Quantitation and characterization of serum transferrin receptor in patients with anemias and polycythemias.

Serum transferrin receptor concentration in patients with anemias and polycythemias was determined. The mean normal value was 258 +/- 82 ng/ml. Comparing with normal values, the higher values were obtained in patients with iron deficiency anemia, autoimmune hemolytic anemia, and polycythemias, while the lower values were obtained in patients with aplsatic anemia. During treatments of patients with iron deficiency anemia and autoimmune hemolytic anemia, serial change of serum receptor was paralleled with that of peripheral reticulocyte counts, suggesting that the circulating receptor values may reflect the activity of bone marrow erythropoiesis. The immunoreactive receptor was migrated at the position of alpha 1-globulin by agarose gel electrophoresis and the isoelectric point(pl) was 3.57 by isoelectric focusing. SDS-polyacrylamide gel electrophorogram of various patients' sera revealed that the autoradiographed band was migrated at the molecular weight of 110,000 daltons in the non-reducing condition and 46,000 and 23,000 daltons in the reducing condition. These bands were also capable of binding to 131I-labelled diferric transferrin. The proposed model of circulating transferrin receptor may be the nicked dimers of 55,000 daltons in which inter- and intra-disulfide bridges were present.