Papers by Ludmila Okruhlicová
Interdisciplinary toxicology, 2011
One of the factors proposed as mediators of vascular dysfunction observed in diabetes is the incr... more One of the factors proposed as mediators of vascular dysfunction observed in diabetes is the increased generation of reactive oxygen species (ROS). This provides support for the use of antioxidants as early and appropriate pharmacological intervention in the development of late diabetic complications. In streptozotocin (STZ)-induced diabetes in rats we observed endothelial dysfuction manifested by reduced endothelium-dependent response to acetylcholine of the superior mesenteric artery (SMA) and aorta, as well as by increased endothelaemia. Changes in endothelium-dependent relaxation of SMA were induced by injury of the nitric oxide radical (·NO)-signalling pathway since the endothelium-derived hyperpolarising factor (EDHF)-component of relaxation was not impaired by diabetes. The endothelial dysfunction was accompanied by decreased ·NO bioavailabity as a consequence of reduced activity of eNOS rather than its reduced expression. The results obtained using the chemiluminiscence meth...
Major civilization diseases that are related to cardiovascular system are accompanied with inflam... more Major civilization diseases that are related to cardiovascular system are accompanied with inflammation. Inflammatory process is known to change function of vascular endothelium which plays a crucial role in atherosclerotic plaque development and related disturbances in heart function. In addition to pharmacotherapy the natural substances have been recommended to reduce incidence and severity of atherosclerotic heart diseases. Therefore, the aim of our study was to examine if acetylcholine (Ach)- modulated heart function may be affected by endotoxin and carotenoids produced by yeast strain Rhodontorula characterized with antioxidative properties. Ach is an important neurotransmitter of the parasympathicus nerve system, opposite to the sympathicus nerve system, slowing the heart functions. The experiment was performed on male Wistar rats. The inflammation was induced with a single dose of endotoxin (LPS E. coli, 1 mg/kg). Rats were treated with yeast biomass (10 mg/kg/day) for 10 day...
Journal of physiology and pharmacology: an official journal of the Polish Physiological Society
Connexin (Cx)-channels can represent one of targets of omega-3 fatty acids (n-3 PUFA) in protecti... more Connexin (Cx)-channels can represent one of targets of omega-3 fatty acids (n-3 PUFA) in protection of cardiovascular system against injury. We investigated the anti-inflammatory effect of 10-day n-3 PUFA intake (30 mg/kg/day for 10 days) on expression of Cx40 isoform in the aorta of Wistar rats injected with a single dose of lipopolysaccharide (LPS, 1 mg/kg, i.p.). LPS resulted in up-regulation of Cx40 expression in the aorta associated with reduced endothelium-dependent relaxation. LPS increased levels of inflammatory markers C-reactive protein and malondialdehyde in circulation as well as NOS activity and CD68 expression in aortic tissue indicating presence of moderate inflammation. N-3 PUFA supplementation decreased expression of both Cx40 and CD68 in aortic tissue and suppressed concentrations of C-reactive protein and malondialdehyde of endotoxemic rats. N-3 PUFA did not improve NO-dependent relaxation of aorta and NOS activity in LPS rats. The results indicate the involvement...
Cardiovascular Research, 2014
One of the most widely used methods of treating oncological patients is ionizing radiation therap... more One of the most widely used methods of treating oncological patients is ionizing radiation therapy. Radiation beam causes damage to the cancer cells which can reduce cancerous mass and leads to recovery of the oncological patients. On the other hand irradiation of other nearby tissues like myocardium can cause some damage which can induce serious health problems leading to the heart ischemia and heart failure. The aim of this work was to study the morphological changes and changes in molecular markers six weeks after irradiation with a single dose of 25 Gy, applied to mediastinal region of Wistar male rats.
Canadian journal of physiology and pharmacology, Jan 27, 2015
In addition to cytostatic treatment and surgery, the most common cancer treatment is gamma radiat... more In addition to cytostatic treatment and surgery, the most common cancer treatment is gamma radiation. Despite sophisticated radiological techniques however, in addition to irradiation of the tumor, irradiation of the surrounding healthy tissue also takes place, which results in various side-effects, depending on the absorbed dose of radiation. Radiation either damages the cell DNA directly, or indirectly via the formation of oxygen radicals that in addition to the DNA damage, react with all cell organelles and interfere with their molecular mechanisms. The main features of radiation injury besides DNA damage is inflammation and increased expression of pro-inflammatory genes and cytokines. Endothelial damage and dysfunction of capillaries and small blood vessels plays a particularly important role in radiation injury. This review is focused on summarizing the currently available data concerning the mechanisms of radiation injury, as well as the effectiveness of various antioxidants, ...
International journal of molecular sciences, 2015
Quercetin (QCT) is flavonoid that possesses various biological functions including anti-oxidative... more Quercetin (QCT) is flavonoid that possesses various biological functions including anti-oxidative and radical-scavenging activities. Moreover, QCT exerts some preventive actions in treatment of cardiovascular diseases. The aim of present study was to explore effects of prolonged administration of QCT on changes induced by repeated application of doxorubicin (DOX) in rat hearts. We focused on the ultrastructure of myocardium, matrix metalloproteinases (MMPs), biometric parameters, and apoptosis induction. Our aim was also to examine effects of QCT on ischemic tolerance in hearts exposed to chronic effects of DOX, and to determine possible mechanisms underlying effects of QCT. Our results showed that QCT prevented several negative chronic effects of DOX: (I) reversed DOX-induced blood pressure increase; (II) mediated improvement of deleterious effects of DOX on ultrastructure of left ventricle; (III) prevented DOX-induced effects on tissue MMP-2 activation; and (iv) reversed effects o...
Physiologia Bohemoslovaca, 1990
Experiments using a cytochemical method showed the presence of a specific precipitate of the aden... more Experiments using a cytochemical method showed the presence of a specific precipitate of the adenylate cyclase (AC) reaction on the sarcolemma and in the subsarcolemmal cisternae and junctional sarcoplasmic reticulum in rat cardiomyocytes. The localization of AC in the given organelles draws attention to the mutual association between Ca2+ ions and cAMP in the modulation of cardiac contractions. Trifluoperazine (TFP) and chlorpromazine (CHP) are known as phenothiazine derivatives inhibiting cellular enzymatic processes dependent on calmodulin and Ca2+. AC is one of these enzyme systems. The administration of TFP and CHP (both in a dose of 0.1 and 3 mmol.1(-1)) did not affect the cytochemical localization of the enzyme. Quantitative determination of 125I-cAMP by RIA showed that CHP inhibited AC activity in both concentrations. TFP, on the other hand, did not inhibit AC activity in 0.1 mmol.1(-1) concentration and actually stimulated its activation in 3 mmol.1(-1) concentration. The d...
Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2009
Hypertension alters expression of connexin-43 (Cx43) in cardiovascular system. The aim of the stu... more Hypertension alters expression of connexin-43 (Cx43) in cardiovascular system. The aim of the study was to investigate the effect of omega-3 polyunsaturated fatty acids (30 mg/day for 2 months) on expression of Cx43 in the aorta of 1-year-old male spontaneously hypertensive rats (SHR). Spatial distribution and expression of Cx43 in aortic wall of SHR and age-matched Lewis rats were determined by immunofluorescent method and Western blot. NO synthase (NOS) activity and endothelium-dependent relaxation of the aorta were measured as well. Immunofluorescent pattern of Cx43 was identified in endothelial and smooth muscle cells of the aorta of all experimental groups studied. However, local decrease in the number and intensity of fluorescent spots and reduced phosphorylation of Cx43 were observed in SHR in contrast to normotensive LEW. Omega-3 fatty acid diet increased Cx43 immunolabeling in endothelium and media of SHR comparing to untreated ones. Parallel, 3-fatty acids significantly el...
Journal of physiology and pharmacology : an official journal of the Polish Physiological Society, 2008
We examined whether thyroid hormones affect myocardial epsilon-PKC signalling, downstream target ... more We examined whether thyroid hormones affect myocardial epsilon-PKC signalling, downstream target substrate, connexin-43 (Cx43) and arrhythmogenesis in non-diabetic and diabetic rats. Diabetes was induced by a single streptozotocin injection (50mg/kg, i.v.). Triiodothyronine (T(3)) was applied by gavage (1microg/kg of body weight for 10 days) to 4 weeks and 9 weeks diabetic and age-matched non-diabetic rats. Western blot analysis of Cx43 and epsilon-PKC, immunofluorescence of Cx43, ultrastructure of cardiomyocytes and myocardial conduction velocity were performed. Isolated perfused heart preparation was used to test ventricular fibrillation susceptibility. T(3) significantly decreased epsilon-PKC expression in non-diabetic and suppressed in diabetic rat heart ventricles. Decline of epsilon-PKC signalling was associated with decrease of Cx43 phosphorylation in diabetic and to a greater extent in non-diabetic rat hearts. However, conduction velocity was significantly decreased in diabe...
Physiological research / Academia Scientiarum Bohemoslovaca, 2008
Direct cell-to-cell communication in the heart is maintained via gap junction channels composed o... more Direct cell-to-cell communication in the heart is maintained via gap junction channels composed of proteins termed connexins. Connexin channels ensure molecular and electrical signals propagation and hence are crucial in myocardial synchronization and heart function. Disease-induced gap junctions remodeling and/or an impairment or even block of intercellular communication due to acute pathological conditions results in derangements of myocardial conduction and synchronization. This is critical in the development of both ventricular fibrillation, which is a major cause of sudden cardiac death and persistent atrial fibrillation, most common arrhythmia in clinical practice often resulting in stroke. Many studies suggest that alterations in topology (remodeling), expression, phosphorylation and particularly function of connexin channels due to age or disease are implicated in the development of these life-threatening arrhythmias. It seems therefore challenging to examine whether compoun...
Physiological research / Academia Scientiarum Bohemoslovaca, 2008
Thyroid hormones (TH) are powerful modulators of heart function, but their arrhythmogenic effects... more Thyroid hormones (TH) are powerful modulators of heart function, but their arrhythmogenic effects are less elucidated. We have examined both acute and long-term action of TH on the heart susceptibility to the ventricular fibrillation (VF) and on the heart ability to terminate VF and restore a sinus rhythm. Triiodothyronine (T3) was applied in the range of 10(-9)-10(-6) mol/l in acute experiments using isolated perfused aged (14-month-old) guinea pig hearts. L-thyroxine (T4) was applied in the dose of 50 microg/100g/day to young (3-month-old) and aged (20-month-old) rats for 2 weeks. The T4 treatment resulted in an increased susceptibility of young, but not adult rat hearts to a hypokalemia-induced VF and facilitated a spontaneous sinus rhythm (SSR) restoration in the latter group. The acute T3 administration in the range of 10(-9)-10(-7) mol/l significantly decreased the susceptibility of an isolated heart to an electrically induced VF and also facilitated the sinus rhythm restorati...
Physiological research / Academia Scientiarum Bohemoslovaca, 2005
Cardiac gap junctions have been implicated in maintaining intercellular electrical and metabolic ... more Cardiac gap junctions have been implicated in maintaining intercellular electrical and metabolic couplings. The abnormalities in connexin-43 (Cx43) lead to conduction defects and contractile dysfunction. We have evaluated the expression and phoshorylation status of Cx43 in the left ventricular myocardium of male and female 16-month-old rats submitted to 14-week L-thyroxine (T4) treatment. Western blot analysis revealed the presence of fully or intermediately phosphorylated and unphosphorylated forms of Cx43. We have found no significant differences in Cx43 expression and phosphorylation between T4-treated and control untreated animals. However, expression of Cx43 was significantly higher in female compared to male rats. We conclude that T4 administration has no effect on Cx43 expression, but there are sex-dependent differences in Cx43 expression in the left ventricles between aging male and female rats.
General physiology and biophysics, 2003
Disorders of intracellular Ca2+ homeostasis and intercellular coupling are thought to be crucial ... more Disorders of intracellular Ca2+ homeostasis and intercellular coupling are thought to be crucial in the initiation and maintenance of malignant arrhythmias. The aim of this study was to investigate possible arrhythmogenic factors in spontaneously hypertensive rats (SHR) as well as their susceptibility to low K+-related arrhythmias. The experiments were performed on isolated hearts of 13 weeks-old SHR and age-matched Wistar Kyoto rats (WKY). Equilibration of the heart by Langendorff perfusion with oxygenated, 37 degrees C warm, standard Krebs solution at a constant pressure was followed by perfusion with low K+ solution for 60 min, unless sustained ventricular fibrillation occurred earlier. Electrocardiogram and epicardial monophasic action potentials (MAPs) were continuously monitored for incidence of arrhythmias and action potential changes. Myocardial tissue was taken for ultrastructural analysis and immunodetection of the main gap junction protein, connexin-43. The results showed...
Molecular and cellular biochemistry, 2000
Tedisamil is antiarrhythmic class III drug with antifibrillating/defibrillating potency linked to... more Tedisamil is antiarrhythmic class III drug with antifibrillating/defibrillating potency linked to enhancement of intermyocyte gap junctional electrical coupling most likely via its sympathomimetic cAMP-related mechanisms. This study was designed to examine the effect of tedisamil on cAMP level in guinea pig hearts in vivo and in vitro in Langendorff preparation. The drug was administered either as a bolus into vena jugularis in dosage 1.0 and 1.5 mg/kg or into the perfusion solution at a concentration of 1.5 x 10(-6) mol/l. In additional experiments, this period was followed by brief 10 min global ischemia, induced by clamping of the aorta or perfusion. After 10 min from the onset of tedisamil administration as well as after 10 min of ischemia the ventricular tissue was immediately frozen for cAMP immunoassay. Tedisamil caused in normal heart small but significant dose-dependent increase of myocardial cAMP (pmol/mg) level in vivo 1.8 and 2.5 vs. 1.4 as well as in vitro 1.1 vs. 0.8 (...
General physiology and biophysics, 1997
Mitochondrial contact sites (MiCS) are structures in the mitochondrial membrane containing the st... more Mitochondrial contact sites (MiCS) are structures in the mitochondrial membrane containing the structure-bound mitochondrial isoenzyme of creatine phosphokinase that participates in the transfer of energy into the cytoplasm. This explains the increased formation of MiCS found in hearts with high metabolic activity. Earlier we demonstrated that enhanced MiCS formation may also be induced by perfusing the heart with increased, but still not cardiodepressive concentrations of Ca2+ (2.2 mmol.l-1) in the perfusate. Nevertheless, neither the molecular mechanism by which Ca2+ ions may induce an increase in MiCS formation, nor the dependence of Ca(2+)-induced MiCS formation on the intracellular Ca2+ level have yet been elucidated. In the present study we investigated the effect of Langendorff-perfusion with 2.2 mmol.l-1 Ca2+ on formation of MiCS in normal as well as in diabetic hearts. The latter, namely, are characterized by altered metabolism as well as Ca(2+)-handling, resulting in eleva...
Bratislavské lekárske listy, 1987
Bratislavské lekárske listy, 1988
Bratislavské lekárske listy, 1990
The model of calcium paradox was used to test the effect of the calcium entry blocker Diltiazem (... more The model of calcium paradox was used to test the effect of the calcium entry blocker Diltiazem (concentration 4.0 mumol.l-1) and of the calmodulin inhibitor Trifluoroperazin (concentration 1.0 mumol.l-1). Application of each preparation resulted in improved cardiac function manifested by restoration of the electrical and contractile activity and by increased coronary flow. Both Diltiazem and Trifluoroperazin exerted a protective effect on the preservation of enzymatic activities and of ultrastructure in conditions of impaired calcium homeostasis.
Bratislavské lekárske listy
Under physiological conditions different parts of the heart reveal superspecialization of the myo... more Under physiological conditions different parts of the heart reveal superspecialization of the myocardium reflected by biochemical, functional, structural and histochemical differences, which are even more pronounced under pathological conditions. Postischemic reperfusion, Ca paradox and injury caused by reactive oxygen species were found to result in transmurally unhomogenous damage of the ventricular wall. In the present experiments isolated perfused rat hearts were subjected to damage by the above mechanism and a different vulnerability of defined parts of the heart was observed. Activities of glycogen phosphorylase, SDH, beta-HBDH, and LDH were studied histochemically in both ventricles, the atria and the specialized conductive system of the heart. Marked decreases of activities were observed in the ventricular muscle. The enzyme activities were less decreased in the atrial muscle. Conductive fibres were the least affected tissue in this respect. The differential changes were mos...
Bratislavské lekárske listy
Polyclonal specific antisera to beta-receptors were prepared by immunization of rabbits with beta... more Polyclonal specific antisera to beta-receptors were prepared by immunization of rabbits with beta-receptors isolated from a dog myocardium according to Becker et al. (1988). Cryostat sections of the dog heart were fixed in paraformaldehyde in PBS, and incubated with polyclonal antisera to beta-receptors. Sections were then washed and incubated in peroxidase-labelled anti-rabbit antibody. After visualization of the tissue-bound peroxidase with diaminobenzidine, sections were dehydrated in graded alcohols and mounted in Canada balsam. The results demonstrate specific reaction of antibodies on the myocyte sarcolemma.
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Papers by Ludmila Okruhlicová