[The role of thyroid hormones in the regulation of electric stability of erythrocyte membranes in rats]. / Rol' tireoidnykh gormonov v reguliatsii élektricheskoi stabil'nosti membran éritrotsitov krysy.

A method of electric breakdown was used for a study of electric stability (durability) of the membranes of erythrocytes isolated from the blood of normal rats and rats with hypo-, hyperthyrosis and thyrotoxicosis. Erythrocytic membrane electric durability was shown to depend on the hormonal status. In particular, an increase in the potential of breakdown of erythrocytes of hyperthyroid rats was shown in comparison with the characteristics of erythrocytes of the other studied populations. Judging by the test thyrotoxicosis was accompanied by a decrease in a degree of physical homogeneity of erythrocytic membranes. There were no differences in electric durability between erythrocytes of normal and hyperthyroid animals.

[Effect of thyroid hormones on the physico-chemical properties of lipids in the liver mitochondria of rats]. / Vliianie tireoidnykh gormonov na fiziko-khimicheskie svoistva lipidov mitokhondrii pecheni krysy.

The administration of thyroxine to rats (300 micrograms per 100 g of body mass intraperitoneally) resulted in a decrease in the content of cardiolipin, cholesterol and an increase in lysophosphatidylethanolamine in rat mitochondria as compared to normal in 48 hours. During the registration of spin-labeled mitochondrial lipids using the EPR method thyroid-related changes in the regulation parameter on Arrenius' charts were detected suggesting the regulation of the physical state of mitochondrial lipids by thyroid hormones. It was assumed that the observed hormone-related modifications of the physicochemical state of mitochondrial lipids illustrated the membranotropic mechanism of the regulation of mitochondrial functions by thyroid hormones.

[Characteristics of the levels of various nucleic acid precursors in the tissues of rabbits with various thyroid conditions]. / Osobennosti soderzhaniia nekotorykh predshestvennikov nukleinovykh kislot v tkaniakh krolikov s razlichnym tireoidnym sostoianiem.

The content of the precursors and metabolites of nucleic acids in the brain and liver of normal rabbits, rabbits with hypothyrosis (thyroidectomy) and hyperthyrosis (100-150 Mg of L-thyroxine per 1 kg of body mass daily for 10-12 days) was determined by liquid chromatography with a high resolution. A decrease in the content of deoxyguanosine, thymine, hypoxanthine, cytosine, thymidine and an increase in the content of inosine, adenine and adenosine in the liver of animals with hypothyrosis were shown. In the brain of these rabbits the level of cytidine was lowered, and the levels of deoxyguanosine, thymine, inosine, hypoxanthine, adenine and uracil were on an increase. An increase in the levels of deoxyguanosine, thymine, adenine, thymidine and a decrease in the levels of cytidine, hypoxanthine, cytosine, adenine and uracil in the liver were noted in hyperthyrosis. In the brain of rabbits with hyperthyrosis an increase in the levels of deoxyguanosine, cytidine, inosine and adenine was combined with a decrease in the levels of thymine and hypoxanthine. These thyroid-dependent changes in the content of registered metabolites and precursors of nucleic acids in tissues suggest that the observed shifts illustrate one of many mechanisms of the regulation of cell metabolism by thyroid hormones.

[Effect of thyroid hormones on heat-induced changes in the EPR-spectra of erythrocytes]. / Vliianie tireoidnykh gormonov na termoindutsirovannye izmeneniia EPR-spektrov éritrotsitov.

An increase in the fluidity of membranes in experimental hyperthyreosis of rats was shown by the registration of EPR-signals labeled with spin probe (5-dosilsterate). Modifications of the physical state of erythrocytic membranes induced in vivo by thyroid hormones were shown to depend on the fatty acid composition of food fats. Thus, the simulation of hyperthyreosis against a background of a diet with more viscous fats (pork lard) was accompanied by a decrease in the fluidity of erythrocytic membranes, whereas food enrichment with polyunsaturated fats (sunflower oil) inhibited the effect of hyperthyreosis on the structural state of membranes. An increase in the fluidity of membranes also resulted from the incubation of erythrocytes of normal animals with physiological concentrations of triiodothyronine (10(-9) M). Under these conditions adding up of thyroxine (10(-7) M) prevented the effect of the first hormone on the structure of membranes. It was assumed that a modifying effect of thyroid hormones in vivo was partially based on rearrangements in the fatty acid composition of membrane lipids.

[Blocking effect of cycloheximide on decreased mitochondrial resistance due to thyroid hormone action]. / Blokiruiushchee vliianie tsiklogeksimida na snizhenie rezistentnosti miokhondrii, vyzvannoe deistviemtireoidnykh gormonov.

Administration of cycloheximide (20-25 micrograms/kg bw twice, interval 24 h) to hyperthyroid rats (300 micrograms/T4/100 g bw i. p. 48 h before sacrifice) inhibited the decrease in mitochondrial resistance to Ca2+ characteristic of hyperthyroidism. It was established in particular that calcium capacitance of the mitochondria and the time of the maintenance of transmembrane potential of these organelles under calcium loading were increased in the mitochondria of hyperthyroid animals given cycloheximide as compared with analogous parameters of the organelles of intact hyperthyroid rats. Moreover, the fluorescence intensity of NADPH in the mitochondria of the first group of animals was 37% greater and the rate of oxidation of these nucleotides several times lower than in the organelles of the second group animals. It is assumed that the described effects of cycloheximide on the mitochondria are linked with the inhibitory effect of the antibiotic on endogenous activity of mitochondrial phospholipase A2.

[Peroxidation of blood serum lipids in rabbits with various thyroid functions]. / Perekisnoe okislenie lipidov syvorotki krovi krolikov s razlichnym tireoidnym sostoianiem.

Chemiluminescent properties of blood serum from rabbits with hypo-, normo- and hyperthyroidism were investigated. The ferrum-induced chemiluminescence of the serum was shown to be decreased both in hypo- and in hyperthyroidism as compared with the normal state. The oxidative capacity of the main substrate of the peroxidation in blood serum--apo-B containing lipoproteins--did not markedly differ in various states of thyroid gland. The efficiency of branched free radical chains was dissimilar; these data suggest that the content of lipid-soluble antioxidants was increased in the lipoproteins in hypo- and decreased in hyperthyroidism. Measuring of the chemiluminescence quenching in the standard chemiluminescent system indicated that the content of water-soluble antioxidants was increased in blood of animals both with hypo- and hyperthyroidism. However, a higher content of water-soluble antioxidants was noted in blood of rabbits with hypothyroidism as compared with the animals with hyperthyroidism.

[Electrical stability of mitochondrial membranes: the role of thyroid hormones and the fat component of the diet]. / Elektricheskaia stabil'nost' membran mitokhondriii: rol' tireoidnykh gormonov i zhirovogo komponenta diety.

Electric stability of the membranes of the mitochondria and liposomes formed from mitochondrial lipids was studied. The mitochondria were isolated from the liver of euthyroid or hyperthyroid rats kept on the diets with varying degree of food fat unsaturation. In the first group animals, butter was used as a fatty component of the diet whereas the second group animals received sunflower oil. The electric stability of the membranes of the mitochondria and respective liposomes appeared lower in the first group animals as compared with those in the second group animals. Hyperthyrosis was accompanied by the increased electrical stability of mitochondrial lipids in both the groups. At the same time the liposomal membranes were similar as regards the electric stability, whereas the electric stability of the mitochondrial membranes in the first group hyperthyroid and euthyroid rats was lower than in the organelles of the second group animals. It is thus assumed that the electric stability of the mitochondria is determined not only by the chemical composition of lipids but also by other factors.

[Thyroid hormones and the level of divalent iron ions in the rabbit liver]. / Tireoidnye gormony i soderzhanie ionov dvukhvalentnogo zheleza v pecheni krolikov.

Experimental hypothyreosis in animals was obtained by means of extirpation of thyroid gland; hyperthyreosis was obtained by thyroxine injections intraperitoneally for 10 days. Content of Fe2+ ions of the free pool (not bound with ferritine) was estimated with the ESR method, after treatment with sodium nitrite. A decrease in Fe2+ ions content is observed in liver homogenate of hypothyroid rabbits, and an increase is observed in that of the hyperthyroid animals. Content of Fe2+ ions in cells of liver tissues correlates with the oxidation capacity of the mitochondrial lipids. The changes in the rate of lipid peroxidation under thyroid pathology is supposed to result from changes in free ferrum content.

[Thyroid hormones and the electrical stability of rat liver mitochondrial membranes]. / Tireoidnye gormony i élektricheskaia stabil'nost' membran mitokhondri pecheni krys.

The electrical stability of mitochondrial membranes isolated from the liver of normal, hypothyroid, hyperthyroid (0.1 mg L-thyroxine per 100 g bw for 9 days) and thyrotoxic (4 mg L-thyroxine per 100 g bw for 6 days) rats was investigated. The electrical stability of mitochondrial membranes was estimated by the amount of potassium acetate required for electrical breakdown of the mitochondria. Of the four mitochondrial populations, the organelles of hyperthyroid and thyrotoxic animals had the most stable membranes, whereas the electrical stability of the mitochondria of normal and hypothyroid rats was approximately the same. It is assumed that the increased electrical stability of the mitochondria seen in hyperthyroid conditions is linked with the hormone-induced modifications in the composition of membrane phospholipids rather than with a direct action of excess thyroxine on the organelles.

[Role of hyperthyroidism and the fatty component of the diet in changes in the fatty acid composition of the liver mitochondrial lipids in rats]. / Rol' gipertireoza i zhirovogo komponenta diety v modifikatsiiakh zhirno-kislotnogo sostava lipidov mitokhondrii pecheni krysy.

The influence of hyperthyrosis and the diet fat component on the hepatic mitochondrial fatty-acidic content was studied in Wistar rats. The animals, divided into two groups, were kept within 20 days on synthetic diets enriched with proteins (18%), carbohydrates (56%), fats (26%), vitamin and salt mixtures. The first group of animals was given the butter diet ("B" group) and the second one received the sunflower-seed oil ration ("S" group). It was found that after three weeks from the beginning of the diet the content of hepatic mitochondrial fatty acids was changed according to the fatty-acidic spectrum of alimentary fats. However, the fatty acid unsaturation indices, i.e. the unsaturated fatty acid % X unsaturated bond number, were not different in both mitochondrial populations studied. Hyperthyrosis (induced by 50 micrograms of thyroxin/100 g body weight within 5 successive days intraperitoneally), simulated in the presence of the above diets, not only intensified changes, caused by the diet in the mitochondrial fatty acid content, but induced further variance in the fatty-acidic spectra, being distinctly seen in the "B" group animals. In particular, hyperthyrosis in these animals was accompanied by a fall of linoleic (25%) and arachidonic (36%) acids in the mitochondrial lipid content, being the main cause of decreasing the mitochondrial lipid unsaturation indices by 26%. The alteration of lipid parameters in mitochondria of hyperthyroid animals of the "S" group was less pronounced, being 6%, 11% and 9%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of thyroid state on the phospholipid regeneration rate of rat liver mitochondria]. / Vliianie tireoidnogo sostoianiia na skorost' obnovleniia fosfolipidov mitokhondrii pecheni krys.

The rate of phospholipid renewal in mitochondria of normal, hypothyroid, hyperthyroid and thyrotoxic rats was studied. Mitochondria were isolated from rat livers 24 and 48 hrs after administration of 3H-glycerol and 14C-palmitic acid. In mitochondria of hypothyroid animals, practically no phospholipid renewal is observed. In mitochondria of hyperthyroid and thyrotoxic rats, the rate of degradation of phospholipids labelled with glycerol, was approximately 1.5 times as low as that in controls. The decrease in the rate of renewal of the fatty acid residues in mitochondrial phospholipids was still more pronounced in hyperthyroid and thyrotoxic animals. Possible reasons for these changes connected with the thyroid state are discussed.

[Transmembrane potential of rat liver mitochondria in hypothyreosis]. / Transmembrannyi potentsial mitokhondrii pecheni krys pri gipotireoze.

Transmembrane potential in liver mitochondria of hypothyroid rats was lower than that in normal animals. In hypothyroid rat mitochondria, the system responsible for maintaining the transmembrane potential was more resistant to the disturbing action of Ca2+ions. This was manifested in both the longer period of transmembrane potential under the limited content of Ca2+ and in the increased maximal dose of Ca2+, which is required for a quick decrease in transmembrane potential. Thyroxine injection (300 micrograms/100 g mass intraperitoneally) made in 48 h almost recovered the transmembrane potential value to that in the normal animals, with a dramatic lowering of the resistance of organelles to the disturbing action of Ca2+ being observed. Apparently, the increase in the resistance of hypothyroid rat mitochondria to the disturbing action of Ca2+ is connected with a reduction in the activity of mitochondrial phospholipids and with deceleration of lipid peroxidation in the mitochondria of hypothyroid animals.

[Effect of hypothyroidism on the structural and functional characteristics of the sarcoplasmic reticulum of rabbit skeletal muscles]. / Vliianie gipotireoza na strukturnye i funktsional'nye kharakteristiki sarkoplazmaticheskogo retikuluma skeletnykh myshts krolika.

Structural and functional characteristics of sarcoplasmic reticulum vesicles (SRV) from skeletal muscle of normal and hypothyroid rabbits were investigated. The rate of Ca2+ absorption was decreased in hypothyroid animals and Ca2-ATPase activity in SRV of these animals was lower than that of control rabbits. The transport ratio (Ca2+/ATP) in hypothyroid rabbits was higher by 20% than in controls. In SRV of hypothyroid animals a decrease in the protein/lipid interaction and higher fluidity of membrane lipids were observed. Administration of L-thyroxine (300 mg/kg of body mass, intraperitoneally) normalized the SR lipids fluidity within about 40 hrs after the injection but did not affect significantly the patterns of protein/lipid interaction. Normal and hypothyroid SRV were similar in their protein spectrum as shown by electrophoresis in polyacrylamide gel. These alterations observed in the SRV structure and function are apparently related to modifications of membrane lipids.

[Thyroid hormones and phospholipase activity in rat liver mitochondria]. / Tireoidnye gormony i aktivnost' fosfolipazy mitokhondrii pecheni krys.

The rate of the hydrolysis of mitochondrial phospholipids isolated from the liver of rats given excess amount of thyroid hormones for a long time was higher than in normal animals. Activation of this process determined by endogenous phospholipase of mitochondria could be also observed in liver mitochondria isolated 2 days after a single injection of L-thyroxine into rats. It is assumed that the hyperthyrosis-induced acceleration of lipid peroxidation in these organelles might be one of the reasons for activation of endogenous phospholipase of mitochondria.

[Thyroid hormones and EPR signals of the liver, brain and blood]. / Tireoidnye gormony i signal EPR pecheni, mozga i krovi.

Experimental hypothyreosis was caused by thyroidectomy, hyperthyreosis developed after intraperitoneal administration of thyroxine into animals within 10 days. In liver and brain preparations amplitudes of EPR signals were decreased with g = 2.00 and g = 1.94, respectively, in hypothyreosis and were increased in hyperthyreosis. The ratio of these signals amplitudes was unaltered in brain tissue but in liver tissue it varied depending on thyroid status. In liver tissue intensity of other signals was increased in hyperthyreosis ad decreased in hypothyreosis, except for the signal with g = 2.25 (cytochrome P = 450) the intensity of which decreased in hyperthyreosis and increased in hypothyreosis. These phenomena appear to be relevant to various disorders of metabolism in pathologies of thyroid glands.

[Hyperthyroidism and the transmembrane potential of rat liver mitochondria]. / Gipertireoz i transmembrannyi potentsial mitokhondrii pecheni krys.

Transmembrane potential of liver mitochondria in hyperthyroid rats was higher than that in euthyroid animals. Besides, a lower resistance to Ca2+ of the system responsible for the maintenance of the transmembrane potential was observed in the preparations from hyperthyroid rats. This was manifested in a decrease of the calcium dose required for the decay of the transmembrane potential and in a shorter period of Ca2+ retention by mitochondria. The observed decrease in the resistance to Ca2+ ions of the potential-maintaining system in hyperthyroid mitochondria is supposed to be determined by the increased activity of mitochondrial endogenous phospholipase.

[Activation of lipid peroxidation in liver mitochondria of rabbits with hyperthyroidism]. / Aktivatsiia perekisnogo okisleniia lipidov v mitochondriiakh pecheni krolikov pri gipertireoze.

Lipid peroxidation (LPO) in liver mitochondria of normal and hyperthyroid rabbits was studied by recording chemiluminescence of mitochondrial suspensions, induced by Fe2+. It was shown that in mitochondria of the hyperthyroid animals, there takes place an increase in the "slow flash" amplitude of chemiluminescence and reduction in the latent period of the luminescence development, as compared to the similar phenomena in normal animals. Characteristic changes were also seen upon recording chemiluminescence of suspensions of the lipids isolated from mitochondria of normal and hyperthyroid animals. These data attest to LPO activation in liver mitochondria during hyperthyrosis. LPO activation is not the result of a direct action of thyroxine on the mitochondria, since the addition of the hormones to organelles in different concentrations (3.25 x 10(-8)- 1.6 x 10(-7) mol/mg protein) did not alter the chemiluminescence parameters. It is suggested that LPO activation seen in liver mitochondria during hyperthyrosis is determined by an increase in the unsaturated index of fatty acids of mitochondrial lipids.

[Decrease of lipid peroxidation in liver mitochondria isolated from rabbits with hypothyroidism]. / Snizhenie perekisnogo okisleniia lipidov v mitokhondriiakh, izolirovannykh iz pecheni krolikov s gipotireozom.

A study was made of chemiluminescence of mitochondria and liposomes formed of mitochondrial phospholipids obtained from the liver of normal and thyroidectomized rabbits. The Fe2+-induced chemiluminescence of mitochondria was characterized by a decrease in the amplitude of "slow flash" and by an increase in the latent period of this parameter occurrence under hypothyrosis. This is accounted for by the decreased rate of lipid peroxidation (LPO) in mitochondria, caused by the deficiency of thyroid hormones in the body. Forty-one hours after a single administration of L-thyroxine (300 micrograms/kgbw) to the rabbits the intensity of chemiluminescense of mitochondria and liposomes not only returned to that of the preparations obtained from the normal animals but even exceeded it approximately 1.5-fold. Apparently, such an abrupt intensification in LPO reactions is consequent on the increased rate of unsaturation of fatty acids in mitochondrial lipids, caused by the hormone administered.

[Hyperthyroidism: increase in the electrical stability of membranes from liver mitochondria lipids]. / Gipertireoz: uvelichenie élektricheskoi prochnosti membran iz lipidov mitokhondrii pecheni.

Electrical stability of the membranes was assessed in bilayer lipid membranes and liposomes. It was shown that the break down potential of the membranes prepared from mitochondrial phospholipids of hyperthyroid rabbits' liver is higher than that for the membranes from mitochondrial lipids of the control animals. It is suggested that the increased electrical stability of the membranes is consequent on the changes in the phospholipid content of liver mitochondrial membranes in hyperthyrosis.

[Changes in spatial organization in sarcoplasmic reticulum membranes in rabbits with experimental thyrotoxicosis]. / Izmenenie prostranstvennoi organizatsii v membranakh sarkoplazmaticheskogo retikuluma pri éksperimental'nom tireotoksikoze krolikov.

The structure of sarcoplasmic reticulum membranes (SR) of skeletal muscles from normal and thyrotoxic rabbits was studied with the use of the fluorescent probe pyrene. It was found that protein globules in SR preparations of thyrotoxic animals were submerged into the lipid bilayer to a greater extent than in the reticulum of normal animals. Electrophoresis in polyacrylamide gel revealed no detectable differences between SR of normal and thyrotoxic rabbits. The ratio protein/lipid in SR membranes remained 2:1 in rabbits with thyrotoxicosis.