Interaction of free fatty acids with the erythrocyte membrane as affected by hyperthermia and ionizing radiation

The interference of hyperthermia and ionizing radiation, respectively, with the effects of capric (100), lauric (120), myristic (140), oleic (cis-181) and elaidic (trans-181) acids on the osmotic resistance of human erythrocytes was investigated. The results are summarized as follows: (A) not only at 37°, but also at 42° and 47°C lauric acid (120) represents the minimum chain length for the biphasic behaviour of protecting against hypotonic hemolysis at a certain lower concentration range and hemolysis promotion at subsequent higher concentrations; (B) with increasing temperatures the protecting as well as the hemolytic effects occur at lower concentrations of the fatty acids; (C) the increase of temperature promotes the extent of hemolysis and reduces the extent of protection against hypotonic hemolysis; (D) Gamma-irradiation of erythrocytes selectively affects the concentration of oleic acid at which maximum protection against hypotonic hemolysis occurs, without altering the minimum concentration for 100% hemolysis.     

Effect of thiol reagents and ionizing radiation on the permeability of erythrocyte membrane for spin-labeled non-electrolytes

Four different thiol reagents: p-chloromercuribenzoic acid (pCMB), mercuric chloride (HgCl2), N-ethylmaleimide (NEM), and 5,5'-dithiobis-(2-nitrobenzoic acid) (DTNB) were employed as agents modifying the transport of a hydrophilic and hydrophobic non-electrolyte spin labels: 4-hydroxy-2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPOL) and 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) into bovine erythrocytes. Gamma-irradiation of erythrocytes amplified the effects of pCMB, HgCl2 and NEM of inhibition of TEMPOL transport and attenuated them in the case of TEMPO transport. These results suggest that the transport of TEMPOL across the erythrocyte membrane is controlled by both superficially and more deeply located membrane -SH groups while only superficial -SH groups control the transport of TEMPO. The lower extent of inhibition of TEMPO transport indicates a higher contribution of diffusion through the lipid phase to the transport of TEMPO across the erythrocyte membrane as compared with TEMPOL.     

Effect of ionizing radiation and Fe2+-induced peroxidation on the lipid phase of erythrocyte membrane preparations

The fluorescent probes, perilene and diphenyl hexatriene, were used to study changes in the lipid phase of erythrocytic ghosts induced by ionizing radiation (100-1000 Gy) and lipid peroxidation initiated by Fe2+ (5-100 microM). Both of the factors were shown to bring about similar changes in the membrane, that is, an increase in the viscosity of the probe localization sites and a decrease in diphenyl hexatriene fluorescence intensity. During the postirradiation incubation of the exposed membranes they were additionally damaged whereas upon peroxidation, most of the changes occurred after 15-min incubation with Fe2+.     

Effect of thiol reactive reagents and ionizing radiation on the permeability of erythrocyte membrane for non-electrolyte spin labels

Summary The paper presents some results on the effect of PCMB and NEM on the transport of non-electrolyte spin labels: TEMPO and TEMPOL across non-irradiated and irradiated porcine erythrocyte. Irradiated erythrocytes exhibited increased inhibitory effect of thiol reactive compounds in the TEMPO and TEMPOL transport compared to non-irradiated erythrocytes.     

Exposure to ionizing radiation decreases hemoglobin binding to erythrocyte membrane

The influence of gamma-radiation at doses 10, 10(2) and 10(3) Gy on binding of hemoglobin to the erythrocyte membrane by inductive--resonance energy transfer in the donor-acceptor pair anthracene-hemoglobin was studied. It was found that binding of hemoglobin to the erythrocyte membrane decreases with increasing dose of gamma-radiation.     

Modification of rat thymocyte membrane properties by hyperthermia and ionizing radiation.

Thymocytes are one the most widely used cell models for the study of radiation-induced interphase death. This cell-type was chosen for the study of hyperthermic and radiation effects on two membrane-related processes implicated in the interphase death of cells: Na+-dependent 2-aminoisobutyric acid (AIB) transport and cyclic 3'-5' adenosine monophsophate formation. The response of AIB transport to heat is dose-dependent, but the biphasic thermal response curve (AIB uptake versus time) differs fom the sigmoidal radiation response curve. Heating thymocytes for 20-30 min at 43 degrees C stimulates AIB uptake. Additional heating at 43 degrees C, however, markedly reduces AIB uptake. Despite the immediate stimulating effect of heat (30 min at 43 degrees C), the thymocyte has already developed irrepairable impairments, as demonstrated by the fractionated heating experiments. The heat-induced impairment of AIB uptake is mainly on the Na+-dependent component of neutral amino-acid transport, affecting primarily the maximal rate of uptake, i.e. Vmax. Additional evidence for heat-induced plasma membrane damage is the alteration in cAMP levels. Heating thymocytes for 30 min or longer at 43 degrees C causes a massive rise in cAMP level within the cell. This differs from thymocytes exposed to radiation where no rise in cAMP is observed.     

Effect of the dose rate on the synergism of combined ionizing radiation and hyperthermia

In experiments with yeast cells it was shown that the synergistic effect of a combination of ionizing radiation and hyperthermia is a function of dose rate. It was demonstrated that the temperature at which radiation is delivered should be elevated to obtain the maximum synergistic effect with the increasing dose rate.     

Membrane effects of ionizing radiation and hyperthermia

Results of numerous studies demonstrate that membranes are important sites of cell damage by both ionizing radiation and hyperthermia. Modification of membrane properties (mainly lipid fluidity) affects the cellular responses to radiation and hyperthermia but former concepts that membrane rigidification sensitizes cells to radiation while membrane fluidization potentiates hyperthermic damage have now been seriously challenged. It seems that the effects of membrane fluidity on cell responses to hyperthermia and radiation are due to an indirect influence on functional membrane proteins. The major role of lipid peroxidation in radiation damage to membranes has also been questioned. The existing evidence makes it unlikely that the interaction between radiation and hyperthermia is determined by the action of both agents on the same membrane components.     

The effect of ionizing radiation on Ca ATPase of erythrocyte membranes

Erythrocyte ghosts were irradiated with doses of 4 x 10(-3)-10(3) Gy. The activity of Ca(2+)-ATPase, the kinetic characteristics of enzyme reaction, the Hill's coefficient, the association constant and a number of La3+ linking centers were determined. The structural--functional peculiarities of Ca(2+)-ATPase changes under exposure to 4 x 10(-3) and 40 Gy of ionizing radiation have been established.     

Effect of gamma radiation on the transport of spin-labeled compounds across the erythrocyte membrane

Summary The effect of ionizing radiation on the non-electrolyte, anion and cation permeability of the erythrocyte membrane was studied by measurement of the reduction rate of appropriate nitroxyl derivatives. Irradiation of bovine erythrocytes in the dose-range of 2–50 krad resulted in a regular dose-dependent increase in the reduction rates of a cation (TEMPO-choline) and a hydrophobic non-electrolyte (TEMPO), and non-regular changes in the reduction rate of a hydrophilic non-electrolyte (TEMPOL). The permeation constant for TEMPO-choline also showed a non-regular response to radiation, similar to the response pattern of other red blood cell parameters. These results also demonstrate that the effects of radiation on the transport of various solutes can be used as a means of distinguishing between different channels of membrane transport.     

Recovery of yeast cells after exposure to ionizing radiation and hyperthermia

Quantitative regularities of recovery of wild-type diploid yeast cells irradiated with gamma-rays (60Co) simultaneously with exposure to high temperatures were studied. It was shown that in conditions of such a combined action the constant of recovery did not depend on the temperature at which the irradiation was carried out. However, with an increase of acting temperature an augmentation in the portion of irreversible component was registered. The analysis of cell inactivation revealed that the augmentation of the irreversible component was accompanied by a continuous increase of cell killing without any postirradiation division after which cells are incapable of recovery. The reproductive death was mainly exerted after ionizing radiation applied alone while in conditions of simultaneous thermoradiation action the interphase killing (cell death without division) predominated. It is concluded on this base that the mechanism of synergistic interaction of ionizing radiation and hyperthermia may be related with cardinal change in mechanisms of cell killing.     

Temperature-dependent abnormalities of the erythrocyte membrane in porcine malignant hyperthermia

The temperature dependence of ATPase activities and stearic acid spin label motion in red blood cells of normal and MH-susceptible pigs have been examined. Arrhenius plots of red blood cell ghost Ca-ATPase and calmodulin-stimulable Ca-ATPase activities were identical for both normal and MH erythrocyte ghosts. Arrhenius plots of Mg-ATPase activity exhibited a break (defined as a change in slope) at 24 degrees C in both MH and normal erythrocyte ghosts. However, below 24 degrees C the apparent activation energy for this activity was less in MH than normal ghosts. To determine whether breaks in ATPase Arrhenius plots could be correlated with changes in the physical state of the red blood cell membrane, the spin label 16-doxyl-stearate was introduced into the bilayer of both erythrocyte ghosts and red blood cells. With both ghosts and intact cells, at each temperature examined, the mobility of the probe in the lipid bilayer, as measured by electron paramagnetic resonance, was greater in normal than in MH membranes. While there were no breaks in Arrhenius plots for probe motion in the erythrocyte ghosts, the apparent activation energy for probe motion was significantly greater in normal than in MH ghost membranes. While there was no break in the Arrhenius plot of probe motion in normal intact red blood cell membranes, there were breaks in the Arrhenius plot of probe motion at both 24 and 33 degrees C in intact MH red blood cell membranes. Based on the altered temperature dependence of Mg-ATPase activity and spin probe motion in membranes derived from MH red blood cells, we conclude that there may be a generalized membrane defect in MH pigs which is reflected in the red blood cell as an altered membrane composition or organization.     

Recovery of yeast cells following the combined action of hyperthermia and ionizing radiation

Consecutive action of elevated temperature (50 degrees C) and gamma-irradiation on yeast cells Saccharomyces cerevisiae was studied. It was shown that yeast cells can recover from lethal thermal and radiation lesions after the combined action of the two factors. The efficiency of recovery does not depend upon the sequence of treatments. Heating (50 degrees C) before or after gamma-irradiation increases the radiation response of yeast when plating the cells on a nutrient agar containing 1.5 M KCl. The synergistic effect decreases with yeast cells kept in water at 28 degrees C before plating. The influence of one factor on the effectiveness of recovery from damages induced by the other was estimated.     

Effect of adenine nucleotides and gamma radiation on the transport of TEMPOL across the erythrocyte membrane

External adenine compounds bring about changes in the transport of hydrophilic molecules across control and irradiated bovine erythrocyte membranes. Changes in the transport induced by incubation of erythrocytes with nucleotides depend on the type of nucleotide and its concentration. The range of nucleotide concentrations over which the stimulatory effect on the transport occurs is established.     

The action of osmolytes on the destructive effect of ionizing radiation,hyperthermia, microwave radiation,and ultrasound

New data on the influence of osmolytes (NaCl, glycerol) on the destructive effect of ionizing radiation, hyperthermia, microwave radiation and ultrasound were obtained from experiments with bacterial cells. The pattern of manifestation of the osmolyte protective effect is presented. It was found that the protective effect of osmolytes from damaging factors (antagonistic interaction) can be detected only within a certain range of agent “doses.” Inside this range, there is an optimum providing the maximum protection. It was shown that, to provide the highest antagonistic effect with increased intensity of one of the agents, a corresponding change in the intensity of the other agent involved in the interaction is required. It is concluded that, in addition to DNA damage, membrane injury and osmotic homeostasis system may be considered as critical targets in cell destruction after the combined action of various environmental factors.     

Mathematical model of a simultaneous combined effect of ionizing radiation and hyperthermia

A mathematical model has been proposed suggesting that the synergistic action of a combination of ionizing radiation and hyperthermia is conditioned by additional lethal damages arising from the interaction of "sub-lesions" induced by both agents. The model describes quantitatively the synergism of the combined action of the agents used and predicts the maximal value of the synergistic effect and conditions in which it can be achieved.     

Effect of ionizing radiation on the membrane potential and electrical input resistance of Chinese hamster fibroblast membranes

X-irradiation with a dose of 8 Gy leads to a sharp decrease in membrane potential of cultured Chinese hamster cells followed by restoration thereof. Changes in the membrane potential are accompanied by a monotonous increase of mean values of input cell resistance. It is assumed that radiation elicits a decrease in the resistance of a plasma membrane and a concurrent increase in the resistance of intercellular gap contacts which lead to impairment of cell interaction.     

Effect of ionizing radiation on the structure and functional properties of the basolateral membrane of small intestine enterocytes

The structural state and transport properties of basolateral membrane of rat small intestine enterocytes after exposure to X-ray irradiation (0.5; 1.0 and 2.0 Gy) were studied. The substantional suppression of the active Ca(2+)-transport process concomitant to versatile changes of the membrane structure involving the surface sites and intramembrane protein-lipid complexes was revealed one day after irradiation. Taking into account the early obtained data on apical membrane functional disorders these results confirm that ionizing radiation in sublethal doses induces the structure-function modification of enterocyte plasma membrane affecting the function of the small intestine epithelial cells.