Mediation of a Receptor Mechanism in the Uptake of Iron from Transferrin by the Hepatocyte

Abstract

Using doubly labeled, purified rat transferrin and isolated rat hepatocytes, it can be shown that transferrin binding to the hepatocyte is specific, saturable and temperature independent. Interaction with the 26,000 receptors per hepatocyte, however, requires iron to be bound to the transferrin. Iron uptake from transferrin by the viable hepatocyte is energy and temperature dependent. The uptake also clearly follows different kinetics to the cell presented with non-transferrin-bound iron and can be altered by withdrawal of pyruvate and amino acids from the medium. The uptake appears to involve the binding of transferrin, followed by the separate transport of iron across the membrane in a complexed form. It is concluded from this study that the uptake of iron from transferrin by the hepatocyte is receptor mediated and consists of at least two distinct steps.