Figure 4
Ferritin is endocytosed by duodenal enterocytes. (A) Immunostaining of duodenal sections from mice fed biotin tagged, PK-treated, scrapie infected mouse brain homogenates with streptavidin-Texas-red shows uptake of biotin tagged material by intestinal epithelial cells (panel 1, arrow-heads). Unabsorbed reactive material is detected in the intestinal lumen (panel 1, arrow, @). Co-immunostaining with rabbit-anti-ferritin antibody followed by goat anti-rabbit-FITC shows co-localization of streptavidin and ferritin reactive material (panels 2 and 3, arrow-heads). Endogenous mouse ferritin cross-reacts with the antibody and is detected in most epithelial cells (panel 2, *). Bar: 10 μm. Inset shows enlarged image of the boxed area. (B) Immunostaining of adjacent section with antibody to ZO-1 demonstrates intact tight junctions in these samples (arrow). (C) Staining with H & E shows optimal preservation of tissue under these experimental conditions.