The magnitude of the initial injury induced by stretches of maximally activated muscle fibres of mice and rats increases in old age
The magnitude of the initial injury induced by stretches of maximally activated muscle fibres of mice and rats increases in old age
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DOI：
10.1113/jphysiol.1996.sp021790
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发表时间：
1996-12-01
影响因子：
5.5
通讯作者：
Faulkner, JA
中科院分区：
文献类型：
--
作者：
Brooks, SV;Faulkner, JA
1.我们的目的是比较不同年龄动物肌肉对拉伸收缩肌肉所致损伤的敏感性。单次拉伸为研究引起收缩损伤的因素提供了一个有效的方法。我们假设，与年轻或成年小鼠相比，对于老年小鼠最活跃的肌肉，在任何给定拉力的单个拉伸过程中，功输入没有什么不同，但对于给定的功输入，损伤的程度更大。每一次拉伸产生的力赤字被计算为最大等轴力的减少，表示为拉伸前最大力的百分比。比较幼年、成年和老年小鼠在体趾长伸肌(EDL)单次拉伸1min后的力缺陷。此外，测量幼年和老年大鼠EDL肌单个通透性纤维段拉伸后立即出现的力缺陷，可以在收缩装置的水平上调查最初的损伤。对于幼鼠、成年鼠和老年鼠最大限度激活的EDL肌肉，在任何给定应变的伸展过程中，没有观察到功输入的差异。此外，对于幼年和成年小鼠的肌肉来说，功和合力不足之间的关系没有什么不同。相比之下，无论是幼鼠还是成年鼠，肌肉的劳力不足关系在老年鼠的肌肉中明显更陡峭。对于老年大鼠肌肉的单个通透性纤维，单次拉伸后即刻的力赤字大于幼年大鼠肌肉的纤维。我们的结论是，老年动物肌肉对收缩引起的损伤的敏感性增加，至少部分存在于肌原纤维中。
1. Our purpose was to compare the susceptibilities of muscles in animals of different ages to the injuries induced by stretching the contracting muscle. Single stretches provide an effective method for studying the factors that contribute to the initiation of contraction-induced injury. We hypothesized that, for maximally activated muscles in old compared with young or adult mice, the work input during a single stretch of any given strain is not different, but for a given work input the magnitude of the injury is greater.2. The force deficit resulting from each single stretch was calculated as the decrease in the maximum isometric force expressed as a percentage of the maximum force prior to the stretch. Force deficits were compared 1 min after single stretches of in situ extensor digitorum longus (EDL) muscles of young, adult and old mice. In addition, measurements of force deficits immediately following single stretches of single permeabilized fibre segments from EDL muscles of young and old rats permitted investigation of the initial injury at the level of the contractile apparatus.3. For maximally activated EDL muscles in young, adult and old mice, no differences were observed for the work input during stretches of any given strain. Furthermore, the relationships between the work and the resultant force deficit were not different for muscles in young and adult mice. In contrast, compared with the work-force deficit relationships for muscles in either young or adult mice, the relationship was significantly steeper for muscles in old mice. For single permeabilized fibres from muscles of old rats, the force deficits immediately after single stretches were greater than those observed for fibres from muscles of young rats. We conclude that the increased susceptibility of muscles in old animals to contraction-induced injury resides at least in part within the myofibrils.