[Features of cholecalciferol hydroxylation in the liver of rats in conditions of D-hypervitaminosis and activity of alpha-tocopherol].

It is shown, that hepatocytes contain two (microsomal and mitochondrial) vitamin D3 25-hydroxylase enzymes, which differ as to their activity and function with maximal activity at different concentrations to substrate, namely at 15 microM and 100 microM of vitamin D3, accordingly. Activity of vitamin D3 25-hydroxylase enzymes of hepatocytes is regulated by cholecalciferol and alpha-tocopherol. The general and microsomal vitamin D3 25-hydroxylase enzymes activity of hepatocytes is lowered, but mitochondrial isoform is increased under D-hypervitaminosis conditions.

[Role of vitamin E in regulation of cholecalciferol hydroxylation in hypovitaminosis D and hypervitaminosis D].

It is established, that dose-dependent influence of vitamin E on vitamin D3 metabolism, is conditioned by degree of cholecalciferol sufficiency. Under a condition of D-hypovitaminosis, contents of 25OHD3 in blood serum is 2-fold reduced and vitamin D3 25-hydroxylase enzymes activity increased in rat hepatocytes. Vitamin E (0.

[Influence of vitamin E application period on the mineral and D-vitamin metabolism in the organism].

It was shown, that influence of vitamin E on mineral and D-vitamin metabolism depends on its doses and application period: physiological doses of vitamin E activate and large doses - inhibit the effect of vitamin D3 in regulation of mineral metabolism in the organism. The duration of application of large doses of vitamin E (higher than 20 physiological doses) during which the negative changes are not determined has not to exceed 10 days.