Larsson L, Li X, Frontera W R
Department of Clinical Neurophysiology and Neurology, Karolinska Hospital, Stockholm, Sweden.
Am J Physiol. 1997 Feb;272(2 Pt 1):C638-49. doi: 10.1152/ajpcell.1997.272.2.C638.
Maximum unloaded shortening velocity (V0) and maximum force normalized to cross-sectional fiber area (specific tension) were determined in 400 single quadriceps muscle cells of young (n = 4, 25-31 yr) and old (n = 4, 73-81 yr) men. Two of the old men were physically very active, and the subjects were divided into young control, old control, and old physically active groups. The expressions of types I, IIa, and IIb myosin heavy chains (MHC) and essential and regulatory myosin light chains were determined by 6 and 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis. V0 was highly dependent on the MHC isoform composition, and a gradient from slow to fast was observed in the sequence I, I-IIa, IIa, IIab, and IIb MHC cells. The V0 values and specific tensions of types I and IIa MHC fibers in the young control group were significantly higher than those in the old control and old physically active groups. Thus the present results provide evidence of qualitative changes in contractile properties of human skeletal muscle in old age, which probably play an important role in the age-related impairment of skeletal muscle function.
在400个来自年轻男性（n = 4，25 - 31岁）和老年男性（n = 4，73 - 81岁）的股四头肌单肌细胞中，测定了最大无负荷缩短速度（V0）和以横截面积纤维面积标准化的最大力量（比张力）。其中两名老年男性身体活动非常活跃，受试者被分为年轻对照组、老年对照组和老年身体活动组。通过6%和12%的十二烷基硫酸钠 - 聚丙烯酰胺凝胶电泳测定I型、IIa型和IIb型肌球蛋白重链（MHC）以及必需和调节性肌球蛋白轻链的表达。V0高度依赖于MHC同工型组成，并且在I、I - IIa、IIa、IIab和IIb MHC细胞序列中观察到从慢到快的梯度。年轻对照组中I型和IIa型MHC纤维的V0值和比张力显著高于老年对照组和老年身体活动组。因此，目前的结果提供了老年时人类骨骼肌收缩特性发生质性变化的证据，这可能在与年龄相关的骨骼肌功能损害中起重要作用。
