Age-related changes in contractile properties of single skeletal fibers from the soleus muscle
Age-related changes in contractile properties of single skeletal fibers from the soleus muscle
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DOI：
10.1152/jappl.1999.86.3.881
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发表时间：
1999-03-01
影响因子：
3.3
通讯作者：
Brown, M
中科院分区：
文献类型：
--
作者：
Thompson, LV;Brown, M
测定了12只12月龄、24月龄、30月龄、36月龄和37月龄的Fischer 344 Brown Norway F1杂交大鼠比目鱼肌的124条单根骨骼肌纤维的绝对峰值力、比张力（单位横截面积的绝对峰值力）、横截面积、最大无负荷缩短速度（V - o；通过松弛试验测定）以及肌球蛋白重链（MHC）异构体组成。所有纤维均表达I型MHC异构体。平均V - o在12月龄到24月龄期间保持不变，但在24月龄到30月龄期间显著下降（从1.71±0.13到0.85±0.09纤维长度/秒）。纤维横截面积在36月龄之前保持恒定，在36月龄时比12月龄的值下降了20%（从5558±232到4339±280μm²）。单根纤维的绝对峰值力在12月龄到24月龄之间显著下降（从51±2×10⁻⁵到35±2×10⁻⁵ N），然后一直保持恒定直到36月龄，此时又下降了43%。与绝对峰值力一样，比张力在12月龄到24月龄之间显著下降了20%，在37月龄时又观察到下降了32%。因此，到24月龄时，纤维横截面积的减少和力的下降之间出现了解离。结果表明，随着年龄增长，收缩特性的变化具有时间特异性且相互独立。导致这些与时间相关和收缩特性特异性变化的潜在机制尚不清楚。肌球蛋白分子动力学的年龄相关变化可能是力产生改变的潜在机制。存在不止一种β/慢MHC异构体可能是V - o随年龄变化的机制。
Peak absolute force, specific tension (peak absolute force per cross-sectional area), cross-sectional area, maximal unloaded shortening velocity (V-o; determined by the slack test), and myosin heavy chain (MKC) isoform compositions were determined in 124 single skeletal fibers from the soleus muscle of 12-, 24-, 30-, 36-, and 37-mo-old Fischer 344 Brown Norway F1 Hybrid rats. All fibers expressed the type I MHC isoform. The mean V-o remained unchanged from 12 to 24 mo but did decrease significantly from the 24- to 30-mo time period (from 1.71 +/- 0.13 to 0.85 +/- 0.09 fiber lengths/s). Fiber cross-sectional area remained constant until 36 mo of age, at which time there was a 20% decrease from the values at 12 mo of age (from 5,558 +/- 232 to 4,339 +/- 280 mu m(2)). A significant decrease in peak absolute force of single fibers occurred between 12 and 24 mo of age (from 51 +/- 2 x 10(-5) to 35 +/- 2 x 10(-5) N) and then remained constant until 36 mo, when another 43% decrease occurred. Like peak absolute force, the specific tension decreased significantly between 12 and 24 mo by 20%, and another 32% decline was observed at 37 mo. Thus, by 24 mo, there was a dissociation between the loss of fiber cross-sectional area and force. The results suggest time-specific changes of the contractile properties with aging that are independent of each other. Underlying mechanisms responsible for the time-dependent and contractile property-specific changes are unknown. Age-related changes in the molecular dynamics of myosin may be the underlying mechanism for altered force production. The presence of more than one beta/slow MHC isoform may be the mechanism for the altered V-o with age.