Iron transfer from ferritin to transferrin. Effect of serum factors.

The transfer of iron from 59Fe-labelled human spleen ferritin to human apotransferrin occurs in the absence of either reducing or chelating agents. The reaction is first order with respect to ferritin and zero order to apotransferrin. The transfer is enhanced by low-Mr substances from human serum such as ascorbate, citrate, bicarbonate and lactate. A mixture of the four molecules at their normal physiological concentrations can increase the iron exchange to the same extent as that observed with an ultrafiltrate of serum. A pathway of intracellular iron mobilization is considered.