Transmembrane transport of iron from extracellular transferrin by lymphoma cells

Abstract

Transferrin is essential for the entry of iron into cells, but whether the entire iron-transferrin complex or only the iron enter is not known. Separation of the cellular from the interparticulate radioactivity is a common problem with such studies. By pelleting cells under oil, we have made precise measurements of the uptake capacity for ⁵⁹Fe of mouse lymphoma RI cells. At 37°C an 18-fold concentration of iron was observed within 30 min; at 0°C this value was about 3-fold. At 37°C a maximus of 18,000 molecules of ¹²⁵I-labelled Fe-transferrin were bound to each cell; this was reduced by about half at 0°C. At 37°C about 10,000–12,000 binding sites for ¹²⁵I-apotransferrin were detected on each cell. From our data we conclude that although essential enters RI cells. It is possible that iron is actively transported and that the receptor population is heterogenous.