EPO, red cells, and serum transferrin receptor in continuous and intermittent hypoxia

Purpose: Erythropoietic response in 10 healthy nonsmoking Volunteers expose d to normobaric hypoxia continuously or intermittently 12 h daily for 7 d w as evaluated in a randomized cross-over study. Methods: An oxygen content o f 15.4% corresponding to an altitude of 2500 m was created by adding nitrog en into room air in a flat. Venous blood samples for hemoglobin (Hb), hemat ocrit (Hct), reticulocytes, serum erythropoietin (S-EPO), red cell 2,3-diph osphoglycerate (2,3-DPG), serum ferritin (S-Ferrit), and serum soluble tran sferrin receptor (S-TransfR) were drawn at 8:00 a.m. Results: S-EPO was inc reased from baseline: values of 22.9 +/- 9.6 and 20.5 +/- 10.1 U.L-1 to 40. 7 +/- 12.9 (P < 0.05) and 35 +/- 14.3 U.L-1 (P < 0.05) after the first nigh t in continuous and intermittent hypoxia, respectively, and remained elevat ed throughout both exposures. Hb and Nct values did not show any significan t changes. Red cell 2,3-DPG rose from baseline a value of 5.0 +/- 0.8 to 5. 9 +/- 0.7 mmol.L-1 (P < 0.05) after the first day in continuous hypoxia and from 5.2 +/- 0.7 mmol.L-1 to 6.1 +/- 0.5 mmol.L-1 on day 3 (P < 0.05) duri ng intermittent hypoxia. The reticulocyte count rose significantly (P < 0.0 5) after 5 d in both experiments. S-transferrin receptor level rose signifi cantly from 2.2 +/- 0.4 and 2.1 +/- 0.5 mg.L-1 to 2.6 +/- 0.5 mg.L-1 and 2. 3 +/- 0.6 mg.L-1 on day 5 (P < 0.05), to 2.7 +/- 0.5 mg.L-1 and 2.5 +/- 0.6 mg.L-1 on day 7 (P < 0.05) under continuous and intermittent hypoxia, resp ectively. Conclusions: We suggest that intermittent exposure to moderate no rmobaric hypoxia 12 h daily for 1 wk induces a similar stimulation of eryth ropoiesis as continuous exposure.