The effect of G60R mutation on barrier-forming function of CLDN-5. Untransfected cells or cells expressing CLDN-5 wild-type (WT) low and wild-type high or G60R were cultured on cell culture inserts for 5 days (MDCKII cells) or 8 days (b.End3 cells) to prepare a well-developed monolayer. (A) TEER and (B) the dilution potential of NaCl were measured and (C) absolute Na⁺ and Cl⁻ permeabilities were calculated. Values represent the mean ± SD. (n = 6). (D) The permeability of sodium fluorescein (377 Da) and (E) 4 kDa of fluorescence-conjugated dextran (FD4) across the monolayers were measured. Values represent the mean ± SD (n = 3).