Effect of Surface Digestion and Metabolic Inhibitors on Appearance of Ferritin in Guinea Pig Erythroblasts In Vitro: Evidences for the Production of Apoferritin on the Erythroblast Cell Membrane

Short-term cultures of guinea pig erythroblasts permitted observation on the micropinocytosis (rhopheocytosis) of ferritin. In the presence of enzymes that attack the cell surface (neuraminidase and trypsin) or of an inhibitor of RNA synthesis (puromycin), accumulation of ferritin in the micropinocytotic vesicle was reduced. No change was seen in presence of lead nitrate, which inhibits transport of iron into hemoglobin-synthesizing cells only slightly. In the presence of potassium cyanide, which inhibits iron transport markedly, ferritin increased two-seven times over controls. The data are compatible with the notion that apoferritin is made on or near the cell surface in response to an excess of iron which accumulates on the cell surface due to failure or overloading of the normal transport mechanism.