Roy R R, Talmadge R J, Fox K, Lee M, Ishihara A, Edgerton V R
Department of Physiological Science and Brain Research Institute, University of California, Los Angeles, California 90095-1761, USA.
J Appl Physiol (1985). 1997 Jul;83(1):280-90. doi: 10.1152/jappl.1997.83.1.280.
The effects of 1 and 10 wk of functional overload (FO) of the rat plantaris with (FOTr) and without daily endurance treadmill training on its myosin heavy chain (MHC) composition were studied. After 1 and 10 wk of FO, plantaris mass was 22 and 56% greater in FO and 37 and 94% greater, respectively, in FOTr rats compared with age-matched controls. At 1 wk, pure type I and pure type IIa MHC fibers were hypertrophied in FO (39 and 44%) and FOTr (70 and 87%) rats. By 10 wk all fiber types comprising >5% of the fibers sampled showed a hypertrophic response in both FO groups. One week of FO increased the percentage of hybrid (containing both type I and type IIa MHC) fibers and of fibers containing embryonic MHC. By 10 wk, the percentage of pure type I MHC fibers was approximately 40% in both FO groups compared with 15% in controls, and the percentage of fibers containing embryonic MHC was similar to that in controls. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analyses showed an increase in type I MHC and a decrease in type IIb MHC in both FO groups at 10 wk, whereas little change was observed at 1 wk. These data are consistent with hypertrophy and transformation from faster to slower MHC isoforms in chronically overloaded muscles. The additional overload imposed by daily endurance treadmill training employed in this study (1.6 km/day; 10% incline) results in a larger hypertrophic response but appears to have a minimal effect on the MHC adaptations.
研究了对大鼠比目鱼肌进行1周和10周功能性过载（FO），以及在有（FOTr）和无每日耐力跑步机训练情况下，其肌球蛋白重链（MHC）组成的影响。在进行1周和10周的FO后，与年龄匹配的对照组相比，FO组比目鱼肌质量分别增加了22%和56%，FOTr组分别增加了37%和94%。在1周时，纯I型和纯IIa型MHC纤维在FO组（分别为39%和44%）和FOTr组（分别为70%和87%）大鼠中出现肥大。到10周时，在两个FO组中，所有占抽样纤维5%以上的纤维类型均表现出肥大反应。1周的FO增加了混合（同时含有I型和IIa型MHC）纤维以及含有胚胎MHC的纤维的百分比。到10周时，两个FO组中纯I型MHC纤维的百分比约为40%，而对照组为15%，且含有胚胎MHC的纤维百分比与对照组相似。十二烷基硫酸钠-聚丙烯酰胺凝胶电泳分析显示，在10周时两个FO组中I型MHC增加，IIb型MHC减少，而在1周时观察到变化很小。这些数据与慢性过载肌肉中肥大以及从较快的MHC亚型向较慢的MHC亚型转变一致。本研究中采用的每日耐力跑步机训练（1.6公里/天；10%坡度）所施加的额外过载导致更大的肥大反应，但似乎对MHC适应性影响最小。
