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Aim: To investigate an effect of hypoxia on the formation of nitric oxide (NO) in the brain and blood of rats and an influence of L-NNA, the NO-synthase inhibitor, and sodium nitrite on NO generation in separate and simultaneous introduction of these compounds in the animal body., Material and Methods: Experiments were conducted on 42 rats of Krushinsky-Molodkina (K-M) line without adaptation to hypoxia and short-term adaptation to hypobaric hypoxia. Animals were intraperitoneally injected with sodium nitrite (0.5 mg/100 g) and the non-specific inhibitor of NO-synthase L-NNA (2.5 mg/100 g) at different times. Changes in NO content were assessed using electron paramagnetic resonance (EPR) by the intensity of nitrosyl Hb-NO complexes in ERP blood spectra., Results and Conclusion: The production of NO in the brain, compared with that in the blood, was significantly reduced, not only under physiological conditions, but also after the administration of moderate doses of NaNO2. In the short-term hypobaric hypoxia, there was the intensification of the processes of the reduction of NO2- to NO and the formation of nitrosyl heme-NO complexes not only in the blood but also in the mammalian brain.

It has been showed that the introduction of nitrocompounds (as nitic oxide donors) in to the compositions of cyclophosphamide and hydroxamic acids for curing animals having leukemia P-388 increased duration of life by 290%. Thereby 40% of animals have recovered. The therapeutic dose cyclophosphamide have been reduced by 6 times.

The aim of the work was to study the role of atorvastatin in the correction of oxidative stress manifestations in patients with coronary heart disease and dyslipidemnia (DLP). It included 122 patients with stable forms of CHD and 20 practically healthy subjects. Plasma lipids and products of lipid peroxidation (dienic conjugates and compounds reacting with 2-thiobarbituric acid), eryhrocyte antioxidative enzymes glutathione peroxidase and superoxide dismutase were determined by standard methods; activity of the ceruloplasmin/transferrin antioxidant system) was measured by electron paramagnetic resonance. The patients underwent 24 hr ECG Holter monitoring. Atorvastatin at a dose of 20 mg/d given during 6 months exerted antioxidative and antiperoxidative effects in 90% of the patients. It normalized parameters of lipid peroxidation and antioxidant protection thereby improving the clinical course of CHD.

Using electronic paramagnetic resonance (EPR), we studied the effect of the peptide cortexin on the content of hemoglobin nitrozyl complexes (Hb-NO-complexes) and other paramagnetic centers (transferrin, methemoglobin) in the blood of rats of Krushynsky-Molodkina line in the experimental hemorrhagic stroke induced by acoustic stress. After the acoustic exposure, the level of Hb-NO-complexes have increased by more than 6 times. The intensity of the EPR signal of the plasma peptide transferrin increased by 1,5 times. The level of blood methemoglobin was also elevated, though not significantly, after the acoustic stress. Cortexin substantially reduces the formation of Hb-NO-complexes and, therefore, the level of nitride oxide while the contents of transferrin and methemoglobin remain intact.

The influence of hypoxia on nitric oxide formation in the blood of Krushinskii-Molodkina rats has been studied by electron paramagnetic resonance. It was found that nitric oxide synthesis in Krushinskii-Molodkina rats is increased compared with that in Wistar rats. A significant enhancement of the EPR signal of Hb-NO complexes in the animal blood was observed after hypoxia simulating the altitude of 5000 m above the sea level, in particular in the presence of sodium nitrite and the NO-synthase inhibitor L-nitroarginine. It was assumed that NO synthesis and nitro-/nitrite- reductase systems are activated under hypoxic conditions.

Treatment with simvastatin (vasilip) at a daily dose of 20 mg combined with conventional cardiac therapy was given for 3 months to 132 patients with coronary heart disease and postinfarction cardiosclerosis with dyslipidemia. Activity of tissue and plasma antioxidative enzymes increased in 60% of the patients and decreased in 40%. Treatment with antioxidants 2-ethyl-6-methyl-3-oxypiridine succinate (mexidol) and ubichinon (cudesan QIO) improved antioxidative status of the patients and clinical picture of cardiac pathology.

Total cholesterol as well as cholesterol of low and high density lipoproteins, lipid peroxidation products (LPP), such as dienic conjugates and compounds reacting with thiobarbituric acid, were measured in a single blood sample from each of the 295 patients with CHD and 20 apparently healthy subjects. FC II and III angina was diagnosed in 142 and 151 CHD patients respectively. Certain samples were used to additionally detect homocysteine, activity of anti-oxidative enzymes (superoxide dismutase and glutathione peroxidase) in erythrocytes and ceruloplasmin/transferrin anti-oxidative system in plasma. Patients with FC III angina had significantly higher LPP levels but lower activity of tissue and plasma anti-oxidative systems than patients with FC II angina or healthy subjects. Patients with stable forms of CHD showed correlation between lipid composition, LPP contents, homocysteine level, and activity of anti-oxidative enzymes.

A possible involvement of nitric oxide in the protective effect of short-term adaptation of Krushinsky-Molodkina rats to mild hypoxia simulating 5000 m above sea level was studied. Nitric oxide proved to have a considerable protective effect on stress-induced disorders in Krushinsky-Molodkina rats as demonstrated using NO-synthase inhibitors and NO monitoring by electron spin resonance under different experimental conditions.

In experiments on mice we studied the effect of individual or combined treatment with mexidol and nitroglycerine on iron-sulfur centers of the mitochondrial respiratory chain, cytochrome P-450 of the endoplasmic reticulum, and nitric oxide formation in the liver tissue. Mexidol had a potent effect on these parameters and protected iron-sulfur centers from oxidation, including that induced by nitroglycerine.

Thirty-two patients with coronary heart disease (CHD)--exertional angina and postinfarction cardiosclerosis with dislipidemia--were treated with dicvertin (2,3-dihydro-3,5,7-trihydroxi-2(3,4-dihydroxiphenyl)-4H-1-benzopyran-4-on), a Russian antioxidant, during two months in a day dose of 80 mg in addition to conventional cardial therapy. The therapy resulted in positive changes including improvement of CHD clinical picture and biochemical serum indices, such as a 6% decrease in cholesterol level, a 12% decrease in low-density lipoproteins cholesterol level, and a 14% increase in high-density lipoproteins cholesterol level. The intensity of lipid peroxidation decreased, the levels of diene conjugates and TBA-reactive products lowered by 38% and 40%, respectively. The fibrinogen level lowered by 20%. The antioxidative status of the patients increased.

The subjects of the study were 36 patients suffering from coronary heart disease with exertional angina and postinfarction cardiosclerosis with dislipidemia. The patients were administered mexidol (2-ethyl-6-methyl-3-oxipyridin succinate), a domestically produced antioxidative agent, for 1 month in a dose of 325 mg/day together with conventional cardial therapy. The result was good and included clinical improvements and improvements in biochemical serum parameters: cholesterol level decreased by 10%, the level of low density lipoprotein cholesterol decreased by 25%, high density cholesterol level elevated by 15%. The intensity of lipid peroxidation lowered, which was manifested by decrease of the level of diene conjugates and TBA-reactive products by 27% and 42%, respectively. The patients' antioxidative status increased.

Ascorbic acid, an effective modulator and regulator of cell metabolism, was shown to induce the production of nitric oxide in E. coli cells. This process was detected by EPR spectroscopy as the generation of a spectral signal typical of nitrosyl-iron-sulfur centers (Fe-S-NO) under anaerobic conditions. Incubation of E. coli cells in the presence of ascorbic acid under aerobic conditions was shown to be accompanied by sodium nitrite formation. It is suggested that ascorbic acid is capable of supporting the system of energy supply to cells in hypoxia caused by reduced oxygen content or treatment with sodium nitrite.

The dynamics of EPR signals from the iron-transporting blood protein Fe(3+)-transferrine after the administration of sodium nitrite and metronidazole to animals was studied. It was shown that exogenin nitric oxide produced by nitrocompounds resulted in the release of iron from Fe(3+)-transferrine.

Ferrous-ascorbate is known to form with nitric oxide paramagnetic nitrosyl ferrous-ascorbate complexes, Fe-AA-NO. These complexes yield on EPR signal with g-factor close to 2.02 and an optical absorption spectrum with maxima at 340, 460, and 600 nm. Fe-AA-NO complexes are unstable in the presence of oxygen. Ferrous-ascorbate complexes promote NaNO2 decay resulting in the formation of NO. Nitric oxide is taken up by Fe-AA complexes to form paramagnetic ferrous-ascorbate nitrosyl complexes, Fe-AA-NO. It is suggested that ferrous-ascorbate complexes can play the role of carriers of NO and, perhaps, O2 in the blood plasma. Nitrosyl ferrous-ascorbate complexes can also be the NO containing factor involved in the blood vessel relaxation (endothelium-derived relaxing factor, EDRF).

Changes in ESR signals from the active form of cyt P-450 in mouse liver samples after administration of some nitro compounds were studied by the ESR method. It is shown that administration of nitro compounds leads to the formation of nitrosyl cyt P-450-NO complexes and a decrease in the ESR signal from cyt P-450 within the first 1-2 h after administration, indicating the inhibition of enzyme activity. It is assumed the nitro compounds induced inhibition of cyt P-450 in the first hours after administration is responsible for the enhancement by imidazoles of the effect of some chemotherapeutic drugs.

Changes in metabolic paramagnetic centers of the liver, kidney, spleen, brain and heart tissues, and blood after sodium nitrite intraperitoneal administration irradiation, or combined action of sodium nitrite and irradiation on mice, were studied using the EPR method. It was shown that irradiation of mice after sodium nitrite administration enhanced the effects induced by sodium nitrite alone: the levels of nitrosyl complexes Heme-NO in the tissues, cytochrome P-450 inhibition, and MetHb were higher.

Ribonucleotide reductase activity (RRA) has been studied in various tumors and spleens of tumor-bearing animals using EPR technique and biochemical methods. The effect of a number of biologically active compounds on RRA has also been studied. RRA in tumor and spleen increases during tumor growth. Inhibitory effect of irradiation, hydroxyurea, nitrosomethylurea and activatory effect of 5-nitrofurans and nitroimidazole derivatives on RRA has been observed. Regulatory factors of RRA and DNA synthesis in vivo have been discussed.

It has been shown by the method of electron photosensitized transfer that N-acetyl group is the main electron-acceptor group in oligomeres of N-acetyl glucose amine (AGA). In n-AGA molecules (n-3.5) interacting with an electron radical products of the breakage of glycoside bond are observed, their concentration rising with an increase of the chain length. The ionic strength does not affect the photosensitized transfer of the electron in chitin oligomeres. Formation of paramagnetic centres in the molecule penta-AGA depends on the medium pH.

Basing on the results of EPR investigations and an analysis of literature data an assumption was made of the new factors in the mechanism of the radiosensitizing action of nitro compounds. It was assumed that irradiation-induced accumulation of toxic products of incomplete reduction of the nitro group of these compounds--nitroso- and hydroxyl amino-derivates--in tumor hypoxic zones played the main role in the radiosensitizing action of nitro compounds.

The nature of electron-acceptor groups in the system of lysozyme with its substrate-inhibitors has been studied in a wide range of pH values by the method of photosensitized electron transfer. In the lysozyme molecule disulphide bonds and peptide groups are the electron--acceptor groups. The nature of radicals in irradiated lysozyme depends on pH. At complex-formation of lysozyme with oligomeres of N-acetylglucosamine the electron transfer from the enzyme molecule to N-acetyl group of the substrate-inhibitor molecule is realized. Under conditions ruling out complex-formation of lysozyme with the inhibitors (N-acetylglucosamine and its dimer) the electrons are localized on disulphide bonds of the protein molecules at alkaline pH and at pH less than or equal to 3 the radicals are observed which are due to the remove of hydrogen atom from the Calpha-atom of the protein polypeptide chain.

The low-temperature ESR-spectroscopy was used to study the irradiated organs and blood of tumor-bearing animals before and after the administration of metronidazole. The ESR signals of metronidazole anion-radicals were registered in tissues of the animals injected with metronidazole: the intensity of these signals correspondent with the tissues preparation content.

Electron structure of N-acetylglucoseamine molecule and its ion-radicals has been studied by quantum-chemical methods CNDO2 and JNDO, and by ESR as well. N-acetyl group is shown to be the only electron acceptor group of AGA molecule. Phototransformations of paramagnetic centres are studied at different pH values.

A study was made of changes in the intensity of the ESR signals in tissues of sarcoma-37 and liver of mice after radiation of the tumor, administration of metronidazole, and after the combined effect of the two factors. The most pronounced changes in the ESR signals were induced by metronidazole. An appreciable increase in the content of nitrosyl complexes in the tumor was noted after the combined effect of metronidazole and radiation which was indicative of the radiation-induced formation of a large number of metronidazole anion-radicals in the tumor.