Cytosolic Ca(2+) levels and DNA synthesis of human umbilical vein endothelial cell cultures are unresponsive to thrombopoietin treatment.
The hormone thrombopoietin (TPO) induces proliferation of megakaryocytic progenitors and augments agonist-induced mobilization of Ca(2+) in platelets. Because the action of TPO is not restricted to the megakaryocytic lineage, we studied the occurrence of TPO receptor mRNA and protein, and effects of TPO on cytosolic Ca(2+) levels and DNA synthesis in human umbilical vein endothelial cell cultures (HUVECs). Polymerase chain reaction following reverse transcription (RT-PCR) of total mRNA revealed that TPO receptor (MPL) mRNA was expressed only at low level in our samples. TPO receptor protein was not detectable in HUVEC lysates investigated by immunoprecipitation and immunoblotting. In contrast to vascular endothelial growth factor (VEGF), TPO did neither alter fura2 fluorescence as a measure of cytosolic Ca(2+) levels nor increase 5-bromo-2'-deoxyuridine incorporation into DNA of HUVECs. In conclusion, our data demonstrate that HUVECs are neither structurally nor functionally responsive to TPO.
Metzen
E
E
Institut of Physiology, Medical Universit of Luebeck, Germany.
Giesen
G
G
Fandrey
J
J
Jelkmann
W
W
D002118:Calcium / Q000378:metabolism*; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003600:Cytosol / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis*; D016228:Endothelial Growth Factors; D004730:Endothelium, Vascular / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D006801:Humans; D008222:Lymphokines; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011994:Recombinant Proteins / Q000494:pharmacology; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013926:Thrombopoietin / Q000494:pharmacology*; D014471:Umbilical Veins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors
D016228:Endothelial Growth Factors; D008222:Lymphokines; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D018121:Receptors, Cytokine; D053628:Receptors, Thrombopoietin; D011994:Recombinant Proteins; D042461:Vascular Endothelial Growth Factor A; D042442:Vascular Endothelial Growth Factors; C082218:MPL protein, human; D004247:DNA; D013926:Thrombopoietin; D002118:Calcium