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Prolonged helium-oxygen hyperbaric (pressure 3,6 MPa) increased diene conjugate and Schiff's base level in plasma and erythrocyte membranes of mice. In those conditions SOD and glucose 6-phosphate dehydrogenase activities were inhibited in erythrocytes. Lipid bilayer microviscosity and cholesterol content of erythrocyte membranes were increased.

The increase of cytochrome P-450 by 34% and its catalytic activity with substrate amidopyrine by 57% as compared with control has been shown under hypoxia (0.029 MPa, 1 h). Hyperoxia (0.2 MPa, 1 h) increases the metabolism of amidopyrine by 148%, benzo[a]pyrene by 158% and aniline by 114% and consecutive affection of hypoxia and hyperoxia--by 247, 45 and 138% correspondingly at fixed cytochrome P-450 amount in both series. The amount of diene conjugates and Schiff's bases under hypoxia increases by 40 and 69% correspondingly, the activity of SOD and catalase decreases by 25 and 23%. The activity of hyperoxia raises the diene conjugate content by 19% at all this SOD activity increases by 95%. Consecutive affection of hypoxia and hyperoxia increases the level of diene conjugates and Schiff's bases by 26 and 23% correspondingly, without changing SOD and catalase activity. The relative microsomal viscosity of lipid layer and zones of enzyme-lipid contacts decreased by 20 and 24% under hypoxia, but under hyperoxia and consecutive affection and hypoxia and hyperoxia it increases by 29-28% and 56-40% correspondingly.

Influence of hypoxia (0.029 MPa, I h) followed by hyperoxia (0.2 MPa, I h) on microsomal oxidation and lipoperoxidation was studied in rat liver and lungs. Distinct increase of cytochrome P-450 catalytic activity with amidopyrine and benzo-a-pyrene as substrates of the I type was found after hypoxia, subsequent hyperoxia resulted in significant increase of amidopyrine and benzo-a-pyrene metabolism in liver and lung tissues and of aniline metabolism in liver tissue. Both hypoxia and hyperoxia led to increase in content of diene conjugates and Schiff bases in liver and lungs, while the increase of diene conjugates in liver and both diene conjugates and Schiff bases in lungs were observed under hyperoxic conditions.

Arginine, preadministered intraperitoneally at a dose of 120 mg per 100 g of body mass before hypoxia, decreased content of diene conjugates by 42-64% and Schiff bases by 7-15% in rat liver and testicular microsomal membranes as compared with control rats nontreated with arginine. Under these conditions cytochrome P-450 catalytic activity with aniline as a substrate was increased by 65-152% and with amidopyrine as a substrate--by 72-148%, respectively. Exogenous arginine inhibited an increase in membranes microviscosity, specific for hypoxic state; relative microviscosity of lipid bilayer was decreased by 36% and of the protein-lipid contact zones--by 84% as compared with control hypoxic animals.

Content of extra erythrocyte hemoglobin (EEH), total peroxidase activity (TPA), tseruloplasmin oxidase activity (TOA) and chemiluminescence intensity have been investigated in plasma. The dose-dependent changes of EEN, TPA, TOA are shown in experiments on the animals under hyperbaric oxygen (HBO) pressure (0.2, 0.3, 0.5, 0.7 MPa from 30 min. to 120 min.) and EEH, TPA--under hyperbaric air (1.1 MPa; 4 hours). All these parameters have been studied in patients treated with HBO for the assessment of HBO efficacy in the clinical investigations. These biochemical parameters may be used as informative tests of the functional state of the organism under HBO and hyperbaric air.

Extra-erythrocyte hemoglobin (EEH) level and total peroxidase activity (TPA) have been analysed in the blood serum and plasma of 44 patients following hyperbaric oxygenation (HBO). The levels of the parameters tested decreased after 3 HBO procedures and remained low to the end of the treatment period in the first group of patients. In the second group of patients, on the contrary, EEH and TPA levels increased after 3 HBO procedures and remained high to the end of the treatment period. In both groups of patients EEH changes correlated with TPA alterations. Possible EEH and TPA determination for the estimation and enhancement of HBO treatment efficacy is discussed.

The effect of pyrazidol on the efficiency of hyperbaric oxygenation (HBO) was investigated. Pyrazidol administration before HBO procedure reduced the intensity of lipid peroxidation in the blood plasma and decreased destabilization of erythrocyte membranes. Exoerythrocyte hemoglobin concentration, total peroxidase activity and glucose-6-phosphate dehydrogenase activity were used as the indexes of membrane stability. The patients pretreated with pyrazidol bore HBO much better than other patients.

A single intraperitoneal arginine injection increases the amidopyrin demethylation on 230% and aniline hydroxylation on 74% in rat liver microsomes. For all this the rate of lipid peroxidation estimated by the number of dienic conjugates and Schiff bases does not change. At the same time the exogenous arginine decreases the lipid bilayer microviscosity on 35% and increases the degree of protein submersion into lipid matrix on 54%. The experiments in vitro confirm the fact of activation in cytochrome P-450 isoform by arginine. A possible arginine effect on microsome membrane is under discussion.

The effect of different conditions of hyperbaric oxygenation (HBO) on content and catalytic activity of cytochrome P-450 in rat liver cytochrome has been studied. The intensity of lipid peroxidation in microsomal membranes has been determined by the content of dien conjugates and Schiff's bases. The rate of amidopyrine demethylation has been shown not to change, but the rate of aniline hydroxylation decreases on 34, 57 and 64% under increase of oxygen pressure up to 0.3, 0.5 and 0.7 MPa correspondingly. The level of dien conjugates increase on 66-87% under all studied conditions of HBO. Cytochrome P-450 content decreases on 45% under the action of 0.7 MPa, but content of Schiff's bases increases on 210% as compared with control.

Arginine (0.5 and 1 mu mol) decreased by 14-17% rates of superoxide anion formation in two systems: HADH-phenazine methosulfate and hydroxylamine autooxidation with nitrotetrazolium blue. These concentrations of arginine decreased by 40-50% formation of diene conjugates and Schiff bases in plasma when lipid peroxidation initiated by iron -ascorbate. Arginine administration before hypoxia decreased lipid peroxidation rate in plasma and liver microsomal membranes of rats.

Content and catalytic activity of cytochrome P-450 were studied using amidopyrine as a substrate of the I type and aniline as a substrate of the II type. In hypoxia content of cytochrome P-450 and metabolism of amidopyrine were increased, while the enzyme content and the substrate metabolism were decreased in hyperoxia.

Changes in the total peroxidase activity (TPA) and extraerythrocyte hemoglobin (EEH) content have been studied in the blood plasma and serum of patients treated with hyperbaric oxygenation (HBO). TPA and EEH content after the 3rd HBO session increased by 38% and 257%, respectively, in the plasma and by 56% and 74%, respectively, in the serum. By the end of HBO therapy course, after the 8th session, plasma level of the parameters under study normalized, while their serum level was higher than baseline. Possible use of the parameters under study for the assessment of HBO efficacy is discussed.

During winter-spring period, animals staying for three days at 2 degrees C develop changes in the substrate specificity of the rat brain mitochondria type A monoamine oxidase. Activity of the blood serum glucose-6-phosphate dehydrogenase, total peroxidase activity and extraerythrocyte hemoglobin level increase as a result of erythrocyte membrane damage. Rat hyperbaric oxygen sensitivity during this period increases. In autumn, 3-day cold exposure causes no changes in the above biochemical indices or hyperbaric oxygen sensitivity.

Hyperoxia after 3-day exposure at 2-4 degrees C induces more obvious disturbance of metabolites in rats than each of the factors separately. Along with decreased arginase activity in the brain and liver by 23 and 32% resp., the urine content decreases as well by 36 and 37% resp. Resistance of these animals against hyperoxia is reduced. But a preliminary 45-day cold-adaptation at 2-4 degrees C leads to a considerable activation of liver arginase and to increased content of urine in brain and liver by 32 and 30%, resp. The activation of arginase--urine system preserves under hyperoxia: the cold-adapted animals prove more resistant against hyperoxia effect. The above dynamic changes seem to be one of possible unspecific biochemical mechanisms of increasing the organism resistance against effects of extreme factors.

The activity of arginase, neutral peptidohydrolase (protaminase) and total intensity of autolysis were determined in the brain and liver of rats on the 1st, 3d, 30th and 45th days animal stay at a temperature of 2-4 degrees C. in the process of rats acclimatization to cold there occurs a correlation in the brain - between the activity of arginase and neutral peptidohydrolase, in the liver - between the arginase activity and total proteolytical activity (autolysis).

Monoamine oxidase, acid peptide-hydrolase activities, intensity of lipid peroxidation in brain and liver tissues, hemoglobin content in blood serum, total peroxidase activity and glucose-6-phosphate dehydrogenase activity were investigated during the cold acclimation within 1-45 days, 4 degrees. Cold stress within 1-3 days destabilized erythrocyte, lysosomal and mitochondrial membranes in the rat tissues studied. At the same time, cold adaptation within 45 days prevented the membrane labilization.

Cold exposition within 3 days at 2-4 degrees caused destabilization of rat erythrocyte membranes. Content of blood serum hemoglobin, total peroxidase activity and the glucose-6-phosphate dehydrogenase activity were increased. Resistance of the animals against high oxygen pressure was reduced. Administration of arginine within 3 days into the animals led to stabilization of membranes and to elevation of rat resistance towards high oxygen pressure.

Activity of glucose-6-phosphate dehydrogenase (G6PD) was increased in blood serum in hypoxic hypoxia, hypoxia and cooling stress. The degree of this alteration depended on duration of the action of the effectors and on oxygen pressure. Adaptation to cooling was characterized by stabilization of enzymatic activity at the new metabolic step. Mechanisms of G6PD activation in blood serum under conditions of extreme states as well as the possibilities of utilization of this phenomenon as a test are discussed.

It has been established that white rats adapted to the low temperature of the environment (45 days 2-4 degrees C) in contrast to the animals undergoing such action during 3 days (cold stress) show resistance to the toxic action of the high oxygen pressure. The considerable removal of convulsions under the action of oxygen, the absence of increase of erythrocyte membrane permeability in the preconvulsive stage of hyperoxia and prevention of changes in the substrate specificity of type A monoamine oxidase both in preconvulsive and convulsive periods of oxygen intoxication are their characteristics.

Activity of glutaminase (both phosphate-dependent and phosphate-independent forms of the enzyme) as well as glutamate decarboxylase activity were studied in hyperoxia (6 ati) and under conditions of protection by means of arginine from the effect of hyperoxia. In hyperoxia activity of phosphate-dependent and phosphate-independent forms of glutaminase was decreased by 45% and 51%, respectively. At the same time, glutamate decarboxylase activity was decreased by 32%. Arginine showed a protective effect, delaying the time of oxygen convulsions onset by 2.5-fold. The low activities of glutaminases were maintained but the glutamate decarboxylase activity was increased and even exceeded the control level by 29%. A mechanism of the protective effect of arginine is discussed.