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Transcytosis and coenzymatic conversion of [(57)Co]cobalamin bound to either endogenous transcobalamin II or exogenous intrinsic factor in caco-2 cells.
MedLine Citation:
PMID:  10878444     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
We have examined the intracellular route, coenzyme conversion and transcytosis rate of [(57) Co]-labeled cobalamin (Cbl) in function of its presentation to the apical side of Caco-2 cells, either free or bound to intrinsic factor (IF). The free-presented Cbl was progressively bound to endogenous transcobalamin II (TCII) which may stem, in part, from a basolateral to apical passage. Its transcytosis was TCII-mediated as it was abolished when antibodies to TCII were added to the apical medium. The apparent permeability coefficient (P(app)) was estimated at 20.8+/-3.6, 103.5+/-17.7, 0.9+/-0.3 x 10(-5) cm/h for TCII-Cbl, IF-Cbl and haptocorrin-Cbl, respectively. Chloroquine inhibited the transcytosis rate of both TCII and IF-bound Cbl in a dose-dependent manner. Approximately 80% of apical Cbl, bound to either exogenous IF or endogenous TCII, was transported to the basolateral side as intact cyano[(57)Co]Cbl whereas the remainder was converted into Ado-Cbl and CH(3)-Cbl within the cells, as shown by HPLC analyses of a 1,000-g pellet and a 12,000-g supernatant. Coenzymatic conversion was virtually abolished by chloroquine. In conclusion, we suggest that apically presented free Cbl is internalized via TCII-dependent transport. The apically internalized CN-Cbl, bound to either IF or TCII, is processed via an acidic vesicle and part of it is converted to coenzymes, whereas bulk of CN-Cbl is transcytosed intact.
Authors:
L Pons; M Guy; D Lambert; R Hatier; J Guéant
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology     Volume:  10     ISSN:  1015-8987     ISO Abbreviation:  Cell. Physiol. Biochem.     Publication Date:  2000  
Date Detail:
Created Date:  2000-10-19     Completed Date:  2000-10-19     Revised Date:  2004-11-17    
Medline Journal Info:
Nlm Unique ID:  9113221     Medline TA:  Cell Physiol Biochem     Country:  SWITZERLAND    
Other Details:
Languages:  eng     Pagination:  135-48     Citation Subset:  IM    
Affiliation:
Laboratoire de Pathologie Cellulaire et Moléculaire en Nutrition, Equipe INSERM 00-14, Faculté de Médecine, Université Henri Poincaré, B.P. 184, 54 505 Vandoeuvre-lès-Nancy Cedex, France.
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MeSH Terms
Descriptor/Qualifier:
Biological Transport / drug effects
Caco-2 Cells
Cell Polarity / physiology*
Chloroquine / pharmacology
Cobalt Radioisotopes
Colchicine / pharmacology
Edetic Acid / pharmacology
Humans
Intrinsic Factor / metabolism*
Transcobalamins / metabolism*
Vitamin B 12 / metabolism*
Chemical
Reg. No./Substance:
0/Cobalt Radioisotopes; 0/Transcobalamins; 54-05-7/Chloroquine; 60-00-4/Edetic Acid; 64-86-8/Colchicine; 68-19-9/Vitamin B 12; 9008-12-2/Intrinsic Factor

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