No description available.

No description available.

No description available.

Reperfusion of the isolated rat heart following 10 min of coronary artery ligation under constant flow conditions results in the development of arrhythmias - premature ventricular contractions (PVCs), ventricular tachycardia (VT) and ventricular fibrillation (VF). Increasing concentrations of magnesium (0 - 4.8 mM) and/or potassium (2.5 - 10.0 mM) attenuate, while calcium (0.6 - 2.4 mM) exacerbates these arrhythmias. The protective effects of magnesium and potassium were additive. Magnesium reduced heart rate, perfusion pressure and developed tension. Potassium reduced perfusion pressure and increased developed tension. These haemodynamic effects contributed to the antiarrhythmic action of magnesium but did not completely account for its antiarrhythmic action. Calcium increased developed tension and heart rate and reduced perfusion pressure. Post-ligation administration of magnesium and potassium also protected against reperfusion arrhythmias. These results demonstrate that reperfusion arrhythmias are significantly affected by the ionic environments of the heart. Superoxide dismutase (5 - 20 Um1-1 ), glutathione (10 -5 - 10-3M), ascorbic acid (10-4 -5 x 10-4 M) and histidine (5 x 10-3 M) when given before coronary artery ligation attenuated the development of reperfusion arrhythmias. Mannitol (2 x 10-2 M) and catalase (100 - 300 Uml-1) did not have any significant effect on reperfusion arrhythmias when given alone but they did potentiate the effect of superoxide dismutase. Glutathione and a combination of superoxide dismutase, catalase and mannitol also reduced the incidence of reperfusion induced ventricular fibrillation when given just before reperfusion. Ferrous ion exacerbated the severity of reperfusion arrhythmias. Mannitol (2 x 10-2 M), catalase (100 uml-1) and histidine (5 x 10-3 M) when given before coronary ligation or just before reperfusion prevented the effect of ferrous ion while superoxide dismutase did not, indicating that the presence of ferrous ion is important for the production of hydroxyl radicals. Pretreatment with 6- OHDA attenuated the incidence of reperfusion arrhythmias but pre-ligation administration of allopurinol had no effect on reperfusion arrhythmias. By perfusing hearts with ferricytochrome C it was possible to show an increased reduction of ferricytochrome C during the first minute of reperfusion which could be prevented by the addition of superoxide dismutase and 6-OHDA treatment. These results provide evidence that oxygen free radicals are produced and may be important in the genesis of reperfusion induced arrhythmias in the isolated rat heart. Adenosine (10-6 M), verapamil (10 -8 - 10-7 M), ZK 36374 (10-10 - 10 -9 M) and sodium nitroprusside (10-6 -10-9 M) attenuate the incidence of reperfusion arrhythmias which may be via a coronary steal effect. Agents which affect arachidonic acid metabolism yielded conflicting results which may reflect nonspecific mechanisms other than inhibition of arachidonic acid metabolism. Glutathione and a mixture of superoxide dismutase, catalase and mannitol when given before coronary ligation and just before reperfusion reduced the increase in 86 rubidium efflux rate constant shown on reperfusion. The effect of glutathione on 86 rubidium efflux may be at least in part due to its vasodilator effect. Superoxide generation by xanthine/xanthine oxidase system increased the rate of efflux of 86 rubidium. A mixture of superoxide dismutase, catalase and mannitol also reduced the transient increase in the rate of release of 3H-noradrenaline shown to be produced on reperfusion after 10 min of ischaemia in the isolated rat heart.

No description available.

Zur Charakterisierung der myokardialen SR Ca2+-Transportaktivität nach experimentellem Myokardinfarkt wurde 10-15 Wochen alten Ratten die linke Koronararterie unterbunden und sechs Wochen später die Funktion und Expression der Ca2+-ATPase des sarkoplasmatischen Retikulums untersucht. Ein Teil der Tiere wurde mit dem Carnitin-Palmitoyl-Transferase-1- Inhibitor Etomoxir behandelt, der die mitochondrale Oxidation von langkettigen Fettsäuren hemmt und dadurch verstärkt Glukoseoxidation bewirkt. Diese Stoffwechselumstellung sollte die Schädigung der myokardialen Funktion und die gestörte zelluläre Ca2+-Homöostase nach Myokardinfarkt vermindern. Die mit Etomoxir behandelten Tiere wiesen nach sechs Wochen eine deutlich verminderte Infarktgröße auf. Durch die CPT-1-Hemmung entstand eine starke biventrikuläre Hypertrophie. Darüber hinaus ergaben sich Hinweise auf den Erhalt einer normalen Wandspannung des linken Ventrikels und einer verbesserten Kontraktilität gegenüber der unbehandelten Gruppe. Unter Etomoxir zeigte die für die diastolische Ca2+ Senkung verantwortliche ATP-abhängige Ca2+-Rückbindung in das SR verbesserte Transportraten. Damit korrelierte der immunchemisch gemessene erhöhte SERCA2a-Proteinspiegel. Die Ergebnisse lassen vermuten, daß es infolge einer Behandlung mit Etomoxir nach Myokardinfarkt zu einer verbesserten Zellstoffwechsellage des ischämisch nicht irreversibel geschädigten Myokards kommt. Dafür scheint die verstärkte Glukoseoxidation bei Hemmung der Oxidation langkettiger Fettsäuren im Herzmuskel verantwortlich zu sein. Die Größe des infarzierten Areals wird begrenzt, dadurch lassen sich zum Teil verbesserte hämodynamische Parameter und gesteigerte SR Ca2+-Transportraten und SERCA2a-Proteinspiegel erklären. Auf die Hämodynamik hat sicherlich auch die durch Etomoxir erfolgte myokardiale Hypertrophie einen wesentlichen Einfluß. Für weitere Studien bleibt abzuklären, durch welchen Mechanismus Etomoxir seine verbessernde Wirkung nach Myokardinfarkt entfaltet. Außerdem ist zu prüfen, ob nach akutem Myokardinfarkt beim Menschen mit dem Prinzip der chronischen Verschiebung der myokardialen Substratverwertung von Fettsäure- nach Glukoseoxidation eine verbesserte Überlebensrate und das Hinauszögern bzw. Verhindern einer Dekompensation des Herzens zu erreichen ist. / To characterise the activity of sarcoplasmic reticulum (SR) Ca2+ after myocardial infarction the left coronary artery of 10-15 week old male rats was ligated; six weeks later function and expression of the SR Ca2+-pump ATPase (SERCA2a) transport in the surviving myocardium was investigated. Part of the animals were treated with the carnithin palmitoyltransferase-1 (CPT-1) inhibitor etomoxir (8mg/kg/d for six weeks) to decrease the oxidation of long chain fatty acids. Due to the drug-induced shift from fatty acid to carbohydrate utilization an attenuated myocardial dysfunction and an improved SR Ca2+ handling homeostasis in the surviving myocardium could be expected. The etomoxir treated rats showed a decreased infarct size six weeks after coronary ligation. Due to CPT-1 inhibition a significant biventricular hypertrophy was observed. In addition, the treatment normalized elevated LVEDP and improved contractility. Compared to sham-operated controls treatment with etomoxir caused an enhanced SR Ca2+ uptake activity that correlated with increased immunoreactive SR Ca2+-ATPase levels. The results suggest that chronic inhibition of CPT-1 after myocardial infarction improves the metabolism of reversible damaged tissue. It appears that increased oxidation of glucose and inhibition of long chain fatty acid oxidation is responsible for this effect. Limitation of the infarct size induces improvement of haemodynamic parameters, increases SR Ca2+ uptake and protein levels of SERCA2a. Further studies are required to find out whether etomoxir is able to delay the development of congestive heart failure in humans and whether it could decrease mortality in patients after myocardial infarction.

This diploma thesis deals with analysis of electrograms recorded from isolated rat hearts. In theoretical part, basic principles of electrocardiography and differences between rat and human EG records are described. Types of arrhythmias and methods for classification and quantification of arrhythmias are also described. Examples of pathologies found during the manual classification and results of the analysis of the QTc interval duration are presented. An occurrence of premature beats is then compared between experimental groups. Finally, the method used for the automatic analysis of electrograms including the graphical user interface is described and the results of its evaluation using real data are presented

Thromboxane A2 (TXA2) and ET-1 have been known to play important roles in modulating vascular contraction and growth. The present study was undertaken to examine the effect of TXA2 on the induction of endothelin-1 (ET-1) mRNA and protein levels in smooth muscle cells derived from rat heart. U-46619, a stable TXA2 mimetic, superinduced preproET-1 mRNA in the presence of cycloheximide in these cells. This effect could be blocked by SQ-29548, a TXA2/prostaglandin H2 receptor antagonist and by actinomycin D, an RNA synthesis inhibitor. In addition, H7, a protein kinase C inhibitor, could abolish the induction. Transient transfection experiment revealed that the elevated ET-1 mRNA level after U-46619 treatment was a result of the activation of ET-1 gene activity. The elevated ET-1 message level was accompanied by increased ET-1 release into the cultured medium. These results show that the short-lived TXA2 can induce potent and long-lived ET-1. These findings support a potential role for ET-1 in the pathogenesis of coronary atherosclerosis and hypertension evoked by TXA2.

Angiotensin II (All) was found to upregulate tissue inhibitor of metalloproteineses-1 (TIMP-1) gene expression in rat heart endothelial cells in a dose and time-dependent manner. The maximal stimulation of TIMP-1 mRNA was achieved by 2 h after the addition of All. This effect was blocked by losartan, an AT1 receptor antagonist and by calphostin C, a protein kinase C inhibitor. Addition of cycloheximide superinduced and actinomycin D abolished the induction. These results suggest that All stimulates TIMP-1 production by a protein kinase C dependent pathway which is dependent upon de novo RNA synthesis. Immunoprecipitation experiment showed an enhanced band of 28 kDa from the conditioned medium of All-treated cultures. Immunoblot analysis revealed that TIMP-1 was detectable in the conditioned medium 4 h after All stimulation. Since endothelial cells line the blood vessels and sense the rise in All associated with hypertension, the TIMP-1 released by these cells may provide an initial trigger leading to cardiac fibrosis in angiotensin-renin dependent hypertension.

IN ENGLISH The ischemia-reperfusion (I/R) injury, which is a consequence of myocardial infarction, represents a major cause of death worldwide. One of the most effective cardioprotective interventions increasing the resistance of hearts to the I/R injury is the adaptation to a chronic hypoxia (CH). However, the molecular mechanisms of CH are still not well understood. The most important factors responsible for the I/R injury are reactive oxygen species (ROS) produced by complexes I and III within the mitochondrial electron transport chain. Potential candidates maintaining ROS at a low level are mitochondrial creatine kinase (mtCK) and two hexokinase isoforms (HK1 and HK2). These enzymes highly support the mitochondrial oxidative phosphorylation by increasing the availability of ADP for complex V of the respiratory chain. In addition, the HK binding to mitochondria inhibits binding of the pro- apoptotic protein BAX, thereby protecting cardiac cells against apoptosis. Besides the mitochondrial CK isoform, there are two cytosolic CK (CKM and CKB) present in cardiomyocytes that help to maintain energy homeostasis. Based on the known anatomical and physiological differences between the left (LV) and the right (RV) ventricles, the first study focused on the comparing ventricles in terms of the energy...