Correlation of in vitro cytotoxicity with paracellular permeability in mortal rat intestinal cells.

Introduction: The rat small intestinal cell line, IEC-18, was used as an in vitro model to differentiate between acute cytotoxicity (AC) and paracellular permeability (PP) of selected chemicals.

Methods: This study compares the low resistance rat intestinal mortal cell line, IEC-18 (transepithelial electrical resistance, TEER=160+/-10 Omega cm(2)) with the high resistance human intestinal cell line, Caco-2 (TEER=900+/-100 Omega cm(2)). The two cell lines differ in state of differentiation, TEER and paracellular permeability characteristics. The IEC-18 cell line is originated from the ileum and resembles more closely the small intestine than the Caco-2. Cytotoxicity was carried out using MTT cell viability assay in 96-well plates for 24-h exposure time. PP was measured using TEER (membrane integrity indicator) and PP markers such as [(3)H]-D-mannitol, lucifer yellow (LY) and FITC-dextran (fluorescein-dextran) on cells grown on inserts.

Results: The data showed that there is a high correlation (R(2)=0.99) between MTT and TEER using IEC-18 cell for 24-h exposure time. IEC-18 is as sensitive as Caco-2 for both MTT and TEER measurements. Decrease in TEER is inversely proportional with increase in PP of tight junction indicators. There is a good correlation between IC(50)'s MTT, TEER and Registry of Cytotoxicity (RC) data.

Discussion: Based on the results from the experiments, IEC-18 can be used as an in vitro model to differentiate between concentrations needed for AC and those required for PP.