Preedy V R, Smith D M, Kearney N F, Sugden P H
Biochem J. 1984 Sep 1;222(2):395-400. doi: 10.1042/bj2220395.
Starvation of 300 g rats for 3 days decreased ventricular-muscle total protein content and total RNA content by 15 and 22% respectively. Loss of body weight was about 15%. In glucose-perfused working rat hearts in vitro, 3 days of starvation inhibited rates of protein synthesis in ventricles by about 40-50% compared with fed controls. Although the RNA/protein ratio was decreased by about 10%, the major effect of starvation was to decrease the efficiency of protein synthesis (rate of protein synthesis relative to RNA). Insulin stimulated protein synthesis in ventricles of perfused hearts from fed rats by increasing the efficiency of protein synthesis. In vivo, protein-synthesis rates and efficiencies in ventricles from 3-day-starved rats were decreased by about 40% compared with fed controls. Protein-synthesis rates and efficiencies in ventricles from fed rats in vivo were similar to values in vitro when insulin was present in perfusates. In vivo, starvation increased the rate of protein degradation, but decreased it in the glucose-perfused heart in vitro. This contradiction can be rationalized when the effects of insulin are considered. Rates of protein degradation are similar in hearts of fed animals in vivo and in glucose/insulin-perfused hearts. Degradation rates are similar in hearts of starved animals in vivo and in hearts perfused with glucose alone. We conclude that the rates of protein turnover in the anterogradely perfused rat heart in vitro closely approximate to the rates in vivo in absolute terms, and that the effects of starvation in vivo are mirrored in vitro.
对300克重的大鼠禁食3天，可使心室肌总蛋白含量和总RNA含量分别降低15%和22%。体重减轻约15%。在体外对工作状态的大鼠心脏进行葡萄糖灌注时，与喂食对照相比，禁食3天可使心室中的蛋白质合成速率降低约40 - 50%。虽然RNA/蛋白质比率降低了约10%，但饥饿的主要影响是降低蛋白质合成效率（蛋白质合成速率相对于RNA）。胰岛素通过提高蛋白质合成效率来刺激喂食大鼠灌注心脏心室中的蛋白质合成。在体内，与喂食对照相比，禁食3天的大鼠心室中的蛋白质合成速率和效率降低了约40%。当灌注液中存在胰岛素时，体内喂食大鼠心室中的蛋白质合成速率和效率与体外值相似。在体内，饥饿会增加蛋白质降解速率，但在体外葡萄糖灌注的心脏中则会降低。当考虑胰岛素的作用时，这种矛盾就可以得到合理的解释。在体内喂食动物的心脏和葡萄糖/胰岛素灌注的心脏中，蛋白质降解速率相似。在体内饥饿动物的心脏和仅用葡萄糖灌注的心脏中，降解速率相似。我们得出结论，从绝对值来看，体外顺行灌注大鼠心脏中的蛋白质周转速率与体内速率非常接近，并且体内饥饿的影响在体外也能体现出来。
