Transepithelial transport of bepridil in the human intestinal cell line, Caco-2, using two media, DMEMc and HBSS

The purpose of this work was to study transepithelial transport of bepridil, an anticalcic agent, through monolayer cells Caco-2, using two experimental media with different chemical components. For experimentation, the measure of the transepithelial electrical resistance (TEER) allowed us to evaluate the state of cells; and the quantities of bepridil have been quantified using a gas chromatography/mass spectrometry system. First, when using the medium alone, without bepridil, Caco-2 cell integrity is, at least, maintained for 8 h using both media. However, for 24-h studies, only the DMEMc medium, rich in essential nutriments, allowed cell integrity to be maintained. Then, with bepridil in HBSS medium, the TEER measurement showed a dose-dependent toxic effect of bepridil, whereas in the DMEMc medium, the toxic effect was only found for the highest dose (12 microg). This difference is probably related to the high binding of bepridil to proteins of the DMEMc medium, therefore minimising the concentration of the free compound. The kinetics of bepridil result from two phenomena: first, an immediate passage of a slight part of bepridil through the cell barrier and second, a high retention of most of the bepridil dose in the cell level. The transfer of bepridil from the apical to the basolateral compartment appears quantitatively and kinetically different using DMEMc or HBSS medium. The retention of the compound in the 'filter with Caco-2 cells' compartment is higher in DMEMc medium (60% at 3 microg) than in HBSS medium (46% at 3 microg), and bepridil entering the basolateral compartment is delayed in the DMEMc medium. This study exhibits the importance of the selected medium on results and interpretation of data and the predominance of DMEMc to study the transport of lipophilic compounds highly retained in cells.