The uptake of cationised ferritin and its subsequent redistribution by gallbladder epithelium in vivo.

Cationised ferritin was injected into the gallbladders of guinea pigs at operation and its subsequent fate studied with an electron microscope over a 24-hr period. The apical cell membrane of the epithelium was tagged and showed patching. The cationised ferritin was internalised into small vesicles, some derived from coated pits, within 5 min. Other vesicles were found at the same time near the lateral cellular membrane. Cationised ferritin was found in lysosomes and in residual bodies in large quantities and occasionally in multivesicular bodies and vesicles near the Golgi apparatus. Clumps of (cationised) ferritin appeared in the lateral intercellular space, 2 hr after exposure, increasing in number with time up to 5 hr. Similar clumps also were found between the basal cell membrane and the lamina rara interna of the basement membrane in a fairly regular pattern. By 5 hr the marker was beginning to pass through the basement membrane. The process was largely complete by 10 hr. Twenty-four hours after injection of cationised ferritin, virtually no marker was found in either the epithelium or underlying connective tissue.