[Pharmacological correction of experimental mitochondrial dysfunction of brain stem neurons by rhytmocor and mildronate].

The results of pharmacological correction of experimental mitochondrial dysfunction in brain stem neurons after single injection of specific respiratory complex I inhibitor rotenone by complex agents mildronate and rhytmocor have been presented. It was shown that 14-days rhytmocor injection promoted the rise of mitochondrial reserve capacity under glutamate and malate oxidation as well as under succinate oxidation. The mildronate injection was accompanied by enhancement of the velocity of phosphorilated mitochondrial respiration in the presence and absence of ADP when both substrates of oxidation were used. Under the brain stem experimental mitochondrial dysfunction, mildronate improved a decreased velocity of phosphorilated mitochondrial respiration and the respiratory control in a more significant degree under glutamate malate as the substrates of oxidation. Simultaneous increase in the respiratory control and in the coefficient of efficacy ofphosphorilation during the correction of experimental mitochondrial dysfunction by rhytmocor could suggest about essential economization of processes in mitochondrial respiratory chain. It was concluded that the main mechanisms of influence on mitochondrial disturbances of both agents were connected to the powerful rise of NAD-related oxidation which allowed to enhance a resistance of mitochondrial respiratory chain and to optimize the mitochondrial function.

[Effect of the hypoxia training on the sensitivity of phenylarsineoxide-induced mitochondrial permeability transition pore opening in the rat heart].

On the mitochondria isolated from the heart tissue of adult rats we studied the sensitivity of mitochondrial permeability transition pore (MPTP) opening to its inductor--phenylarsine oxide (PAO) after mitochondrial swelling, registered by spectrophotometric technique at n = 520 nm. In adult rat under influence of two modes of normobaric intermittent hypoxic training (IHT): i) softer but prolonged one induced by breathing in normobaric chamber with 11% O2 gas mixture, 15 minuets sessions with 15 minuets rest intervals, 5 times daily (first mode) and ii) more severe but shorter one induced by breathing with 8% O2 gas mixture (second mode) were used. The intensity of lipid peroxidation and antioxidant defense mechanisms in rat organism were estimated before and after IHT by measuring malon dialdehyde (MDA) content and enzymatic activity of superoxide dismutase (SOD) and catalase (CAT) in the blood and the liver. It has been shown that IHT in the first mode didn't essentially influence both on PAO induced, cyclosporin A--sensitive mitochondrial swelling and indexes of lipid peroxidation as well as the SOD and CAT enzymatic activity. It was established that IHT in the second mode caused pronounced increase in MDA content both in the blood and the liver by 67% and 32% respectively; considerable augmentation of SOD activity in this tissues (by 49% and 32% respectively) and CAT activity (by 18% and 43% respectively). Moreover, in forty five days the activity of SOD exceeded its initial level in three times in both the blood and the liver. It has been established that IHT in the second mode provoke to twice decrease in PAO-induced mitochondrial swelling as compared with mitochondria of the control group, and even in forty five days after IHT stopping the protective effect on mitochondrial PTP opening was well-preserved. These effects were completely abolished in the presence of an inhibitor--cyclosporin A (10(-5) mol/l) that demonstrated mitochondrial swelling to be due to the mitochondrial PTP opening. Our experiments showed that the influence of IHT in more severe mode decreased the sensitivity of mitochondria to the PAO in rat heart mitochondria. Thus resistance of the mitochondrial membrane to an inductor of PTP opening--PAO increase under the influence of IHT in the second mode.

[Exogenous L-arginine modulates mitochondrial and microsomal oxidation in acute and intermittent normobaric hypoxia]. / Moduliatsiia ekzohennym L-arhininom mitokhondrial'noho ta mikrosomal'noho okysnennia pry hostrii ta periodychnii normobarychnii hipoksiï.

It is known that protective effects of adaptation to intermittent hypoxia are mediated partly by stimulating of some mitochondrial and microsomal enzymes activity. Our objective was to investigate whether exogenous NO (L-arginine) or NO blocker (L-NNA) modulate mitochondrial and microsomal oxidation during acute hypoxia (AH) and intermittent hypoxic training (IHT). In control rats AH (inhalation of 7% O2, 30 min) provoked a decrease of ADP-stimulated liver mitochondrial respiration. However, the pattern of oxidation substrates was different from normoxic controls. In the presence of succinate, an increase of the Chance respiratory coefficient and the phosphorylation rate and a decrease of O2 uptake efficacy with simultaneous activation of aspartate aminotransferase activity were observed. Simultaneously, oxidation of a-ketoglutarate, an NAD-dependent substrate, was inhibited. IHT caused reorganization of mitochondrial energy metabolism favoring NAD-dependent oxidation and improving the protection against acute hypoxia. After 14 days of normobaric IHT (10% O2, 15-min sessions with 15 min rest intervals, 5 times daily), in comparison to controls acute hypoxic challenge in the presence of succinate resulted in an increase of the Chance respiratory coefficient, the ADP/O ratio and the phosphorylation rate, in activation of both aspartate and alanine aminotranferases, and in less lipid peroxidation. The microsomal oxidation was not changed under AH per se but significantly decreased (by 37%) during acute hypoxic test after ITH. These findings indicated a more efficient use of oxygen under hypoxic conditions after IHT pre-conditioning. The combination of IHT with L-arginine treatment (600 mg/kg intraperitoneally, daily before IHT sessions) provoked more pronounced decrease of tissue oxygen consumption and microsomal oxidative processes in comparison with IHT animals. L-arginine effects were abolished by the NO-synthase blocker L-NNA. We conclude that the combination of IHT with NO-donor treatment provokes a decrease in aerobic link of energy regulation thereby increasing the tolerance to episodes of acute hypoxia.

[Regulation of oxidative phosphorylation by liver mitochondria receptors after adaptation by rats to periodic normal pressure and acute hypoxia]. / Retseptorna rehuliatsiia okysliuval'noho fosforyluvannia mitokhondrii pechinky za adaptatsiï shchuriv do periodychnoï normobarychnoï i hostroï hipoksiï.

It is known that NO-dependent mechanisms are involved in mitochondrial adaptive reactions to different factors. The object of this study was to investigate the role of cholino- and adrenoreceptors in NO-dependent reactions of rat liver mitochondria to acute hypoxia (AH) and intermittent hypoxic training (IHT). Eight groups of Wistar male rats participated in the study. Animals of Gr. I underwent daily i.p. saline injections during 14 days. Gr. II was examined after a single AH test (inhalation of 7% O2, 30 min) with the same saline treatment. Another six groups were exposed to IHT (11% O2, 15-min sessions with 15 min rest intervals, 5 times daily during 14-days), at that 15 min before every IHT session animals underwent i.p. treatment: Gr. III and IV--saline, Gr. V--L-arginine, Gr. VI--NO synthase blocker L-NNA, Gr. VII--L-arginine with alpha-, beta-adrenoblockers phentolamine and obzidane, Gr. VIII--L-arginine with M- and N-cholinoreceptor blockers athropine and benzohexonium. After IHT Gr. IV-VIII were exposed to a single AH test and decapitated just after that. In control rats AH provoked: 1) in the presence of succinate, a 33% augmentation of ADP-stimulated mitochondrial respiration (V3) with a 18% decrease of O2 uptake efficiency (ADP/O ratio); 2) in the presence of alpha-ketoglutarate, a NAD-dependent substrate, no changes in V3 were observed, also 21% augmentation of ADP/O ratio registered. These events were accompanied by 36% increase in succinate dehydrogenase (SDG) activity, two-fold augmentation of malon dialdehyde (MDA) content and 43% increase in diene conjugates (DK). IHT caused reorganization of mitochondrial energy metabolism improving the protection against acute hypoxia. A decrease by 40% in activation of mitochondrial respiration in the presence of succinate (V3--by 40% and V4--by 34%), a reduction of MDA and DK content (by 32% and 20%, respectively), an increase in SGD activity by 31% was observed in Gr. IY compared to Gr. II. Extra exogenous NO (Gr.Y) did not influence V3 and V4 in the presence of succinate, but in the presence of alpha-ketoglutarate decreased them by 9% and 29%, respectively, as well as ADP/O ratio by 28% on the background of SDG inhibition by 24% and the decrease of MDA content by 34%, that is reduced aerobic energy supply and reactive oxygen species production. L-arginine effects were abolished by L-NNA. Effects of cholinoreceptor blockers over L-arginine (Gr. VIII) resembled effects of AH: considerable activation of succinate and alpha-ketoglutarate oxidation in stage V3 by 44% and 75%, respectively, was observed which was accompanied by a decrease in ADP/O by 21% and 31%, and V3/V4 by 15% and 28%, respectively, in comparison to Gr.Y. It indicates that effects of L-arginine are mediated mainly by cholinoreceptors. The effects of adrenoreceptors blockade strengthened the combined effects of IHT with L-arginine treatment, confirming primary role of cholinoreceptors in NO-dependent mitochondrial reactions to IHT. Thus, oxygen uptake and its effective usage depend on dynamic status of adreno- and cholinoreceptors. We conclude that protective effects of the combination of IHT with NO-donor treatment under acute hypoxia are mainly realized through cholinoreceptors.