Ferritin turnover in plasma: an opportunistic use of blood removed during exchange transfusion.

The concentration of plasma ferritin was measured in serial samples of blood removed from six preterm neonates undergoing exchange transfusion for hyperbilirubinemia. The average plasma ferritin concentration in the infants was 218 ng/ml compared with 47 ng/ml in the donors. The mean concentration of ferritin decreased an average of 62 ng/ml during the exchange transfusions. The plasma ferritin half-life was computed to be 2.5 and 5.5 min in the two infants weighing 2,000 and 2,500 g compared with a half-life of 4 min in the rat. In four infants weighing between 1,000 and 1,180 g, the half-life ranged from 9.1 to 34 min. These data support the concept of a rapid plasma ferritin turnover and indicate that ferritin may transport a large amount of iron through the plasma compartment in spite of its low concentration.