Chronic exposure to stretch-shortening contractions results in skeletal muscle adaptation in young rats and maladaptation in old rats
Chronic exposure to stretch-shortening contractions results in skeletal muscle adaptation in young rats and maladaptation in old rats
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DOI：
10.1139/h06-033
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发表时间：
2006-10-01
影响因子：
3.4
通讯作者：
Alway, Stephen E.
中科院分区：
文献类型：
--
作者：
Cutlip, Robert G.;Baker, Brent A.;Alway, Stephen E.
本研究的目的是研究年轻和年老大鼠骨骼肌对慢性拉伸缩短周期（SSCs）的反应。老龄大鼠（30月龄，n = 5）和幼龄大鼠（12周龄，n = 6）的背屈肌在体内每周暴露3次，每次暴露80个最大ssc，持续4.5周。骨骼肌反应的特征是等长和动态性能，以及肌肉湿质量和暴露期后的定量形态学分析。在开始接触时，年轻组和老年组的表现没有统计学差异。然而，在暴露结束时，发现了统计学上的差异，年轻动物的表现显著提高，而年老动物的表现显著下降。治疗肢体左胫骨前肌（TA）的肌肉湿量在年轻的动物中显著大于年老的动物（p < 0.001），而在对侧TA没有差异。两组小鼠均未见退行性肌纤维或非细胞间质变化，但老年小鼠暴露肢体的细胞间质体积显著增加（p = 0.01），这表明存在炎症反应。因此，长期暴露于ssc会导致幼龄动物的生产性能显著提高和肌肉肥大，而老龄动物的生产性能显著降低和细胞间质反应增加。这些发现表明，即使在没有退化的情况下，年龄也可能损害骨骼肌适应重复性机械负荷的能力。
The objective of this research was to investigate skeletal muscle response to a chronic administration of stretch-shortening cycles (SSCs) in young and old rats. Dorsiflexor muscles of old (30 months, n = 5) and young (12 weeks, n = 6) rats were exposed 3 times/week for 4.5 weeks to a protocol of 80 maximal SSCs per exposure in vivo. Skeletal muscle response was characterized by isometric and dynamic performance, as well as by muscle wet mass and quantitative morphological analyses following the exposure period. The performance of the young and old groups was not statistically different at the start of the exposure. By the end of the exposure, however, a statistical difference was noted, as performance increased significantly in the young animals and decreased significantly in the old animals. Muscle wet mass of the left tibialis anterior (TA) in the treated limb was significantly greater in the youngthan in the old animals (p < 0.001), whereas there was no difference in the contra-lateral TA. No degenerative myofibers or changes in non-cellular interstitium were noted in either age group, but a significant increase was observed in the volume of the cellular interstitium in the exposed limb of the old animals (p = 0.01), which is indicative of an inflammatory response. Thus, a chronic exposure of SSCs results in significant performance increase and muscle hypertrophy in young animals, and a significant performance decrease and an increased cellular interstitial response in old animals. These findings suggest that age may impair the ability of skeletal muscle to adapt to repetitive mechanical loading, even in the absence of degeneration.