Modulation of hydrogen sulfide synthesis improves heart function and endothelium-dependent vasorelaxation in diabetes.

Diabetes dramatically increases the risk of cardiovascular complications. The endothelial dysfunction and diastolic heart dysfunction are associated with a decreasing level of hydrogen sulfide (H2S) and inhibition of the activity of endothelial nitric oxide synthase (NOS) in diabetes. The aim of this study is to investigate the effect of modulation of H2S synthesis on heart functions and vasorelaxation in diabetes. The dl-propargylglycine and l-cysteine were administered intraperitoneally. H2S content in the heart tissue, markers of oxidative stress, inducible NOS and constitutive NOS (cNOS) activities, endothelium-dependent vasorelaxation of the aortic rings, and heart function were studied. We demonstrate that our combination increased H2S synthesis 13 times and cNOS activity 5 times in the heart tissue of diabetic rats. Increasing NO and H2S production caused improvement and restoration of endothelium-dependent relaxation of aorta, effective arterial elastance, and diastolic heart function in diabetic rats. The endothelium-dependent relaxation increased 2.4 times; effective arterial elastance decreased by 47%. The end-diastolic myocardial stiffness decreased 2.2 times. Thus, modulation of H2S synthesis leads to increased cNOS activity by up to 5 times in the cardiovascular system. Increasing NO and H2S production restored endothelium-dependent relaxation of aorta and improved heart function in diabetes.

Stimulation of the endogenous hydrogen sulfide synthesis suppresses oxidative-nitrosative stress and restores endothelial-dependent vasorelaxation in old rats.

Hydrogen sulfide (H2S) is an endogenous gas transmitter with profound effects on the cardiovascular system. We hypothesized that stimulation of H2S synthesis might alleviate age-associated changes in vascular reactivity. Pyridoxal-5-phosphate (PLP), the coenzyme of H2S-synthesizing enzymes, was administrated to old male Wistar rats per os at a dose of 0.7 mg/kg body mass once a day for 2 weeks. H2S content in the aortic tissue, markers of oxidative stress, inducible nitric oxide synthase (iNOS) and constitutive nitric oxide synthase (cNOS), arginase activities, and endothelium-dependent vasorelaxation of the aortic rings were studied. Our results showed that PLP restored endogenous H2S and low molecular weight S-nitrosothiol levels in old rat aorta to the levels detected in adults. PLP significantly reduced diene conjugate content, hydrogen peroxide and peroxynitrite generation rates, and iNOS and arginase activity in the aortic tissue of old rats. PLP also greatly improved acetylcholine-induced relaxation of old rat aorta (47.7% ± 4.8% versus 18.4% ± 4.1% in old rats, P < 0.05) that was abolished by NO inhibition with N-nitro-l-arginine methyl ester hydrochloride (L-NAME) or H2S inhibition with O-carboxymethylhydroxylamine (O-CMH). Thus, PLP might be used for stimulation of endogenous H2S synthesis and correction of oxidative and nitrosative stress and vessel tone dysfunction in aging and age-associated diseases.

[PYRIDOXAL-5-PHOSPHATE RESTORES HYDROGEN SULFIDE SYNTHES AND REDOX STATE OF HEART AND BLOOD VESSELS TISSUE IN OLD ANIMALS].

It was shown the alterations in hydrogen sulfide (H(2)S) metabolism and the development of oxidative and nitrozative stress in cardiovascular system by aging. The administration of pyridoxal-5-phosphate as cofactor of H(2)S synthesizing enzymes restored endogenous H(2)S level and redox state in the heart and aorta tissues. Under these conditions, the following indicators of oxidative stress were significantly decreased in heart and aorta tissues: superoxide generation rate (·0(2)(-)) and hydroxyl (·OH) anion radicals, compared with significantly elevated levels of these parameters in old animals. We also found the reduction of non-enzymatic (diene conjugates and malonic dialdehyde) and enzymatic (uric acid, LTC(4) and TxB(2)) lipid oxidation products levels in old rats under H(2)S synthesis stimulation that confirms the restriction of oxidative stress. An important consequence of endogenous synthesis stimulation of hydrogen sulfide during aging is a decrease of nitrozative stress, such as iNOS activity and nitrate reductase, as well as recovery of constitutive NO synthase activity, indicating the importance of this gas transmitter in cardiovascular system. Thus, stimulation of hydrogen sulfide endogenous synthesis contributed to reduced production of reactive oxygen species (oxidative stress) and nitrogen (nitrozative stress) in heart and aorta tissues with aging. The presence of a pronounced antioxidant effect and modulating influence of pyridoxal-5- phosphate in the redox state of heart tissue and blood vessels during aging suggests cardioprotective properties of the substance and prospects for future research.

NO-ERGIC CONTROL OF BLOOD CIRCULATION IN THE MEDULLA OBLONGATA OF RATS WITH EXPERIMENTAL HEMIPARKINSONIZM UNDER EXPOSURE TO CONTINUOUS LIGHT.

The study was conducted on rats with unilateral damage to dopaminergic (DA) neurons in substantia nigra of the midbrain (experimental hemiparkinsonism). Degeneration of dopaminergic (DA) neurons was accompanied by hyperactivity of those neurons that remained intact and responded to apomorphine (Apo) test by rotational movements. Depending on the number of rotations, three groups of animals were defined. In the medulla oblongata of rats with unilateral damage to dopaminergic (DA) neurons, a significant increase in the activity of inducible NO-synthase (iNOS) was observed, while the activity of constitutive NO-synthase (cNOS) tended to decrease compared with that in control rats. An activation of neuronal NO-synthase (nNOS) in those rats by injections of L-arginine in the medullary nuclei was accompanied by weakening of the hemodynamic effects compared to those in control rats. An exposure of animals to continuous light for three weeks was accompanied by increasing the number of damaged DA-ergic neurons in substantia nigra. At that, a significant decrease in cNOS activity in the medulla oblongata was observed, leading to the inhibition of de novo synthesis of nitric oxide (NO). The reduction of NO synthesis in the medulla oblongata neurons of rats with experimental hemiparkinsonism following their exposure to continuous light was also evidenced by the reduction.

The role of hydrogen sulfide in diastolic function restoration during aging.

The objective of the study was to examine the effect of exogenous hydrogen sulde donor; sodium hydrosulfide (NaHS), on thefree radical generation, cNOS uncoupling in the myocardium, and diastolicfunction in old rats. To evaluate diastolic function of the heart, we used pressure-volume (PV) conductance catheter system (Millar Instruments, USA). It was shown that H2S levels in. the isolated mitochondria and whole heart homogenates obtained from old age rats were significantly lower comparing with adult animals. The markers of combined oxidative and nitrosative stress (the rate of 0 2° H generation, pools of H202, diene conjugates, malondialdehyde, uric acid, the activity of iNOS, nitrate reductase, and NO pools) were increased in the old hearts in line with cNOS uncoupling. Such changes in NOS coupling resulted in the loss of diastolic relaxation (decrease of the rate of relaxation of the left ventricle (dp/dtmin) by 33%, 3-times increase of the end-diastolic pressure, 1.5-time increase of the time constant of left ventricular relaxation (Tau g) and 2-time increase of the end-diastolic stiffness). It has been found that NaHS inhibits oxidative and nitrosative stress, restores cNOS coupling and constitutive de novo synthesis of nitric oxide (NO), which promotes an improvement of the diastolic function (increase of the dp/dtmin by 20% and decrease of Tau g by 13%) . Key words: aging; cNOS uncoupling; heart; hydrogen sulfide; nitrosative stress; oxidative stress.

MITOCHONDRIAL DYSFUNCTION IN THE AGING HEART IS ACCOMPANIED BY CONSTITUTIVE NO-SYNTHASES UNCOUPLING ON THE BACKGROUND OF OXIDATIVE AND NITROSATIVE STRESS.

We investigated the sensitivity of mitochondrial permeability transition pore (MPTP) opening to its inductor calcium, as well as indicators of oxidative and nitrosative stress in adult and old rat heart mitochondria and heart tissues. The coupling index of constitutive Ca2+/calmodulin-dependent NO-synthase (сNOS) was calculated based on experimentally found parameters. The aging is characterized by oxidative and nitrosative stress, which accompanied by a decrease of the cNOS coupling index and an increased sensitivity of MPTP to calcium. We found that in the heart mitochondria of old rats such oxidative stress indicators as the rate of generation of superoxide (• O2 - ) and hydroxyl (• OH) anion radicals were significantly increased (in 4 and 2,7 times respectively). Also, increased levels of urea and products of early lipid peroxidation ­ conjugated dienes display the intensification of oxidative stress. Such indicators of nitrosative stress as nitrate reductase and iNOS activity were also enhanced. At the same time under aging the NO2 - pools, generated when the heart oxygenation is normal, nitrosothiols pools and the activity of cNOS were decreased. It is due to the enhanced level of cNOS uncoupling, resulting in increased oxidative stress. It was also shown the lower level of hydrogen sulfide (H2S) in old rat heart mitochondria. Thus, we observed the increased sensitivity of MPTP to calcium, due to decreased concentration of its inhibitors nitric oxide and hydrogen sulfide and increased levels of its inducers ROS and RNS in old rat heart mitochondria.

[PHYSICAL EXERCISE TRAINING CAN- CELS CONSTITUTIVE NOS UNCOUPLING AND INDUCED VIOLATIONS OF CARDIAC HEMODYNAMICS IN HYPERTENSION (PART III)].

In the heart and heart mitochondria spontaneously hypertensive rats investigated the effect of physical exercise training (swimming in a moderate and excessive training mode) on the physiological indicators of cardiac hemodynamics and biochemical parameters that characterize the level of oxidative and nitrosative stress. The index of coupling Ca(2+)-dependent constitutive NO-synthases (cNOS = eNOS + nNOS) and biochemical index of dysfunction were calculated. It turned out that both modes of training is completely restored, and even exceed the reference values in untrained rats Wistar conjugate cNOS state and Ca(2+)-dependent synthesis of nitric oxide (NO). Intensity regime of exercise on the border of functionality have been ineffective for improving the functional state of the cardiovascular system and hypertension can provoke it further. Moderate physical training regime, on the contrary, improves the diastolic function of the heart due to an increase dP/dtmin, reducing end-diastolic pressure and a significant reduction in end-diastolic stiffness. Moderate exercise decreased peripheral resistance and cardiac afterload, as indicated by the decrease in end-systolic pressure and arterial stiffness, which contributed to more efficient and energy-saving of heart work. Improve physiological indicators of cardiac hemodynamics and functional state of the heart in moderate mode of training correlated with changes in both the calculated indices. Moderate mode of training is recommended as a simple physiological preconditioning method for the prevention of cardiac dysfunction, hypertension as a result of state uncoupling cNOS and the resulting excessive generation of superoxide and, conversely, inhibition of Ca(2+)-dependent synthesis of NO.

[EFFECT OF PROPARGYLGLYCINE UPON CARDIOHEMODYNAMICS IN OLD RATS].

Aging increases the risk of cardiovascular diseases. The objective of this study was to show the effect of propargylg- lycine (PPG) upon cardiohemodynamics in old rats. We used pressure-volume (PV) conductance catheter system (Millar Instruments, USA) in order to evaluate systolic and diastolic function in vivo. It has been shown that introducted PPG (11,31 mg/kg) decrises both arterial stiffness (by 1,5 times) and end-diastolic stiffness (by 2,1 times) in old rats. Using PPG in heart mitochondria resulted in increasing levels of H2S (by 112%), NO2- (by 162%) and in growing activity of cNOS (by 3 times). Additionally, PPG decreased the mitochondrial pools of the uric acid, the marker of the superoxide (*O2-) formation and of the ATP degradation. These results suggest that PPG activates alternative ways of H2S synthesis, stimulates the NO and H2S synthesis and suppresses the ATP degradation and *O2 formation. These actions of PPG improve arterial stiffness and end-diastolic stiffness.

[NOS UNCOUPLING IS ACCOMPANIED WITH INDUCTION OF THE OXIDATIVE STRESS AND THE CARDIOHEMODYNAMICS DISTURBANCES IN HYPERTENSION].

We compared the performance of cardiaohemodynamics and indicators of oxidative and nitrosative stress in the heart and aorta in normotensive Wistar rats (WKR) and spontaneously hypertensive rats (SHR). On the basis of experimentally determined parameters to calculate cNOS uncoupling index and biochemical index of function (BIF) in these organs of the cardiovascular system. In the heart, and especially in the aorta of SHR develop a combined oxidative and nitrosative stress that leads to cNOS uncoupling, BIF lowering that correlate with lowering of systolic and diastolic functions, inhibition of the efficiency Frank-Starling mechanism, oxygen consumption of the heart and increasing arterial stiffness. We made the assumption of the existence of the vicious circle of enhancing oxidative stress in organs of the cardiovascular system due to additional superoxide generation by uncoupling cNOS.

[ENDOTHELIAL MONOCYTEACTIVATING FACTOR II CANCELS OXIDATIVE STRESS, CONSTITUTIVE NOS UNCOUPLING AND INDUCED VIOLATIONS OF CARDIAC HEMODYNAMICS IN HYPERTENSION (PART II)].

The purpose of this study was to investigate the effect of EMAP II on free radical state of the heart and blood vessels, to restore cNOS coupling and cardiac hemodynamics in spontaneously hypertensive rats. It was found that, due to the combined inhibition of oxidative and nitrosative stress, EMAP I quickly restores impaired in hypertension constitutive de novo synthesis of NO by restoring cNOS coupling. Restoration by EMAP II of constitutive de novo synthesis NO abolished cardiac and endothelial dysfunction in spontaneously hypertensive rats. In hypertension, the introduction of EMAP II helped to improve the performance of the pumping function of the heart (stroke volume increased by 18.2 %, cardiac output -22 %), an arterial stiffness decreased by 23.2 %, process of relaxation of the left ventricle improved, due to decreased in 4,7 times myocardial end-diastolic stiffness.

[Nanocerium restores the erythrocytes stability to acid hemolysis by inhibition of oxygen and nitrogen reactive species in old rats].

In experiments in vivo the effect of nanocerium (cerium oxide nanoparticles) on the stability of red blood cells to acid hemolysis, levels of both ROS and RNS generation and H2S pools in plasma and erythrocytes of old rats were investigated. In red blood cells of old rats the proton penetration into the matrix of erythrocytes showed a significant raising and the fate of labile "aging" erythrocytes in old animals compared with adult were up- regulated. These phenomena paralleled with significant up-regulation of ROS and RNS generation. Introduction for 14 days per os to old rats 0.1 mg/kg of nanocerium fully restored resistance of erythrocytes to acid hemolysis by ROS and RNS in both plasma and erythrocytes reduction. Nanocerium decreased the erythrocytes and, conversely, significantly increased the plasma's pools of H2S.

[HYDROGEN SULFIDE DONOR, NAHS, RECOVERS CONSTITUTIVE NO SYNTHESIS AND ENDOTHELIUM-DEPENDENT RELAXATION OF ISOLATED AORTA IN OLD RATS].

The objective of this study was to show the effect of H2S donor, NaHS on the endothelium-dependent vasorelaxation, free radical state and cNOS uncoupling in old rats. In the aorta of old rats a combined oxidative and nitrosative stress develops that leads to cNOS uncoupling and decreased constitutive synthesis of the NO. That biochemical changes correlate with lowering of the endothelium-dependent relaxation of aortic smooth muscles (7.5 ± 1.4%, compared with 64.9 ± 3.5% in adults). It was found that, due to the combined inhibition of oxidative and nitrosative stress, NaHS restores constitutive de novo synthesis of NO by restoring cNOS coupling. Additionally, NaHS improves endothelium-dependent vasorelaxation by increasing (by 6.5 times) Ach-induced relaxation of aortic smooth muscles.

[CA²âº ACCUMULATION IN ISOLATED RAT HEART MITOCHONDRIA UNDER MAINTENANCE OF MITOCHONDRIAL POTENTIAL].

It is known that mitochondria can accumulate calcium, which regulates energy metabolism and cell death. About 90% of energy of cardiomyocytes is synthesized in mitochondria. Heart cells are also affected by the rapid changes in the Ca²âº concentration in the cytoplasm. Therefore, mitochondrial Ca²âº-accumulation ability is crucial. The aim of our work was to study the accumulation of Ca²âº in isolated rat heart mitochondria in the presence of mitochondrial potential and different extramitochondrial Ca²âº concentrations. Isolated organelles were loaded with fluorescent dye Fluo-4 AM (2.5 µmol/l) at a temperature of 26°C for 30 min. It has been revealed that under these conditions high mitochondrial potential was maintained sufficiently, which is necessary for the functioning of the calcium transporting system in organelles. We established that mitochondria have a limited ability to store ionized calcium, as addition of Ca²âº ion in concentrations of 10, 20, 50 µmol/l ensures a certain level of accumulation in organelles with further fluorescent signal growth cessation. Addition of 100 µmol/Ca²âº to isolated mitochondria resulted in a significant increase in fluorescence intensity (46% in the fifth minute, compared to the fluorescence when 20 µmol/l Ca²âº was added) and likely to activation of cation release. It was shown that ruthenium red (10⁻5 mol/l), an inhibitor of Ca²âº-uniporter, prevented accumulation of calcium ions in organelles by 89%, in the presence of 100 µmol/ Ca²âº. It was clearly seen that heart mitochondria require Mg²âº-ATP complex (3 mmol/l) to accumulate Ca²âº, likely to maintain the inner membrane potential, activity of Ca²âº uniporter and energetic processes in organelles. Thus, the process of Ca²âº accumulation in rat heart mitochondria requires the maintenance of mitochondrial potential, activity of Ca²âº-uniporter, depends on extramitochondrial Ca²âº concentration and presence of Mg²âº-ATP complex.

[BRAIN FOCAL ISCHEMIA-REPERFUSION CAUSES A DECREASED RESISTANCE OF ERYTHROCYTES FROM VENOUS BLOOD TO ACID HEMOLYSIS, WHICH IS PREVENTED BY ECDYSTERONE].

We investigated the resistance of erythrocytes from rat brain venous blood to acid hemolysis in the dynamics of brain ischemic period (15, 30, 45 and 60 min), as well as in the early (5 min) and distant (24h) period of brain reperfusion. Brain ischemia-reperfusion was made in rats that received ecdysterone (standartized extract of Serratula coronata) within 18 days (per os, 1 mg/kg). Analysis of the kinetic curves of acid hemolysis showed a pronounced (60 times, from 1.45 to 85.85% at 60 min of brain ischemia and at 5 min of brain reperfusion, respectively) increase of unstable erythrocytes that hemolyzed easily (< 2.5 min). In the preconditioned rats, this increase was only 8-fold. During the period of brain ischemia, with a maximum at 15th minute, in the venous blood from brain the diene conjugates (DK) pools increased from 2.40 to 9.48 ng/mg protein and LTC4 pools increased from 1.49 to 5.98 pmol/mg protein. Even more pools of DC and LTC4 were increased at 5th min of brain reperfusion. In animals received ecdysterone, during ischemia and early reperfusion period, both pools of DC and LTC4 in venous blood were lower than that in the controls. The latter implies a possible antiradical mechanism of the protective effect of ecdysterone.

[THYMIC HORMONES, ANTIOXIDANT ENZYMES AND NEUROGENESIS OF BULBUS OLFACTORIUS IN RATS WITH PARKINSONISM: THE EFFECT OF MELATONIN].

The adult rats received both neurotoxin 6-hidroxidophamine and neurotoxin and melatonin. It was investigated a link between the disturbances of the brain antioxidant enzymes activity and thymic endocrine function, as possible pathogenic factors of parkinsonism, with changes in the number of neural stem cells (NSC) in the bulbus olfactorius. Rats with motor asymmetry in the apomorphine test and significant damage of the dopaminergic neurons in the-substantia nigra have decreased levels of superoxide dismutase, catalase and glutathione peroxidase activities in striatum (1.3-1.4 times) and blood thymulin content (8 times) compared to control group. On the contrary, examined indices were not changed in rats without motor asymmetry and correspondingly partly damaged neurons. The number of nestin(+)-cells in the bulbus olfactorius of rats without motor asymmetry increased from 91.2% to 99.3% and remained unchanged after melatonin administration course (10 mg/kg during 18 days). Melatonin administration resulted in the decrease in the number of nestin(+)-cells along with significant elevation of the decreased antioxidant enzymes activity and blood thymulin content in rats with circulatory movements. Possibilities of the enhancement of NSC differentiation in bulbus olfactorius into neuronal direction in such animals has been discussed. The conclusion about the potential use of melatonin as a neuroprotector in parkinsonism therapy has been made.

[Estimation of ATP-dependent K(+)-channel contribution to potential-dependent potassium uptake in the rat brain mitochondria].

The effect of potassium on state 4 respiration (substrate oxidation in the absence of ADP) was investigated. It was shown that potential-dependent potassium uptake in the brain mitochondria results in mitochondrial depolarization. Taking into account depolarization effect of potassium, the contribution of the endogenous proton leak as well as K(+)-uptake to the respiration rate was calculated. It was shown that such estimation allows the share of ATP-dependent potassium channel contribution to potential-dependent potassium uptake to be determined by polarographic method.

[The effect of ATP-dependent K(+)-channel opener on transmembrane potassium exchange and reactive oxygen species production upon the opening of mitochondrial pore].

The effect of mitochondrial ATP-dependent K(+)-channel (K(+)ATP-channel) opener diazoxide (DZ) on transmembrane potassium exchange and reactive oxygen species (ROS) formation under the opening of mitochondrial permeability transition pore (MPTP) was studied in rat liver mitochondria. The activation of K(+)-cycling (K(+)-uptake and K(+)/H(+)-exchange) by DZ was established with peak effect at < or = 500 nM. It was shown that MPTP opening as well resulted in the activation of K(+)-cycling together with simultaneous activation of Ca(2+)-cycle in mitochondria. In the absence of depolarization Ca(2+)-cycle is supported by MPTP and Ca(2+)-uniporter. The stimulation of K(+)/H(+)-exchange by MPTP opening led to the activation of K(+)-cycle, but further activation of K(+)/H(+)-exchange resulted in MPTP inhibition. Under the same conditions the decrease in mitochondrial ROS production was observed. It was proposed that the decrease in ROS formation together with K(+)/H(+)-exchange activation could be the constituents of the complex effect of MPTP inhibition induced by K(+)ATP-channel opener.

Effect of potential-dependent potassium uptake on production of reactive oxygen species in rat brain mitochondria.

The effect of potential-dependent potassium uptake on reactive oxygen species (ROS) generation in mitochondria of rat brain was studied. It was found that the effect of K+ uptake on ROS production in the brain mitochondria under steady-state conditions (state 4) was determined by potassium-dependent changes in the membrane potential of the mitochondria (ΔΨm). At K+ concentrations within the range of 0-120 mM, an increase in the initial rate of K(+)-uptake into the matrix resulted in a decrease in the steady-state rate of ROS generation due to the K(+)-induced depolarization of the mitochondrial membrane. The selective blockage of the ATP-dependent potassium channel (K(ATP)(+)-channel) by glibenclamide and 5-hydroxydecanoate resulted in an increase in ROS production due to the membrane repolarization caused by partial inhibition of the potential-dependent K+ uptake. The ATP-dependent transport of K+ was shown to be ~40% of the potential-dependent K+ uptake in the brain mitochondria. Based on the findings of the experiments, the potential-dependent transport of K+ was concluded to be a physiologically important regulator of ROS generation in the brain mitochondria and that the functional activity of the native K(ATP)(+)-channel in these organelles under physiological conditions can be an effective tool for preventing ROS overproduction in brain neurons.

[Biochemical mechanisms of the cardioprotective effect of the K(ATP) channels opener flocalin (medicinal form) in ischemia-reperfusion of myocardium].

In experiments on the anaesthetized dogs with modeling of experimental ischemia (90 min) and reperfusion (180 min) of myocardium it was investigated changes of biochemical processes in arterial blood at intragastric introduction of medicinal form (tablets) of flocalin (the fluorine-containing opener of ATP-sensitive potassium channels) in a dose 2,2 mg/kg. The data analysis allowed to define a few possible mechanisms of cardioprotective action offlocalin, which prevented the opening of a mitochondrial permeability transition pore (MPTP) and inhibition of apoptosis induced by it. They consist, from one side, in activating of the constitutive de novo biosynthesis of nitric oxide by cNOS, from other side, in suppression of inducible nitric oxide de novo synthesis by iNOS in such way to prevent the formation of toxic peroxynitrite by co-operation of surplus nitric oxide with superoxide anion, thereby limits the generation of toxic active forms of nitrogen (*NO2) and oxygen (*OH). The first effect of flocalin takes place due to limitation the degradation of L-arginine by arginase which keeps substrat for cNOS, second--due to the inhibition of superoxide generation, in particular, by xanthine oxidase (marker uric acid), lipoxigenase (marker LTC4) and cyclooxygenase (marker TxB2). Because LTC4 have coronaroconstrictory, arrhythmogenic and chemoattractory properties in the conditions of myocardial ischemia, inhibition of its production both with superoxide generation (markers H2O2 and diene conjugates) may be the another mechanisms of flocalin's cardioprotection. Powerful antiischemic action of flocalin (marker nitrite anion) as the mechanisms of cardioprotection is possible as well as inhibition of ATP and GTP degradation (marker hypoxanthine+xanthine+inosine levels in the blood) and, possibly, stimulation ofhaem degradation by haem oxygenase (markers total bilirubin and Fe in the blood). Diminishing content of free arachidonic acid in arterial blood can testify inhibition of cellular membranes phospholipides degradation by phospholipase A2 as a result of flocalin cardioprotection.

[The effect of ATP-dependent K(+)-channel opener on the functional state and the opening of cyclosporine-sensitive pore in rat liver mitochondria].

The effect of mitochondrial ATP-dependent K(+)-channel (K+(ATP)-channel) opener diazoxide (DZ) on the oxygen consumption, functional state and the opening of cyclosporine-sensitive pore in the rat liver mitochondria has been studied. It has been established that K+(ATP)-channel activation results in the increase of the oxygen consumption rate (V4(s)) and the uncoupling due to the acceleration of K(+)-cycling, the decrease in state 3 respiration rate (V3) and the respiratory control ratio (RCR). Under K+(ATP)-channel activation an inhibition of oxidative phosphorylation takes place which reduces the rate of ATP synthesis and hydrolysis as well as ATP production and consequently results in the seeming increase of P/O ratio. It has been shown that the increase in ATP-dependent K(+)-uptake accompanied by the opening of mitochondrial permeability transition pore (MPTP) leads to dramatic uncoupling of the respiratory chain due to simultaneous activation of K(+)- and Ca(2+)-cycling supported by MPTP and Ca(2+)-uniporter as well as K(+)-channels and K+/H(+)-exchange. K+(ATP)-channel activation leads to the partial inhibition of MPTP, but insufficient for the restoration of mitochondrial functions. Elimination of Ca(2+)-cycling after MPTP opening is necessary to return mitochondrial functions back to the control level which shows that MPTP could serve as the mechanism of reversible modulation of bioenergetic effects of K+(ATP)-channel activation.