The effect of ageing and immobilization on structure and function of human skeletal muscle fibres
The effect of ageing and immobilization on structure and function of human skeletal muscle fibres
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DOI：
10.1113/jphysiol.2003.046276
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发表时间：
2003-10-15
影响因子：
5.5
通讯作者：
Bottinelli, R
中科院分区：
文献类型：
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作者：
D'Antona, G;Pellegrino, MA;Bottinelli, R
活检样本取自7名青年(Yo，年龄30.2±-2.2岁)、7名老年(El，年龄72.7+/-2.3岁)受试者和2名右腿制动3.5个月的老年受试者(El-imm，年龄分别为70岁和75岁)。研究了以下主要参数：(1)用SDS-PAGE测定样品的肌球蛋白重链(MHC)亚型分布；(2)用SDS-PAGE测定肌球蛋白重链(MHC)亚型组成的大群(n=593)单个肌纤维的横截面积(CSA)、比力(P-o/Csa)和最大缩短速度(V-o)；(3)用体外运动试验测定肌球蛋白亚型上的肌动蛋白滑动速度(V-f)；(4)用定量SDS-PAGE测定单个肌球蛋白纤维中肌球蛋白的浓度。在EL和EL-IMM中，MHC异构体分布向快异构体方向移动，向快异构体移动的程度更大。在EL中，更一致地，在EL-IMM中，我们观察到混合纤维的比例高于YO，并注意到MHC新生儿的存在以及包含两个以上MHC异构体的不寻常的混合纤维的存在。P-o/CsA在1型和2A型纤维中按YO-->；EL-->；EL-IMM顺序显著降低。I型和2A型纤维的V-O值在EL组显著低于YO组，而在EL-IMM组显著高于YO组，即制动多于抵消年龄相关性的V-O下降。对于V-f，没有观察到后一种现象。肌球蛋白1的V-f在EL和EL-IMM均低于YO。肌球蛋白2X上的V-f在EL比YO低，肌球蛋白2A也有类似的趋势。肌球蛋白浓度在I型和2A型纤维中按YO-->；EL-->；EL-IMM顺序降低，并与同一受试者相应类型纤维的PO/CSA值呈线性相关。实验表明：(1)肌球蛋白浓度是老化过程中和固定后单纤维P-o/CSA降低的主要决定因素；(2)由于肌球蛋白本身性质的变化，老化与单纤维的V-o降低有关，而在肌球蛋白功能没有改变的情况下，固定与较高的V-o有关。
Biopsy samples were taken from vastus lateralis muscle of seven young (YO, age 30.2 +/- 2.2 years), and seven elderly (EL, age 72.7 +/- 2.3 years) subjects and two elderly subjects whose right leg had been immobilized for 3.5 months (EL-IMM, ages 70 and 75). The following main parameters were studied: (1) myosin heavy chain (MHC) isoform distribution of the samples, determined by SDS-PAGE; (2) cross-sectional area (CSA), specific force (P-o/CSA) and maximum shortening velocity (V-o) of a large population (n = 593) of single skinned muscle fibres, classified on the basis of MHC isoform composition determined by SDS-PAGE; (3) actin sliding velocity (V-f) on pure myosin isoforms determined by in vitro motility assays; (4) myosin concentration in single fibres determined by quantitative SDS-PAGE. MHC isoform distribution was shifted towards fast isoforms in EL and to a larger extent in EL-IMM. In EL and, more consistently, in EL-IMM we observed a higher percentage of hybrid fibres than in YO, and noted the presence of MHC-neonatal and of unusual hybrid fibres containing more than two MHC isoforms. P-o/CSA significantly decreased in type 1 and 2A fibres in the order YO --> EL --> EL-IMM. V-o of type I and 2A fibres was significantly lower in EL and higher in EL-IMM than in YO, i.e. immobilization more than counteracted the age-dependent decrease in V-o. The latter phenomenon was not observed for V-f. V-f on myosin 1 was lower in both EL and EL-IMM than in YO. V-f on myosin 2X was lower in EL than in YO, and a similar trend was observed for myosin 2A. Myosin concentration decreased in type I and 2A fibres in the order YO --> EL --> EL-IMM and was linearly related to the PO/CSA values of corresponding fibre types from the same subjects. The experiments suggest that (1) myosin concentration is a major determinant of the lower P-o/CSA of single fibres in ageing and especially following immobilization and (2) ageing is associated with lower V-o of single fibres due to changes in the properties of myosin itself, whereas immobilization is associated with higher V-o in the absence of a change in myosin function.