Accumulation of vitamin C (ascorbate) and its oxidized metabolite dehydroascorbic acid occurs by separate mechanisms.
J Biol Chem
; 270(21): 12584-92, 1995 May 26.
Article
en En
| MEDLINE
| ID: mdl-7759506
ABSTRACT
It is unknown whether ascorbate alone (vitamin C), its oxidized metabolite dehydroascorbic acid alone, or both species are transported into human cells. This problem was addressed using specific assays for each compound, freshly synthesized pure dehydroascorbic acid, the specially synthesized analog 6-chloroascorbate, and a new assay for 6-chloroascorbate. Ascorbate and dehydroascorbic acid were transported and accumulated distinctly; neither competed with the other. Ascorbate was accumulated as ascorbate by sodium-dependent carrier-mediated active transport. Dehydroascorbic acid transport and accumulation as ascorbate was at least 10-fold faster than ascorbate transport and was sodium-independent. Once transported, dehydroascorbic acid was immediately reduced intracellularly to ascorbate. The analog 6-chloroascorbate had no effect on dehydroascorbic acid transport but was a competitive inhibitor of ascorbate transport. The Ki for 6-chloroascorbate (2.9-4.4 microM) was similar to the Km for ascorbate transport (9.8-12.6 microM). 6-Chloroascorbate was itself transported and accumulated in fibroblasts by a sodium-dependent transporter. These data provide new information that ascorbate and dehydroascorbic acid are transported into human neutrophils and fibroblasts by two distinct mechanisms and that the compound available for intracellular utilization is ascorbate.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Ácido Ascórbico
/
Ácido Deshidroascórbico
Límite:
Humans
/
Male
Idioma:
En
Revista:
J Biol Chem
Año:
1995
Tipo del documento:
Article
País de afiliación:
Estados Unidos