[The functional state of the mitochondrial respiratory chain of the small intestine enterocytes of the rats under the low dose rate X-ray total external exposure].

The influence of the low-rate ionizing radiation (0.055 Gy/min) at the doses of 0.1; 0.5 and 1.0 Gy on the functional state of the mitochondria respiratory chain of the rat small intestine enterocytes was investigated. The dysfunction of the electron transport chain enzymes and changes in the content of cytochromes b, c, a in the mitochondrial inner membrane were revealed 1, 12 and 24 hours after exposure to radiation. The revealed disorders indicate early membrane sensitivity to the radiation effect. The inhibition of the H+ -ATPase activity in the studied dose range indicates the decrease of the mitochondrial energy capacity.

[Functioning of the antioxidant system in epithelial cells of small intestine under the influence of ionizing radiation of low dose rate].

The investigations of the functional state of the antioxidant system in epithelial cells from rat small intestine in dynamics after X-ray irradiation (0.1; 0.5 and 1.0 Gy) at a low absorbed dose rate (55 mGy/min) were performed. The obtained results point out the ambiguity of the antioxidant system reaction to the activation of oxidative processes at different doses of irradiation. The multidirectional changes of these antioxidant enzymatic activities whose functioning is characterized by the early post-irradiation recovery depending on the value of the absorbed dose were observed. The sensitivity of superoxide dismutase, glutathione transferase and glutathione peroxidase in mitochondria of epithelial cells to the irradiation exposure in the investigated range of absorbed doses was shown.

[Effect of chronic ionizing irradiation on the structural properties of the apical and mitochondrial membranes of small intestine enterocytes].

The different ways of the radiation-induced effect were revealed in the investigations of chronic ionizing radiation influence in total doses of 0.3, 0.6 and 1.0 Gy (0.0072 Gy/day) on the structural properties of the apical and of the mitochondrial membranes of small intestine enterocytes. The modification of the physical properties of the membrane surface area, the decrease of the structural order of the lipid component and conformational changes of the proteins were shown to be specific for the apical membrane. The disturbance of the dynamic properties and topography of the internal mitochondria membrane was revealed in the investigation of the inductive-resonance energy transfer between the pairs of the fluorophores: tryptophan-pyrene, tryptophan-ANS, pyrene-ANS.

[The comparative characteristics of the transmembrane ionic currents and the caffeine-induced responses of the smooth-muscle cells in the normal jejunum and under ionizing radiation exposure]. / Sravnitel'naia kharakteristika transmembrannykh ionnykh tokov i kofeinindutsirovannykh otvetov gladkomyshechnykh kletok toshchei kishki v norme i pri vozdeistvii ioniziruiushchei raidatsii.

A comparative investigation of transmembrane ion currents and caffeine-induced responses of single smooth muscle cells isolated from the circular layer of rat small intestine was carried out by the method of "patch-clamp". No reliable difference in potential-dependent and amplitude-kinetic characteristics of transmembrane ion currents in cells of intact and irradiated with dose of 3 Gy rats was revealed. In cells of irradiated animals external application of caffeine (4 mM) was not accompanied by strong quick-inactivated transient Ca(2+)-dependent potassium current as in control. The results obtained suggest that single whole-body X-ray irradiation with dose of 3 Gy does not lead in 5 days to any reliable alteration of potential-controlled channels of rat small intestine smooth muscle cell plasma membranes causing at the same time the disturbance of Ca-binding function of intracellular pools.

[Study of physical properties of the apical membrane of enterocytes of rat small intestine under the effects of ionizing radiation]. / Issledovanie fizicheskikh svoistv apikal'noi membrany énterotsitov tonkogo kishechnika krys pri vozdeistvii ioniziruiushchego izlucheniia.

The effect of X-ray radiation in doses of 1.0 and 3.0 Gy (1 day after irradiation) on physical properties of the apical membrane of rat small intestine enterocytes is studied. It is shown that the fluidity of the bulk lipids doesn't change but the fluidity of the boundary lipids increases after irradiation. The data on quenching of the tryptophane fluorescence by pyrene and magnesium ions indicates apparently the irradiation--induced protein aggregation in membrane.

[Effect of ionizing radiation on the structure and functional properties of the basolateral membrane of small intestine enterocytes]. / Vliianie ioniziruiushchei radiatsii na strukturu i funktsional'nye svoistva bazolateral'noi membrany énterotsitov tonkogo kishechnika.

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.

[The use of a model water-lipid system for the study of the electric function of Ca2+, Mg2+-ATPase of the sarcoplasmic reticulum]. / Ispol'zovanie model'noi vodno-lipidnoi sistemy dlia izucheniia élektricheskoi funktsii Ca2+, Mg2+-ATP-azy sarkoplazmaticheskogo retikuluma.

The method of dynamic capacity in the model organic phase-water system was used to investigate a possibility of studying the electrical function of Ca2+,Mg2+-ATPase from sarcoplasmic reticulum of the rabbit hind limb skeletal muscles. Decane and decane solution of azolectin were used as an organic phase. It is stated that in the model systems the sarcoplasmic reticulum Ca2+,Mg2+-ATPase did not cause ATP-dependent changes in the boundary Volta potential (delta phi) irrespective of the presence of polyvalent cation chelates in the organic phase. The fragmented sarcoplasmic reticulum is able of realizing Mg-ATP, Ca2+-dependent generation of delta phi only with phospholipids present in the organic phase. It is supposed that generation of delta phi of the fragmented sarcoplasmic reticulum is due to the active transport of calcium ions by the reticulum Ca2+,Mg2+-ATPase.

[Structural changes in the sarcoplasmic reticulum membrane of skeletal muscles at the early stage of x-ray irradiation]. / Strukturnye izmeneniia membran sarkoplazmaticheskogo retikuluma skeletnykh myshts na rannem étape rentgenovskogo oblucheniia.

A single X-ray irradiation of the rabbit hindlimbs in a dose of 0.24 C/kg evokes a decrease in fluorescence of the ANS probe bound with membranes of the sarcoplasmatic reticulum as a result of the decrease of binding sites, binding constant as well as the quantum output of the probe. A decrease in fluorescence of tryptophan residues of Ca-ATPase localized in membranes and attenuation of interaction of its SH-group with dithionitrobenzoic acid has been also observed at early postradiation terms (1 and 24 h). The obtained results evidence for structural rearrangements occurring in membranes of the sarcoplasmic reticulum under the effect of ionizing radiation. Changes in conformation of CA-ATPase molecules contribute much to this process.

[Electrogenic activity of Ca2+-ATPase fragments of the sarcoplasmatic reticulum during the early stages of radiation injury]. / Elektrogennaia aktivnost' Ca2+-ATPazy fragmentov sarkoplazmaticheskogoretikuluma na rannem étape ostrogo luchevogo porazheniia.

It is established that local X-ray irradiation of the rabbit hind limb produces a decrease in Ca2+, Mg2+-ATP-dependent formation of electric potentials difference on the membrane of the sarcoplasmic reticulum (SR). These results agree with the observed decrease in the Ca2+-ATPase activity of SR membranes and increase in their electric conduction after irradiation.

[The effect of ionizing radiation on Ca 2+-ATPase activity from the sarcoplasmic reticulum of rabbit skeletal muscles]. / Vliianie ioniziruiushchei radiatsii na aktivnost' Ca 2+-ATP-azy sarkoplazmaticheskogo retikuluma skeletnykh myshts krolika.

It is established that a decrease in the Ca2(+)-ATPase activity in the sarcoplasmic reticulum membranes 1 and 24 hours after the local X-ray irradiation of rabbit hind limb by a dose of 0.21 Cl/kg is caused mainly by a change in the enzymic microenvironment and a damage of native protein-lipid interactions essential for the functional activity of Ca2(+)-ATPase.

[The effect of ionizing radiation with low dose rate on the state of electron transfer chain of enterocyte mitochondria of rat small intestine].

The influence of ionizing radiation with low absorbed dose rate (55 mGy x min(-1)) in 1, 12 and 24 hours after irradiation in doses of 0.1; 0.5 and 1.0 Gy on functional state of the electron transfer chain of the rat small intestine mitochondria was investigated by assessment of the oxygen consumption rate. The uncoupling of oxidation and phosphorylation, a decrease of phosphorylation rate and inhibition of ATP hydrolysis reactions were established in mitochondria in dependence on the irradiation dose and time interval after irradiation. The functional peculiarities of the oxidation-phosphorylation coupling sites of the mitochondrial electron transfer chain were detected.

[The content of phospholipids and free fatty acids in the sarcoplasmic reticulum membranes in the early stage of an x-ray radiation lesion]. / Soderzhanie fosfolipidov i svobodnykh zhirnykh kislot v membrannakh sarkoplazmaticheskogo retikuluma na rannem étape porazheniia rentgenovskim izlucheniem.

One and 24 h following single X-irradiation (0.21 C/kg) of rabbit hind leg the content of free fatty acids and phospholipid lysoforms increased in the sarcoplasmic reticulum (SR) membrane of skeletal muscles. The results obtained are important in estimating the mechanisms of action of ionizing radiation on the structural and functional properties of SR.

[Effects of irradiation on fatty acid structure of membrane lipids of the sarcoplasmic reticulum]. / Deistvie rentgenovskogo izlucheniia na zhirno-kislotnyi sostav lipidov membran sarkoplazmaticheskogo retikuluma.

It has been shown that single local X-irradiation (0.21 C/kg) of the rabbit hind limb in the early period of acute radiation injury (1 and 14 h) causes a decrease in saturation of sarcoplasmic reticulum membrane lipids. It is mainly connected with a decreased saturation of the total fraction of phosphatidyl serine, phosphatidyl inositol and phosphatidyl choline. The above changes can increase permeability of the sarcoplasmic reticulum membranes for Ca(2+)-ion after X-irradiation.

[The role of Ca2+-ATpase and its hydrophobic component in the release of Ca2+ from skeletal muscle sarcoplasmic reticulum]. / Uchastie Ca2+-ATPazy i ee gidrofobnogo fragmenta v osvobozhdenii Ca2+ iz sarkoplazmaticheskogo retikuluma skeletnykh myshts.

The Ca2+ permeability of proteoliposomes containing Ca2+-ATPase of sarcoplasmic reticulum and its hydrophobic fragment was investigated, using the method of synthetic penetrant ions and the radioisotopic method. The former method was used to determine the diffusional membrane potential formed by Ca2+ concentration gradient. It was demonstrated that Ca2+-ATPase, whose active center is oriented outside, has and asymmetric conductivity, i. e., it facilitates the rapid efflux of Ca2+ from proteoliposomes. This efflux is stimulated by the membrane potential positive inside. The hydrophobic fragment of Ca2+-ATPase forms a Ca2+-channel with a high conductivity for Ca2+. This channel is responsible for the Ca2+ efflux from sarcoplasmic reticulum.

[Ionic permeability of sarcoplasmic reticulum membranes damaged by x-rays]. / Ionnaia pronitsaemost' membran sarkoplazmaticheskogo retikuluma pri porazhenii rentgenovskim izlucheniem.

As early as 1 and 24 h following single local X-irradiation (0.21 C/kg) of rabbit hindlimbs an increase was noted in the permeability of skeletal muscle sarcoplasmic reticulum membranes for Ca2+, K+ and Na+. The effect was maximum 1 h after irradiation and more pronounced for K+ and Na+ than Ca2+.

[The effect of ionizing radiation on the structure of the hydrophobic fragment of Ca-ATPase in skeletal muscle sarcoplasmic reticulum]. / Vliianie ioniziruiushchei radiatsii na strukturu gidrofobnogo fragmenta Ca-ATFazy sarkoplazmaticheskogo retikuluma skeletnykh myshts.

Early (1 and 24 h) after X-irradiation with a dose of 0.21 C/kg changes occurred in the acceptability of the polypeptide chain parts of sarcoplasmic reticulum Ca-ATPase for the effect of trypsin. The analysis of the results of studying the structural and functional properties of a hydrophobic fragment of this enzyme in the control and after irradiation permitted to define the part of the Ca-ATPase polypeptide chain that provided ion selectivity of the fragment.