FIGURE 4 .

Butyrate facilitates redistribution of ZO-1 and occludin during calcium switch-induced tight junction assembly Caco-2 cells were grown in normal DMEM for 2–3 d to confluence and subjected to incubation with a low-calcium medium for 16 h. When calcium was switched back into the medium in the absence or presence of butyrate at 2 mmol/L for indicated times, the cell monolayers were fixed and the distribution of ZO-1 (A) and occludin (B) in intercellular junctions was visualized by probing the target proteins with specific antibodies. The fluorescence images were obtained with a confocal laser scanning microscope (scale bars = 20 μm).