[Vitamin A esters and their hydrolysis in different organs and tissues]. / Efiry vitamin A i ikh gidroliz v razlichnykh organakh i tkaniakh

Hydrolysis of retinylpalmitate and retinylacetate was studied in rat blood, liver tissue, intestine, testes, placenta and embryonic liver. The retinylpalmitate hydrolase activity was observed only in walls of small intestine and, less distinctly, - in liver tissue of some animals. Retinylpalmitate was hydrolyzed in rat liver very slowly, that was determined apparently by the metabolic requirements of the organism. The retinylpalmitate hydrolase activity occurred in dog blood after absorption of vitamin A oil solutions. This phenomenon was probably related to an increased secretion of pancreatic enzymes into blood after the loading with oils.

[Effect of thyroxine and hydrocortisone on the content of retinol and retinyl palmitate in liver tissue, kidney and blood of rats, loaded with high doses of retinyl acetate]. / Vliianie tiroksina i gidrokortizona na coderzhania retinola i retinilpal'mitata v peeheni, pochkakh i krovi krys, poluchayshikh vysokie dozy retinilatsetatata.

Administration of hight doses of retinyl acetate into rats caused an increase in content of retinol in liver tissue and kidney and retinyl palmitate in liver tissue, kidney and blood. The simultaneous administration of thyroxine decreased the accumulation of retinol and retinyl palmitate in liver tissue. At the same time, in kidney content of retinol was increased but content of retinol and retinyl palmitate in blood and retinyl palmitate in kidney did not differ from the values estimated in the control group. The simultaneous administration of retinyl acetate and hydrocortisone decreased the accumulation of retinol and retinyl palmitate in liver tissue, increased the content of vitamin A in blood and did not influence its content in kidney.

[Oxidative conversion of vitamin "A" in rats with different allowances of it]. / Okilsitel'nye prevrashcheniia vitamina A y krys v usloviiakh razlichnogo obespecheniia etim vitaminom

The effects of vitamin "A" insufficiency and of its toxic doses on the activity of alcoholdehydrogenase oxidizing retinol and ethanol and on that of aldehydoxidase, oxidizing retinal in the liver, kidneys and small intestine of rats were studied. It is shown that in case of "A"-vitamin insufficiency are on the rise processes of oxidative transformation of retinol and retinal associated with an increased activity of alcoholdehydrogenase and aldehoxidase. Against the background of toxic doses of vitamin "A" THe activity of alcoholdehydrogenase in the organs under investigation is inhibited and that of aldhydoidase in the small intestine rises.

[Hydrolytic splitting of vitamin A esters in the blood]. / K voprosu o gidroliticheskom rasshcheplenii éfirov vitamina A v krovi

The retinol and retinylpalmitate content along with the retinylacetate and retinylpalmitate-hydrolase in the blood of the portal vein and in the peripheral blood from the superficial vein of the hind limb of dogs was determined in chronic experiments before and 1, 2, 3 and 4 hours after administration of the vitamin A preparations into the small intestine fistula. The introduction of an oily retinylacetate solution into the fistula was attended both by an increase of the retinylpalmitate content in the blood plasma and the appearance therein of the retinyl-palmitat-hydrolase activity. Introduction of an aquous-colloidal solution of retinyl-palmitate caused a rise in the latter's content in the blood but was not accompanied by the appearance of the retinyl-palmitate-hydrolase activity. In the blood taken on an empty stomach no capacity for retinyl-palmitate hydrolysis was in evidence. It is presumed that the emergence of the retinyl-palmitate activity in the blood following introduction of precisely the oily retinylacetate solution is due to an intensified supply of the pancreatic enzymes into the blood in response to the fat load. The retinylacetate-hydrolase activity was continually present in the blood and did not vary in its intensity in the dynamics of absorption.

[Effect of experimental hyper- and hypothyrosis on the level of various forms of vitamin A in various tissues of albino rats]. / Vliianie éksperimental'nogo giper- i gipotireoza na soderzhanie razlichnykh form vitamina A v nekotorykh tkaniakh belykh krys.

A method allowing simultaneous assay of the tissue content of three forms of vitamin A (alcohol, ester, aldehyde) was applied for investigation of these forms in liver, kidneys, adrenals and blood plasma in rats with experimental hyper- and hypothyreosis. It is established that compared to control rats, hyperthyroid animals show increased content of vitamin A-alcohol in adrenals with simultaneous decrease in liver of vitamin A-alcohol and especially of its ester. It is supposed that these changes are directly induced by the action of thyroxine on vitamin A metabolism in tissues. During hyperthyreosis, content of vitamin A (alcohol and ester) in liver sharply falls and there is a tendency towards its decrease on blood plasma and adrenals. Approximately the same ratio of alcohol and ester of vitamin A in kidneys indicated its intensive metabolism in this organ. As judged from the absence of changes in content of vitamin A-aldehyde in organs, activation as well as suppression of the function of thyroid gland apparently is not followed by an increase in oxidative transformation of vitamin A in tissues.