Lewis S E, Kelly F J, Goldspink D F
Biochem J. 1984 Jan 15;217(2):517-26. doi: 10.1042/bj2170517.
The growth of one smooth and three individual striated muscles was studied from birth to old age (105 weeks), and where possible during the later stages of foetal life also. Developmental changes in protein turnover (measured in vivo) were related to the changing patterns of growth within each muscle, and the body as a whole. Developmental growth (i.e. protein accumulation) in all muscles involved an increasing proportion of protein per unit wet weight, as well as cellular hypertrophy. The contribution of the heart towards whole-body protein and nucleic acid contents progressively decreased from 18 days of gestation to senility. In contrast, post-natal changes in both slow-twitch (soleus) and fast-twitch (tibialis anterior) skeletal muscles remained reasonably constant with respect to whole-body values. Such age-related growth in all four muscle types was accompanied by a progressive decline in both the fractional rates of protein synthesis and breakdown, the changes in synthesis being more pronounced. Age for age, the fractional rates of synthesis were highest in the oesophageal smooth muscle, similar in both cardiac and the slow-twitch muscles, and lowest in the fast-twitch tibialis muscle. Despite these differences, the developmental fall in synthetic rates was remarkably similar in all four muscles, e.g. the rates at 105 weeks were 30-35% of their values at weaning. Such developmental changes in synthesis were largely related to diminishing ribosomal capacities within each muscle. When measured under near-steady-state conditions (i.e. 105 weeks of age), the half-lives of mixed muscle proteins were 5.1, 10.4, 12.1 and 18.3 days for the smooth, cardiac, soleus and tibialis muscles respectively. Old-age atrophy was evident in the senile animals, this being more marked in each of the four muscle types than in the animal as a whole. In each muscle of the senile rats the protein content and composition per unit wet weight, and both the fractional and total rates of synthesis, were significantly lower than in the muscles of younger, mature, animals (i.e. 44 weeks). In the soleus the decreased synthesis rate appeared to be related to a further fall in the ribosomal capacity. In contrast, the changes in synthesis in the three remaining muscles correlated with significant decreases in the synthetic rate per ribosome.(ABSTRACT TRUNCATED AT 400 WORDS)
研究了一条平滑肌和三条不同的横纹肌从出生到老年（105周）的生长情况，在可能的情况下，也研究了胎儿后期的生长情况。蛋白质周转（体内测量）的发育变化与每条肌肉以及整个身体内不断变化的生长模式相关。所有肌肉的发育性生长（即蛋白质积累）涉及单位湿重中蛋白质比例的增加以及细胞肥大。从妊娠18天到衰老，心脏对全身蛋白质和核酸含量的贡献逐渐减少。相比之下，出生后慢肌（比目鱼肌）和快肌（胫骨前肌）骨骼肌相对于全身值的变化保持相对稳定。所有四种肌肉类型中这种与年龄相关的生长伴随着蛋白质合成和分解的分数率逐渐下降，合成的变化更为明显。同一年龄段，食管平滑肌的合成分数率最高，心肌和慢肌相似，快肌胫骨肌最低。尽管存在这些差异，但所有四种肌肉中合成率的发育性下降非常相似，例如，105周时的合成率是断奶时的30 - 35%。这种合成的发育变化在很大程度上与每条肌肉内核糖体能力的降低有关。在接近稳态条件下（即105周龄）测量时，平滑肌、心肌、比目鱼肌和胫骨肌的混合肌肉蛋白半衰期分别为5.1、10.4（此处原文可能有误，结合前文推测可能是12.1）、12.1和18.3天。老年动物出现明显的老年萎缩，这在四种肌肉类型中的每一种都比整个动物更为明显。在老年大鼠的每条肌肉中，单位湿重的蛋白质含量和组成以及合成的分数率和总率均显著低于年轻成熟动物（即44周）的肌肉。在比目鱼肌中，合成率的降低似乎与核糖体能力的进一步下降有关。相比之下，其余三种肌肉的合成变化与每个核糖体合成率的显著降低相关。（摘要截断于400字）
