FIGURE 1.

CA-MLCK expression alters tight junction ion selectivity in vivo but not in vitro. A, paracellular FITC flux was increased by 54 ± 29% in the proximal colon of CA-MLCK (gray bar) transgenic mice relative to wild type (WT) littermates (white bar) (n = 8 wild type and 6 CA-MLCK mice). B, dilution potentials were recorded and mucosal and serosal NaCl concentrations were varied as indicated. Representative tracings from CA-MLCK (black line) and wild type (gray line) proximal colon are shown. C, PNa⁺/PCl⁻, calculated from stable dilution potentials, was elevated in CA-MLCK transgenic mice (gray bar) relative to wild type (WT) littermates (white bars) (n = 18 wild type and 13 CA-MLCK mice). D, induction of CA-MLCK expression (gray bar) reduced TER in Caco-2 monolayers. E, CA-MLCK expression (gray bar) in Caco-2 monolayers had no effect on ion selectivity (*, p ≤ 0.05; **, p ≤ 0.01, S.E.).