Effect of ascorbate in the reduction of transferrin-associated iron in endocytic vesicles.
Externally added ascorbate or NADH effectively reduced ferricyanide and promoted the exit of Fe3+ originated from acid-destabilized transferrin contained inside endocytic vesicles. The effect of ascorbate was mediated by an ascorbate uptake system, and the effect of NADH was mediated by the membrane-associated oxidoreductase. At physiological concentrations of both ascorbate and NADH, the ascorbate transport and the NADH-oxidoreductase system were additive as measured by the rate of reduction of ferricyanide and by the mobilization of transferrin-associated iron. The results indicate that Fe3+ reduction may occur by a non-enzymatic reaction with ascorbate transported into the vesicle lumen. The ascorbate-mediated reduction of iron derived from transferrin occurring in the endosome could play a major role in cellular iron uptake.
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Departamento de Biología, Facultad de Ciencias, Universidad de Chile, Santiago.
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D000818:Animals; D001205:Ascorbic Acid / Q000494:pharmacology*; D001692:Biological Transport; D002462:Cell Membrane / Q000378:metabolism; D004705:Endocytosis / Q000502:physiology*; D005292:Ferricyanides / Q000378:metabolism; D007501:Iron / Q000378:metabolism*; D009243:NAD / Q000378:metabolism; D010084:Oxidation-Reduction; D011817:Rabbits; D014168:Transferrin / Q000378:metabolism*
D005292:Ferricyanides; D014168:Transferrin; D009243:NAD; C007931:hexacyanoferrate III; D007501:Iron; D001205:Ascorbic Acid