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Vitamin B12 in the blood
Last reviewed: 19.11.2021
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Reference values (normal) concentration of vitamin B 12 in serum: neonates - 160-1300 pg / ml in adults - 200-835 pg / ml (mean values of 300-400 pg / mL).
Vitamin B 12 (cyanocobalamin) is necessary for the normal maturation of red blood cells. It performs the function of coenzyme in the synthesis of nucleic acids (DNA and RNA) and methionine from homocysteine. Methionine is necessary for the conversion of folic acid into folinic, which provides the normoblastic type of hematopoiesis. In addition, vitamin B 12 provides the synthesis of lipoproteins in myelin tissue and glutathione. Therefore, deficiency of vitamin B 12 is accompanied by the development of megaloblastic anemia, neutropenia and neurological disorders (funicular myelosis). Immunodeficiency at insufficiency of vitamin B 12 is associated with the formation of neutrophils gipersegmentirovannyh differing oxygen-reduced activity bactericidal mechanism as is necessary for the destruction of intracellular bacteria and viruses.
To vitamins of group B 12 belong several cobalamins, contained exclusively in products of animal origin. Alimentary vitamin B 12 deficiency is rarely reported. Absorption of vitamin B 12 occurs in the distal parts of the ileum. It is possible only after the formation of a vitamin complex with an internal factor - glycoprotein, secreted in the stomach. The specific transporter protein transcobalamin II carries the transport of cobalamin in the blood plasma. Absorption of the vitamin depends on the following factors: secretion of the internal factor in the stomach; the integrity of the mucosa of the distal ileum; presence in the plasma of transcobalamin II in sufficient quantity. Vitamin B 12 is necessary for the growth of some intestinal bacteria that interfere with the absorption of this vitamin, competing for it with intestinal cells. Therefore, the intestinal microflora can influence the absorption of vitamin B 12.