Figure 4.

Representative confocal images of double immunofluorescence staining of claudin-15 (green) and occluding (red) (A) (n = 3) and quantitative RT-PCR (B) (n = 3) in wild-type and cldn15^−/− mice. Bar, 100 µm. Activation of SGLT1 increases glucose-induced J^Na_MS under short-circuit conditions in cldn15^−/− mice: Representative I_sc trace of glucose-induced I_sc changes in cldn15^−/− and wild-type mice (C), where, indicated by the arrows, glucose was added to the mucosal side, the final concentration of glucose is shown in mM; and the concentration dependence of the glucose-induced I_sc (D). The curve was fit to the Michaelis–Menten equation (n = 3 and 6, wild-type, and cldn15^−/− mice, respectively). Where error bars are absent, they are smaller than the symbol used. The 10 mM glucose-induced short-circuit current changes (I_sc) (E) and ²²Na⁺ unidirectional flux changes (J^Na) (F) were measured simultaneously the same as Figure 1 (n = 7 and 7, M to S and S to M, respectively). Where indicated by the arrows, glucose was added to the mucosal side. The effect of S3226 on glucose-induced ΔI_sc (G) and ΔJ^Na (H) (n = 5 and 5, M to S and S to M, respectively). Where indicated by the arrows, glucose was added to the mucosal side. Each point represents the mean ± SE. Where error bars are absent, they are smaller than the symbol used. * p < 0.05 as compared with the baseline control.