The Transport, Uptake, and Storage of Ferritin in Human Epidermis

Rapid access of circulating materials to all epidermal cells to the level of the barrier layer has been demonstrated by utilizing ferritin. With the exception of granular cells, in which the material was often diffusely distributed, ferritin was membrane-bound and appeared to enter cells only via pinocytotic vesicles. These membrane-bound organelles, which contained ferritin, stained positively for acid phosphatase, indicating their lysosomal nature. The ferritin was aggregated within the cell by membrane merging of these vesicles. Ferritin was also deposited within lysosomes containing melanin granules.