[Complex study of the rat heart at isoproterenol damage].

Introduction of isoproterenol (an agonist of beta-adrenoreceptors) to rats is one of the widespread experimental models of cardiac failure. It is caused by damage of cardiomyocytes with the subsequent development of substitutive fibrosis. The purpose of the given work was the complex characteristic of cardiac function by means of invasive and noninvasive (echocardiography and impedansometry) methods of research. Isoproterenol was injected twice with a daily interval in dozes 85, 120, 150 or 180 mg/kg. Echocardiographic study of the heart in 2 weeks revealed obvious attributes of cardiac failure (left ventricular dilatation, lowered ejection fraction) in the groups which have received high cumulative dozes of isoproterenol (300-360 mg/kg). The catheterization of the left ventricle in these groups has shown raised enddiastolic pressure, decreased maximal rate of pressure development and fall, and also lowered indices of myocardial contractility and relaxability. In the groups which have received smaller isoproterenol dozes, apparent decrease in relaxability parameters (constants of isovolumic and auxovolumic relaxation) has been revealed at only slightly changed parameters of contractility. A strong correlation between echocardiographic and invasive parameters of myocardial contractility has been found. The phase analysis of the cardiac cycle has shown a lengthening of isometric phases of contraction and relaxation, as well as duration of ejection due to shortening duration of filling of both ventricles. Cardiomyocytes isolated from hearts with obvious cardiac failure responded to electrostimulation by arrhythmic contractions and also by much slowed and incomplete removal of free Ca++ from the myoplasm. Results allow to conclude that relatively smaller extent of myocardial damage is accompanied by decreased relaxability at slightly changed contractility, while at greater degree of damage both processes fail, but delay of relaxation still prevails.

[The similarity and difference in the action of adriamycin and hydrogen peroxide on the myocardium].

The oxidative stress in cardiomyocytes is a component of cardiotoxic action of adriamycin. To distinguish the importance of this component we have compared initial effects of hydrogen peroxide and adriamycin on the contractile function and a tone of coronary vessels of the isolated rat heart. Adriamycin in concentration 3 mcM distinctly reduced developed pressure and heart rate, but raised coronary vessel tone. The concentration 1 mcM was inefficient at usual perfusion rate, but practically prevented rise in developed pressure and rates of its rise and fall at increased perfusion rate. Hydrogen peroxide also dose-dependently reduced developed pressure, but rates of its rise and fall were reduced to a lesser degree, while the heart rate slightly raised, and coronary vessel tone was reduced. Thus, the initial actions of hydrogen peroxide and adriamycin on the heart considerably differ. It suggests that the oxidative stress is not the main component of cardiotoxic action of adriamycin, at least, in its application in concentrations close to therapeutic ones.

[The study of hypotensive action of dinitrosyl-iron complex with glutathione containing drug oxacom in healthy volunteers].

On the basis of earlier executed studies of hypotensive effect of dinitrosyl iron complexes (DNIC) with glutathione, the drug has been created in industrial conditions named oxacom. Preliminary pharmacological studies of oxacom have not revealed negative qualities. The drug has been now tested in 14 healthy men in whom at single intravenous introduction it caused typical response - a decrease of diastolic as well as systolic arterial pressure on 24-27 mmHg through 3-4 min with subsequent very slow restoration in 8-10 hours. The heart rate after initial rise was quickly normalized. Echocardiography revealed unaltered cardiac output in spite of reduced cardiac filling by 28%. The multilateral analysis of clinical and biochemical data has revealed an absence of essential alterations which could lead to pathological consequences. The drug is recommended for carrying out of the second phase of clinical trial. The comparative study of the efficiency of hypotensive action of oxacom, S-nitrosoglutathione (GS-NO) and sodium nitrite (NO2) in rats has shown that the duration of effect was the greatest at oxacom action.

[Mitochondrial antioxidant SkQl decreases intensity of ventricular arrhythmias caused by epinephrine].

Preventive action of new antioxidant SkQ1 has been studied in rats on model of cardiac arrhythmia caused by epinephrine. The SkQ1 substance was given in dosages from 0.02 up to 20 moles/kg per os 2 weeks prior to experiment. Intravenous bolus introduction of epinephrine (10 or 6 mkg/kg in different experimental series) caused an immediate rise of arterial pressure in average by 19% and decrease in heart rate in average by 44%. The degree of changes of these parameters was approximately identical in all groups. Arrhythmia in the form of ventricular extrasystolia arose in the first 5 min. The total number of extrasystoles, and index of arrhythmia intensity have been 2-3 times lower in rats receiding SkQ1 in doses of 0.5, 2 and 20 moles/kg. It was combined with increased survival rate of animals. Smaller dosages of SkQ1 (0.02-0.1 moles/kg) were ineffective. Results have shown that administration of mitochondrial antioxidant SkQ1 raises stability of the myocardium to arrhythmogenic action of epinephrine.

[Acute and postponed action of adriamycin on the contractile function and antioxidant status of the myocardium].

Functional, biochemical and morphological studies of rat cardiac muscle after single injection of adriamycin (2.2 mg/kg) were carried out. The myocardium was taken for studies in 2 hours and in 2-3 weeks after adriamycin injection. The isolated heart was perfused retrogradely with Krebs solution and left ventricular isovolumic pressure and perfusion pressure were continuously monitored. Two-fold increase in perfusion rate was accompanied by raised developed pressure, heart rate and perfusion pressure which in the given conditions reflected a tone of coronary vessels. The cardiac contractile function of rats that received adriamycin 2 hours before, remained unaltered as compared to control group, however, perfusion pressure was raised by 26%. These hearts responded to H2O2 introduction (100 microM) into coronary vessels by more profound fall in developed pressure, which fell to 31 +/- 8% after 40 minutes vs. 61 +/- 5% in the control group (p<0.01). In two-three weeks after adriamycin injection, both cardiac contractile function and its responsiveness to oxidative stress induced by H2O2 introduction did not differ from the control, however, perfusion pressure remained elevated and this was accompanied by slowed myocardial relaxation. The myocardial concentration of malonic dialdehyde was moderately increased in adriamycin-treated group in both terms while the activity of antioxidant enzymes (SOD, GPHx and catalase) remained unaltered. Results showed an absence of the direct connection between myocardial antioxidant status and the contractile function changes at adriamycin action.

[Protective effect of mitochondrial antioxidant SkQl at cardiac ischemia and reperfusion].

Mitochondria are believed to be both main origin and target of oxidative stress in cells. In the present study we used novel mitochondria-targeted antioxidant SkQ1 using triphenylphosphonium cation as a driver. The substance was alimentary given to rats daily during 3 weeks in varying doses, from 0.5 to 250 mol/kg/day. The isolated hearts were perfused by standard procedure, the isovolumic left ventricular pressure was recorded. After stabilization period the hearts were subjected to 30-min total normothermic ischemia with subsequent 50-min reperfusion. Arrhythmic disorders at the onset of reperfusion were significantly less pronounced in SkQ1 groups 0.5 and 5 mol/kg, the arrhythmia index for first 30-min was 1.3+/-0.3 and 1.8+/-0.6, respectively, vs. 5.7+/-1.3 in control experiments. By the end of reperfusion a significantly better recovery of heart rate was observed in SkQ1 groups 0.5 and 250 mol/kg and that of developed pressure - in SkQ1 group 0.5 mol/kg. As a result, a recovery of the double product of developed pressure and heart rate by the end of reperfusion was almost twice higher in groups SkQ1 0.5 and 250 mol/kg (55+/-5 and 58+/-8%, respectively), vs. the control (30+/-4%, p<0.05). Results suggest that the protective action of SkQ1 at postischemic reperfusion may be due to increased myocardial antioxidant status.

[Modification of the FF neuropeptide enhances its hypertensive effect].

Neuropeptide FF (H-Phe-Leu-Phe-Gln-Pro-Gln-Arg-Phe-NH2) injected intravenously temporarily enhanced the arterial pressure (AP) and the heart rate (HR). However, its role in the regulation of blood circulation is obscure. To study the properties of the molecule, its analogue was synthesized, in which proline in position 7 was substituted with glycine, and leucine in the position 2 with norleucine. Modified neuropeptide FF (FFm) also temporarily and in a dose-dependent manner increased the AP and HR; however, the equal degree of increase was reached at doses of FFm being 5-7 times lesser as compared with the natural peptide. The application of the FFm at hemorrhagic shock excluded mortality of animals during the experiment, considerably increased the degree of AP and HR restoration in the remaining experiments, and improved the survival of animals in 24 hours. It has been found that the level of antibodies to the fragment of hFF1 receptor in the serum is lower in spontaneously hypertensive rats SHR as compared with Wistar rats, but it is increased in patients of cardiological profile as compared with donors. The findings suggest involvement of neuropeptide FF in the regulation of blood circulation; however, the precise mechanisms remain to be determined.

[Penetrating peptide inhibitor of the myosin light chain kinase suppresses hyperpermeability of vascular endothelium].

Nonapeptide H-Arg-Lys-Lys-Tyr-Lys-Tyr-Arg-Arg-Lys-NH2 corresponding to a modified sequence of autoinhibitory region of myosin light chain kinase (MLCK) was synthesized from L-amino acids and from D-amino acids. Using nuclear magnetic resonance spectroscopy it has been demonstrated that D-peptide is significantly more stable in human blood plasma than its L-enantiomer. D-peptide accumulated in cultured human umbilical vein endothelial cells suppressed development of hyperpermeability in endothelial monolayer induced by thrombin addition. Following intravenous administration D-peptide decreased the extent of lung oedema in rats induced by infusion of oleic acid in bloodstream. Thus, the peptide molecules based on an autoinhibitory peptide of MLCK may serve as a prototype for development of a novel antioedematous drugs that directly affect the MLCK-dependent motile processes in vascular endothelium.

[Action of a nitric oxide donor dinitrosyl complex of iron with glutathione on hemodynamics in rats and monkeys].

We studied action of a nitric oxide donor, dinitrosyl complex of iron (DNIC) with glutathione as a ligand on the hemodynamics of normotensive Wistar rats, spontaneously hypertensive rats (SHR), and monkeys. Intravenous DNIC introduction (2-120 mg/kg) rendered fast (1-2 min) hypotensive effect combined with increased heart rate by 10-25%. Second phase of the effect in Wistar rats was characterized by slowed recovery of arterial pressure and heart rate up to initial level. A gradual DNIC breakdown in blood occurred during this period associated with increased NO accumulation in organs with intensive oxidative metabolism (liver, heart, and kidney). Duration of hypotensive effect in all animals depended on dose, this dependence was most expressed in SHR.

Mechanisms of oxidative modification of low density lipoproteins under conditions of oxidative and carbonyl stress.

Low-molecular-weight aldehydes (glyoxal, methylglyoxal, 3-deoxyglucosone) generated on autooxidation of glucose under conditions of carbonyl stress react much more actively with amino groups of L-lysine and epsilon-amino groups of lysine residues of apoprotein B-100 in human blood plasma low density lipoproteins (LDL) than their structural analogs (malonic dialdehyde (MDA), 4-hydroxynonenal) resulting on free radical oxidation of lipids under conditions of oxidative stress. Glyoxal-modified LDL aggregate in the incubation medium with a significantly higher rate than LDL modified by MDA, and MDA-modified LDL are markedly more poorly absorbed by cultured human macrophages and significantly more slowly eliminated from the rat bloodstream upon intravenous injection. Studies on kinetics of free radical oxidation of rat liver membrane phospholipids have shown that ubiquinol Q(10) is the most active lipid-soluble natural antioxidant, and suppression of ubiquinol Q(10) biosynthesis by beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitors (statins) is accompanied by intensification of lipid peroxidation in rat liver biomembranes and in LDL of human blood plasma. Injection of ubiquinone Q(10) protects the human blood plasma LDL against oxidation and prevents oxidative stress-induced damages to rat myocardium. A unified molecular mechanism of atherogenic action of carbonyl-modified LDL in disorders of lipid and carbohydrate metabolism is discussed.

Effect of beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitor atorvastatin on contractility of the isolated rat heart under normal conditions and during oxidative stress.

Long-term administration of beta-hydroxy-beta-methylglutaryl coenzyme A reductase inhibitor atorvastatin to rats was accompanied by an increase in the relative weight of the heart and decrease in the rate of pressure development in the isovolumic heart. During oxidative stress induced by addition of 100 microM H2O2 to the perfusate, the decrease in contractile function was more pronounced that in the control. Our results indicate that administration of atorvastatin is accompanied by a decrease in myocardial contractility, which becomes more pronounced under conditions of oxidative stress.

[Effect of ubiquinone on contractile function and antioxidant status of the myocardium in spontaneously hypertensive rats].

During the period of aging of spontaneously hypertensive rats (SHR) between 6 and 13 weeks the systolic arterial pressure increased from 131+/-2 up to 176+/-3 mm Hg while in the control group of WKY rats it reached 122+/-2 mmHg. The hypertension was combined with myocardial hypertrophy -- the relative weight of SHR heart was 24% higher. The contractile myocardial function of the isolated isovolumic heart of SHR group did not differ from WKY group in a wide range of coronary perfusion rates. During oxidative stress induced by 40-min intracoronary introduction of H(2)O(2) function of hypertrophied SHR hearts fell significantly deeper. This coincided with decreased myocardial activity of superoxide dismutase and glutathione peroxidase by 29-30%, and increased catalase activity by 18%. The rate of generation of active forms of oxygen (hydroxyl radicals HO(.-)) in mitochondria from SHR hearts was higher as compared with WKY. Thus, the development of hypertension was combined with decreased antioxidant protection of the myocardium. The addition of ubiquinone to drinking water (approximately 10 mg/kg/day) for 6 weeks did not affect arterial pressure level, but was associated with two times lesser degree of myocardial hypertrophy. The hearts of SHR that received ubiquinone differed from those not treated with ubiquinone by increased maximal level of myocardial contractile function, and by improved myocardial relaxability and distensibility. After administration of H(2)O(2), myocardial function of SHR was kept on higher level. That was combined with less myocardial oedema, better preservation of antioxidant enzymes and reduced rate of succinate-dependent generation of superoxide radicals in mitochondria from hearts of ubiquinone treated SHR. The results have shown, that administration of ubiquinone to rats with hereditary hypertension reduces degree of myocardial hypertrophy, improves functional properties of the myocardium, promotes effective protection of antioxidant enzymes and increases the resistance of the cardiac muscle to oxidative stress.

[Variability of hemodynamic parameters and resistance to stress damage in rats of different strains].

Total power of heart rate variability and baroreflex sensitivity were significantly smaller in the August rats than in the Wistar rats, but adrenal and plasma catecholamine contents were considerably higher in the former ones. 1 hour after stress (30 min in cold water), plasma catecholamine was increased 2-fold in Wistar rats, while in August rats the adrenaline concentration increased only by 58% and the were no changes in noradrenaline content. At the same time, activation of catecholamine metabolism in the adrenal glands was similar in both groups. The oxidative stress induced by hydrogen peroxide depressed the contractile function of isolated heart in the August rats to a smaller extent as compared to Wistar rats, control ones and after the cold-water stress. This effect correlated with more pronounced stability ofantioxidant enzymes in the August rats. It seems that the greater resistance to stress damage in the August rats is mediated by enhanced power of defense mechanisms both at systemic and cellular levels.

[Evolution of concept and metabolic basis of ischemic dysfunction of the myocardium].

Myocardial contractile function during acute as well as chronic ischemia is reduced due to activation of a number of metabolic energy protecting mechanisms. Their abolition during reperfusion, associated with oxidative stress and incomplete restoration of function may cause cellular apoptosis due to impairment of aerobic ATP resynthesis. Strategy of postischemic reperfusion of the heart should be based on the use of natural protective mechanisms providing preferential restoration of high energy phosphates. The state of mitochondria is decisive for survival or restoration of function of cells.

[Effect of granulocyte-macrophage colony stimulating factor on the function and regeneration of myocardium in rats with experimental infarction].

To test the reparative capacity of stromal cells in myocardial infarction, rats were injected with granulocyte-monocyte-colony stimulating factor (GM-CSF) (leukomax), a cytokine known by its ability to raise a level of stromal cells in the blood, during first three days after coronary artery ligation. Only 10 of 17 rats (59%) survived 4 weeks in this group compared with 16 of 24 (67%) among rats not treated with leukomax. Echocardiographic and electromanometric studies showed that in both groups ventricular (LV) dilatation which developed during first hours after surgery persisted throughout 6-8 weeks and was combined with decreased ejection fraction and elevated LV end diastolic pressure. These alterations correlated with infarct size which varied from 0 to 28% of left ventricular weight in both groups. There were no statistically significant differences in functional and morphometric measurements between groups receiving and not receiving GM-CSF. However this result may be inconclusive due to small number of investigated animals and broad variation of ischemic zone size in each group.

[The regulatory role of oxygen radicals in myocardial cells]. / Reguliatornaia rol' kislorodnykh radikalov v miokardial'nykh kletkakh.

The paper reviews participation of primary active forms of oxygen in the processes of regulation of intracellular metabolism. Action of the primary forms of oxygen upon the myocardium contractile function depends on their concentration: their moderate increase enhances the rate and strength of contractions whereas higher concentrations diminish the contraction strength by inhibiting Ca2+ inflow from without. For NO the latter effect might be compensated by absence of coronary vessels dilatation. The level of the active forms of oxygen in the cells is subsidiary to the antioxidant system, and loss of the latter's components might trigger the apoptosis process and, consequently, some diseases.

[Protective effect of hydrophilic ubiquinone on cardiac muscle during oxidative stress]. / Vliianie gidrofil'noi formy ubikhinona na serdechnuiu myshtsu pri okislitel'nom stresse.

AIM: To assess effects of long term administration of a natural antioxidant ubiquinone on isoproterenol induced myocardial injury. METHODS: Rats were given hydrophilic ubiquinone with water for 8 weeks. RESULTS: Long term use of ubiquinone did not affect myocardial ultrastructure and relative myocardial weight. The dose of isoproterenol used in this study exerted moderate damaging action evidenced by disappearance of glycogen from sarcoplasm, development of edema, and partial destruction of mitochondrial cristae. These effects were associated with lowering of maximal magnitude of contractile function of the isolated heart and augmentation of superoxide radicals release in perfusate. These changes (except disappearance of glycogen) were not present in hearts of ubiquinone fed rats. Compared with controls mitochondria isolated from hearts of ubiquinone fed rats had higher respiratory control and more than twice lower rate of superoxide generation. CONCLUSION: As damaging effects of isoproterenol are mediated by augmented generation of active forms of oxygen the results obtained allow to suggest that myocardium of ubiquinone fed animals is characterized by elevated power of the antioxidant system.

Heart resistance to oxidative stress in rats of different genetic strains.

In August rats reperfusion after regional myocardial ischemia in situ or intracoronary administration of hydrogen peroxide less significantly suppressed contractile activity of the heart compared to Wistar rats. Activities of catalase and superoxide dismutase in the myocardium during reperfusion remained unchanged in August rats. In Wistar rats a profound inhibition of cardiac function was accompanied by a decrease in enzyme activity.

[The protective action of ubiquinone at ischemia and reperfusion]. / Zashchitnoe deistvie ubikhinona (koénzima Q(10)) pri ishemii i reperfuzii serdtsa.

Effects of prolonged consumption of ubiquinone on myocardial injury caused by ischemia and reperfusion were studied in reperfused rat hearts. Wistar rats received lipophylic or hydrophilic forms of ubiquinone for 6-8 weeks with chow or water, respectively. Isolated isovolumic hearts with a constant volume latex balloon in the left ventricular cavity were subjected to total normothermic ischemia (25 min) and subsequent reperfusion (50 min). Time course of ischemic contracture and its level in both groups of ubiquinone treated animals were similar to those in controls. However recovery of left ventricular developed pressure after reperfusion was significantly better in both ubiquinone groups (54-/+9, 65-/+7, and 24-/+4 mm Hg in animals treated with lipophylic and hydrophylic ubiquinone and controls, respectively, p<0.01). As a result the developed pressure and heart rate product reflecting maximal aerobic capacity of the heart was also better restored. Both ubiquinone groups demonstrated absence of increased coronary tone that was characteristic for control animals. Mitochondria isolated from reperfused hearts of ubiquinone treated rats showed better preservation of structure and respiratory control. Rate of succinate-dependent generation of superoxide radicals determined with a spin trap TIRON in mitochondria from hearts of rats treated with hydrophylic ubiquinone (35-/+8 mmol O(2) /min/g) was approximately twice lower (p<0.05) than in control group (74-/+12 mmol O(2) /min/g) while the value in lipophylic ubiquinone group (48-/+9 mmol O(2) /min/g) did not differ significantly from the control. The results evidence that prolonged consumption of water-soluble ubiquinone increases resistance of rat myocardium to injuring action of reperfusion.