Figure 4.

Internalization of claudins 2, 4, and 7 and occludin in enterocytes of stressed pups at 72 hours. Frozen sections of small intestines of pups submitted to the NEC protocol or DF controls were examined for occludin (green) and claudins (green) 2, 4, and 7 by immunofluorescence (top row in each group). Merged images (bottom row in each group) also show β-actin (red) and DAPI nuclear staining (blue). In DF mice, claudin 2, 4, and occludin were present mainly at TJs, and claudin 7 was detected along cellular membranes. In pups stressed for 72 hours, occludin and claudins 2, 4, and 7 were found throughout the cytoplasm; the association of claudins 2 and 4 with TJs was decreased, whereas the association of occludin with TJs was only focally decreased in villi and a small amount was found throughout the cytoplasm. n = 3 to 6 per group. Scale bar = 40 μm.