Uptake of lactoferrin by the liver. II. Endocytosis by sinusoidal cells.

Because of the controversy on the cell type involved in lactoferrin (Lf) uptake by the liver we localized injected Lf by immunofluorescence, light microscopic autoradiography, and light and electron microscope cytochemistry with Lf-peroxidase conjugates. These conjugates were essentially taken up by their Lf moiety as shown by competition experiments. By any procedure, Lf was almost exclusively found in the sinusoidal cells as well as in the wall of the central veins. These data directly demonstrate that both endothelial and Kupffer cells are responsible for Lf uptake by the liver.