Abstract
The transport of cadmium across Caco‐2 monolayers in vertical alignment, in combination with the Ussing chamber technique, was investigated. The Caco‐2 cells were grown in Dulbecco's Modified Eagle Medium and the cells were seeded on six‐well Snapwell® polycarbonate inserts (Costar) at a density of 3 × 105 cells/cm2. Accumulation and transport studies were performed after 14 days, when the cells had formed a monolayer. Cells were evaluated for confluence by monitoring of transepithelial electric resistance (TEER) during the whole cell growth phase and by inspection with a confocal laser scanning microscope. Electrophysiological measurements were made on cell monolayers mounted in Ussing chambers. The tissue parameters potential difference (dP0), current (I C), and short‐circuit current (I SC), as well as TEER, were recorded. There was no significant influence of transport direction (apical–basolateral or basolateral–apical) on cadmium absorption. Exposure of Caco‐2 cells to different cadmium concentrations resulted in a reduction of cadmium accumulation in Caco‐2 cells from 38% (at 1 µM Cd) to 13% (at 10 µM Cd). At all cadmium concentrations (except 5 µM), the actual cadmium transport was approximately 5%. Time course of cadmium accumulation showed an initial rapid phase followed by a phase of slow cadmium accumulation. Transport from inner cell to receiving side took place at a constant speed. Exposure of Caco‐2 cells to high doses of cadmium (>100 µM) resulted in a reduced TEER. It can be concluded that a combination of Caco‐2 cell model and Ussing chamber system represents an appropriate model for simulation of cadmium absorption and probably for investigations of transport processes of other heavy metals.
Published Version
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