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Biologic Turnover Rate of Cyanocobalamin (Vitamin B12) in Human Liver

AMA Arch Intern Med. 1958;101(2):306-309. doi:10.1001/archinte.1958.00260140138020.
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The availability of γ-emitting radioactive cyanocobalamin (vitamin B12) Co60 with a relatively slow rate of radioactive decay has made possible an estimate of the biologic turnover-rate of cyanocobalamin in the liver of man. There are several previously reported observations which suggest that this rate might be much slower for cyanocobalamin than for some of the other watersoluble vitamins, such as thiamine, nicotinic acid (niacin), and ascorbic acid. The interval between total gastrectomy and the development of megaloblastic anemia is usually several years.1,2,3 Studies in pernicious anemia have shown that the interval between cessation of therapy and appearance of relapse will be greater than 6 months in 50 to 70% of the cases and in excess of 12 months in 25% of the cases.4,5 Pitney and Beard 6 measured the serum cyanocobalamin level of a patient for 18 months after total gastrectomy, and they found that the


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