EGFP-occludin mice are partially protected from TNF-induced occludin redistribution, barrier dysfunction, and fluid secretion. (A) Jejunal epithelia were isolated from wild-type and EGFP-occludin transgenic mice. Occludin, EGFP-occludin, and actin content were assessed by immunoblotting. (B) Jejunum was harvested from wild-type and EGFP-occludin mice 120 min after TNF injection. Wild-type tissue was labeled for occludin (top; green in merge) and F-actin (red). EGFP-occludin (top; green in merge) and labeled F-actin (red) are shown for transgenic animals. Regions of the tight junction completely lacking in occludin (arrows) develop in TNF-treated wild-type but not EGFP-occludin transgenic mice. Bar, 10 µm. (C) In vivo perfusion assays were used to assess paracellular BSA flux in wild-type mice and EGFP-occludin mice injected with TNF (gray bars) or vehicle (white bars; n = 6). (D) In vivo perfusion assays of water movement in wild-type and EGFP-occludin mice injected with TNF (gray bars) or vehicle (white bars; n = 6). Error bars indicate mean ± SEM.