Comparison of amphibian whole-cell and cell-free activity towards different transferrins.

1. A cell-free preparation from immature-erythrocytes of the bullfrog (Rana catesbeiana) was about equally active towards iron bound to homologous, rabbit or human transferrin. 2. In contrast with the cell-free system, whole immature erythrocytes exhibited optimum, intermediate or low uptake of iron from the above and from other transferrins.