Fig. 4. The cellular location of punctate kfCFTR immunofluorescence in FW controls (a small minority of cells) and SW animals (all cells), as determined by optical sections in the confocal microscope, was in apical crypts approximately 7 µm deep. The transitional phases included many cells with punctate kfCFTR immunofluorescence well below the surface. It would appear kfCFTR distribution in FW is diffuse, then condenses in the first 24 h after salinity transfer, prior to moving kfCFTR to the apical membrane at approximately 48 h. Columns with different letters are significantly different (P<0.05 or better; single-classification ANOVA followed by a Bonferroni post-test).