Dehydroascorbic acid and ascorbic acid transport systems in the guinea pig ileum

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Abstract
The transport properties of dehydroascorbic acid and ascorbic acid in membrane vesicle preparations of guinea pig ileum were evaluated. Na-dependent transport of ascorbic acid in the brush-border membrane was confirmed, and an Na-independent mechanism was found in the basolateral membrane. The electrically neutral oxidized form of vitamin C is transported by an Na-independent mechanism at both cell surfaces. Transport of each substrate is saturable and exhibits cis-inhibition and trans-stimulation in the presence of structural analogues. Additional studies on ascorbate metabolism will be necessary to support a comprehensive model of intestinal handling of vitamin C.