Erythropoietin stimulates a rise in intracellular free calcium concentration in single early human erythroid precursors.
Erythropoietin and granulocyte-macrophage colony-stimulating factor (GM-CSF) stimulate the differentiation and proliferation of erythroid cells. To determine the cellular mechanism of action of these growth factors, we measured changes in intracellular free calcium concentration [( Cac]) in single human erythroid precursors in response to recombinant erythropoietin and GM-CSF. [Cac] in immature erythroblasts derived from cultured human cord blood erythroid progenitors was measured with fluorescence microscopy digital video imaging. When stimulated with erythropoietin, [Cac] in the majority of erythroblasts increased within 3 min, peaked at 5 min, and returned toward baseline at 10 min. The percentage of cells that responded to erythropoietin stimulation increased in a dose-dependent manner. Additional stimulation with GM-CSF in cells previously exposed to erythropoietin resulted in a second [Cac] increase. Immature erythroblasts treated with GM-CSF followed by erythropoietin responded similarly to each factor with a rise in [Cac]. The source of transient calcium is intracellular since erythroblasts were incubated in medium devoid of extracellular calcium. Our observations suggest that changes in [Cac] may be an intracellular signal that mediates the proliferative/differentiating effect of hematopoietic growth factors.
Miller
B A
BA
Department of Pediatrics, Pennsylvania State University, Hershey 17033.
Scaduto
R C
RC
Tillotson
D L
DL
Botti
J J
JJ
Cheung
J Y
JY
D001826:Body Fluids / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism*; D003115:Colony-Stimulating Factors / Q000494:pharmacology; D004900:Erythroblasts / Q000187:drug effects / Q000378:metabolism*; D004921:Erythropoietin / Q000494:pharmacology*; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D006133:Growth Substances / Q000494:pharmacology; D006412:Hematopoietic Stem Cells / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D007231:Infant, Newborn; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D011994:Recombinant Proteins / Q000494:pharmacology
D003115:Colony-Stimulating Factors; D006133:Growth Substances; D011994:Recombinant Proteins; D004921:Erythropoietin; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D002118:Calcium