Erythropoietin Secretion to Hypoxia Is Enhanced with an Expanded Plasma Volume after a Bout of Exercise in Warm Environment

Abstract

BACKGROUNDErythropoietin (EPO) secretion is a critical determinant for hematological adaptation to hypoxia, which is associated with the level of hypoxemia. Plasma volume (PV) expansion and the resultant hemodilution is observed even after a bout of exercise especially in warm conditions. With these as background, we tested the hypothesis that EPO secretion to hypoxia was enhanced with an expanded PV after a bout of exercise in a warm condition.METHODSEight healthy young men underwent two identical trials which differs only ambient temperature (Ta) during exercise. In a thermoneutral condition, baseline blood sample was taken, then subjects performed a 72‐min intense‐intermittent exercise (8 sets of 4 min at 80% VO2max ‐5 min at 20% VO2max) under cool (Ta, 20°C) and warm (Ta, 30°C) conditions. Twenty‐three hours after exercise, they exposed to hypoxia (14.4%) for 3 hours and blood sample was taken at the middle and the end of exposure. We determined percent change in PV (%ΔPV) from baseline and serum EPO. Also, esophageal (Tes) and mean skin temperature (Tsk) were measured during exercise.RESULTSDuring exercise, Tsk was significantly (p < 0.05) higher in warm than cool trial while Tes was comparable between trials. %ΔPV at 23 hours after excise was significantly higher in warm than cool trial. Serum EPO during exposure significantly increased from baseline in both trials and we found significant effects of interaction (trial x time) in serum EPO, indicating that EPO response to hypoxia was enhanced during warm trial.CONCLUSIONSEPO release to hypoxia was enhanced with expanded PV after a bout of exercise especially in a warm condition.Support or Funding InformationThis study was supported in part by a Grant‐in‐Aid for Scientific Research (17H03741) and a Grant‐in‐Aid for challenging Exploratory Research (16K13020), from Japan Society for the Promotion of Science for Kazunobu OkazakiThis abstract is from the Experimental Biology 2019 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.