Abstract:

Objective   To explore the effects ofdifferent hypoxia training methods on EPO-EPOR to provide a theoretical and application basis for using hypoxia training.   Methods   After adaptability training and exhaustive tests,90 rats were selected from 120 male SD rats (6week old) and randomly divided into 9 groups:the normoxia quiet control group, the continuing hypoxia group, the intermittent  hypoxia group, the normaxia training group, the living-high and training-high group(HiHi), the living-high and training-low group(HiLo), the living-low and training-high group(LoHi), the normoxia training group after HiHi, and the normoxia training group after HiLo. During a 6-week experimental period, 13.6% concentration of oxygen (equal to  an altitude of 3 500 m) was introduced into the hypoxic chamber.Rats that had undergone hypoxia training were introduced to a treadmill. The speed of training was 30m/min in hypoxia and 35m/min in normoxia. Then the rats were trained 5d/week and weresacrificed after 6 weeks. RQ-PCR, immunohistochemistry and Western blot were used to determine the mRNA and protein levels of HIF-1αin the skeletal muscle to probe further into the mechanisms of acclimatization in the skeletal muscle.   Results    Compared with the LoLo group, the mRNA level of EPO and EPOR in both the HiHi group (P＜0.01) and the HiLo group（P＜
0.05）significantly increased. In the normoxia training group after HiHi, the mRNA level of EPO in the serum significantly increased (P＜0.05), and the mRNA level of EPO and EPOR in skeletal muscle decreased significantly; while in the normoxia training group after HiLo, the mRNA level of EPO in the skeletal muscle significantly decreased (P＜0.05).   Conclusion  It is concentration of oxygen rather than hypoxia that causes changes in the level of EPO, which may be related to exposure time of hypoxia. The mRNA level of EPO in the skeletal muscle is negatively related to that of EPO in the serum（r=-0.676）, also, the mRNA levels of EPO and EPOR in the skeletal muscle are closely related.

Key words: Hypoxia-training； EPO；  EPOR；  Skeletal muscle; Rats, sprague-dawley