Amino acid and hormonal control of macromolecular turnover in perfused rat liver. Evidence for selective autophagy.
Amino acid and hormonal control of macromolecular turnover in perfused rat liver. Evidence for selective autophagy.
复制标题
DOI：
10.1016/s0021-9258(18)47825-8
复制
发表时间：
1987-10
期刊：
影响因子：
--
通讯作者：
B. Lardeux;G. E. Mortimore
中科院分区：
文献类型：
--
作者：
B. Lardeux;G. E. Mortimore
在先前用[6- 14 C]乳清酸体内标记的喂食大鼠的灌注肝脏中研究了氨基酸、胰岛素和胰高血糖素对RNA降解的控制;在0.5 mM胞苷抑制再利用的情况下，根据[14 C]胞苷的释放测定了速率。循环灌注肝脏的研究表明，血浆氨基酸在10倍（10倍）正常浓度下抑制RNA分解85%。用已知的调节氨基酸混合物（Leu、Met、Pro、Trp和His）获得类似的抑制，而单独的亮氨酸（0.8mM）使降解降低47%。以单通道模式进行的血浆氨基酸水平分级灌注显示，在氨基酸剥夺的整个范围内（0至10倍正常水平），RNA降解的加速与蛋白质分解的加速相同（分别为3.19和3.15% h-1），并且两者都受到胰岛素的同等抑制（2.4微克h-1）。然而，胰高血糖素（10微克h-1）在刺激RNA方面远不如蛋白质周转有效。两种剂量反应的直接比较显示，在正常氨基酸水平的1倍和2倍下存在强烈的解离。这些发现支持了这样一种观点，即在氨基酸和胰岛素剥夺期间，RNA和蛋白质在单个大自噬区室中降解。然而，胰高血糖素似乎诱导了第二条途径，其中被隔离的RNA与蛋白质的比例被选择性地降低。电镜观察表明，在这些条件下，含有粗面内质网的空泡与含有光滑内质网的空泡的比例减少了近80%。
The control of RNA degradation by amino acids, insulin, and glucagon was investigated in perfused livers of fed rats previously labeled in vivo with [6-14C] orotic acid; rates were determined from the release of [14C]cytidine in the presence of 0.5 mM cytidine to suppress reutilization. Studies with cyclically perfused livers showed that plasma amino acids at 10 times (10X) normal concentrations inhibited RNA breakdown by 85%. Similar inhibition was obtained with a known regulatory amino acid mixture (Leu, Met, Pro, Trp, and His), whereas leucine alone (0.8 mM) decreased degradation by 47%. Perfusions carried out in the single-pass mode with graded levels of plasma amino acids revealed that the acceleration of RNA degradation over the full range of amino acid deprivation (0 to 10X normal levels) was the same as that for protein breakdown (3.19 and 3.15% h-1, respectively), and both were equally suppressed by insulin (2.4 micrograms h-1). Glucagon (10 micrograms h-1), though, was far less effective in stimulating RNA than protein turnover. A direct comparison of the two dose responses revealed a strong dissociation at 1 and 2 times normal amino acid levels. These findings support the notion that RNA and protein are degraded within a single macroautophagic compartment during amino acid and insulin deprivation. Glucagon, however, appeared to induce a second pathway in which the proportion of sequestered RNA to protein was selectively reduced. Electron micrographs showed that the ratio of vacuoles containing rough as compared with smooth endoplasmic reticulum was decreased by nearly 80% under these conditions.