title: Erythropoietin binding to the red cell membranes.
abstract: Some characteristics of Epo binding to the red cell membranes were investigated in a system in which the hormone was added to a suspension of cells in a mixture of normal serum phosphate buffered saline (1:7 (V/V)), testing the unbound Epo. Epo binding shows a gradual decrease during the maturation of red cells (0.15 U/ml packed erythrocytes, 0.285 U/ml reticulocytes and 0.375 U/ml erythroblasts from a total of 1.4 U/ml). The binding is also time- and pH-dependent. The amounts of Epo bound within 60 min are independent of temperature, but after 120 min a dissociation of the hormone-receptor complex occurred at 23 and 37 degrees; at 4 degrees C the binding continue, although at a very low rate. RBC membranes bound the hormone at pH 7.8-8 and release it at pH 6.5. The "in vivo" stimulation of beta receptors with isoproterenol increases the erythropoietic response caused by Epo, suggesting a possible relation with the adenylcyclase system.
mesh_terms: D000740:Anemia / Q000097:blood; D000818:Animals; D004910:Erythrocyte Membrane / Q000378:metabolism*; D004921:Erythropoietin / Q000097:blood* / Q000302:isolation & purification / Q000494:pharmacology; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007545:Isoproterenol / Q000494:pharmacology; D051379:Mice; D011485:Protein Binding; D011817:Rabbits; D011943:Receptors, Adrenergic, beta / Q000187:drug effects; D012156:Reticulocytes / Q000378:metabolism; D013696:Temperature; D013997:Time Factors
chemical_list: D011943:Receptors, Adrenergic, beta; D004921:Erythropoietin; D007545:Isoproterenol