Model Experiments for the Study of Iron Transfer from Transferrin to Ferritin

Abstract

1 The transfer of iron from transferrin to ferritin was followed using radioactive tracers. It was a passive process which was unaffected by the iron moving against a concentration gradient. 2 A reducing agent was essential and had three functions:–(a) to assist in removal of iron from transferrin; (b) to form a ferrous chelate as an intermediate; (c) to ensure that iron is in the ferrous form for uptake on to the ferritin. Ascorbic acid was the best of those reducing agents tested. 3 Transfer was enhanced by chelators. The iron chelate formed on removal of iron from transferrin must be stable enough to effect removal of iron from transferrin, but not so stable as to prevent formation of the ferritin iron complex. 4 Increasing concentrations of chelator, reducing agent or ferritin all enhance percentage iron transfer. 5 The reaction is pH dependant and is at a maximum at 7.3. 6 Transfer is dependant on the iron content of the transferrin and ferritin used. Transferrin with 50% or less iron saturation does not transfer iron. Ferritin takes up most iron when it is about 50% iron saturated. 7 The α, β and γ fractions of ferritin were isolated and their order of iron uptake from transferrin found to be > α > β > γ.