Receptors for recombinant erythropoietin in human bone marrow cells

Abstract

Human recombinant erythropoietin, labelled with ¹²⁵I, was saturably bound to high affinity receptors, k_a=1.5×10⁹M⁻¹, of bone marrow cells from 10 patients with various haematological disorders. Binding of labelled erythropoietin was specific, with less than 0.01% cross-reactivities of TSH, hCG and renin substrate (angiotensinogen). Binding capacity averaged 3×10⁻¹⁴ moles/10⁶ cells. Binding was maximal within 30 min at 37 °C. Low binding, less than 15% of that to bone marrow cells, was found to peripheral blood buffy coat, while erythrocytes and BALL cells did not bind labelled erythropoietin. Autoradiography showed binding of label confined to 4–5% of the bone marrow cells.

Key words:

• autoradiography
• binding kinetics