title: Comparative response of EPO and soluble transferrin receptor at high altitude.
abstract: OBJECTIVE
  Soluble transferrin receptor (sTfR) classically raises with increased erythropoiesis, along with the rise in erythropoietin (EPO). However, the specific effect of altitude-induced erythropoiesis on sTfR remains poorly documented. This study investigated the response of sTfR during high-altitude exposure in human and verified that sTfR was related to EPO response in this case.
  
  
  METHODS
  EPO, sTfR, red cell volume (RCV), ferritin, and iron intake were measured during: 1) experiment A (N = 8, 31 d at 5000-8848 m), at sea level (SL), and at the simulated altitude of 5000, 6000, 7000, and 8000 m; and 2) during experiment B (N = 10, 7 d at 4350 m), at SL, after 3, 5, and 7 d at 4350 m and 1-2 d after return to SL (RSL).
  
  
  RESULTS
  In experiment A, progressive decompression from SL to 8000 m induced a large parallel rise in EPO (33.8-fold) and sTfR (5.9-fold), whereas ferritin was dramatically decreased and iron intake reduced. RCV was increased after 31 d of decompression. In experiment B, EPO peaked at day 3 at 4350 m, then declined later at altitude and returned to baseline values at RSL, whereas sTfR progressively rose at altitude (+86%) and remained elevated during RSL (+64%). Ferritin progressively declined at 4350 m, whereas iron intake was unchanged. RCV was not enhanced after exposure to 4350 m.
  
  
  CONCLUSIONS
  In summary, sTfR mirrors EPO response for a given level of altitude hypoxia but differs from EPO response during transitory phases, such as early acclimatization or reoxygenation. Analysis of sTfR may therefore account for altitude-related erythropoiesis, at a time when EPO is blunted.
authors.affiliation: ARPE, Laboratory Cellular and Functional Responses to Hypoxia, Faculty of Medicine, Bobigny, France. paul.robach@ensa.jeunesse-sports.fr
authors.forename: Paul
authors.initials: P
authors.lastname: Robach
authors.forename: Yvonne
authors.initials: Y
authors.lastname: Fulla
authors.forename: Klaas R
authors.initials: KR
authors.lastname: Westerterp
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Richalet
mesh_terms: D000531:Altitude; D004911:Erythrocyte Volume; D004921:Erythropoietin / Q000097:blood*; D006801:Humans; D011990:Receptors, Transferrin / Q000097:blood*
chemical_list: D011990:Receptors, Transferrin; D004921:Erythropoietin