1. Monolayer cultures of the human HCT-8 adenocarcinoma cell line were established on porous cell culture inserts.

2. Results: P-Gp-positive HCT-8 adenocarcinoma cells from electrophysiologically highly resistant monolayers (>2000 Ohm x cm2) upon culture on porous cell culture inserts (0.45 μm) within several days, which show a very low paracellular permeability for mannitol (<0.23 pmol/h/cm2).