The diurnal response of muscle and liver protein synthesis in vivo in meal-fed rats.
The diurnal response of muscle and liver protein synthesis in vivo in meal-fed rats.
复制标题
膳食喂养大鼠体内肌肉和肝脏蛋白质合成的昼夜反应。
作者：
P. Garlick;D. J. Millward;W. James
1.通过持续静脉输注[（14）C]酪氨酸测定大鼠组织中蛋白质合成的速率。已经开发了一种改进方法，用于根据输注结束时组织中游离和蛋白结合氨基酸的比放射性计算单个组织中蛋白合成速率。该技术提供了更高的准确性，并允许标记的氨基酸的更多选择。血浆中游离酪氨酸的比放射性用于计算血浆酪氨酸通量，这是全身蛋白质合成速率的指数。2.年轻雄性Wistar大鼠每24 h仅允许进食4 h。测定了单次饲喂后不同时间肝脏和肌肉中酪氨酸通量和蛋白质合成速率。3.酪氨酸流量没有改变后，喂养，甚至饥饿48小时后。4.肌肉中蛋白质合成的平均分数速率为7.2%/天，即每天被替换的蛋白质质量的比例。饥饿48 h后，死亡率下降。此外，肌肉蛋白质合成速率与大鼠的生长速率相关。5.在肝脏中，蛋白质合成的平均分数速率为50%/天。进食后和饥饿48小时后，该比率均无变化。与肌肉相反，这表明蛋白质质量的变化伴随着蛋白质分解速率的变化，而不是合成速率的变化。
1. The rate of protein synthesis in rat tissues was measured by constant intravenous infusion of [(14)C]tyrosine. A modification has been developed for the method of calculating the rate of protein synthesis in individual tissues from the specific radioactivity of the free and protein-bound amino acid in tissue at the end of the infusion. This technique gives greater accuracy and allows a greater choice of labelled amino acids. The specific radioactivity of free tyrosine in plasma was used to calculate the plasma tyrosine flux, an index of the rate of protein synthesis in the whole body. 2. Young male Wistar rats were allowed access to food for only 4h in every 24h. The tyrosine flux and the rate of protein synthesis in liver and muscle at different periods of time after a single feed were estimated. 3. The tyrosine flux did not alter after feeding nor even after starvation for 48h. 4. The average fractional rate of protein synthesis in muscle was 7.2%/day, i.e. the proportion of the protein mass which is replaced each day. The rate rose after eating and declined during starvation for 48h. In addition the rate of muscle protein synthesis correlated with the growth rate of the rat. 5. In liver the average fractional rate of protein synthesis was 50%/day. There was no change in the rate after eating nor after starvation for 48h. In contrast with muscle this suggests that the changes in protein mass were accompanied by changes in the rate of protein breakdown rather than synthesis.