Hepatocyte Iron Uptake - A Plasma Membrane Process or an Endosomal Process ?

The mechanisms by which eucaryotic cells accumulate iron from transferrin are still controversial, as visualized by the two major counterparts,the plasma-membrane model (1) and the endocytotic model (2). Recent studies suggest, however, that the two models rather than being contradictory are complementary, differing only in expression in different cells (3). Thus, in hepatocytes iron uptake from transferrin is largely linked to plasma membrane symport proton- and electron-fluxes (3),whereas in reticulocytes receptor-mediated endocytosis predominates (2,4). As to be expected, in hepatocytes iron uptake is extremely sensitive to oxygen. Similar sensitivity is not found in reticulocytes (5).