Conde R D, Scornik O A
Biochem J. 1976 Aug 15;158(2):385-90. doi: 10.1042/bj1580385.
Fractional rates of synthesis and degradation of liver porteins were estimated during the rapid restoration of liver mass observed in protein-depleted mice when they are fed with an adequate diet. 1. Net protein gain was fastest 12h after the nutritional shift, when it reached a rate of 48% per day. 2. The RNA/protein ratio in livers of protein-depleted animals was essentially the same as in normal livers; it increased by a maximum of 13% 12h after the nutritional shift. 3. Rates of protein synthesis in vivo were measured by the incorporation into liver protein of massive amounts of L-[1-14C]leucine. In protein-depleted animals, the rate of synthesis per mg of RNA was 72% of that in normal livers. Normal rates were recovered within 12h of the nutritional shift. 4. The fraction of newly synthesized protein retained by the liver was studied after they were pulse-labelled by the intravenous injection of radioactive leucine, and, 5 min later, pactamycin (an inhibitor of the initiation of protein synthesis); 3h later the livers in both experimental situations retained 58% of the newly synthesized protein. 5. Fractional rates of protein degradation were estimated either from the difference between the synthesis of stable liver proteins and the net protein increase, or by the disappearance of radioactivity from the liver protein previously labelled by the administration to the mice of NaH14CO3. Both procedures demonstrated a large decrease in the rate of protein degradation during liver growth.
在蛋白质缺乏的小鼠摄入充足饮食后肝脏质量快速恢复的过程中，对肝脏蛋白质的合成和降解分数率进行了评估。1. 营养转换后12小时净蛋白质增加最快，达到每天48%的速率。2. 蛋白质缺乏动物肝脏中的RNA/蛋白质比率与正常肝脏基本相同；营养转换后12小时最多增加13%。3. 通过大量L-[1-¹⁴C]亮氨酸掺入肝脏蛋白质来测量体内蛋白质合成速率。在蛋白质缺乏的动物中，每毫克RNA的合成速率是正常肝脏的72%。营养转换后12小时内恢复到正常速率。4. 通过静脉注射放射性亮氨酸进行脉冲标记，5分钟后注射放线菌酮（一种蛋白质合成起始抑制剂），研究肝脏保留的新合成蛋白质的比例；3小时后，两种实验情况下的肝脏都保留了58%的新合成蛋白质。5. 蛋白质降解分数率通过稳定肝脏蛋白质合成与净蛋白质增加之间的差异来估计，或者通过给小鼠注射NaH¹⁴CO₃预先标记的肝脏蛋白质中放射性的消失来估计。两种方法都表明肝脏生长过程中蛋白质降解速率大幅下降。
