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Autooxidation of low-density lipoproteins during incubation at 37 degrees C was accompanied by accumulation of LPO products, decrease in UV autofluorescence (FUV), and increase in autofluorescence in the visible band (FVIS). The degree of low-density lipoprotein modification was estimated by calculating the FVIS/FUV ratio. A positive correlation was revealed between this ratio and concentration of thiobarbituric acid-reactive LPO products (r=0.76, p<0.001). Autooxidation of low-density lipoproteins increased availability of tryptophanyls for fluorescence quenchers and inductive resonance energy transfer from tryptophanyls to adducts formed in the reaction of apoprotein and LPO products. These changes probably play a role in the decrease in FUV.

Dynamics of lipoprotein oxidation in blood plasma was studied by Cu-induced plasma oxidation in 114 patients with atherosclerosis of lower extremities of various severity with and without ischemic heart disease. Preparedness of plasma lipoproteins to oxidation in patients was higher than in healthy subjects. Degree of oxidizeability increased with increase of severity and extent of atherosclerosis and was highest in patients with atherosclerosis of lower extremities and ischemic heart disease. There were no significant differences between groups of patients with various severity and extent of atherosclerosis in levels of total cholesterol and triglycerides as well as in other parameters of lipid spectrum. Correlation analysis revealed no relationship between age of patients and degree of plasma oxidizeability.

The aim of this study was to determine the concentration parameters and time-course of copper-induced oxidation in serum and whole blood plasma. We investigated the oxidizability of undiluted and (2-60-fold) diluted whole plasma (prepared with citrate as an anticoagulant) and serum by monitoring the change in the level of conjugated dienes, ketodienes and malondialdehyde in the samples. The kinetic curves of the accumulation of different lipid peroxidation (LPO) products had similar S-shape, but they differed by a number of quantitative parameters--lag-time, time of improvement and the level of maximal rate of oxidation, as well as time of improvement of the maximal accumulation and maximal amount of LPO products. When the LPO products were formed in undiluted plasma and serum, the lag phase of 2-2.5 h for conjugated dienes and ketodienes, and 11-12 h for malondialdehyde was observed. Oxidation profile showed a negligibly short period of inhibition followed by rapid oxidation for all investigated LPO products when plasma and serum were diluted at least 10-fold. The rate of accumulation and amount of LPO products decreased in the following order: conjugated dienes > ketodienes > malondialdehyde. Choice of blood plasma or serum and a dilution factor strongly influenced intensity of copper-induced LPO. Anticoagulant (sodium citrate), that was used by preparation of plasma, possessed an inhibitory action on LPO, due to formation of copper-citrate chelates. Dilution of plasma and serum increased LPO through lowering of influence of water-soluble antioxidants, but action of fat-soluble antioxidants (dissolved in the lipid phase of lipoprotein particles) by was unchanged. These results indicate that measurement of lipid oxidation induced in vitro in the whole plasma or serum might be more relevant model of the lipoprotein oxidation in the blood than the in vitro oxidation of single isolated lipoproteins.

In patients with coronary heart disease oxidizability of lipids during Cu(2+)-induced oxidation of blood plasma inversely correlated with fibrinogen content. A positive correlation was found between the amount of lipid peroxidation products in the plasma from these patients and fibrinogen content. The increase in fibrinogen content was associated with high levels of total lipids and triglycerides and low concentration of high-density lipoprotein cholesterol. In vitro experiments demonstrated that fibrinogen reduces oxidizability of blood plasma. Our results suggest that the decrease in lipid oxidizability at high concentration of fibrinogen in patients with coronary heart disease is related to predominant oxidation of fibrinogen and its competition with plasma lipids during Cu(2+)-induced oxidation.

Magnetic resonance spectroscopy revealed structural modifications of human plasma lipoproteins during peroxidation induced by copper sulfate in vitro. Decreased molecular mobility of fatty acid chains in lipoprotein lipids was demonstrated.

The effect of metal cations on copper-catalyzed lipid peroxidation (LPO) of low density lipoproteins (LDL) was examined. The presence of metal cations in the incubation media containing LDL (0.8 mg protein/ml) and CuSO4 (0-80 microM) influenced on LPO of LDL as evident by the measurement of TBARS. With the concentrations of CuSO4 less than 10 microM, the metal cations caused an increase in LDL peroxidation. Zn2+ appeared to be the most effective inductor, Mn2+ was less effective, and the influence of Ca2+ and Mg2+ was insignificant. With greater CuSO4 concentrations Mg2+ showed no effect on TBARS formation in LDL while the addition of other nontransition metal cations to the incubation mixture led to the inhibition of LDL peroxidation. The capacity for inhibition decreased in the row Mn2+ > Zn2+ > Ca2+ > Mg2+. The possible mechanism explaining these results may be in the competition of metal ions for copper binding sites on LDL. Our results allow to suggest the existence of two types of copper binding sites on LDL, tight-binding sites which are non-effective in LPO and effective weak-binding sites.

Copper-catalyzed lipid peroxidation (LPO) in low density lipoprotein (LDL) and two subfractions of high density lipoprotein (HDL2 and HDL3) isolated from human serum was studied. The levels of LPO were estimated as thiobarbituric acid-reactive substances (TBARS). The amount of TBARS increased in a time-dependent manner when either LDL, HDL2 or HDL3 (0.4-1.2 mg protein/ml) was incubated at 37 degrees C during 4 h with phosphate-buffered saline containing CuSO4 (2-80 microM). The increase in CuSO4 concentration to some value therewith caused the enhancement of the rate of TBARS formation but the following increase in CuSO4 concentration beyond that value didn't already affect the kinetics of LPO in lipoproteins. It was also shown that the lesser was the concentration of lipoprotein the lesser CuSO4 concentration was needed to reach maximal rate of TBARS formation. The data obtained point to the versatility of the mechanism of copper-catalyzed oxidation of low and high density lipoproteins and suggest that the decisive role in the process belongs to copper ions bound to lipoprotein particle.

Platelet aggregation induced by native and oxidized low-density lipoproteins (LDL) was studied. The minimal LDL concentration necessary for platelet activation was no more than 0.2 mg/ml. The aggregation rate increased when LDL concentration rose from 0 to 0.4-0.6 mg/ml for native LDL and to 0.2-0.4 mg/ml for oxidized LDL. The platelet aggregation induced by oxidized LDL appeared to be higher than that induced by the same concentration of native LDL. The dependence of aggregation rate on the degree of LDL peroxidation was linear up to MDA concentration equal to 3-4 mg/ml. Further LDL peroxidation leads only to the negligible increase in the induced aggregation rate.

The activation of freshly isolated human blood monocytes and neutrophils monitored by oxidized human plasma lipoproteins (LP) was measured by detecting luminol-amplified chemiluminescence. The activation was accompanied by production of superoxide radicals. This finding was confirmed by measuring superoxide dismutase-sensitive reduction of cytochrome c. Incubation of monocytes or neutrophils with low-density lipoproteins (LDL) resulted in the accumulation of lipid peroxidation (LPO) products which were assayed by the 2-thiobarbituric acid test. Data from inhibitory analysis suggest that the hydroxyl radical scavenger, mannitol, had no appreciable effect on the accumulation of LPO products during the incubation of LDL with either cell type. However, catalase, superoxide dismutase, the metal ion chelators desferrioxamine and EDTA, as well as the free radical scavenger, butylated hydroxytoluene, markedly decreased the accumulation of LPO products in the medium--by 88%, 67%, 38%, 52%, and 47%, respectively, after incubation of LDL with monocytes, and by 65%, 47%, 41%, 65%, and 100% after incubation of LDL with neutrophils. These results indicate that activation of monocytes and neutrophils by oxidized LP intensifies LPO which proceeds via a free-radical mechanism that is superoxide-dependent and is catalyzed by transition metals.

The tissue oxygen concentration, the serum antioxidant system state and the serum malondialdehyde (MDA) concentration were studied in patients with hepatitis B. The good correlations were studied in patients with hepatitis B. The good correlations between MDA concentration in patients serum and the oxygen concentration in tissues (R-0.79), and the cytoplasmic enzymes activity (R-0.75 for lactate dehydrogenase; R-0.75 for alanine transferase) were found. On the other hand, it was shown an antioxidant activity decrease of ceruloplasmin-transferrin system in patients serum. It is proposed, that the tissue hypoxia and the decrease of the serum antioxidant activity are the general factors leading to the MDA accumulation in the serum of patients with hepatitis B.

It is shown that the dynamics of lipid peroxidation (LPO) in patients with purulent meningitis is unspecified in character and is encountered both in meningococcal and pneumococcal infection. The level of secondary LPO products and the degree of hyperfermentemia, which are determined according to the dynamics of changes in the activity of aspartate transaminase, are objective characteristics of the severity of the patient's condition and reach maximum on the 5th day of the disease. The correlation between the dynamics of the primary LPO products and the ceruloplasmin/transferin coefficient allows the severity of the disease to be prognosticated.

Human erythrocytes were incubated for 5 h at 37 degrees C with lipoproteins (LP), preliminary oxidized to different extent, as assessed by thiobarbituric acid (TBA) test. Cholesterol content in the cells was increased by 12-14% after incubation with low-density lipoproteins (LDL) along with augmentation of order parameter and rotational correlation time of spin-labeled stearic acids incorporated into membranes. If erythrocytes were incubated with oxidized LDL, containing 2.5-4 times more TBA-reactive material than native ones, cellular content of cholesterol was increased by 24-28%. In contrast, high-density lipoproteins (HDL2 and HDL3) removed cholesterol from cell membranes, when incubated with erythrocytes. This was followed by increased fluidity of membrane lipid phase as detected by the spin probe method. Oxidation of HDL2 and HDL3 decreased their ability to accept cholesterol from cell membranes. No detectable accumulation of TBA-reactive material was observed in the samples during the incubation. The antioxidant, butylated hydroxytoluene (BHT), in the concentration of 10(-5) M did not influence the cholesterol transfer between LP and erythrocytes. Hence, the effects of lipid peroxidation (LPO) on the cholesterol transfer seem to result from LP alterations by oxidation rather than from free radical reactions occurring during the incubation. By increasing cholesterol-donating ability of LDL and inhibition of cholesterol-accepting capacity of HDL lipid peroxidation in LP may activate cholesterol accumulation in blood vessel cells and thus contribute to atherosclerosis.

Lipid oxidation blood levels, activity of serum antioxidative system and erythrocytic membranes were investigated in the time-course of treatment of 145 pregnant females with nephropathies of various severity. More pronounced improvement of the parameters studied and elimination of late gestosis symptoms were revealed in the treatment with antioxidative preparations, lipostabil and solcoseryl. Regardless of treatment pattern in pregnancies complicated by severe nephropathy there were improvements noted, as a rule, in presence of pharmacological management but after its withdrawal the signs of the diseases relapsed (2-6 days after). Continuation of pregnancy up to the terms when the fetus was expected to be born viable was considered as the main target of the aforementioned treatment.

The cholesterol transfer between human erythrocytes and main classes of serum lipoproteins (LP) from healthy donors and artery-coronary disease patients was studied (artery-coronary disease is the main manifestation of atherosclerosis). It is shown that low-density lipoproteins (LDL) are capable of transporting cholesterol to erythrocytes, which lack the specific receptors for LDL. The cell cholesterol content in comparison with erythrocytes incubated without LDL was increased by 11.4%. The effect was even higher in case of LDL, isolated from serum of artery-coronary subjects (the cell cholesterol content was increased by 33.8%). High-density lipoproteins (HDL) accept cholesterol from cell membranes. However, cholesterol-accepting properties of HDL from artery-coronary disease patients were suppressed as compared with normal HDL. Both discovered events must promote the cholesterol accumulation in cell membranes in atherosclerosis. As it is shown by the spin probe method, lipid peroxidation (LPO) causes the disturbance of the structural organization of LP and as the consequence of that--the increase of LDL cholesterol-donating ability and the decrease of HDL cholesterol-accepting ability. The greater LDL are oxidized, the more cholesterol they transport to erythrocytes during incubation. The greater is the level of HDL peroxidation, the stronger their cholesterol-accepting function is suppressed. These results suggest that LPO can play an important role in LP modification, the disturbance of their interaction with cell surface and the cholesterol accumulation in cells in atherosclerosis.

Rats were treated with oxygen under the pressure of O-4 excessive atmospheres (ati) within 1 hr. Under the pressure of 2 ati content of ceruloplasmin was increased, while concentration of transferrin and content of lipid peroxidation products were decreased in blood serum. The level of ceruloplasmin and transferrin was unaltered, while lipid peroxidation was augmented under the pressure of 3-4 ati. At the same time, in vitro content of these proteins did not alter in blood serum, while concentration of the lipid peroxidation products was increased under the pressure of 2 ati. The system of ceruloplasmin-transferrin appears to be involved in regulation of lipid peroxidation in blood serum under conditions of hyperbaric oxygenation.

The blood serum ceruloplasmin, transferrin, malonic dialdehyde, iron and copper levels have been measured in donors. These parameters varied in groups of subjects aged 20-29 and 30-45, no age-associated differences being recorded within both the groups. Certain differences have been revealed between the donors who furnished their blood more or less than 3 times a year. The results of this investigation may be useful in clinical screenings of donors.