Figure 5.

Permeability of the mucosal epithelium probed with LY at 2 mM concentration of PEs. Sections of mucosal explants cultured for 1 h with LY in the absence or presence of 2 mM NaC or DDM, respectively. In addition, the sections were immunolabeled for ApN, a brush border enzyme, or for EEA-1, a marker for early endosomes. In the controls, a string of EEA-1-positive subapical punctae shows uptake of LY into apical early endosomes of the enterocytes, whereas the cytosol is only weakly labeled. Lateral labeling and strong staining of the lamina propria are also seen, indicating a paracellular passage of LY through the tight junctions. At 2 mM, both NaC and DDM frequently caused LY to enter the enterocyte cytosol, indicating a leakage through the cell membrane, but endocytic uptake was not observed. Asterisks indicate enterocytes in the process of exfoliation. Inserts show enlarged image details. Bars: 20 µm.