Document Detail

Incorporation and metabolic conversion of cyanocobalamin by Ehrlich ascites carcinoma cells in vitro and in vivo.
MedLine Citation:
PMID:  1111594     Owner:  NLM     Status:  MEDLINE    
1. Cyano [57 Co] cobalamin bound to murine transcobalamin, associates with Ehrlich ascites carcinoma cells. Association was found to be dependent on temperature, and to require between 7.2 - 10-5 and 2 - 10-4 M ionized calcium. 2. Association was blocked by vinblastine and colchicine, but not cytochalasin, suggesting that microtubules may be involved in this phenomenon. 3. Although irreversible association of radioactivity with cells was observed within minutes, appearance of significant radioactivity associated with the intracellular B12 binder, and conversion of cyanocobalamin to methyl- and 5'deoxyadenosylcobalamin required more than 18 h of incubation. 4. A pool of free vitamin B12 was found in cell extracts. This was composed of metabolically-active cobalamins characteristic of the interior of the cell, and not of cyanocobalamin recently incorporated. 5. Incorporation of 57Co-labelled vitamin B12 by these cells involves two major processes: a rapid irreversible association of transcobalamin-B12 complex following reaction with a presumably calcium-dependent receptor, and a much later entry of vitamin into the cytoplasm to become exposed to enzymes and associated with an intracellular binder.
K Peirce; T Abe; B A Cooper
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Biochimica et biophysica acta     Volume:  381     ISSN:  0006-3002     ISO Abbreviation:  Biochim. Biophys. Acta     Publication Date:  1975 Feb 
Date Detail:
Created Date:  1975-05-17     Completed Date:  1975-05-17     Revised Date:  2009-10-27    
Medline Journal Info:
Nlm Unique ID:  0217513     Medline TA:  Biochim Biophys Acta     Country:  NETHERLANDS    
Other Details:
Languages:  eng     Pagination:  348-58     Citation Subset:  IM    
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MeSH Terms
Biological Transport
Blood Proteins / metabolism*
Calcium / pharmacology
Carcinoma, Ehrlich Tumor / metabolism*
Carrier Proteins / metabolism
Cobalt Radioisotopes
Colchicine / pharmacology
Cytochalasins / pharmacology
Cytoplasm / metabolism
Ferritins / pharmacology
Microtubules / metabolism
Vinblastine / pharmacology
Vitamin B 12 / metabolism*
Reg. No./Substance:
0/Blood Proteins; 0/Carrier Proteins; 0/Cobalt Radioisotopes; 0/Cytochalasins; 64-86-8/Colchicine; 68-19-9/Vitamin B 12; 7440-70-2/Calcium; 865-21-4/Vinblastine; 9007-73-2/Ferritins

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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