Claudin-1 and claudin-3 are required for a high glucose-induced reduction in paracellular permeability. (A) The effect of high glucose (HG = 25 mmol/L) on the transepithelial electrical resistance (TER) of SMG-C6 cells. n = 8. (B,C) The effect of HG on the paracellular flux of 4-kDa FITC-dextran (B) and 40-kDa FITC-dextran (C). n = 6. (D,E) Western blot (D) and densitometry analysis (E) of claudin-1 (Cln-1), Cln-3, and Cln-4 after transfecting SMG-C6 cells with Cln-1-specific shRNA. n = 3. (F,G) Western blot (F) and densitometry analysis (G) of Cln-1, Cln-3, and Cln-4 after transfecting SMG-C6 cells with Cln-3-specific shRNA. n = 3. (H) TER of Cln-1-knockdown cells and Cln-3-knockdown cells. n = 6. (I,J) Paracellular flux of 4-kDa FITC-dextran (I) and 40-kDa FITC-dextran (J) in Cln-1-knockdown cells and Cln-3-knockdown cells. n = 6. * p < 0.05 and ** p < 0.01.