Effects Of Hypoxia Training On The Expression Of HIF-1mRNA And The Iron Metabolism In Skeletal Muscle Of Rats

Iron is utilized by the body for oxygen transport, storage and ATP synthesis,energy production and there for iron is essential to athlete. Iron is needed for thesystemization of Hemoglobin (Hb) and Myoglobin(Mb).Exercise and hypoxia couldchange iron status of body. For Hypoxia training, hypoxia and exercise play a dualstimulation. It could improve the ability to carry and use oxygen. Mb of skeletalmuscle can accept and store oxygen transported by Hb. Hypoxia can stimulateskeletal muscle to adaptive changes in iron metabolism. It has been not much reportedthat the regulatory mechanism of the changed iron status and iron metabolism inmuscle during hypoxia training. The present study investigated the effects of hypoxiatraining on iron metabolism in skeletal muscle in vivo and the hypoxia on ironmetabolism in L6cells in vitro in order to illuminate the molecular regulatorymechanism of iron metabolism in hypoxia training.Methods：The experiments in vivo：Thirty-two male SD rats were randomly divided intofour groups: the normal control group (NC), the normal exercise group (NE),thehypoxia control group (HC), and the hypoxia exercise group(HE). The rats wererespectively run (21-25m/min,1h/d) or exposured to hypoxia (13.6%,8h/d) and thenwere sampled after5weeks. The total iron content of skeletal muscle weredetermined by atomic absorption spectra-photometer.The expression of HIF-1mRNAin muscle were determined by RT-PCR and the expression of transferring receport1(TfR1),divalent metal transporter1(DMTI:DMTI (IRE) and DMTI (non IRE) andferroportin l (FPN1))in gastronomies of rats were determined by Western Blot.The experiments in vitro: L6rat skeletal muscle cells were randomly divided intothree groups, and were exposured to hypoxia of0h,12h and24h. Isotope tracingmethod was used to determine the iron uptake and release. Iron content of labile ironpool was investigated by flow cytometry and the expression of TfR1,DMT1 （IRE）,DMT1（non IRE）and hypoxia-inducible transcription factor-1（HIF-1） inL6cells were observed by Western Blot.Results：1Effects of Hypoxic Training on Skeletal Muscle in Rats：(1) Compared with NC, the iron content of skeletal muscle of NE,HC and HEgroups were significantly increased, and HE group was much higher than NE and HCgroups（P<0.01）.(2) The HIF-1mRNA of HC and HE groups were much higher than the NC andNE groups (P<0.01).(3)Compared with NC, the expression of DMT1,TfR1in NE, HC, HE weresignificantly increased (P <0.05, P<0.01).The expression of FPN1in NE and HCwere significantly lower than that of NC (P <0.05, P <0.01), while the expression ofFPN1in HE group was significantly increased (P<0.01) than the other three groups.The expression of DMT1, TfR1and FPN1in HE were much higher than the NE andHC groups (P<0.01).2Effects of hypoxia on L6cells：（1）Compared with0-h hypoxia group,12-h hypoxia group exhibitedsignificantly increased iron uptake and LIP (P <0.05), as well as decreased ironrelease (P <0.01).（2）Not only iron uptake and release, but also LIP in24-h hypoxia group weresignificantly decreased, compared with those in0-and12-h hypoxia groups (P <0.01).（3）The expressions of HIF-1, DMT1(IRE), DMT1(non-IRE) and TfR1in12-h hypoxia group were significantly increased, compared with those in0-h hypoxiagroup (P <0.01). On the contrary, the expressions of DMT1(IRE), DMT1(non-IRE)and FPN1in24-h hypoxia group were significantly decreased compared with those inthe other two groups. However, the expression of TfR1in24-h hypoxia was higherthan those in0-and12-h hypoxia groups (P <0.05or P <0.01).Conclusions： （1）The results in vivo suggested that the iron storage of skeletal muscle wasincreased after the moderate exercise and exposure to hypoxia. While the hypoxiatraining was much more useful to improve the iron content of skeletal muscle.（2）The results in vitro suggested hypoxia plays an important role in ironmetabolism of skeletal muscle cells. Moderate hypoxia can increase iron uptake anddecrease iron release, resulting in higher LIP, but a prolonged hypoxia induces adisordered iron metabolism of skeletal cells.（3）During hypoxia，HIF-1was playing a key role on skeletal muscle of ironmetabolism。...