Stirewalt W S, Low R B, Slaiby J M
Biochem J. 1985 Apr 15;227(2):355-62. doi: 10.1042/bj2270355.
The insulin sensitivity of protein synthesis and glucose incorporation into glycogen by the soleus and epitrochlearis muscles from fed rats and 24 h-starved rats was determined in vitro during the first and second hours of incubation after isolation of the muscles. Rates of protein synthesis by both muscles from fed rats in the first hour of incubation were 2-fold higher than in the second hour and were not increased by insulin. Rates of protein synthesis during the first hour in the presence of 6000 microunits of insulin/ml were increased in soleus, but not in epitrochlearis, muscles from starved rats. Rates of protein synthesis in both muscles from fed and starved rats were increased significantly by insulin during the second hour. High concentrations of insulin caused a marked stimulation of the rates of glucose incorporation by both muscles from fed and starved rats in both the first and second hours of incubation. The insulin sensitivity of glucose incorporation during the second hour, defined as the concentration of insulin causing half-maximal stimulation, was increased 10-fold for both muscle types from starved rats (soleus, 65 microunits/ml; epitrochlearis, 45 microunits/ml) relative to muscles from fed rats (soleus, 600 microunits/ml; epitrochlearis, 500 microunits/m). The insulin sensitivity of protein synthesis in the second hour was greater for soleus muscles from starved rats (65 microunits/ml) than from fed rats (500 microunits/ml). In contrast, the insulin sensitivity of protein synthesis in epitrochlearis muscles from starved rats was significantly decreased (225 microunits/ml) compared with fed rats (25 microunits/ml Maximal rates achieved by high concentrations of insulin were not different from those in the same muscle from fed rats. It is suggested that protein synthesis, in distinction to glucose utilization, may be resistant to insulin stimulation during periods of acute starvation in muscles with fibre compositions similar to the epitrochlearis, but not in muscles with fibre compositions similar to the soleus. Partial reversal of the resistance observed in vitro for epitrochlearis muscles from starved rats may be due to the loss of factors which suppress the effect of insulin in vivo.
在分离肌肉后的孵育的第一小时和第二小时期间，在体外测定了喂食大鼠和饥饿24小时大鼠的比目鱼肌和肱三头肌对蛋白质合成以及葡萄糖掺入糖原的胰岛素敏感性。喂食大鼠的两种肌肉在孵育第一小时的蛋白质合成速率比第二小时高2倍，且不受胰岛素影响。在每毫升含有6000微单位胰岛素的情况下，饥饿大鼠的比目鱼肌在第一小时的蛋白质合成速率增加，但肱三头肌未增加。在第二小时，喂食和饥饿大鼠的两种肌肉的蛋白质合成速率均因胰岛素而显著增加。在孵育的第一小时和第二小时，高浓度胰岛素均显著刺激了喂食和饥饿大鼠的两种肌肉的葡萄糖掺入速率。第二小时葡萄糖掺入的胰岛素敏感性，定义为引起半最大刺激的胰岛素浓度，相对于喂食大鼠的肌肉（比目鱼肌，600微单位/毫升；肱三头肌，500微单位/毫升），饥饿大鼠的两种肌肉类型均增加了10倍（比目鱼肌，65微单位/毫升；肱三头肌，45微单位/毫升）。饥饿大鼠比目鱼肌在第二小时蛋白质合成的胰岛素敏感性（65微单位/毫升）高于喂食大鼠（500微单位/毫升）。相比之下，饥饿大鼠肱三头肌蛋白质合成的胰岛素敏感性（225微单位/毫升）与喂食大鼠（25微单位/毫升）相比显著降低。高浓度胰岛素达到的最大速率与喂食大鼠相同肌肉中的速率没有差异。这表明，与葡萄糖利用不同，在急性饥饿期间，具有类似于肱三头肌纤维组成的肌肉中的蛋白质合成可能对胰岛素刺激有抗性，但具有类似于比目鱼肌纤维组成的肌肉则不然。在体外观察到的饥饿大鼠肱三头肌的抗性部分逆转可能是由于体内抑制胰岛素作用的因子丧失所致。
