title: Pharmacodynamics of recombinant human erythropoietin in murine bone marrow.
abstract: OBJECTIVE
  Originally approved for three times/week dosing, recombinant human erythropoietin (rhEPO) is now often used at weekly intervals. We have studied rhEPO in mice to better understand why the extended dosing interval retains efficacy.
  
  
  METHODS
  C57Bl/6 mice received a single sc. dose of rhEPO (3,000 IU/kg). Bone marrow and blood were collected at 8 h and 1, 2, 5 and 7 days. Staining for TER-119 and CD71, pulse labeling with bromodeoxyuridine, annexin-V binding and vital staining with 7-aminoactinomycin D: were used cell cycle and apoptosis in erythroblasts by four color flow cytometry.
  
  
  RESULTS
  A wave of proliferation and/or maturation progressed through all erythroblasts, resulting in the emigration of immature reticulocytes into the periphery. An increase in the fraction of erythroblasts in S and G2M was found, but suppression of apoptosis was not.
  
  
  CONCLUSIONS
  Most of the effects of rhEPO occurred 48 h after dosing, when the concentration of rhEPO was less than 1% of Cmax, suggesting that the processes set in motion by rhEPO can continue after rhEPO concentrations fall. Our observation of apoptosis in erythroblasts even when rhEPO concentrations were high suggests that regulatory mechanisms which down-regulate erythropoiesis are also engaged.
authors.affiliation: Discovery Research, Centocor Research & Development, Inc., Radnor, SP 19087, USA. pbugelsk@cntus.jnj.com
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Bugelski
authors.forename: Thomas
authors.initials: T
authors.lastname: Nesspor
authors.forename: Amy
authors.initials: A
authors.lastname: Volk
authors.forename: Joanne
authors.initials: J
authors.lastname: O'Brien
authors.forename: Dorie
authors.initials: D
authors.lastname: Makropoulos
authors.forename: Kim
authors.initials: K
authors.lastname: Shamberger
authors.forename: Paul W
authors.initials: PW
authors.lastname: Fisher
authors.forename: Ian
authors.initials: I
authors.lastname: James
authors.forename: Danielle
authors.initials: D
authors.lastname: Graden
authors.forename: Renold J
authors.initials: RJ
authors.lastname: Capocasale
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects; D001853:Bone Marrow / Q000187:drug effects*; D002453:Cell Cycle / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D015672:Erythroid Precursor Cells / Q000187:drug effects; D004921:Erythropoietin / Q000493:pharmacokinetics / Q000494:pharmacology*; D005260:Female; D005434:Flow Cytometry; D051379:Mice; D008810:Mice, Inbred C57BL; D011994:Recombinant Proteins; D012016:Reference Values; D012156:Reticulocytes / Q000187:drug effects
chemical_list: D011994:Recombinant Proteins; D004921:Erythropoietin