Uptake of cationized ferritin by colonic epithelium.

Guinea-pig, rat and mouse were used in this electron microscopic study to demonstrate endocytosis in absorptive and goblet cells of the surface epithelium of the colon. Cationised ferritin was used as the electron dense tracer which attached in vivo to negatively charged membrane components. Both coated and uncoated vesicles entered the cells. The major pathway for the vesicles was to the secondary lysosomes and occurred within 10-30 min. This demonstrates a new pathway of absorption in the adult rodent colon with potential for the uptake of macromolecules. It may provide new clues to the immunology, physiology and pathology of the tissue.