[Features of vitamin D3 metabolism in liver cells in experimental diabetes mellitus]. / Osobennosti obmena vitamina D3 v kletkakh pecheni pri éksperimental'nom sakharnom diabete.

The uptake of vitamin D3 by the liver cells and its hydroxylation in the hepatocytes of rats at experimental diabetes has been studied. It is proved that in this pathology the disturbances of vitamin D3 exchange in the rat liver take place. It is concluded that the lowering of the level of absorption of vitamin D3 by hepatocytes and its transportation to these cells from reticulocytes as well as the inhibition of vitamin D3-25-hydroxylase liver systems can be the most probable cause of these disturbances.

[Vitamin D3 metabolism in the liver of pregnant rats]. / Obmen vitamina D3 v pecheni beremennykh krys.

The exchange of vitamin D3 in the liver of pregnant rats has been studied. Incorporation of (3H)-vitamin D3 into the liver of pregnant rats on the 13th and 21st day of pregnancy made up 85% and 90% respectively of the intensity of absorption of the summary label by controlled animals. It is found that the period of exchange of (3H)-cholecalciferol in these animals increases with prolongation of pregnancy. The 25-hydroxylation of vitamin D3 in the liver of rats on the 13th and 21st day of pregnancy significantly decreases and makes up 30% and 50% of its hydroxylation in the nonpregnant rats.

[Vitamin D3 transport across the intestines and its metabolism in the liver of rats with alloxan diabetes]. / Transport vitamina D3 cherez kishechnik i ego obmen v pecheni krys pri alloksanovom diabete.

Vitamin D3 intestinal transport and liver metabolism were studied in rats with alloxan-induced diabetes. The condition was induced by i.v. alloxan injection in a dose of 40 mg/kg b.m. Diabetes development was monitored by blood serum glucose measurements, carried out for 30 days. [3H]-cholecalciferol absorption in the rat intestine was found inhibited in the diabetic animals as against the reference animals, which fact results in disordered entry of vitamin D3 to the body. [3H]-cholecalciferol absorption by the liver is reduced in the examined condition, and the time of its metabolism is increased more than threefold as against the reference animals. The share of vitamin D3 hydroxylation by the liver of diabetic rats is also significantly reduced. The described disorders are responsible, among other things, for the reduction of the levels of vitamin D3 active metabolites in the blood serum of rats with experimental diabetes.

[The effect of unilateral nephrectomy on vitamin D metabolism in pregnant rats]. / Vliianie odnostoronnei nefréktomii na obmen vitamina D u beremennykh krys.

Unilateral nephrectomy causes a decrease in provision of vitamin D dihydro derivatives in pregnant rats, which correlated with the development of hypocalcemia and hypophosphatemia as well as with an increased content of parathyroid hormone. Fetuses of these females contained less amount of mineral components and active metabolites of vitamin D. Neonates, being born by these females with the nephrectomy, had vitamin D deficiency, which was manifested as a decrease in content of active vitamin D metabolites and minerals as well as an increase in activity of alkaline phosphatase and in the content of parathyroid hormone.

[Metabolism of vitamin D3 administered in liposomes in rat liver]. / Metabolizm vitamina D3, vvedennogo v liposomakh, v pecheni krys.

Incorporation of [3H]-cholecalciferol into the liver and the rate of its conversion into 25-OH-D are significantly larger after intravenous administration of this vitamin into liposomes than its dissolution in ethanol. The latter may be due to a different distribution of vitamin D3 in the cells of the liver. Incorporation of [3H]-vitamin D3 in reticulocytes suggests that its cells are a locus for storage of vitamin D, from which the latter is transported into hepatocytes where its 25-hydroxylation proceeds.

[Effect of varying vitamin D status in the body on intestinal absorption and metabolism of vitamin D in the rat liver]. / Vliianie razlichnoi obespechennosti organizma vitaminom D na ego vsasyvanie v kishechnike i metabolizm v pecheni krys.

The absorption of [3H]-vitamin D3 in the intestine and its hydroxylation in the liver were higher in vitamin D-deficient rats than in vitamin D-treated ones. The higher is the vitamin content in the organism, the greater part of the label is occupied by unchanged vitamin D3. It is supposed that both absorption of the vitamin in the intestine and its 25-hydroxylation in hepatocytes may decrease with a rise of the vitamin D3 amount. This activates a mechanism of protection from the vitamin D redundancy.

[Structural-functional changes in plasma lipoproteins during vitamin D-deficient rickets in children]. / Strukturno-funktsional'nye izmeneniia lipoproteinov plazmy krovi pri vitamin-D-defitsitnom rakhite u detei.

The lipid composition and structure of low- and high-density lipoproteins (LDL and HDL) have been studied in children with the vitamin D-deficient rachitis. An increase of the cholesterol content in the atherogenic LDL against a background of its decrease in the antiatherogenic HDL has been revealed, that is analogous to the observed changes under the atherosclerosis development in adults. Due to the studies in the amino acidic composition and determination of the nature and quantity of the charged groups of lipoprotein particles accessible for titration definite, certain disturbance in the structure of lipoproteins are observed as such that may cause disturbances in their functional activity.

[Structural properties and lipid-binding characteristics of plasma fibrinogen and gamma-globulins in vitamin D-deficient rickets]. / Strukturnye osobennosti i lipidsviazyvaiushchaia sposobnost' fibrinogena i gamma-globulinov plazmy krovi pri vitamin-D-defitsitnom rakhite.

Structure properties and lipid-binding ability of fibrinogen and gamma-globulins were studied in blood plasma of children with rickets. Content of cholesterol and its esters, developing complexes with fibrinogen, was found to increase simultaneously with a decrease in the phospholipids, containing in the protein fraction, under conditions of the disease. Surface charge of the proteins studied, especially of fibrinogen, was altered, thus demonstrating the distinct impairments of their structure and functions. Lipid environment appears to be of importance in functional activity of these proteins.

[Erythrocyte membrane proteins in experimental D-hypovitaminosis]. / Izuchenie belkov membrany éritrotsitov pri éksperimental'nom D-gipovitaminoze.

Content of rat erythrocyte membrane proteins was studied in experimental rickets as well as during treatment of the disease with various doses of vitamin D3. Distinct alterations in content of spectrin and protein 3 simultaneously with approximately constant level of membrane total proteins were observed in D-hypovitaminosis. Composition of main membrane proteins tended to be normalized after administration of vitamin D3 (400 IU) into the animals with experimental rickets within 10 days, while the vitamin at a dose exceeding 100-fold the physiological requirements, caused a decrease in the content of membrane proteins. Alterations in molecular structure of erythrocyte membranes appear to be among the factors responsible for inhibition of erythrocyte functional activity in rickets.

[Structural characteristics of integral protein-3 of rat erythrocyte membranes in hypovitaminosis D]. / Strukturnye osobennosti integral'nogo belka-3 membran érytrotsitov krys pri D-gipovitaminoze.

The amino acid composition, lipid-binding ability, the values of pK and binding capacity of negatively charged sites of the integral protein-3 from erythrocyte membranes are determined for rats in norm and under conditions of D-hypovitaminosis. Protein-3 binding of phosphatidyl choline and sphingomyelin considerably decreases, while that of cholesterol and lanosterol increases with the unchanged amino acid composition under conditions of D-hypovitaminosis. This leads to the enhancement of the protein electro-negativity as its carboxylic groups and histidine imidazole become more accessible for titration. An increase of the negative charge of protein-3 with D-hypovitaminosis is supposed to be responsible for inhibition of the anionic transport realized by it through the forces of electrostatic repulsion.

[Effects of sterols having different chemical structure and squalene on osmotic resistance of erythrocytes]. / Vliianie sterinov razlichnoi khimicheskoi struktury i skvalena na osmoticheskuiu stoikost' éritrotsitov.

The effects of sterols having different chemical structure and squalene on osmotic resistance of erythrocytes were studied. Changes in sterol and squalene content in the membranes were induced by incubation of erythrocytes with liposomes containing the additive. A decrease of the osmotic resistance of erythrocytes was shown to correlate with a cholesterol decrease in the membranes. Cholesterol caused a stabilizing effect on the membranes. 7-Dehydroxycholesterol which, unlike cholesterol, has an additional double bond in the B ring stabilizes the erythrocyte membranes in a greater degree than does cholesterol. Injection of cholesterol oleate causes extensive hemolysis of erythrocytes. Injection of squalene into non-cyclic erythrocyte membranes does not change osmotic resistance of the erythrocytes.

[Disturbanes in electrostatic balance of erythrocyte membranes in experimental D-hypovitaminosis]. / Narushenie balansa elektrostaticheskikh vzaimodeistvii v membranakh zritrotsitov pri zksperimentalvnom D gipovitaminoze.

Violation of electrostatic balance in the erythrocyte membranes with experimental D-hypovitaminosis is determined by the method of potentiometric titration. It is pronounced in modification of quantity and pK of accessible polar groups and in a decrease in total membrane electronegative charge. This violation is supposed to be provoked by a considerable increase in cholesterol content in the membranes and to reflect a modification in the character and bond strength of protein lipid complexes caused by interaction of cholesterol with membrane components. The role of the membrane components polar groups in binding an additional quantity cholesterol and decreasing in permeability of erythrocyte membranes under conditions of D-hypovitaminosis are discussed.

[Effect of sterols on erythrocyte membrane properties in experimental rickets]. / Vliianie sterinov na svoistva membran éritrotsitov pri éksperimental'nom rakhite.

Experimental rickets in rats was accompanied by a distinct increase in content of cholesterol and its esters, scvalene, lanosterol and 7-dehydrocholesterol in erythrocyte membranes with simultaneous decrease in content of total phospholipids. The alterations in lipid composition of erythrocyte membranes led to an increase in osmotic stability, to a decrease in glucose utilization and 45Ca incorporation into the erythrocytes. Acidic erythrogramms indicated an appearance in circulation of erythrocytes resistent to the effect of acidic hemolytics. Content of all the sterols studied was decreased in erythrocyte membranes after administration of liposomes into animals with experimental rickets; this demonstrates the relationship between the properties of the arythrocytes and sterole composition of their membranes. Incubation of erythrocytes with liposomes containing cholesterol or free from cholesterol caused a decrease or accumulation of cholesterol in the cell, respectively.

[Sterol content of rabbit erythrocyte membranes normally and in atherosclerosis]. / Vmist steryniv u membranakh erytrotsytiv kroliv u normi i za aterosklerozu

The sterol composition of erythrocyte membranes was studied in norm and under experimental atherosclerosis. It is shown that in the normal animals the content of cholesterol in the membranes increases with age and practically reaches a relatively constant value by 5-6 months. In the experimental animals being on the atherogenic diet the amount of cholesterol in the membranes a month later is practically identical to the control. 5-6 months after the experiment the content of cholesterol in the membranes decreases as compared to the norm by 38 and 65%, respectively. On the basis of the IR- and UV-spectra one may suppose that with atherosclerosis in the C27-sterol fraction besides cholesterol, there appears sterol containing C=O-group, the mutual orientation of which relative to the neighbouring functional group is different as compared in the norm. The deepest changes in the qualitative composition of erythrocyte membranes is observed 5-6 months later when there appears some products of cholesterol or its precursor transformation. Such a modification of the sterol composition causes a change in the membrane permeability.