有氧训练对骨骼肌生理功能的影响
【摘要】目的：研究4～6wk跑台训练对雄性SD大鼠腓肠肌肌球蛋白 (myosin heavy chain，MHC)收缩功能的影响。
方法：实验以40只雄性SD大鼠为研究对象，将其随机分为对照组和训练组。
运动训练组大鼠进行连续4～6wk强度约为75％VO2max(18.5～24m／min，坡度为0°，每次运动50min，每天2次)的跑台训练，反转录聚合酶链式反应(RT—PCR)腓肠肌MHC mRNA含量，以免疫组化方法检测肌球蛋白肌纤维的改变情况及横截面积的大小，同时运用电刺激观察训练后腓肠肌等长收缩最大张力。
结果：①连续4～6wk跑台训练后,MHCⅡx、MHCⅡb mRNA含量分别是安静对照组的109％(P0.05)和108％(P0001)，MHCⅡb和MHCⅠmRNA变化不明显。
②训练后肌球蛋白转变为以Ⅰ型慢型纤维为主，同时肌纤维横截面积增大。
③方波脉冲刺激后6wk训练组等长收缩最大张力较对照组显著增加(P0.01)。
结论：短期耐力训练后,MHC中的两种慢型MHC异形体－MHCⅡx、MHCⅡb基因表达增加，肌纤维横截面积增加，等长收缩最大张力增加。
【关键词】有氧运动；肌球蛋白； mRNA；横截面积【Abstract】Objective:To investigate the effect of treadmill training on the contractile function of gastrocnemius myosin heavy chain (MHC) of SD rat. Methods: Applied 40 male SD rats as the investigated objects and randomly divided them into control group and training group (T—group). The treadmill training of T—group rats were continuously trained for 4~6 weeks at the intensity of about 75% VO2max (185～24m／min,gradient of 0°,each motion lasting 50 minutes,twice a day). Detect the content of gastrocnemius MHC mRNA by gastrocnemius reverse transcription polymerase chain reaction (RT—PCR),and detect the changes of MHC muscle fiber and its size of cross section area (CSA) through immunohistochemistry. Meanwhile,apply the electric stimulation to determine the maximal tension of isometric contraction of post—training gastrocnemius. Result:①After the continuous treadmill training for 4~6 weeks,the contents of total MHC,MHC I,MHC IIx,MHC IIa mRNAs were 105%(P0.05),105%(P0.05),109%(P0.01) and 108%(P0.01) of that of the resting control group,respectively,and the contents of mRNA of MHC IIb did not change significantly. The percentage of MHC I mRNA in total MHC mRNA increased while that of MHC II mRNA decreased after aerobic training.②The maximal tension of isometric contraction of the T—group with 6 weeks of training increased significantly compared with the control group by pulse stimulation of square wave(P0.01). Conclusion: The expression of genes of MHC I,MHC IIx,MHC IIa,the CSA of muscle fibers and the maximal tension of isometric contraction were all increased after the short—term endurance training. The percentage of MHC II mRNA decreased but that of MHC I mRNA increased when the training was completed. The results suggested that the aerobic exercise may promote the increase of the contractile function of MHC. And aerobic training may cause the transformation of MHC II muscle fibers to MHC I.【Key words】Aerobic exercise;Myosin heavy chain; mRNA;Cross section area长期耐力训练能导致肌纤维及其MHC异形体由快型向慢型转变。
这一点已有大量的研究采用组织化学、免疫组织化学和蛋白电泳方法在蛋白水平上进行了证实[1~3]。
但对于运动训练中MHC异形体mRNA的变化，本研究采用RT—PCR、免疫组化及方波脉冲刺激等技术，观察4～6wk耐力训练对大鼠骨骼肌肌球蛋白收缩功能的影响，通过检测MHC各异形体mRNA的变化和肌纤维横截面改变，探讨运动训练影响其变化的可能因素。
1材料与方法1.1实验动物：雄性SD大鼠20只，体重230±16g，随机分为对照组(n=10)和训练4wk组(n=10)，训练5wk组(n=10)，训练6wk组(n=10)。
所有动物实验前均未进行过跑台运动。
1.2试剂：一抗为鼠源性抗骨骼肌肌动蛋白及快缩型肌球蛋白重链（MHCⅡ）单克隆抗体，ABCam产品。
二抗为偶合碱性磷酸酶的抗鼠 IgG，SIGMA产品。
1.3运动方式：训练组动物每天进行两次运动训练，每次50min，跑速为18.5m／min～24m／min，坡度为0°，运动强度为70％～75％VO2max。
持续训练4～6wk[4]。
1.4半定量RT—PCR检测腓肠肌MHC和α—actin表达水平。
2结果2.1有氧训练对腓肠肌MHC表达的影响：经过4周耐力训练，训练组肌球蛋白总MHC表达是对照组的105％ （P0.01）。
MHCⅡa和MHCⅡx mRNA表达较对照组显著增加 （P0.05， P0001）。
训练前后各MHC亚型在总MHC中的比例分另Ⅱ是253％ vs 254％（MHCⅠ)、245％ vs 252％（MHCⅡa）、24.9％ vs 25.6％ （MHCⅡx）和25.3％ vs23.7％（MHCⅡb）。