title: Erythropoietin causes down regulation of colony-stimulating factor (CSF-1) receptors on peritoneal exudate macrophages of the mouse.
abstract: We have shown that erythropoietin (epo), the primary regulator of erythrocyte formation, diminished the binding to peritoneal exudate macrophages (PEM) of the principal macrophage growth regulator, colony-stimulating factor (CSF-1). The effect of epo on 125I-CSF-1 binding was dose-dependent; at a concentration of 1-2 U of epo/ml (10(-10) M), CSF-1 binding was almost completely suppressed. Erythropoietin did not compete with CSF-1 for occupancy of the latter's receptors. The effect of epo on CSF-1 binding occurred at 37 degrees C but not at 2 degrees C, and during the continuous exposure of PEM to epo at 37 degrees C we found that CSF-1 binding reached a nadir at 1 h and recovered to pre-exposure levels in 7 h. Our novel results are consistent with the notion that specific receptors for epo exist on the cell surface of PEM and that binding of epo sets in motion a series of cellular events resulting in the internalization of CSF-1 receptors. Thus epo causes down regulation of CSF-1 receptors on PEM. We have previously shown that epo causes suppression of CSF-induced granulocyte-macrophage colony formation by mouse bone marrow cells. The results we present here provide a possible mechanism for these results.
mesh_terms: D000818:Animals; D001681:Biological Assay; D003115:Colony-Stimulating Factors / Q000378:metabolism*; D004921:Erythropoietin / Q000494:pharmacology*; D007700:Kinetics; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D011956:Receptors, Cell Surface / Q000187:drug effects / Q000378:metabolism*; D016184:Receptors, Colony-Stimulating Factor
chemical_list: D003115:Colony-Stimulating Factors; D011956:Receptors, Cell Surface; D016184:Receptors, Colony-Stimulating Factor; D004921:Erythropoietin