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Posted on: Aug 23, '08

Vitamin B12

Vitamin B12
Vitamin B12 or cyanocobalamin is a complex corrinoid compound containing four pyrrole rings that surround a single
cobalt atom.

Humans obtain Vitamin B12 exclusively from animal dietary sources, such as meat, eggs and milk. Vitamin B12 requires
intrinsic factor, a protein secreted by the parietal cells in the gastric mucosa for absorption. Vitamin B12 and
intrinsic factor from a complex that attaches to receptors in the ileal mucosa, where proteins known as transcobalamins
transport the Vitamin B12 from the mucosal cells to the blood and tissues. Most Vitamin B12 is stored in
the liver as well as in the bone marrow and other tissues.

Vitamin B12 and Folate are critical to normal DNA synthesis, which in turn affects erythrocyte maturation. Vitamin
B12 is also necessary for myelin sheath formation and maintenance. The body uses its B12 stores very economically,
reabsorbing Vitamin B12 from the ileum and retuning it to the liver so that very little is excreted.

Clinical and laboratory findings for B12 deficiency includes neurological abnormalities, decreased serum B12 levels
and increased excretion of methylmalonic acid. The impaired DNA synthesis associated with Vitamin B12 deficiency
causes macrocytic anaemia. These megaloblasts and in decreased erythrocyte survival.

Pernicious anaemia is a macrocytic anaemia caused by Vitamin B12 deficiency that is due to lack of intrinsic factor.
Low Vitamin B12 deficiency.

Preservatives such as fluorides and ascorbic acid interfere with this assay. Excessive exposure of the specimen to
light may alter Vitamin B12 result.

Methodology of Test: Chemiluminescence.

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