Urbanchek M G, Picken E B, Kalliainen L K, Kuzon W M
Division of Plastic and Reconstructive Surgery, Department of Surgery, University of Michigan, Ann Arbor, 48109-0340, USA.
J Gerontol A Biol Sci Med Sci. 2001 May;56(5):B191-7. doi: 10.1093/gerona/56.5.b191.
We tested the hypothesis that denervated muscle fibers account for part of the specific force (sF(o)) deficit observed in muscles from old adult (OA) mammals. Whole muscle force (F(o)) was quantified for extensor digitorum longus (EDL) muscles of OA and young adult (YA) rats. EDL muscle sF(o) was calculated by dividing F(o) by either total muscle fiber cross-sectional area (CSA) or by innervated fiber CSA. Innervated fiber CSA was estimated from EDL muscle cross sections labeled for neural cell adhesion molecules, whose presence is a marker for muscle fiber denervation. EDL muscles from OA rats contained significantly more denervated fibers than muscles from YA rats (5.6% vs 1.1% of total CSA). When compared with YA muscle, OA muscle demonstrated deficits of 34.1% for F(o), 28.3% for sF(o), and 24.9% for sF(o) calculated by using innervated CSA as the denominator. Denervated muscle fibers accounted for 11.3% of the specific force difference between normal YA and OA skeletal muscle. Other mechanisms in addition to denervation account for the majority of the sF(o) deficit with aging.
我们验证了一个假说，即去神经支配的肌纤维是老年成年（OA）哺乳动物肌肉中所观察到的比力（sF(o)）不足的部分原因。对OA大鼠和年轻成年（YA）大鼠的趾长伸肌（EDL）进行了全肌肉力量（F(o)）的定量分析。EDL肌肉的sF(o)通过将F(o)除以总肌纤维横截面积（CSA）或支配纤维CSA来计算。支配纤维CSA是根据标记了神经细胞黏附分子的EDL肌肉横截面估算得出的，神经细胞黏附分子的存在是肌纤维去神经支配的一个标志。OA大鼠的EDL肌肉中去神经支配的纤维比YA大鼠的肌肉显著更多（分别占总CSA的5.6%和1.1%）。与YA肌肉相比，OA肌肉的F(o)降低了34.1%，sF(o)降低了28.3%，以支配CSA为分母计算的sF(o)降低了24.9%。去神经支配的肌纤维占正常YA和OA骨骼肌之间比力差异的11.3%。除了去神经支配外，其他机制是衰老过程中sF(o)不足的主要原因。
