The Plasma Disappearance of Intravenously Administered Cobalt58 Vitamin B12*

Hall, Charles A.

doi:10.1172/jci104148

Cited by 13 publications

(3 citation statements)

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“…These values represented 2.2 and 3.1 fold increases for 'TC I and 'TC I1 distribution volumes, respectively when compared to the T-1824 plasma volumes. These results are comparable to those previously reported for both protein bound and free radioactive Bla (Hall 1960).The differences in the distribution volumes for 57C~-B12 labelled transcobalamins when compared with the T-1824 space are most likely due to equilibration of the B12-labelled transcobalamins with a rapidly exchanging compartment. The observed difference cannot be explained by differences in the size of the transcobalamins (TC I mol.…”

Section: Studies Bysupporting

confidence: 89%

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

Hom

1967

Scandinavian Journal of Haematology

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The plasma turnover of radioactive vitamin B12 bound in vitro to each of the two plasma binders (transcobalamins) was studied after intravenous injection. The observed T 1/2 values for the radioactive B12 were 9–10 days when bound to transcobalamin I and about 1.5 hours when bound to transcobalamin II. In both cases, the plasma curves yielded similar final slopes, corresponding to T 1/2 values of 9.3 and 9.8 days. In the study with transcobalamin II, this is shown to be due to rapid reappearance in the plasma of the radiocobalt label bound to transcobalamin I.

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Section: Studies Bysupporting

confidence: 89%

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

Hom

1967

Scandinavian Journal of Haematology

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“…I because his sampling differed and he analysed a different portion of the complex disappearance curve. Hom also postulated a rapid and widespread extracellular distribution of TC-11-vitamin-B, 2 , but we could not demonstrate injected vitamin B12 in extracellular fluid other than plasma (Hall, 1960).…”

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confidence: 72%

TRANSPORT OF VITAMIN B₁₂ IN MAN

Hall¹

1969

Br J Haematol

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“…After the administration of radioactive cyanocobalamin, radioactivity in plasma and bile will not reflect the behaviour of physiological vitamin B12 until a relatively long time has elapsed (Okuda, Grasbeck & Chow, 1958;Reizenstein, 1959b;England, Clarke, Down & Chanarin, 1973). In the presence of rapid fluxes from the plasma (Hall, 1960) and into the plasma, experiments in vivo which involve the sequential measurement of plasma radioactivity after the acute administration of labelled cyanocobalamin are liable to difficulties of interpretation, since plasma radioactivity reflects the net result of release and uptake and will be profoundly influenced by non-steady-state conditions of release from heterogeneous pools.…”

Section: Discussionmentioning

confidence: 99%

Heterogeneity of Hepatic Vitamin B12 in the Rat after Parenteral Cyanocobalamin

Cooksley

1975

Clinical Science

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1. The rate of radioactive vitamin B12 excretion into plasma and bile from the isolated perfused rat liver and into bile in vivo has been measured after the intramuscular injection of radioactive cyanocobalamin at various time-intervals before study. 2. With an interval of labelling of 10 or more days, the release of radioactive vitamin B12 over 4 h by the isolated perfused liver was linear and constituted approximately 3-5% and 1% of the hepatic radioactivity into plasma and bile respectively. 3. In contrast, after a shorter period of prelabelling (less than 7 days), there was a biphasic release of radioactive vitamin B12: an initial rapid rate followed by a slower rate after about 1 h of perfusion. The total radioactive vitamin B12 was considerably increased (e.g. 25% and 5% of hepatic radioactivity into plasma and bile respectively during a 4 h perfusion of a liver labelled 18 h previously). Confirmation of coexisting stable and labile pools of intrahepatic vitamin B12 was provided by: (a) the patterns of hepatic release after double labelling with 57Co-labelled and 58Co-labelled cyanocobalamin at different times before liver perfusion; (b) the rates of biliary excretion of 57Co-labelled and 58Co-labelled vitamin B12 in vivo after different periods of prelabelling. 5. The rate and pattern of release were not altered by changes in the quantity of precursor cyanocobalamin, by phenobarbitone treatment or by the addition of cycloheximide to the perfusion. 6. The injection into rats of subcellular preparations of rat liver labelled in vivo with radioactive vitamin B12 demonstrated that hepatic heterogeneity did not depend on physical compartmentation. 7. Despite the rapid release rate from the liver of recently administered radioactive cyanocobalamin, the hepatic radioactivity increased progressively with time after labelling in vivo, in contrast to the other tissues, where it decreased. In the presence of rapid bidirectional fluxes the ability of the liver to store vitamin B12 can be largely explained by the reduction in the rate of hepatic release that continues for about 10 days after parenteral administration of cyanocobalamin.

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The Plasma Disappearance of Intravenously Administered Cobalt58 Vitamin B12*

Cited by 13 publications

References 5 publications

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

TRANSPORT OF VITAMIN B₁₂ IN MAN

Heterogeneity of Hepatic Vitamin B12 in the Rat after Parenteral Cyanocobalamin

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The Plasma Disappearance of Intravenously Administered Cobalt58 Vitamin B12*

Cited by 13 publications

References 5 publications

Plasma Turnover of 57Cobalt‐Vitamin B12 Bound to Transcobalamin I and II

Plasma Turnover of 57Cobalt‐Vitamin B12 Bound to Transcobalamin I and II

TRANSPORT OF VITAMIN B12 IN MAN

Heterogeneity of Hepatic Vitamin B12 in the Rat after Parenteral Cyanocobalamin

Contact Info

Product

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About

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

Plasma Turnover of ⁵⁷Cobalt‐Vitamin B₁₂ Bound to Transcobalamin I and II

TRANSPORT OF VITAMIN B₁₂ IN MAN