Studies on the partition of transferrin‐donated iron in rabbit reticulocytes

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Abstract
Summary. Reticulocytes with high cytosolic non-haem radioiron content were prepared by adding metabolic inhibitors. The cells were then reincubated without the inhibitors for various periods of time. Cytosol was prepared from the labelled cells and fractionated on a Sephadex G-100 column on which four main non-haem radioiron containing peaks could be distinguished. During reincubation the 59Fe content of these cytosol fractions changed in different ways. The high molecular weight fraction showed little metabolic activity, indicating that this fraction is not utilized for haem synthesis when iron is in excess in the cytosol. The second non-haem radioiron containing peak eluted with the haemoglobin moiety. This non-haem iron binding substance proved to be rather stable: 1 mM EDTA could not remove a significant amount of iron from it. During reincubation its radiorion content decreased almost linearly with time. Two further peaks eluted in the low molecular weight region. Their kinetics during reincubation suggest that these peaks represent those non-haem iron components of the cytosol which can reversibly move from the cytosol into the stroma compartment.