Functional and subcellular changes in the isolated rat heart perfused with oxidized isoproterenol.

The isolated rat heart failed to generate contractile force within 10, 15 and 60 min upon perfusion with medium containing 100, 50 and 20 mg/l oxidized isoproterenol respectively, whereas the contractile force was depressed by about 85% of control following a 90 min perfusion with 10 mg/l oxidized isoproterenol. Swelling of mitochondria and sarcoplasmic reticulum, and disruption of the contractile proteins were seen in all hearts failing due to oxidized isoproterenol. Furthermore, calcium uptake activity, but not calcium binding of the microsomal fraction from hearts perfused with oxidized isoproterenol was depressed, whereas mitochondrial calcium binding and uptake activities were unaffected. Perfusion of the hearts with oxidized isoproterenol did not change the mitochondrial or microsomal ATPase activities; however, mitochondrial phosphorylation rate, state 3 respiration and RCI values were significantly depressed. These results indicate changes in subcellular mechanisms during the induction of myocardial necrosis and contractile failure due to oxidized isoproterenol.     

Irreversible changes in oxidative phosphorylation activity of the mitochondrial membrane from hearts subjected to hypoxia and reoxygenation

The present study was designed to elucidate irreversible biochemical changes in the mitochondrial membrane of hearts subjected to hypoxia and subsequent reoxygenation in a rabbit heart Langendorff preparation. Significant changes in the mitochondrial calcium uptake, ATPase, and oxidative phosphorylation activities were seen in the heart receiving 30 to 60 min of hypoxic perfusion. These changes were accompanied by deleterious alterations in contractile function. Among hypoxia-induced changes in biochemical activities of isolated mitochondria, only oxidative phosphorylation activity was found to be irreversible upon reoxygenation. This is compatible with the findings of reoxygenation-induced incomplete recovery of tissue ATP level, once decreased by hypoxic perfusion. In the electron microscopic study, the heart receiving 60 min of hypoxic perfusion showed contracted sarcomeres, vacuolization and electron lucency of the mitochondria which were not restored by the subsequent reoxygenation. The results suggest that an inability of the mitochondrial membrane to produce high-energy phosphate primarily induces lack of ATP required for cardiac mechanical activity and membrane integrity, which in turn leads to the impairment of myocardial cell function.     

Energy metabolism and contractile function in rat heart during graded, isovolumic perfusion using 31P nuclear magnetic resonance spectroscopy

The isolated, perfused heart is known to exhibit a linear relation between aortic pressure, coronary flow rate, oxygen consumption and contractile function (rate-pressure product) over a wide range of aortic pressures. Our study sought to determine whether the cytosolic phosphorylation potential [( ATP]/[ADP][Pi]) is the link between mitochondrial respiration and contractile function in this preparation. 31P NMR spectroscopy was used to measure phosphate metabolite levels in isovolumic rat hearts during graded perfusion from 1.6 to 12.8 ml/min/g. It was found that an increase in contractile function paralleled the increase in flow rate, but that marked changes in creatine phosphate, inorganic phosphate and hydrogen ion concentration occurred only at lower flow rates. The cytosolic phosphorylation potential showed a high, positive correlation with contractile function at flow rates below 7.2 ml/min/g, which suggested that mitochondrial respiration was oxygen-limited and that the heart was ischemic. Thus, when oxygen limits myocardial oxidative phosphorylation, cytosolic energy metabolite levels may limit contractile function. At the higher flow rates studied, other metabolic controls may operate to link mitochondrial respiration and workload.     

Mitochondrial damage during ischemia determines post-ischemic contractile dysfunction in perfused rat heart

Possible mechanisms underlying sodium overload-induced ischemia/reperfusion injury in perfused rat hearts were examined. Massive accumulation of myocardial Na(+) occurred during ischemia, suggesting cytosolic sodium overload in cardiac cells. Treatment of the pre-ischemic heart with 0.3 micromol/l tetrodotoxin or 3 micromol/l ethyl-isopropyl amiloride enhanced post-ischemic contractile recovery (72 or 82% of initial vs 24% for untreated group), which was associated with suppression of tissue Na(+) accumulation (138 or 141% of initial vs 270% for untreated group), restoration of tissue high-energy phosphates, and preservation of the ability of mitochondria to produce ATP in the ischemic/reperfused heart. The release of cytochrome c from the ischemic heart was observed, which was blocked by treatment of the pre-ischemic heart with these agents. The improvement of post-ischemic contractile recovery by these agents was closely correlated with the ability of mitochondria to produce ATP during ischemia. To examine the effects of sodium overload on mitochondrial function, isolated mitochondria were incubated in the presence of various concentrations of Na(+). Na(+) induced mitochondrial membrane perturbations such as depolarization of the membrane potential, mitochondrial swelling, cytochrome c release from isolated mitochondria, and a reduction in oxidative phosphorylation. These events in the isolated mitochondria were not blocked by the presence of the above agents. The results suggest that cytosolic sodium overload in cardiac cells may induce deterioration of the mitochondrial function during ischemia and that this mitochondrial damage may determine post-ischemic contractile dysfunction in perfused rat hearts.     

Impairment of mitochondrial and sarcoplasmic reticular functions during the development of heart failure in cardiomyopathic (UM-X7.1) hamsters

The oxidative phosphorylation as well as calcium transporting properties of heart mitochondria and calcium transport activities of the fragments of the sarcoplasmic reticulum (microsomes) were studied during the life span of cardiomyopathic hamsters (UM-X7.1). Control healthy hamsters of the same age group were used for comparison. No changes in the oxidative phosphorylation ability of cardiomyopathic mitochondria were seen at early and moderate stages of heart failure; however, at severe stages, mitochondrial respiratory functions, but not the ADP:0 ratio, were impaired. Both creatine phosphate and ATP contents were decreased without any significant changes in the ATPase activities of myofibrils from the failing hearts. Heart mitochondria from cardiomyopathic animals at severe stages of failure exhibited less calcium binding and uptake activities in comparison with the control values whereas no changes in the mitochondrial calcium binding and uptake were seen in cardiomyopathic hamsters which showed no clinical signs of heart failure. Although mitochondrial calcium binding in cardiomyopathic hearts at early and moderate stages of failure was decreased, mitochondrial calcium uptake was not significantly different from the control. Microsomal calcium binding activity, unlike calcium uptake activity, was decreased in the hearts of cardiomyopathic hamsters without any signs of heart failure. Both calcium binding and calcium uptake activities of microsomes from animals with early, moderate and severe heart failure were less in comparison with the control values but were not associated with any changes in the Ca2+-stimulated ATPase activity. These results suggest that changes in the process of mitochondrial energy production and mitochondrial Ca2+-transport may be secondary to other factors whereas alterations in the sarcoplasmic reticular Ca2+-transport may lead to the development of heart failure in the cardiomyopathic hamsters.     

Sodium accumulation during ischemia induces mitochondrial damage in perfused rat hearts

OBJECTIVE: The present study aimed to elucidate the involvement of sodium overload and following damage to mitochondria during ischemia in the genesis of ischemia/reperfusion injury of perfused rat hearts. METHODS: Isolated, perfused hearts were exposed to different durations (15-35 min) of ischemia followed by 60-min reperfusion. At the end of ischemia or reperfusion, myocardial sodium and calcium contents and myocardial high-energy phosphates were determined. The cardiac mitochondrial ability to produce ATP was measured using saponin-skinned bundles. The effects of sodium on the mitochondrial membrane potential and the oxidative phosphorylation rate were examined using isolated mitochondria from normal hearts. RESULTS: Post-ischemic recovery of left ventricular developed pressure decreased in an ischemic duration-dependent manner. Ischemia induced an increase in myocardial sodium, but not calcium. This increase was dependent on the duration of ischemia. The oxygen consumption rate of skinned bundles from the ischemic heart decreased at the end of ischemia. Incubation of mitochondria with various concentrations of sodium chloride or sodium lactate in vitro resulted in a depolarization of mitochondrial membrane potential and a decrease in ATP-generating activity. This decrease was not restored after elimination of sodium compounds. CONCLUSIONS: The present findings suggest that ischemia induces an increase in sodium influx from the extracellular space and that accumulated sodium may induce irreversible damage to mitochondria during ischemia. This mitochondrial dysfunction may be one of the most important determinants for the genesis of ischemia/reperfusion injury in perfused rat hearts.     

Glycogen synthase kinase 3 inhibition slows mitochondrial adenine nucleotide transport and regulates voltage-dependent anion channel phosphorylation

Inhibition of glycogen synthase kinase (GSK)-3 reduces ischemia/reperfusion injury by mechanisms that involve the mitochondria. The goal of this study was to explore possible molecular targets and mechanistic basis of this cardioprotective effect. In perfused rat hearts, treatment with GSK inhibitors before ischemia significantly improved recovery of function. To assess the effect of GSK inhibitors on mitochondrial function under ischemic conditions, mitochondria were isolated from rat hearts perfused with GSK inhibitors and were treated with uncoupler or cyanide or were made anoxic. GSK inhibition slowed ATP consumption under these conditions, which could be attributable to inhibition of ATP entry into the mitochondria through the voltage-dependent anion channel (VDAC) and/or adenine nucleotide transporter (ANT) or to inhibition of the F(1)F(0)-ATPase. To determine the site of the inhibitory effect on ATP consumption, we measured the conversion of ADP to AMP by adenylate kinase located in the intermembrane space. This assay requires adenine nucleotide transport across the outer but not the inner mitochondrial membrane, and we found that GSK inhibitors slow AMP production similar to their effect on ATP consumption. This suggests that GSK inhibitors are acting on outer mitochondrial membrane transport. In sonicated mitochondria, GSK inhibition had no effect on ATP consumption or AMP production. In intact mitochondria, cyclosporin A had no effect, indicating that ATP consumption is not caused by opening of the mitochondrial permeability transition pore. Because GSK is a kinase, we assessed whether protein phosphorylation might be involved. Therefore, we performed Western blot and 1D/2D gel phosphorylation site analysis using phos-tag staining to indicate proteins that had decreased phosphorylation in hearts treated with GSK inhibitors. Liquid chromatographic-mass spectrometric analysis revealed 1 of these proteins to be VDAC2. Taken together, we found that GSK-mediated signaling modulates transport through the outer membrane of the mitochondria. Both proteomics and adenine nucleotide transport data suggest that GSK regulates VDAC and that VDAC may be an important regulatory site in ischemia/reperfusion injury.     

Postischaemic reperfusion injury in the isolated rat heart: effect of ruthenium red.

STUDY OBJECTIVE--The aim was to investigate the effect of attenuating mitochondrial calcium uptake with ruthenium red on myocardial function and the resultant necrosis following prolonged ischaemia and reperfusion in isolated rat hearts. Mitochondrial dysfunction, secondary to increased calcium uptake, has been implicated as an important mediator of reperfusion injury in the heart. DESIGN--To examine the role of mitochondrial calcium uptake in mediating ischaemic and reperfusion injury, isolated rat hearts were perfused with ruthenium red (n = 6), a polysaccharide dye which inhibits calcium uptake by mitochondria, and were compared to control perfused hearts (n = 7). After stabilisation, hearts were subjected to 60 min no flow ischaemia, immediately followed by 40 min reperfusion. EXPERIMENTAL MATERIAL--Hearts were used from male Wistar rats weighing 300-350 g. MEASUREMENTS AND MAIN RESULTS--Cardiac high energy phosphates (ATP, phosphocreatine, inorganic phosphate) and pH were continuously monitored during ischaemia and reperfusion using phosphorus magnetic resonance spectroscopy. Contractility (dP/dT), coronary flow, creatine kinase release, and the time to the onset of ischaemic contracture were also measured. No differences in metabolic abnormalities or time to peak contraction during ischaemia were found between groups, suggesting that ruthenium red does not alter the metabolic consequences of ischaemia. However, upon reperfusion, the following differences in the ruthenium red perfused hearts were observed when compared to control hearts (p less than 0.05): ATP and phosphocreatine recovery were more complete, myocardial contractility was greater, coronary flow was greater, and myocyte necrosis was attenuated. CONCLUSIONS--Combined with the known inhibitory effect of ruthenium red on mitochondrial calcium uptake, these data suggest that an important component of myocardial injury following ischaemia and reperfusion in the isolated rat heart is the result of mitochondrial calcium accumulation.     

Digitalis cardiotoxicity: cellular calcium overload a possible mechanism

Summary Isolated perfused guinea pig (Langendorff) heart was employed to determine if the myocardial mechanical dysfunction (mechanical toxicity) produced by toxic concentration of ouabain (1 M) was accompanied by alterations in mitochondrial function. Ouabain (1 M) produces a transient increase in the myocardial contractile force and then a continuous decline in the left ventricular mechanical function. Mitochondria isolated from ouabain perfused hearts showed a significantly higher rate of⁴⁵Ca²⁺ uptake and reduction in oxidative phosphorylation. The rate of ATP generation was reduced by almost 50% at the time of contracture development. Verapamil or nifedipine, when combined with ouabain in the perfusion medium, delayed or abolished the mechanical toxicity in a dose dependent manner. The mitochondria isolated from these hearts demonstrated normal rate of Ca²⁺ uptake and ATP generation capacity. The data indicate that the cardiac mechanical dysfunction induced by toxic doses of ouabain may be associated with mitochondrial Ca²⁺ overload and dysfunction and that the Ca²⁺ channel blockers may have a protective effect.     

Adrenochrome uptake and subcellular distribution in the isolated perfused rat heart

Adrenochrome uptake and its subcellular distribution were examined using isolated perfused rat heart preparation. The heart was perfused for 30 min with a medium containing 1 to 50 mg/l of 14C-adrenochrome and the subcellular fractions were isolated to measure their radioactivities. A decline in contractile force, a rise in resting tension and an increase in adrenochrome uptake by the heart were seen to depend upon the time of perfusion and the concentration of adrenochrome in the medium. The sarcolemmal fraction had the highest uptake of adrenochrome and this was followed by the microsomal fraction; some accumulation of adrenochrome was also observed in the myofibrillar and mitochondrial fractions. Either 10 or 20 min reperfusion of the heart previously exposed to 25 mg/l of adrenochrome, resulted in approximately 50 or 37% of the radioactivity remaining in the heart; this indicates irreversible binding of adrenochrome to the tissue. Reperfusion of the heart showed restoration of the resting tension but the contractile force did not show any recovery. Propranolol and iproniazid, which have been shown to inhibit the adrenochrome induced cardiotoxicity, reduced adrenochrome uptake by the heart, and prevented adrenochrome-induced depression in contractile force and rise in resting tension. These results indicate that adrenochrome is taken up by the heart and induces cardiac disturbances through its action on different subcellular organelles in the myocardium.     

Enhancement of post-hypoxic contractile and metabolic recovery of perfused rat hearts by dl-propranolol: possible involvement of non-beta-receptor mediated activity.

The present study was undertaken to elucidate a possible role of non-beta-receptor mediated effects in dl-propranolol-induced enhancement of post-hypoxic contractile and metabolic recovery in perfused rat hearts. The rat hearts were perfused for 30 min under reoxygenated conditions following 15 min-substrate free-hypoxic perfusion, and the cardiac performance and myocardial metabolism were examined. Hypoxia induced complete cessation of cardiac contractile force, depletion of myocardial high-energy phosphates, release of ATP metabolites and creatine kinase from the heart. Subsequent reoxygenation produced little recovery of cardiac contractile activity and tissue high-energy phosphates, further enhancement of the release of creatine kinase and the accumulation of tissue calcium. Treatment of the hypoxic hearts with dl-propranolol, d-propranolol and atenolol was performed during 5 to 15 min of hypoxic perfusion. dl-Propranolol and d-propranolol at the concentration of 45 microM elicited a significant recovery of cardiac contractile activity and restoration of myocardial high-energy phosphates. This treatment also resulted in a suppression of the release of creatine kinase and ATP metabolites and the tissue calcium accumulation observed during hypoxia and/or reoxygenation. However, such beneficial effects were not seen in hearts treated with 45 microM atenolol. dl-Propranolol and atenolol, but not d-propranolol, in a concentration of 45 microM have been shown to reveal beta-adrenoceptor blocking action. Thus, the results suggest the involvement of non-beta-receptor mediated effects of propranolol in the enhanced post-hypoxic contractile and metabolic recovery of the perfused rat heart. The non-beta-receptor mediated activity of these drugs appears to be related to their ability to suppress the maximal driving frequency of left atrial preparations.     

Changes in high-energy phosphate compounds of isolated rat hearts during Ca-free perfusion and reperfusion with Ca

Isolated rat hearts were perfused with a glucose-containing modified Tyrode solution at 37°C, according to Langendorff. After a 15 min stabilization period, the hearts were perfused for 4 min with a Ca²⁺-free medium and subsequently reperfused with Ca²⁺-containing medium. Reperfusion with Ca²⁺ caused irreversible loss of electrical and mechanical activity of the hearts (calcium paradox). After 30 s of reperfusion with Ca²⁺, myocardial creatine phosphate (CP) and ATP levels were decreased by 65% and 45% respectively. In the same period there was an increase in creatine (15%), ADP (85%) and AMP (2800%). Continued reperfusion with Ca²⁺ resulted in a gradual decrease in the tissue concentration of all compounds. The effluent fluid contained large amounts of creatine and AMP, and relatively minor amounts of CP, ATP and ADP. The results show that reperfusion with Ca²⁺-containing medium, after a short Ca²⁺-free period, produces a sudden and severe decline of myocardial high-energy stores, prior to the release of these compounds.     

Energy metabolism in the perfused, arrested rabbit heart

Energy metabolism of quiescent cardiac muscle was studied in the isolated rabbit heart preparation perfused at constant pressure by the Langendorff technique. Oxygen consumption (MVo2), coronary flow rate (CFR) and the steady state concentrations of high energy phosphate compounds were determined in hearts rendered asystolic using modified Krebs-Henseleit (KH) media containing 11 mM glucose as substrate. Basal MVo2 and CFR were significantly higher in hearts arrested by Ca2+ depletion (low Ca KH) compared to K+ excess (high K KH). Substitution of glucose in low Ca KH with a mixture containing glutamate, fumarate and pyruvate (low Ca KH + GFP) resulted in a 25% increase in the basal MVo2 but a 20% decline in CFR. Supplementing the low Ca perfusate with 30 g/l dextran (low Ca KH + dextran) depressed both the basal MVo2 (35%) and CFR (75%). Differences in the basal MVO2 under the different perfusion conditions were not accompanied by significant changes in the tissue levels of ATP, CrP or Cr. Compared to low Ca KH arrested hearts, those perfused with low Ca KH + GFP or low Ca KH + dextran did, however, show significantly lower tissue levels of ADP, AMP and Pi, but higher cytosolic ratios of [ATP]/[ADP][Pi] and [CrP]/[Cr][Pi]. As a consequence of the higher phosphorylation potential the free energy of ATP hydrolysis increased. There was no significant difference in any of these parameters between high K KH and low Ca KH perfused hearts. It is concluded that in the perfused, arrested heart none of the parameters that are used to describe the myocardial energetic state, e.g. free [ADP] or the cytosolic [ATP]/[ADP][Pi] ratio, uniquely correlates with the basal metabolic rate as estimated from MVO2 measurements.     

Catecholamine-induced myocardial cell damage: catecholamines or adrenochrome

Recent evidence suggests that catecholamine-induced myocardial damage may be due to the cardiotoxic property of its non-physiological metabolite, adrenochrome. We investigated whether catecholamine-mediated myocardial damage is the result of catecholamine stimulation per se or the consequence of physiological or non-physiological metabolites. In the Langendorff perfused rat heart, fresh epinephrine (10(-6) M) solution increased cumulative lactate dehydrogenase (LDH) release when the perfusion pressure was 100 cm but not 65 cm, 3640 +/- 665 v. control 545 +/- 45 mIU/g/35 min respectively (P less than 0.01). In the left atrial perfused rat heart working against a hydrostatic pressure of 100 cm, fresh epinephrine (10(-6) M) solution produced the greatest increase in cumulative LDH release, 9346 +/- 1806 v. control 472 +/- 47 mIU/g/45 min respectively (P less than 0.01). Beta 1 but not alpha 1 adrenergic stimulation provoked enzyme leakage. Beta-adrenoceptor antagonism with atenolol 10(-5) M prevented catecholamine-induced leakage. Physiological metabolites of epinephrine viz metanephrine 10(-6) M, dihydroxymandelic acid 10(-6) M, vanillylmandelic acid 10(-6) M, and the non-physiological metabolite adrenochrome 10(-6) M to 10(-4) M did not increase the cumulative LDH release over 45 min. When adrenochrome 10(-4) M was perfused for 120 min enzyme release occurred, albeit only a third of that induced by epinephrine 10(-6) M over 45 min. We demonstrate that epinephrine-induced myocardial cellular damage is due to the direct effect of catecholamine stimulation acting on the beta-adrenergic receptor. The amount of left ventricular work appears to determine the extent of cellular damage. Physiological metabolites and the non-physiological metabolite, adrenochrome are not responsible for catecholamine-induced myocardial cellular damage. Epinephrine 10(-6) M caused a positive inotropic effect, whereas adrenochrome 10(-4) M induced contractile failure. Contractile failure was due to a negative inotropic effect and coronary artery vasoconstriction. Adrenochrome induces myocardial cellular damage and contractile failure but only in a concentration of 10(-4) M, this concentration does not appear to have pathophysiological relevance.     

Changes in high-energy phosphate compounds of isolated rat hearts during Ca2+-free perfusion and reperfusion with Ca2+.

Isolated rat hearts were perfused with a glucose-containing modified Tyrode solution at 37°C, according to Langendorff. After a 15 min stabilization period, the hearts were perfused for 4 min with a Ca²⁺-free medium and subsequently reperfused with Ca²⁺-containing medium. Reperfusion with Ca²⁺ caused irreversible loss of electrical and mechanical activity of the hearts (calcium paradox). After 30 s of reperfusion with Ca²⁺, myocardial creatine phosphate (CP) and ATP levels were decreased by 65% and 45% respectively. In the same period there was an increase in creatine (15%), ADP (85%) and AMP (2800%). Continued reperfusion with Ca²⁺ resulted in a gradual decrease in the tissue concentration of all compounds. The effluent fluid contained large amounts of creatine and AMP, and relatively minor amounts of CP, ATP and ADP. The results show that reperfusion with Ca²⁺-containing medium, after a short Ca²⁺-free period, produces a sudden and severe decline of myocardial high-energy stores, prior to the release of these compounds.     

Protective effects of amiodarone pretreatment on mitochondrial function and high energy phosphates in ischaemic rat heart

The effects of the antianginal and antiarrhythmic drug amiodarone on mitochondrial function and high-energy phosphate content were assessed during normothermic ischaemic cardiac arrest and reperfusion in Langendorff-perfused rat heart. Total ischaemia for 30 min at 37 degrees C produced highly significant changes in mitochondrial oxidative phosphorylation and high-energy phosphate content. Pretreatment of the rats with one single dose of amiodarone (20 mg/kg i.v., 30 min before killing) markedly attenuated the deleterious effect of ischaemia on mitochondrial function and slightly reduced ATP depletion. In normally perfused hearts, amiodarone pretreatment did not modify any parameter of mitochondrial respiratory function nor did it influence high-energy phosphate or glycogen content. After reperfusion for 15 min, amiodarone-treated hearts showed improved recovery of mitochondrial oxidative phosphorylation and tissue high-energy phosphate content as compared to control hearts. Pretreatment of hearts with amiodarone did not reduce ischaemia-induced leakage of total adenylic nucleotides but highly significantly reduced lactate dehydrogenase release during reperfusion. These results indicate that amiodarone could exert substantial protection on the infarcting myocardium.     

Antibodies to the ADP/ATP carrier, an autoantigen in myocarditis and dilated cardiomyopathy, penetrate into myocardial cells and disturb energy metabolism in vivo

We identified the ADP/ATP carrier, located within the inner mitochondrial membrane, to be an organ- and conformation-specific autoantigen in myocarditis and dilated cardiomyopathy. We also showed that autoantibodies to the ADP/ATP carrier inhibit the nucleotide transport in vitro. Specific binding of the autoantibodies to the carrier was demonstrated by radioimmunoassay and the immunoblot technique; the inhibition of the nucleotide transport was determined by the inhibitor stop method. To establish if these autoantibodies might also affect cardiac energy metabolism in vivo, we measured whether they are capable of penetrating into myocytes and whether subcellular ATP/ADP ratios and phosphorylation potentials of ATP change in hearts of guinea pigs that have been immunized with the isolated ADP/ATP carrier. An intracellular deposition of autoantibodies was observed by direct immunofluorescence and by immunoperoxidase staining on cryosections of the myocardial tissue of animals immunized with the ADP/ATP carrier. Furthermore, binding of autoantibodies to mitochondrial membrane structures was shown by immunoelectron-microscopic methods. The cytosolic and intramitochondrial distribution of adenine nucleotides in stimulated, isolated perfused hearts of guinea pigs immunized with the ADP/ATP carrier was measured by nonaqueous fractionation. Compared with controls performing equal external heart work, the cytosolic ATP decreased in the immunized animals, whereas the mitochondrial ATP increased strongly; ADP concentrations showed an opposite change. Thus, a resultant cytosolic decrease and a marked mitochondrial increase of the ATP/ADP ratio was established. As a consequence, the cytosolic-mitochondrial phosphorylation potential of ATP was diminished. These findings demonstrate that antibodies against intracellular antigens are able to penetrate into living cells, and that autoimmunity to the ADP/ATP carrier may contribute to the pathophysiology of myocarditis and dilated cardiomyopathy by causing an autoantibody-mediated imbalance between intracellular energy delivery and demand.     

Dissociation between cardiac cyclic AMP and myocardial contractility induced by verapamil, calcium and magnesium ions.

Isolated, perfused rat hearts were used to study the effects of verapamil, excess calcium ions or excess magnesium ions on changes in heart cyclic AMP and myocardial force of contraction. Verapamil caused a dose-dependent decrease in force of contraction and a nondose-related reduction in cyclic AMP. Perfusion of hearts with medium containing 5 mM calcium produced a significant rise in cyclic AMP, but no change in contractile force. The depressant effects of verapamil on contractility and cyclic AMP were reversed by 5mM calcium; excess calcium in the perfusion fluid also containing verapamil prevented the myocardial depressant effects of verapamil. Acutely elevating the magnesium concentration in the perfusion medium decreased force of contraction, accentuated the negative inotropic effect of verapamil, but did not decrease cyclic AMP or enhance the verapamil-induced reduction in cyclic AMP.     

病毒性心肌炎小鼠心肌线粒体结构和功能变化

目的:探讨病毒性心肌炎(VMC)小鼠心肌线粒体结构和功能变化。方法:雄性Balb/c小鼠随机分为柯萨奇B3病毒(CVB3)感染组和对照组。分别采用电镜和形态计量学方法观察心肌线粒体形态、数量和膜磷脂定位,酶细胞化学法分析线粒体细胞色素氧化酶(CCO)和琥珀酸脱氢酶(SDH)活性,反相高效液相色谱法测定心肌组织腺苷酸(ATP、ADP和AMP)含量。结果:CVB2感染组小鼠心肌线粒体大量破坏,膜磷脂严重缺失、定位改变,CCO和SDH活性降低,腺苷酸(ATP、ADP和AMP)含量下降。结论:VMC心肌线粒体结构严重破坏、功能明显下降,心肌细胞存在产能障碍。     

Effect of chronic vitamin D deficiency on chick heart mitochondrial oxidative phosphorylation

Chicks were raised for 3 to 4 weeks either on a normal (vitamin D supplemented) or a rachitogenic diet. The Ca²⁺ content of the serum, heart tissue and heart mitochondria was significantly decreased in chicks raised on a rachitogenic diet. In mitochondria isolated from calcium deficient hearts, the rate of ADP induced state 3 respiration and 2,4-DNP uncoupled respiration were significantly decreased. Furthermore, the ATP content of heart tissue was significantly decreased in calcium deficient hearts. These data suggest that an overall deficiency in energy production via oxidative phosphorylation exists in chronic calcium deficiency secondary to vitamin D deficiency. When vitamin D deficient chicks were orally dosed with vitamin D₃, serum calcium level and state 3 respiration rate returned to normal indicating that the above changes are reversible. Although previous studies have indicated that excess Ca²⁺ has deleterious effects on mitochondria, the results of the present study suggest that optimal mitochondrial function is dependent upon vitamin D dependent phenomena, including maintenance of calcium concentration within a relatively narrow range.