Calculation of Na+/Cl− Selectivity in Tight Junctions between Epithelial Cells by Methods of Nonlocal Electrostatics with Pole Models of Dielectric Function without an Overscreening Effect

Abstract

A mathematical model of Na⁺/Cl⁻ selectivity in tight junctions (TJs) between epithelial cells was developed. It was demonstrated that Na⁺/Cl⁻ selectivity in TJs depends on the total charge of amino-acid residues of claudin macromolecules within TJs, as well as on the ion-distribution coefficients between TJs and free solution. It was demonstrated that the obtained formulas predict a change of Na⁺/Cl⁻ selectivity in TJs for Cl⁻/Na⁺ selectivity if the sign of the total charge of amino-acid residues in TJ changes. The calculated Na⁺/Cl⁻ selectivity value for MDCK cells coincides with the experimental data of (Colegio et al., 2002). To calculate a change in ion-solvation energy during their transition to TJs, formulas for nonlocal electrostatics with one-, two-, and three-pole models of dielectric function without taking into account the overscreening effect were used.