[Exchange of vitamin D3 in placenta and fetal liver]. / Obmen vitamina D3 v platsente i pecheni ploda.

Metabolism of [3H]-vitamin D3 in placenta and fetus liver of rats on the 20-21st day of pregnancy was investigated. Biosynthesis in vivo of 25-hydroxyvitamin D3 occurs in placenta and fetus liver and the maximum observed 25-hydroxylation composes 15% in placenta and 13% in the fetus liver. It has been shown, that C-25-hydroxylation of vitamin D3 in the microsomal and mitochondrial fractions of hepatocytes take place. It has been concluded that placenta and fetus liver, although to not very much degree, is able to realize vitamin D3 metabolism independent of mother's organism.

[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.

[Calcium-binding ability of integral protein 3 from erythrocyte membranes of rats with experimental hypovitaminosis D]. / Kal'tsiisviazyvaiushchaia sposobnost' integral'nogo belka 3 membran éritrotsitov krys pri éksperimental'nom D-gipovitaminoze.

Binding of calcium by protein 3 from the erythrocyte membranes is studied in norm and under experimental D hypovitaminosis. It is shown that calcium ions are bound by protein 3 from the erythrocyte membranes of normal animals. Binding of Ca2+ by protein 3 in animals with experimental rickets increases, that correlates with a rise of its total electron-negative charge of protein in case of the given pathology.

[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.

[Lipid composition and activity of certain enzymes in membranes of intestinal epithelium microvilli in rats with experimental hypercholesterinemia]. / Lipidnyi sostav i aktivnost' nekotorykh fermentov membram mikrovorsinok kishechnogo épiteliia krys pri éksperimental'noi giperkholesterinemii.

It is established that in membranes of small intestine epithelial cells microvilli in rats, which were administered cholesterol for a long time, the content of this sterol and its esters as well as of phospholipids is different. Differences in the content of lipids are a reason of changes in the sucrose, alkaline phosphatase and leucilamino-peptidase activities. These changes are accompanied by an increase on the molar cholesterol esters-free cholesterol ratio in blood plasma and cholesterol-phospholipids ratio in the microvilli membranes. Beta-sitosterol administered to experimental animals incorporates into the intestine plasma membranes, blocks up the transfer sites, inhibiting cholesterol absorption, which evidently decreases the sterol content in blood serum.