[Effect of melaxen on free radical processes intensity and some antioxidant enzymes activity in rats liver and blood serum under type 2 diabetes mellitus].

The effect of melaxen on free radical processes and activity of superoxide dismutase and catalase in rats with type 2 diabetes mellitus (T2DM) has been investigated. It was established that melaxen administration to diabetic rats caused a decrease of the intensity of free radical processes as evidenced a decrease of the lipid peroxidation primary products content and biochemiluminescence parameters. The activity of the antioxidant enzymes changed towards normal values. These effects were probably induced by the correction of the melatonin level at the result of the melaxen action.

[The dose-dependent influence of 3,5-dicarbometoxyphenylbiguanide on activity of the glutathione antioxidant system in heart and blood serum of rats with the experimental myocardial infarction].

Administration of a synthetic compound with predicted anti-ischemic and cardioprotective activity, 3,5-dicarbometoxyphenilbiguanide,--to rats with experimental myocardial infarction led to a decrease in the lipid peroxidation level, glutathione peroxidase activity, the level of reduced glutathione, activity of NADP-isocitrate dehydrogenase in the heart and blood serum, and also activity of glucoso-6-phosphate dehydrogenase in heart in comparison with their levels in untreated animals with myocardial infarction. This may be attributed to a decrease of free radical processes and reduction of antioxidant system loading. At the same time the increase glutathione reductase activity observed under these conditions in the heart and and blood serum probably associated with specific influence of 3,5-dicarbometoxyphenilbiguanide on this enzyme.

Effect of 3,5-dicarbomethoxyphenylbiguanide on free radical homeostasis in rats with experimental myocarditis.

Administration of 3,5-dicarbomethoxyphenylbiguanide to rats with experimental epinephrine-induced myocarditis was followed by a decrease in activity of marker enzymes for cardiomyocyte cytolysis in the blood serum. This agent also decreased the intensity of free radical processes and had a normalizing effect on aconitase activity in the heart and blood serum of rats with myocarditis.

[Catalytic properties of glutathione reductase from rats liver at norm and toxic hepatitis].

Homogeneous preparations of liver glutathione reductase (GR, EC 1.6.4.2.), obtained from control rats and animals with toxic hepatitis, catalytic properties of this enzyme have been investigated. A number of the enzyme properties did not change under conditions of hepatitis. These included electrophoretic mobility (R(f) = 0.23 +/- 0.01), molecular mass (104 +/- 5.20 kDa), pH-optimum (7.4 +/- 0.37). There was similarity in pK values of functional groups. At the same time, decrease in affinity of enzyme to a substrate and coenzyme and occurrence substrate-linked inhibition was observed under conditions of this pathology. There were some differencies in regulation of GR activity by metabolites of tricarboxylic acid cycle.

Effect of N-[Imino(4-morpholyl)methyl]guanidine on the oxidative status in rats with toxic hepatitis.

The hepatoprotective and antioxidant properties of a synthetic biguanide N-[imino(4-morpholyl)methyl]guanidine (IMMG) were prognosticated by the method of computer prediction. Administration of IMMG was accompanied by a decrease in serum transaminase activity in rats with toxic hepatitis, which reflects inhibition of hepatocyte cytolysis. IMMG treatment was followed by a decrease in biochemiluminescence parameters reflecting the intensity of free radical oxidation. We revealed an increase in activity of aconitase, which was reduced during toxic hepatitis. The content of citrate in the liver and serum was returned to normal under these conditions. IMMG also increased activities of superoxide dismutase and catalase and total antioxidant activity in rat liver. Our results suggest that the hepatoprotective effect of IMMG is associated with its antioxidant activity.

[Melatonin as a corrector of free radical oxidation processes during toxic damage of liver in rat].

Biochemiluminiscense parameters (light sum and maximum flash) show that free radical oxidation intensity (increased in serum blood of rats with toxic hepatitis) is decreased upon the treatment with melatonin. At the same time, the tg a2 value (reflecting the total antioxidant activity) changes toward the normal level, which indicated a decrease in the degree of antioxidant system mobilization. Superoxide dismutase and catalase activities (increased in the liver and blood serum of rats with toxic hepatitis) also showed the tendency to decrease upon the melatonin administration. Evidently, melatonin can act as a factor correcting the oxidative stress caused by the toxic damage of liver.

Oxidative status and citrate concentration in rat tissues during experimental hyperthyroidism and melatonin treatment.

Biochemiluminescence increased, while aconitate hydratase activity and citrate accumulation in tissues of the liver and heart and blood decreased in rats with experimental hyperthyroidism. These changes reflect activation of free radical oxidation, damage to enzyme molecules with reactive oxygen species, and impaired utilization of citrate under pathological conditions. Melatonin treatment during hyperthyroidism normalized aconitate hydratase activity and citrate concentration. Biochemiluminescence study showed that the effect of melatonin is related to antioxidant activity of this hormone, inhibition of free radical oxidation, and suppression of reactive oxygen species generation.

[Subcellular localization, purification, and various catalitic properties of aspartate aminotransferase from Spirodela polyrhiza].

Intracellular distribution of aspartate aminotransferase (AAT) in Spirodela polyrhiza (Lemnaceae), strain SJ, has been studied by differential centrifugation. The bulk of the enzyme (73% of total cellular content) was localized in the cytoplasm and 24% activity was localized in chloroplasts. Purified cytoplasmic and chloroplastic isozymes differed by their affinity for substrates. The reaction balance was shifted towards direct and reverse transamination in the cytoplasm and chloroplast, respectively. Competitive inhibition of AAT by excessive substrates and enzyme affinity modulation by certain intermediates of the tricarboxylic acid cycle (isocitrate, succinate, and citrate) were observed. Possible involvement of AAT isozymes in the coordination of carbon and nitrogen metabolism through the regulation of 2-oxoglutarate synthesis and utilization in different cellular compartments is discussed.

[Regulatory properties of glucose-6-phosphate dehydrogenase from rat liver under conditions of the intensification of free-radical oxidation stimulated by toxic hepatitis].

Rat liver oxidative stress caused by toxic hepatitis is accompanied by increased activity of glucose-6-phospate dehydrogenase (EC 1.1.1.4.9; G6PDG). Electrophoretically homogenous G6PDG preparations purified from livers control rats and animals with hepatitis had specific activity of 4.13 and 6.54 EU, respectively. Fe2+ and Cu2+ ions showed non-competetive type inhibition of G6PDG at normal and under pathological condition, whereas Ca2+ activated G6PDG. Hydrogen peroxide exhibited mixed type inhibition of G6PD (K(i) 0.36 mM and 0.95 mM at norm and experimental toxic hepatitis, respectively). The participation of oxidised and reduced glutathione in G6PDG activity regulation has been shown.

Glutathione system and activity of NADPH-generating enzymes in the liver of intact rats and animals with toxic hepatitis receiving melatonin.

Melatonin administered to intact animals increased glutathione concentration and activities of glutathione peroxidase, glutathione reductase, NADP-isocitrate dehydrogenase, and glucose-6-phosphate dehydrogenase in the liver. In animals with toxic hepatitis melatonin treatment decreased glutathione concentration and enzyme activities, which was probably associated with inhibition of free radical oxidation under the influence of this hormone.

[The oxidative effects of melatonin, the content of citrate and the activity of aconitate hydratase in the rat liver in toxic hepatitis].

When melatonin was injected into the liver of rats with toxic hepatitis, there was a reduction in the rate of free radical processes and in the mobilization of the antioxidative system, as estimated by the parameters of biochemiluminescence and the level of α-tocopherol, which is likely to be accounted for by the antioxidative effect of this hormone. The administration of melatonin to intact animals causes a reduction in the activity of aconitate hydratase and an increase in the level of citrate, which reflects the enhancement of the antioxidative potential as it promotes the decreased hydroxyl radical formation in the Fenton reaction. Metatonin-induced elevations in citrate levels and changes in the activity of aconitate hydratase were observed in the liver of animals with toxic hepatitis as compared with those not receiving the hormone, which seems to be associated with the less mobilization of the antioxidative system in the presence of melatonin that is able to produce an antioxidative effect.

Catalytic properties of glucose-6-phosphate dehydrogenase from pea leaves.

A homogeneous preparation of glucose-6-phosphate dehydrogenase (G6PDH, EC 1.1.1.49) with a specific activity of 3.88 U/mg protein was isolated from pea (Pisum sativum L.) leaves. The molecular mass of the G6PDH is 79 +/- 2 kD. According to SDS-PAGE, the molecular mass of the enzyme subunit is 40 +/- 3 kD. The Km values for glucose-6-phosphate and NADP are 2 and 0.5 mM, respectively. The enzyme has a pH optimum of 8.0. Mg2+, Mn2+, and Ca2+ activate the enzyme at concentrations above 1 mM. Galactose-6-phosphate and fructose-6-phosphate inhibit the G6PDH from pea leaves. Fructose-1, 6-bisphosphate and galactose-1-phosphate are enzyme activators. NADPH is a competitive inhibitor of the G6PDH with respect to glucose-6-phosphate (Ki = 0.027 mM). ATP, ADP, AMP, UTP, NAD, and NADH have no effect on the activity of the enzyme.