Iron increases the uptake of ascorbate and the expression of its transporter SVCT1

In the past years, we have been focusing on the effects of ascorbic acid (Vitamin C) on cellular uptake of iron and the proteins involved. We have found that the regulation of the acquisition of iron by ascorbic acid is extensive. Since cellular processes are usually flexible and bi‐directional we hypothesize that iron is involved in the metabolism of ascorbate . The hypothesis was tested by conducting ascorbic acid uptake and transport studies in the presence or absence of intracellular iron in the human intestinal Caco‐2 cell line. In an attempt to explain the achieved results, we investigated the protein expression of the apical membrane‐associated ascorbate transporter SVCT1 by Western Blot and ELISA measurements. The results showed that 24 h of iron (FeCl 2 ·4 H 2 O) incubation increased the uptake of ascorbate by 285% compared to non‐iron treated cells. We also observed that the protein expression of SVCT1 increased in iron treated cells and decreased when the cells were treated with ascorbic acid. Due to these results, mechanistic studies were conducted using a protein kinase C (PKC) inhibitor and also a SVCT1 inhibitor in order to further explain the results. Preliminary data suggest that PKC is involved in the iron stimulatory effect of ascorbate uptake. We conclude that iron is an enhancer of ascorbate uptake in human intestinal Caco‐2 cells. This study was funded by the Swedish Council for Environment, Agricultural Sciences and Spatial Planning (Formas) [Grant no. 222‐2004‐1889] and the Dr. Per Håkansson Foundation.