Effects of insulin in vitro on protein turnover in rat epitrochlearis muscle.
Effects of insulin in vitro on protein turnover in rat epitrochlearis muscle.
复制标题
体外胰岛素对大鼠滑车上肌蛋白质周转的影响。
DOI：
10.1042/bj2100323
复制
发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Low,RB
中科院分区：
文献类型：
--
作者：
Stirewalt,WS;Low,RB
用放射性示踪技术，以tRNA结合氨基酸的放射性为蛋白质合成的前体，测定了离体大鼠上滑车肌蛋白质合成和降解的速率。在氨基酸和葡萄糖存在下以及在胰岛素不存在下孵育3小时，组织保持蛋白质合成的线性速率。然而，在这些条件下，肌肉处于负氮平衡，蛋白质降解速率超过蛋白质合成速率。在稳态条件下的标记，tRNA结合的亮氨酸，苯丙氨酸和缬氨酸的特定放射性显着小于其各自的值在孵育介质中，在介质中的浓度从1到10倍，在正常大鼠血清中的变化。胰岛素引起基于tRNA的蛋白质合成速率的剂量和时间依赖性增加，在5和50 ng胰岛素/ml时，速率增加一倍以上。在较低的生理浓度的胰岛素下，直到与激素孵育的第三小时才观察到蛋白质合成的刺激，而在较高浓度下的蛋白质合成速率在第二小时期间升高。胰岛素刺激葡萄糖转化为糖原没有延迟。胰岛素对蛋白质合成速率的延迟刺激作用使组织达到接近零的氮平衡。激素的存在也阻止了在没有激素的情况下孵育第三小时所见的蛋白质降解速率的增加。这些研究表明，在蛋白质代谢和敏感性的蛋白质合成作用的生理浓度的胰岛素的孵育大鼠上滑车肌的可行性，并表明该制剂是一个合适的实验模型，用于研究的控制蛋白质代谢的快速收缩骨骼肌。
Rates of protein synthesis and degradation were measured in the isolated rat epitrochlearis muscle by radiotracer techniques, by using the specific radioactivity of tRNA-bound amino acid as precursor for protein synthesis. The tissue maintained linear rates of protein synthesis for 3 h of incubation in the presence of amino acids and glucose and in the absence of insulin. Under these conditions, however, the muscles were in negative nitrogen balance, with rates of protein degradation exceeding rates of protein synthesis. Under steady-state conditions of labelling, the specific radioactivities of tRNA-bound leucine, phenylalanine and valine were significantly less than their respective values in the incubation medium, at concentrations in the medium varying from 1 to 10 times those in normal rat serum. Insulin caused a dose- and time-dependent increase in tRNA-based protein synthesis rates, more than doubling rates at 5 and 50 ng of insulin/ml. At the lower, physiological, concentration of insulin, the stimulation of protein synthesis was not observed until the third hour of incubation with the hormone, whereas the rate of protein synthesis at the higher concentration was elevated during the second hour. There were no delays in the stimulation by insulin of glucose conversion into glycogen. The delayed stimulatory effects of insulin on the rate of protein synthesis brought the tissue to a nitrogen balance near zero. The presence of the hormone also prevented the increase in the rate of protein degradation seen in the third hour of incubation in the absence of the hormone. These studies demonstrate the viability of the incubated rat epitrochlearis muscle with respect to protein metabolism and sensitivity to the protein anabolic effects of physiological concentrations of insulin, and indicate that the preparation is a suitable experimental model for the study of the control of protein metabolism in fast-twitch skeletal muscle.