Smith O L
Am J Physiol. 1986 Oct;251(4 Pt 1):E379-84. doi: 10.1152/ajpendo.1986.251.4.E379.
To test the rate of protein degradation in muscles under more physiological conditions, in vitro methods were adapted for use in rats whose skeletal muscles had been isolated intact by an evisceration procedure. Under pentobarbital anesthesia the vessels to the gastrointestinal tract were ligated, the organs removed, and the liver left in situ. Normal rectal temperature was maintained, glucose was given to prevent hypoglycemia and the animals were studied for a 2-h period. For the present experiments, evisceration was carried out after protein synthesis was blocked with cycloheximide so that the accumulation of the amino acid tyrosine (not metabolized) in the plasma of the preparation could be used to indicate the rate protein was degraded in the peripheral tissues. When normal fed rats (270 g) were eviscerated, the concentration of plasma tyrosine increased postoperatively, but, if the rats were fasted 20 h and then eviscerated, tyrosine accumulation was significantly enhanced. After 2 h, it was 50% greater than in the fed controls. Refeeding for 3 h completely prevented this effect. The results suggest that the rate of overall skeletal muscle protein degradation can be measured by the use of eviscerated rats and that this rate is sensitive to short periods of food deprivation.
为了在更接近生理状态的条件下测试肌肉中蛋白质的降解速率，对体外方法进行了调整，用于通过去内脏手术完整分离出骨骼肌的大鼠。在戊巴比妥麻醉下，结扎通向胃肠道的血管，切除器官，肝脏保留原位。维持正常直肠温度，给予葡萄糖以防止低血糖，并对动物进行2小时的研究。在本实验中，在用环己酰亚胺阻断蛋白质合成后进行去内脏手术，以便制备物血浆中氨基酸酪氨酸（未代谢）的积累可用于指示外周组织中蛋白质的降解速率。当正常喂食的大鼠（270克）去内脏后，血浆酪氨酸浓度术后升高，但如果大鼠禁食20小时后再去内脏，酪氨酸积累会显著增强。2小时后，其比喂食对照组高50%。重新喂食3小时可完全防止这种影响。结果表明，使用去内脏大鼠可以测量整体骨骼肌蛋白质的降解速率，并且该速率对短期食物剥夺敏感。
