Binding of erythropoietin to CFU-E derived from fetal mouse liver cells.
The binding of recombinant erythropoietin (EPO) to fetal mouse liver cells (FMLC) was investigated using a radioiodinated derivative which retained full biological activity. FMLC were fractionated using a preformed Percoll density gradient. Using the fractionated FMLC, the ability to form CFU-E colonies in a semisolid culture was examined, and the binding of [125I]EPO was measured. The highest specific binding of [125I]EPO was observed in a fraction with a density between 1.062 and 1.076 g/ml. The same fraction showed the highest ability to form CFU-E-derived colonies. After suspension culture of FMLC with EPO for 2 days, differentiated erythroid cells with higher density markedly increased. The specific binding of [125I]EPO to these cells almost disappeared with differentiation. Scatchard analysis with cells of the CFU-E-enriched fraction showed a nonlinear curve, suggesting the existence of two classes of binding sites. One binding site was high-affinity (Kd1 = 0.41 nM), and the other low-affinity (Kd2 = 3.13 nM). These results suggest that the expression of EPO receptors on the erythroid cells is highest in CFU-E.
Fukamachi
H
H
Saito
T
T
Tojo
A
A
Kitamura
T
T
Urabe
A
A
Takaku
F
F
D000818:Animals; D002478:Cells, Cultured; D003584:Cytological Techniques; D004921:Erythropoietin / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D007457:Iodine Radioisotopes; D008099:Liver / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D051379:Mice / Q000196:embryology*
D007457:Iodine Radioisotopes; D004921:Erythropoietin