Flaim K E, Li J B, Jefferson L S
Am J Physiol. 1978 Aug;235(2):E231-6. doi: 10.1152/ajpendo.1978.235.2.E231.
The effects of thyroxine (T4) on protein turnover in skeletal muscle were studied using normal, thyroidectomized (thyrex), and hypophysectomized (hypox) rats. Thyrex rats had a depressed growth rate that was accompanied by 50% reductions in the level of RNA and the rate of protein synthesis in gastrocnemius muscle, as determined in the perfused hemicorpus. Protein synthetic efficiency (protein synthesis per unit RNA) was decreased by 18%. Daily treatment of thyrex rats with T4 at different dose levels for up to 16 days led to improved growth rates, elevated RNA concentrations, and increased protein synthesis rates. The primary effect of T4 was to increase the protein synthetic capacity of muscle. Protein degradation, determined in the perfused hemicorpus, and activity of a lysosomal protease, determined in unperfused muscle, were reduced in the thyrex condition. Treatment of thyrex rats with T4 increased protein degradative rates, but not protease activity. Hypox rats, which also exhibited depressed skeletal muscle protein synthesis, responded to T4 and combined T4 and growth hormone with marked improvements in protein synthesis.
利用正常大鼠、甲状腺切除大鼠（thyrex）和垂体切除大鼠（hypox）研究了甲状腺素（T4）对骨骼肌蛋白质周转的影响。甲状腺切除大鼠生长速率降低，同时，如在灌注半体中所测定的，腓肠肌中RNA水平和蛋白质合成速率降低了50%。蛋白质合成效率（每单位RNA的蛋白质合成）降低了18%。用不同剂量水平的T4每日处理甲状腺切除大鼠长达16天，导致生长速率提高、RNA浓度升高以及蛋白质合成速率增加。T4的主要作用是增加肌肉的蛋白质合成能力。在灌注半体中测定的蛋白质降解以及在未灌注肌肉中测定的溶酶体蛋白酶活性，在甲状腺切除状态下降低。用T4处理甲状腺切除大鼠增加了蛋白质降解速率，但未增加蛋白酶活性。垂体切除大鼠也表现出骨骼肌蛋白质合成降低，对T4以及T4与生长激素联合使用有反应，蛋白质合成有显著改善。
