Hypoxic Exercise On The Impact Of Rat’s Skeletal Muscle Proliferation

1 PurposeThe purposes of this investigation are to observe the overall changes in proliferation in skeletal muscle fibers and their changes among different muscle fiber types after hypoxic adaptive exercise.2 Materails and MethodsAdult male Sprague-Dawley rats,weighing 228～253g,were randomly allocated to four groups(normoxia control group,normobaric training group,hypoxia group and hypoxic exercise group) according to independent variables.The 4 weeks concentric exercises were adopted at the speed of 20m/min,with running time from 10min to 60min.All rats were killed by pentobarbital sodium through intraperitoneal infection immediately after exercise.All organs were then snap frozen in liquid nitrogen and stored at -80℃.The expression of proliferating cell nuclear antigen (PCNA) were detected by immunohistochemistry and identificated of muscle fiber types by useing modified method of the mitachromatic dye-ATPase.Images acquired from stained sections were analyzed with Image-Pro Plus.3 Results3.1 Normobaric training can induced large increases(P<0.01) of the proliferation in gastrocnemius muscle fibers compared with normobaric quiet groups,increasing 50.4%at 7 days,58.3%at 14 days,81.3%at 21 days and 62.9%at 28 days.3.2 Compared with normobaric hypoxia,chronic hypoxia induced a significant increase(P<0.01) in the proliferation in the gastrocnemius muscle fibers after 14 days increased 65.3%,21 days increased 99%and 28 days increased 42.3%,and at 7 days,the proliferation in the gastrocnemius muscle fibers also increased 24.8%(P＜0.05).3.3 The proliferation in gastrocnemius muscle fibers under hypoxic training were elevated remarkable(P＜0.01) at 7 days,14 days and 21 days comparing normobaric training groups and normobaric groups.But at 28 days,the proliferation in gastrocnemius muscle fibers under hypoxic training were decreased significantly(P＜0.01) compared 7 days,14 days and 21 days.3.4 The proliferation in gastrocnemius muscle fiber typesⅠwas more significant than in muscle fiber typesⅡ.4 Conclusions4.1 Both hypoxia and hypoxic exercise can stimulate skeletal muscle fibers proliferation to generate muscle fibers.Thus,the adaptability of skeletal muscle are improving.4.2 Normobaric training,hypoxia and hypoxic exercise also can induced large increases of the proliferation in muscle fibers.This shows that hypoxic training stimulate biggest boost the proliferation of muscle fibers.4.3 The proliferation in muscle fiber typesⅠwas more significant than in muscle fiber typesⅡ.This shows that hypoxic training stimulate differently among different type of muscle fibers.Muscle fiber typesⅠhave the biggest ability of repairing and proliferation.