Transport of ascorbic acid in gastric epithelial cells in vitro

The normal human stomach contains high concentrations of ascorbic acid in both the mucosa and gastric juice, but the mechanism of ascorbic acid transport in the stomach is unknown. To understand more, ascorbic acid accumulation in gastric epithelial cell lines was investigated. Ascorbic acid was transported into gastric epithelial cells (Kato III and AGS cell lines) and accumulated up to eight-fold against a concentration gradient, as measured by high-performance liquid chromatography with electrochemical detection. Kinetic analysis using both non-radioactive and radioactive sources of ascorbic acid showed that ascorbic acid accumulation was mediated by one saturable concentration-dependent transport system with a K m of 3–11 μmol/l and V max of 0.8–0.9 nmol/10 8 cells/min. These data suggest that ascorbic acid uptake in gastric mucosal cells may be facilitated by a high-affinity saturable transport activity. Loss of intracellular ascorbic acid from Kato III and AGS cells was slower than seen in vivo which may limit the usefulness of these cell lines as a physiological model for the secretion of mucosal ascorbic acid into gastric juice.