Figure 5.

Coated buds and 60-nm vesicles in polarized cells containing basolaterally directed tracers. Endosomal tubules containing basolaterally applied TF-HRP and apically applied IgA-gold. The TF-HRP serves to identify endosomal elements accessible from the basolateral surface, and the IgA-gold demonstrates that these elements also process apically derived tracer. Fig. 3 shows that TR are routed preferentially to the basolateral border, and significant amounts of the IgA are also routed basolaterally from the endosome. (a) Double arrowheads indicate coated buds containing concentrated TF-HRP reaction product. The small arrow indicates clathrin lattice. (b) Cytoplasmic coats are seen on the tubules (small arrows) and on apparently free 60-nm-diam vesicles (larger arrows) that contain concentrated TF-HRP and IgA-gold tracer. as, IgA-gold on apical surface; J, junctional complex; bs, basolateral surface with TF-HRP within intercellular space. Bars, 0.1 μm.