved postischemic recovery of the function and reduced the leakage of lactate dehydrogenase from reperfused hearts. These beneficial effects were accompanied by a better preservation of tissue content of ATP, the total adenine nucleotides, phosphocreatine, and the total creatine at the end of reperfusion. Inhibition of xanthine oxidase by AP substantially decreased pre- and postischemic release of xanthine and uric acid and increased postischemic release of hypoxanthine into the coronary effluent. Despite this, AP treated hearts did not exhibit a reduction in hydroxyl radical adduct formation in the effluents at reperfusion assessed by the spin-trap measurements. The results suggest that AP may protect the heart from ischemia/reperfusion injury due to enhanced energy provision rather than by prevention of oxygen-derived free radical formation.     

Protection of ischemic myocardium by exogenous phosphocreatine (neoton): pharmacokinetics of phosphocreatine, reduction of infarct size, stabilization of sarcolemma of ischemic cardiomyocytes, and antithrombotic action

The effect of exogenous phosphocreatine on ischemic myocardium was studied in experimental infarction in rabbits and in total ischemia of pig heart tissue (in vitro). It is shown that single dose administration of phosphocreatine is followed by its rapid clearance from blood plasma (with a half lifetime of 4-6 min), but constantly high plasma concentration of phosphocreatine can be maintained by its intravenous infusion. When administered by this method into rabbits during experimental myocardial infarction, phosphocreatine reduces by 40% the size of the necrotic zone. Morphological electron microscopic studies using a lanthanum tracer method showed significant protection of the sarcolemma of cardiomyocytes in the perinecrotic zone by phosphocreatine. In vitro studies on the model of total ischemia also showed significant protection of cardiac sarcolemma from irreversible ischemic injury and reduction in the rate of high-energy phosphate depletion in the presence of phosphocreatine in the extracellular space. Additionally, it is demonstrated that creatine kinase released during myocardial infarction into the blood flow and exogenous phosphocreatine administered intravenously may significantly inhibit platelet aggregation by rapid removal of ADP, and thus potentially improve microcirculation during myocardial infarction.     

Influence of low extracellular Ca2+ ions on the cardiac function changes induced by verapamil in the perfused rabbit heart

We tested the hypothesis that the myocardial effects of verapamil (VER) could be enhanced by decreasing the extracellular Ca2+ concentration ([Ca2+]o) in the isolated rabbit heart at 37 degrees C. After perfusion with standard Krebs - bicarbonate solution containing 1.27 mM Ca2+, for a 30-min period of stabilization and 15 min of control, groups of hearts were perfused for an additional 60 min with solutions containing one of the following: 1.27 mM Ca2+ (control group), 0.23 mM Ca2+ (low [Ca2+]o group), 1.27 mM Ca2+ plus 10(-7) M VER (VER group), or 0.23 mM Ca2+ plus 10(-7) M VER (combination, CBN group). These concentrations of [Ca2+]o and VER produce submaximal responses in our preparation. We found that the heart rate - LV pressure product (RPP) in the CBN group fell rapidly to 0 in the first 2-3 min of perfusion, this response being significantly lower than in the other two groups for the first 15 min. Electromechanical dissociation (EMD) appeared in one of six hearts at 60 min and in four of six hearts at 30 min in the low [Ca2+]o and VER groups, respectively, whereas it occurred in the CBN group in all hearts at 3 min. Depolarization rate (DR) fell by 10% in the low [Ca2+]o and VER groups versus a reduction of 45% in the CBN group (P less than 0.05) during the last 45 min of perfusion. The PR interval increased by 300% in the CBN group, a much greater and significant change (P less than 0.05) than in the hearts exposed to VER or low [Ca2+]o.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of various reperfusion regimens on the recovery of myocardial contractile function after total ischemia

Isolated guinea pig hearts were subjected to 25-min total ischemia at 37 degrees C followed by 30-min reperfusion. The product of the left ventricular isovolumic systolic pressure and heart rate representing the cardiac work index was restored to 33 +/- 5% of initial value and diastolic pressure (DP) remained substantially elevated by 47 +/- 9 mm Hg if reperfusion was resumed with initial rate 10 ml/min. The gradual restoration of perfusion rate initiating from 2 or 4 ml/min was performed in other series, and was associated with slower but higher recovery of cardiac work and lower DP by the end of reperfusion. The similar result was observed when reperfusion was resumed with initial rate but a modified solution was used for first 5 min. In which Ca++ content was reduced while K+ and Mg++ elevated. In this case final recovery of cardiac work was 59 +/- 2% and DP completely returned to initial level. It is suggested that optimal reperfusion mode should be associated with slower work recovery.     

The influence of exaprolol upon the ischaemic rat heart and its interaction with sarcolemmal (Na+ + K+)-ATPase

The capability of cyclohexylphenol exaprolol of protecting the ischaemic myocardium during ischaemic cardiac arrest was assessed in the isolated working rat heart. Exaprolol added to the perfusion medium in a dose of 10(-7) mol.l-1 only minimally influenced the left ventricular function (reduced the stroke volume by 18.84% and cardiac output by 14.63%). The hearts were subjected to global ischaemia for 75 min at 26 degrees C and subsequently reperfused for 60 min at 37 degrees C. The recovery of left ventricular function following reperfusion, expressed as a percentage of preischaemic functional performance was used as an indicator of the ischaemic tolerance of the heart. The effect of exaprolol on sarcolemmal (Na+ + K+)-, Mg2+- and Ca2+-ATPase activities was also examined. Exaprolol-pretreated hearts revealed better postischaemic recovery of the left ventricular dP/dt max and stroke volume as well as improved efficiency in the transformation of chemical energy to mechanical work. Exaprolol in 10(-4) mol.l-1 concentration significantly stimulated the specific activity of sarcolemmal (Na+ + K+)-ATPase. Possible mechanisms of the salutary effect of exaprolol on the ischaemic heart are discussed.     

Dispersion of cell-to-cell uncoupling precedes low K+-induced ventricular fibrillation

We hypothesize that hypokalemia-related electrolyte imbalance linked with abnormal elevation of intracellular free Ca2+ concentration can cause metabolic disturbances and subcellular alterations resulting in intercellular uncoupling, which favor the occurrence of malignant arrhythmias. Langendorff-perfused guinea pig heart (n = 44) was subjected to a standard Tyrode solution (2.8 mmol/l K+) followed by a K+-deficient solution (1.4 mmol/l K+). Bipolar ECG of the left atria and ventricle was continuously monitored and the incidence of ventricular fibrillation was evaluated. Myocardial tissue sampling was performed during stabilization, hypokalemia and at the onset of fibrillation. Enzyme activities of succinic dehydrogenase, glycogen phosphorylase and 5-nucleotidase were determined using in situ catalytic histochemistry. The main gap junction protein, connexin-43, was labeled using mouse monoclonal antibody and FITC conjugated goat antimouse antibody. Ultrastructure was examined by transmission electron microscopy. The free Ca2+ concentration was measured by the indo-1 method in ventricular cell cultures exposed to a K+-free medium. The results showed that sustained ventricular fibrillation appeared within 15-30 min of low K+ perfusion. This was preceded by ectopic activity, episodes of bigeminy and tachycardia. Hypokalemia induced moderate reversible and sporadically irreversible subcellular alterations of cardiomyocytes and impairment of intercellular junctions, which were heterogeneously distributed throughout myocardium. Patchy areas with decreased enzyme activities and diminished immunoreactivity of connexin-43 were found. Furthermore, lack of external K+ was accompanied by an increase of intracellular Ca2+. The prevention of Ca2+ overload by either 1 mmol/l Ni2+ (Na+/Ca2+ inhibitor), 2.5 micromol/l verapamil, 10 micromol/l d-sotalol or 10 micromol/l tedisamil was associated with the protection against fibrillation. The results indicate that hypokalemia induces Ca2+ overload injury and disturbances in intercellular coupling. Dispersion of these changes throughout the myocardium may serve as the basis for microreentry circuits and thus favor fibrillation occurrence.     

Endoxin-mediated myocardial ischemia reperfusion injury in rats in vitro

Myocardial ischemia reperfusion results in an increase in intracellular sodium concentration, which secondarily increases intracellular calcium via Na(+)-Ca2+ exchange, resulting in cellular injury. Endoxin is an endogenous medium of digitalis receptor and can remarkably inhibit Na+/K(+)-ATPase activity. Although the level of plasma endoxin is significantly higher during myocardial ischemia, its practical significance is unclear. This research is to investigate whether endoxin is one of important factors involved in myocardial ischemia reperfusion injury. Ischemia reperfusion injury was induced by 30 min of global ischemia and 30 min of reperfusion in isolated rat hearts. Heart rate (HR), left ventricular developed pressure (LVDP), and its first derivative (+/-dp/dtmax) were recorded. The endoxin contents, intramitochondrial Ca2+ contents, and the Na+/K(+)-ATPase activity in myocardial tissues were measured. Myocardial damages were evaluated by electron microscopy. The endoxin and intramitochondrial Ca2+ contents in myocardial tissues were remarkably higher, myocardial membrane ATPase activity was remarkably lower, the cardiac function was significantly deteriorated, and myocardial morphological damages were severe in myocardial ischemia reperfusion group vs. control. Anti-digoxin antiserum (10, 30 mg/kg) caused a significant improvement in cardiac function (LVDP and +/-dp/dtmax), Na+/K(+)-ATPase activity, and myocardial morphology, and caused a reduction of endoxin and intramitochondrial Ca2+ contents in myocardial tissues. In the present study, the endoxin antagonist, anti-digoxin antiserum, protected the myocardium against the damages induced by ischemia reperfusion in isolated rat hearts. The results suggest that endoxin might be one of main factors mediating myocardial ischemia reperfusion injury.     

P-31 Nuclear Magnetic Resonance Analysis of Brain: II. Effects of Oxygen Deprivation on Isolated Perfused and Nonperfused Rat Brain

Phosphatic metabolite (perchloric acid extractable) concentrations of cerebral tissues were analyzed by phosphorus-31 nuclear magnetic resonance (P-31 NMR) spectroscopy following external perfusion of the isolated rat brain (30 min or 60 min) under the following conditions: (a) constant perfusion pressure with either fluorocarbon- or erythrocyte-based medium, and (b) constant perfusate flow rate (3 ml/min) with the erythrocyte-based medium. Metabolite concentrations of control perfused brains were compared with those in nonperfused controls to provide a basis for detecting any qualitative or quantitative changes in cerebral metabolite composition. Metabolic responses of perfused brains to ischemia (incomplete ischemia, 83% reduction in flow for 10 min; transient complete ischemia for 1.5 or 2 min) were evaluated immediately after the ischemic episode and at selected time points during reperfusion (3 and 15 min). Alterations in cerebral metabolite levels induced by hypoxia were analyzed using a nonperfused rat brain model. Irrespective of the perfusion method employed, the phosphatic metabolites of control perfused rat brains were identical quantitatively to those of the nonperfused controls. Cerebral ischemia resulted in significantly increased levels of ADP, AMP + IMP, Pi, fructose 1,6-diphosphate, and glycerol 3-phosphate (global ischemia only), whereas ATP and phosphocreatine (PCr) levels declined significantly. The magnitude of these changes varied with the severity of the ischemia; however, following 15 min of control reperfusion metabolite levels had reverted to preischemic values. Significant perturbations in tissue phosphoethanolamine (3.84 delta resonance) content were evident at various time points during ischemia and postischemic recovery, which varied according to the perfusion conditions. In contrast to the changes observed in response to ischemia, hypoxia affected only cerebral high-energy phosphate levels. ATP and PCr levels were reduced, while a concomitant, essentially equimolar, increase in Pi and ADP was observed. The present studies indicate that in terms of phosphatic metabolites, the control equilibrated isolated perfused rat brain is quantitatively and qualitatively indistinguishable from the nonperfused rat brain in vivo regardless of the perfusion conditions (constant flow versus constant pressure). The metabolic responses to ischemia and hypoxia, as measured by P-31 NMR, were consistent with the pattern of changes reported elsewhere. Overall, P-31 NMR spectroscopic evaluation of the intact rat brain provides a potential experimental context for dynamic measures of cerebral metabolism under exogenously controlled conditions. Th     

Early hypoxic contracture of the myocardium in adult and newborn rats]

The effect of 30 min substrate free hypoxia (H) on isometric tension was studied in isolated myocardium (M) of adult (A) and newborn (N) rats. The perfusion with 50% Na+ H solution caused in AM the development of H contracture which was more than 50% higher than control contracture. H perfusion with 0.1 mM Ca2+, 1.0 mM La3+, and 10.0 mM of caffeine provides the discrimination of control and hypoNa+ contractures. It is assumed that early H contracture in AM is a result of inability of Ca-sequestering system to accumulate intracellular Ca2+ and Ca2+ influxing through the sarcolemma. In myocardium of N rats Na-Ca exchange is proposed as a main source of Ca2+ for H contracture development.     

Formation of products of anaerobic metabolism in the ischemic myocardium

The effect of ischemia on the formation of products of anaerobic metabolism and their release into the cardiac effluent in isolated perfused guinea pig hearts was studied. During 30 min normothermal ischemia, the myocardial ATP and phosphocreatine levels decreased to 34% and 15% of the initial values, respectively. The net alanine formation in ischemia was approximately a stoichiometric glutamate decrease; the increase in the tissue malate content corresponded to the aspartate----oxaloacetate----malate anaplerotic flux, the succinate production being commensurable to alpha-ketoglutaric acid formation in the alanine aminotransferase reaction. Using 1H-NMR, it was shown that the release of trace amounts of lactate, alanine, succinate, creatine and pyruvate into cardiac effluents occurred during the first 5 minutes of reperfusion. The rate of metabolite release decreased in the following order: lactate much greater than alanine greater than succinate greater than creatine. By the 30th minute of reperfusion, the decrease in the tissue levels of these metabolites to preischemic values was accompanied by the recovery of ATP and phosphocreatine to 65% and 90% of the initial levels, respectively. The data obtained suggest that the formation and release of alanine, creatine or succinate as well as lactate from ischemic myocardium may testify to significant disturbances in energy metabolism of the myocardium.     

Effects of Ca2+ withdrawal on diaphragmatic fiber tension generation

The effects of extracellular Ca2+ withdrawal were studied on isolated diaphragmatic muscle fibers and compared with the effects on the papillary, soleus, and extensor digitorum longus (EDL) contractility, using the same in vitro model. Diaphragmatic fibers were obtained from 15 rats, and papillary muscles, soleus, and EDL were obtained from 10 animals. Isometric force generated in response to 1-Hz supramaximal electrical stimulation was measured with a highly sensitive photoelectric transducer. After control measurements, perfusion with a Krebs solution depleted of calcium (0 Ca2+) was started while the fibers were continuously stimulated (4 times/min) and twitches recorded. For the papillary fibers, perfusion with zero Ca2+ was followed by an immediate decrease in twitch tension, complete twitch abolition occurring within 3 +/- 1 min after zero-Ca2+ exposure. Diaphragmatic fibers behaved similarly, although twitch abolition was delayed (10 +/- 3 min after 0-Ca2+ exposure). For the soleus fibers, the twitch amplitude amounted to 38 +/- 10% of control (62% decrease on the average) after 30 min of zero-Ca2+ exposure, no twitch abolition being noted even after 1 h of Ca2+-free exposure. The twitch amplitude of the EDL fibers amounted to 75 +/- 7% of control (25% decrease) after 30 min of zero-Ca2+ exposure. The recovery kinetics for the four fiber types after reexposure to Ca2+-containing solution were also different, with papillary and diaphragmatic fibers recovering completely within 2.5 +/- 0.5 and 4 +/- 0.5 min, respectively. By contrast, neither the soleus nor the EDL showed complete recovery after 30 min.(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of myosin ATPase inhibition on metabolic and functional recovery of isolated rat heart after global ischemia

The effect of myosin ATPase inhibitor, 2,3-butanedione monoxime (BDM) used in the range of concentrations 1.25–10.0 mM), on recovery of functions of isolated rat heart subjected to normothermic (37 °C) total ischemia for 35 min has been investigated. BDM perfusion was performed at a flow rate of 4 ml/min during 5 min before ischemia (BDM-I) or before 25-min reperfusion (BDM-R). Control hearts were perfused with Krebs solution at the same flow rate. The highest functional recovery of heart and coronary vessels was observed during infusion of 2.5 mM BDM before ischemia. At the end of reperfusion ATP and phosphocreatine (PCr) content in hearts of this group was significantly higher whereas the level of lactate was two times lower than in control; total creatine content (ΣCr) did not differ from the initial level. Similar but less pronounced changes in the improvement of aerobic metabolism and maintenance of ΣCr after reperfusion were also observed in the case of infusion of 2.5 mM BDM before reperfusion. They were consistent with reduced recovery of functions of heart and coronary flow compared with these parameters observed in the BDM-I group. 2.5 mM BDM caused almost 2-fold decrease in release of cardiac lactate dehydrogenase into myocardial perfusate in the BDM-I and BDM-R groups (compared with control); this suggests lower damage of cell membranes. These results suggest that improvement of energy supply of postischemic cardiomyocytes may be a key factor determining cardioprotector effectiveness of short-term administration of BDM before ischemia.