Variation of peptide transporter (PepT1 and HPT1) expression in Caco-2 cells as a function of cell origin.

Caco-2 cell cultures are a widely used in vitro model for the small intestinal drug transport, although large differences have been reported for actively transported substrates from different laboratories. Therefore, we compared three different Caco-2 clones: (1) from the American Culture Tissue Collection (ATCC), (2) from the German Cancer Research Center (DKFZ) in Heidelberg, and (3) from the University Hospital in Marburg in different passage numbers regarding their morphology, multilayers, and tight junction formation, as well as expression of the peptide transporters, HPT1 and PepT1. We determined tight junction formation by measurement of the transepithelial electrical resistance, multilayer formation by confocal laser scanning microscopy, the expression of PepT1 and HPT1 by RT-PCR, indirect immunofluorescence and the permeability of the PepT1 substrate, cephradine. Morphology and TEER-values varied strongly between the different clones. The expression of PepT1 and HPT1 increased in the following order: HD > ATCC > MR. Indirect immunofluorescence revealed a heterogeneous distribution of the transporters in ATCC-cells, whereas it was homogeneous in HD-cells. Only a very weak expression was found in MR-cells. While in ATCC-cells expression of transporters decreased with increasing passage number, it increased in HD-cells. Expression levels were congruent with the transport of cephradine. Expression of PepT1 and HPT1 was strongly affected by the culture conditions. Under identical culture conditions, Heidelberg (HD) Caco-2 cells seemed to be an appropriate in vitro cell culture model for the transport of actively transported drugs, because interpassage changes are low and the transporter distribution was homogeneous throughout the monolayer.