International Journal of Cell Cloning, Vol 7, 156-167, Copyright © 1989 by AlphaMed Press
Expression and characterization of erythropoietin receptors on normal human bone marrow cells
S Hoshino, M Teramura, M Takahashi, T Motoji, K Oshimi, M Ueda and H Mizoguchi
Department of Medicine, Tokyo Women's Medical College, Japan.
We studied the specific binding of 125I-labeled bioactive recombinant human
erythropoietin (Epo) to human bone marrow mononuclear cells (BMNC) obtained
from normal subjects. The 125I-labeled Epo bound specifically to the BMNC.
Scatchard analysis of the data showed two classes of binding sites; one
high affinity (Kd 0.07 nM) and the other low affinity (Kd 0.38 nM). The
number of Epo binding sites per BMNC was 46 +/- 16 high-affinity receptors
and 91 +/- 51 low-affinity receptors. The specific binding was displaced by
unlabeled Epo, but not by other growth factors. Receptor internalization
was observed significantly at 37 degrees C, but was prevented by the
presence of 0.2% sodium azide. These findings indicate that human BMNC
possess two classes of specific Epo receptors with characteristics of a
hormone-receptor association.
