Effect of O(2)/O(3) atmosphere on the rate of osmotic hemolysis of bovine erythrocytes in the presence of some antioxidants.

Purified red blood cells, exposed to an ozone atmosphere, show an increased rate of hemolysis on sudden osmotic stress. To determine this effect of ozone in the presence of natural antioxidants, bovine red blood cells, used as models, were suspended in blood plasma, or in physiological saline with one of the following antioxidants: albumin, glutathione, uric acid, glucose and a vitamin E analog (trolox). After exposure of the suspensions to oxygen and oxygen/ozone atmospheres the rates of osmotic hemolysis were measured, using a stop-flow technique, and compared with rates measured in air-exposed controls. Blood plasma, containing all natural antioxidants, caused a decreased rate of osmotic hemolysis of cells exposed to oxygen and also decreased the effect of ozone. Trolox cancelled the oxygen effects only. Albumin, glutathione and uric acid tended to protect the cells from the hemolytic effects of ozone. The antihemolytic effect of glucose, seen only in some samples, may depend on uncontrolled factors. The alteration of the rates correlates with an increased fluidity of red cell membranes exposed to ozone.

Decrease in 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO) EPR signal in ozone-treated erythrocyte membranes.

In ozone-treated erythrocyte membrane suspension a slow decrease occurs in the EPR signal of 2,2,6,6-tetramethyl-piperidine-1-oxyl (TEMPO). Because of the absence of such a phenomenon in control membranes and ozonized buffer, this effect must be caused by reaction of nitroxide radicals with products of ozone reactions with membrane components. To find out which components are responsible for the decrease in EPR signal we studied this effect in simple model systems. The same phenomenon was observed both in lipid and protein systems treated by ozone. For unsaturated fatty acids, the correlation between the rate of decrease in EPR signal and the number of double bonds in the lipid molecule was very strong. This suggests that the observed decrease in the nitroxide radical TEMPO EPR signal in ozone-treated erythrocyte membranes is a complex process, but probably the most important reaction is recombination of nitroxide radicals with organic free radicals produced both in the process of lipid peroxidation and ozonolysis of double bonds.

Electron paramagnetic resonance studies of membrane fluidity in ozone-treated erythrocytes and liposomes.

Doxyl stearate spin probes which differed in the attachment of the nitroxide free radical to the fatty acid have been used to study membrane fluidity in ozone-treated bovine erythrocytes and liposomes. Analysis of EPR spectra of spin labels incorporated into lipid bilayer of the erythrocyte membranes indicates an increase in the mobility and decrease in the order of membrane lipids. In isolated erythrocyte membranes (ghosts) the most significant changes were observed for 16-doxylstearic acid. In intact erythrocytes statistically significant were differences for 5-doxylstearic acid. The effect of ozone on liposomes prepared from a lipid extract of erythrocyte lipids was marked in the membrane microenvironment sampled by all spin probes. Ozone apparently leads to alterations of membrane dynamics and structure but does not cause increased rigidity of the membrane.

Electron paramagnetic resonance studies of proteins in ozone-treated erythrocyte membranes.

The sulfhydryl group specific spin labels have been used to study the membrane proteins in the bovine and human erythrocyte membranes treated with ozone. The ratio hw/hs, determined from the respective peak amplitudes of the resulting EPR spectra of 3-maleimido-1-oxyl-2,2,5,5-tetramethylpyrrolidine bound to the ozone treated membranes, was shown to be elevated following an increased ozone concentration. The ratio of the central to high-field peak amplitude h0/h-1, a measure of the rotational correlation time, determined from EPR spectra of ozonized membranes covalently labeled with 4-(iodoacetamido)-1-oxyl-2,2,5, 5-tetramethylpyrrolidine was shown to be diminished. The changes in the erythrocyte membranes treated with ozone, observed for both spin labels, indicate a dose dependent increase in the mobility of membrane proteins.

Critical cell volume and shape of bovine erythrocytes.

The relationship between erythrocyte shape and the critical cell volume was investigated. Agents able to increase the critical cell volume induced three main stable shapes of erythrocytes: discocytic, stomatocytic, and echinocytic. The absence of correlation between shape and critical cell volume under isoosmotic conditions suggests that relative differences between the surface areas of the inner and the outer leaflet of the cell membrane do not influence the critical volume of a cell.

The effect of arsenate and vanadate ions on the critical cell volume of bovine erythrocytes.

Arsenate, used as an inhibitor of glycolysis, decreases the critical cell volume of erythrocytes, whereas orthovanadate, used as an accelerator of dephosphorylation of phosphatidyl-inositol-4,5-biphosphate, exerts an opposite effect. The ATP-dependent changes of the critical cell volume do not depend on the phosphorylation state of phosphatidylinositol. An interaction of the membrane skeleton with the lipid-protein matrix has been proposed as a regulation mechanism of the critical cell volume of erythrocytes.

The effect of ATP on the order and the mobility of lipids in the bovine erythrocyte membrane.

The order and the mobility of the lipids in the membrane were measured by the ESR method for the erythrocytes with both normal and modified intracellular concentration of ATP. The lipid order did not depend on the ATP level, but the lipid mobility was affected by the intracellular ATP concentration. The lipid mobility was higher in the cells with a larger concentration of ATP.

Effect of the level of ATP and of the state of spectrin on osmotic properties of bovine erythrocytes.

The effect of the intracellular level of ATP and of the state of spectrin on the critical cell volume of bovine erythrocyte was studied. The state of spectrin was changed by thermal denaturation, which for the bovine red cell took place at similar temperature as for the human erythrocyte. The increase of the ATP level and the spectrin denaturation increased the critical cell volume, while metabolic starvation decreased it. The changes of the ATP level did not influence the critical volume after the denaturation of spectrin. The results suggest that the ATP-dependent effect on the critical cell volume was caused by an alteration of the membrane extensibility due to the change of the membrane skeleton-lipid bilayer interaction(s).

The interaction of fructose-1,6-biphosphate aldolase with liposome membranes: a spin probe technique study.

Thermotropic properties of liposome membranes prepared of bulk bovine erythrocyte membrane lipids, native, or aldolase-modified, were investigated by the ESR method. Breaks were observed in the log 2T parallel vs 1/T plots for two spin labels: tempopalmitate and 5-doxyl-palmitate methyl ester. These phenomena have been interpreted as reflecting structural changes near the lipid bilayer polar heads region. Upon modification with aldolase, the temperature at which the breaks occurred was decreased for both spin probes.

Effect of DIDS on osmotic properties of bovine erythrocytes.

The effect of DIDS on osmotic properties of bovine erythrocytes was studied. The isoosmotic volume, the amount of intracellular solutes, and the osmotically non-active volume were not influenced by DIDS. An increase of osmotic fragility of erythrocytes upon DIDS treatment was evident and identical both in NaCl and in NaCl + KCl hypotonic solutions. These results suggest that the critical cell volume decreases. The link between the effect of DIDS on the membrane skeleton extractability and on the osmotic fragility was postulated.

Osmotic properties of bovine erythrocytes aged in vivo.

The osmotic properties of bovine erythrocytes aged in vivo were studied by the modified microhematocrit method. The osmotic fragility of older red cells decreases due to their larger relative osmotically non-active volume. Relative critical cell volume of bovine erythrocytes does not alter significantly with cell age. The age dependent change in the osmotic fragility of human red blood cells, the reverse of that found for bovine erythrocytes, is due to a different alteration of the critical cell volume during intravascular erythrocyte aging.

A method for the determination of the filtration coefficient for spherical bilayers prepared from bulk erythrocyte membrane lipids.

Water transport through spherical lipid bilayers consisting of bovine red cell lipids has been studied. A new experimental method for the determination of volume flow induced by concentration gradient is described. Changes of the filtration coefficient indicate phase transition in membrane lipid taking place at 33-36 degrees C.

Modification of some properties of spherical lipid membranes induced by the association with fructose-1,6-bisphosphate aldolase.

The influence of fructose-1,6-bisphosphate aldolase, as a membrane peripheral protein, on some electrical and transport properties of spherical lipid membranes was investigated. It was found that the association of the enzyme with the membrane did not effect markedly the electrical conductance or capacity of the membrane but decreased the water filtration coefficient and the cationic transferance number. The enzyme association also modifies temperature characteristics of the membrane parameters.

Phase transitions in spherical bilayer membranes prepared of bulk erythrocyte membrane lipids.

The phase transitions of spherical lipid bilayers built of bovine red cell lipids have been studied. The electrical and ESR measurements revealed some conformational changes in lipid bilayers taking place at 36-38 degrees C.

The effects of glutaraldehyde and osmium tetroxide on the erythrocyte membrane. A spin label study.

A nitroxide spin label probe technique was applied to study the interaction between glutaraldehyde or osmium tetroxide (OsO4) amd the membranes of horse erythrocytes, ghosts and liposomes prepared from erythrocyte lipids. Two major conclusions have been established: (1) Reaction of the fixation reagents with the membrane is selective. OsO4 reacts predominantly with lipids and glutaraldehyde with membrane proteins. (2) The lipid-protein interactions change after pretreatment by OsO4 or glutaraldehyde.