Biomedical subjects

O V Akopova

Publications and source records attributed to O V Akopova.

11 recordsLinked to original sources

PubMed2005

[Nitric oxide suppresses permeability transition pore opening and enhances calcium uptake in mitochondria in vivo].

The influence of an NO donor, nitroglycerine (NG) on Ca2+ accumulation in rat heart and liver mitochondria was studied. A rapid dose-dependent increase in Ca(2+)-uptake was observed within 5 min after NG injection in vivo, with a peak in NG concentration of 0.5-1.0 mg/kg body weight. There is a correlation between a dose-dependent increase in Ca(2+)-accumulating capacity of mitochondria and sharp dose-dependent rise in stable NO metabolites level (NO2-, NO3- and nitrosothiols) and reactive oxygen species (H2O2 and hydroxyl radical, *OH) as well as lipid oxidation products (diene conjugates), the markers of the oxidative damage of the organelles in mitochondria in comparison to a whole tissue (liver) where only moderate increase of ROS and NO metabolites was detected. A 20-30-fold increase of NO3- level from 32. +/- 2.6 to 736.4 +/- 96.5 nmol/mg protein (p < 0.05) and from 45.4 +/- 6.2 to 1395.0 +/- 121.1 nmol/mg protein (p < 0.05) in liver and heart mitochondria respectively also provide a strong evidence for nitrosative stress. The results obtained suggest that calcium elimination from cytosol and its increased accumulation in mitochondria (likely dependent on permeability transition pore blockade by NO) could account for the cardioprotective action of NG although resulted in the development of oxidative stress with following long-term alterations of the energy supply and metabolism of subcellular structures.

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PubMed2003

[Effect of inductors and inhibitors of the mitochondrial permeability transition pore on its opening and release of unidentified mitochondrial factor].

The release of an unidentified substance (factor) induced by sulfhydryl group (SH) modifier and mitochondrial permeability transition pore (MPT) inductor phenylarsine oxide (PAO) has been found in vitro on isolated guinea-pig and rat heart mitochondria. The factor was also released at oxidative stress. The factor release induced by PAO was inhibited by cyclosporin A (CsA), the MPT inhibitor. Protective actions of antioxidants melatonin and trolox in vitro and in vivo, as well as dithiothreitol (DTT) and diethylmaleat (DEM) were studied. The influences of nitric oxide (NO) donor, sodium nitroprusside (SNP) on the mitochondrial factor release were also studied. We have shown the participation of this agent in the regulation of factor formation after inhibition of NO-synthase activity (NOS) by aminoguanidine. The data were obtained about MPT-opening after Ca2+ loading and under the influence of the MPT inductor PAO, inhibited by CsA. The results obtained on isolated mitochondria are in a good agreement with the those on the isolated guinea-pig heart after myocardial ischemia-reperfusion. It was concluded that mitochondria are essential for the factor formation and its release under ischemia-reperfusion of the myocardium.

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PubMed2002

Effect of L-arginine on Na+,K+-ATPase activity in rat aorta endothelium.

The effect of L-arginine on the Na+,K+-ATPase activity in rat aorta endothelium was studied at its physiological concentrations in the range of 10(-6)-10(-3) M. The enzyme activity was 35.5% increased by low concentrations of L-arginine (<or=10(-5) M) and its activity was 32.3-37.1% decreased at the L-arginine concentrations of 10(-4)-10(-3) M. A similar inhibition (by 34.5-42.8%) was also found in the presence of a NO-donor nitroglycerol (10(-4)-10(-3) M). An optical isomer of L-arginine, D-arginine, at the concentrations of <or=10(-5) M also increased the enzyme activity by 37.1%, but its inhibiting effect was much less pronounced and was 15.7% at the D-arginine concentration of 10(-3) M. An inhibitor of NO-synthase, L-NAME (NG-nitroarginine, methyl ester), failed to inhibit Na+,K+-ATPase. However, the presence of L-NAME abolished the inhibition of Na+,K+-ATPase by high concentrations of L-arginine. Thus, the effect of L-arginine on the endothelial Na+-pump depended on its concentration, and it is suggested that the enzyme inhibition by high concentrations of L-arginine should be associated with activation of the endogenous synthesis of NO.

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PubMed2000

[Endothelial factors in the regulation of Na+, K(+)-ATPase].

Endothelial vasoactive agents such as endothelin, angiotensin, nitric oxide and others are essential in regulation of the Na-pump functions in vascular and others tissues. In our review the intracellular mechanisms of activating and inhibition of the Na+,K(+)-ATPase by endothelial vasoactive agents are discussed. In the control of vascular tone and heart function as well as the regulation of the Na-pump endothelial vasoactive agents act individually or in close interaction with other physiologically active substances including the ouabain-like factor, endogenous inhibitor of the Na-pump. Some aspects ouabain-like factor physiological action are under the discussion. Recent advances in study and comprehension of intracellular mechanisms the mediating role of endothelial agents in Na-pump regulation are reviewed also.

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PubMedDate not supplied

[Endogenous factors in regulating Na+,K+-ATPase in small intestinal mucosa].

In the combination of gel- and ion exchange chromatography low-molecular weight (Mm < 1000 Da) fractions of tissue extracts of small intestine epithelium with high activity towards the Na+,K(+)-ATP-ase were obtained. The influence of these fractions on the Na+, K(+)-ATP-ase of small intestine epithelium and rat renal cortex is studied and discussed.

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PubMedDate not supplied

[Effect of sodium nitroprusside on Na+, K+-ATPase of rat myocardium and renal cortex].

The influence of NO donor, sodium nitroprusside (SNP) in concentrations of 10(-5)-10(-3) M, on the Na-pump activity in membrane preparations (microsomes) of rat miocardium and renal cortex was studied. A correlation has been observed between Na-pump activation by 31.4% and 73.6% and increase in thiol group content by 45.0% and 94.0% in native microsomes of myocardium and renal cortex by low concentrations of SNP (10(-5)-10(-4) M). The Na-pump activation as well as the increase in the number of DTNB-reactive thiol groups was abolished after the detergent treatment (0.025% sodium dodecylsulphate); however, the detergent by itself exerted similar influence on Na-pump activity and thiol group content in microsomes. A comparable effect of other oxidants (hydrogen peroxide and nitroglycerine) on SH-group content in microsomes of renal cortex was also shown. A conclusion was made that non-specific oxidative action of SNP on some membrane structures in microsome preparations led to their exposure and activation of the Na-pump by demasking of its latent activity.

Animals↗

PubMedDate not supplied

[Effect of Ca2+ on induction of the mitochondrial pore opening in the rat myocardium].

The mitochondrial role opening (MPT) induced by Ca2+ has been studied in isolated rat heart mitochondria. MPT was characterized as cyclosporine A-inhibited swelling accompanied by the loss of membrane potential (deltapsim) and Ca2+ efflux after the Ca2+ -loading which was followed spectrophotometrically after the Ca2+ -arsenaso-III complex formation. It has been shown that in suspension of isolated mitochondria MPT was activated by low (with maximum at about 20 microM Ca2+) and high concentrations of Ca2+ (the concentration curve shows a saturation at about 1.0-1.5 mM). In all the cases an access of Ca2+ ions to the matrix space of the mitochondria was necessary for MPT induction. MPT activated by low concentrations of Ca2+ was accompanied by slow decrease of deltapsim and slow release of Ca2+, enhanced by ruthenium red (RR), and was independent of the substrate used (glutamate or succinate). It had not been observed if the respiratory chain was inhibited, even if the Ca2+ access to the inner mitochondrial membrane was provided by Ca2+ -ionophore A23187. At high Ca2+ concentrations rapid Ca2+ -uptake and release via Ca2+ -uniporter (inhibited by ruthenium red) followed by extensive swelling (pore formation) have been observed. It had been supposed that rapid MPT at high concentrations of Ca2+ was the result of Ca2+ entrance to the mitochondrial matrix and depolarisation of the mitochondrial membrane. The data obtained show two different mechanisms of Ca2+ -induced MPT. The one is sensitive to the redox-state of the electron transport chain and is abolished if the respiration is inhibited. The other is independent of mitochondrial respiration and needs only Ca2+ access to the inner mitochondrial membrane and Ca2+ binding to some specific sites leading to MPT opening.

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PubMedDate not supplied

[Decrease of mitochondrial sensitivity to Ca2+-induced pore opening during long-term incubation].

It is shown that mitochondria of rat myocardium exhibit high sensitivity to Ca2+-induced permeability transition pore (PTP) during an hour after their isolation. The threshold Ca2+ concentrations necessary to induce PTP are as low as 25-50 nmol/mg of protein. Apparent K(Ca) constant of Ca2+-dependent PTP activation is 40 microM. Incubation of mitochondria during 2, 3 and 4 hours after their isolation leads to gradual increase in K(Ca) values up to 0.4 microM, which is accompanied by simultaneous decrease in sensitivity of mitochondria to pore opening. A correlation is supposed between changes of kinetic parameters of Ca2+-uniporter and changes in sensitivity of mitochondria to Ca2+-induced permeability transition.

Animals↗

PubMedDate not supplied

[Effect of nitric oxide donors on Ca2+-uptake in the rat heart and liver mitochondria].

The influence of NO donors, nitroglycerin (NG) and sodium nitroprusside (SNP), on Ca2+- uptake in rat heart and liver mitochondria is studied. It is shown that in vivo NG causes a rapid dose-dependent increase of Ca2+-uptake in rat heart mitochondria most pronounced at 0,5-1,0 mg/kg weight NG. This sharp increase of Ca2+-uptake is not accounted for by changes in membrane potential of mitochondria (deltapsim) because deltapsim is not influenced by less than 1,0 mg/kg NG, and moreover, decrease by approximately 30% is observed at 1,0-1,5 mg/kg NG. In vitro, on the contrary, a concentration-dependent decrease in Ca2+-uptake caused by NG as well as SNP is observed together with simultaneous decrease of deltapsim and concentration-dependent release of Ca2+ from mitochondria via Ca2+-uniporter as the result of partial depolarisation of mitochondrial inner membrane. The data obtained give an evidence that increase in Ca2+-uptake caused by NO donor in vivo takes place independently of changes in deltapsim and also is not resulted from a direct action of NO on Ca2+-uniporter. These observations allow us to suppose that activation of mitochondrial Ca2+-uptake in vivo and corresponding decrease in cytosolic Ca2+ concentration could be involved in vasodilatory action of nitric oxide.

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PubMedDate not supplied

[Calcium release from the rat liver mitochondria during collapse of the membrane potential].

Ca(2+)-release from rat liver mitochondria after protonophore (carbonyl cyanide m-chlorophenylhydrazone, CCCP)-induced membrane depolarisation is studied. It is shown that the release of calcium is accompanied by an increase of the inner mitochondrial membrane permeability as the result of the opening of permeability transition pore (PTP). Calcium is released from mitochondria through the uniporter working in reverse mode and also by PTP mechanism which accounts for ruthenium red (RR)-insensitive component of total. Ca(2+)-release. Unlike Ca2+, the strontium release from the mitochondria is completely sensitive to RR, specific uniporter blocker, which shows the absence of rapid Sr(2+)-efflux mechanisms other than uniporter of bivalent cations. The data obtained also give an evidence that the lifetime of the open state of the pore is limited, and barrier properties of the mitochondrial membrane are restored after the closure of the pore.

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PubMedDate not supplied

[Relese of Ca2+ from mitochondria after mitochondrial membrane depolarisation].

With the aid of specific inhibitors of Ca(2+)-uniporter (ruthenium red) and mitochondrial permeability transition pore, PTP (cyclosporine A) it is shown that PTP opening takes place after loading the rat liver mitochondria with calcium and depolarisation of mitochondrial membrane with protonophore (carbonyl cyanide m-chlorophenyl hydrazone, CCCP), and the pore opening accounts for accelerated efflux of calcium from mitochondrial matrix as well as availability of "rapid" component of two-exponential kinetic curve of Ca(2+)-efflux. An analysis of kinetic data of Ca2+ transport after membrane depolarisation also confirms our earlier observations that time frame of the pore open state is restricted, and membrane integrity is restored before all the calcium load is delivered into incubation medium. The absence of additivity between the shares of Ca(2+)-uniporter and PTP in Ca(2+)-transport is observed, and conclusion is made that partial share of PTP in calcium transport is not a constant, but a variable constituent which is diminished to zero as soon as the Ca(2+)-uniporter activity reaches its maximum after the abolition of membrane potential with CCCP. Based on some observations, it is supposed also that PTP inactivation takes place during calcium translocation across the mitochondrial membrane, which could account for limited release of Ca2+ from mitochondrial matrix through the pore itself as well as relatively narrow limits of the pore open state in comparison with time scale of complete cation release from depolarised mitochondria.

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