Stein T P, Leskiw M J, Buzby G P, Giandomenico A L, Wallace H W, Mullen J L
Am J Physiol. 1980 Oct;239(4):E294-E300. doi: 10.1152/ajpendo.1980.239.4.E294.
[15N]glycine (95+%) was infused into 170- to 220-g rats at a constant rate of 2-8 mg [15N]glycine/h for 2-24 h. Two sets of experiments were done. In one set, the rats were killed at varying time intervals, the liver was removed, and the fractional rate of liver protein synthesis was estimated from the amount of 15N incorporated into liver protein, the enrichment of the liver tissue free amino nitrogen, and the time course. In the second set of experiments, the rats were killed after a [15N]glycine infusion of 18-22 h. The whole-body protein synthesis rate was estimated from the urinary 15N enrichment at plateau by the method of Picou and Taylor-Roberts (Clin. Sci. 36: 288-296, 1967). It was compared against the value found by measuring the 15N enrichment of the whole-rat homogenate and calculating the synthesis rate from the formula of Garlick et al. [Biochem. J. 136: 935-945, 1973). The results are i) The 15N enrichment of glycine in either liver protein or liver tissue free amino acids was proportional to the 15N enrichment of the mixed protein or tissue free amino acids, respectively. ii) Continuous infusion-isotopic plateau methods underestimate the fractional protein synthesis rate of rat liver. iii) The methods of Picou and Taylor-Roberts and of Garlick et al. gave similar values for the whole-body protein synthesis rate.
将[15N]甘氨酸（95+%）以2-8毫克[15N]甘氨酸/小时的恒定速率注入体重170-220克的大鼠体内，持续2-24小时。进行了两组实验。在一组实验中，在不同时间间隔处死大鼠，取出肝脏，根据掺入肝脏蛋白质中的15N量、肝脏组织游离氨基氮的富集情况以及时间进程来估算肝脏蛋白质合成的分数速率。在第二组实验中，在[15N]甘氨酸注入18-22小时后处死大鼠。采用皮库和泰勒-罗伯茨的方法（《临床科学》36: 288-296, 1967），根据平台期尿中15N的富集情况估算全身蛋白质合成速率。将其与通过测量全鼠匀浆的15N富集情况并根据加里克等人的公式（《生物化学杂志》136: 935-945, 1973）计算合成速率所得到的值进行比较。结果如下：i）肝脏蛋白质或肝脏组织游离氨基酸中甘氨酸的15N富集分别与混合蛋白质或组织游离氨基酸的15N富集成正比。ii）连续输注-同位素平台法低估了大鼠肝脏的蛋白质合成分数速率。iii）皮库和泰勒-罗伯茨的方法以及加里克等人的方法得出的全身蛋白质合成速率值相似。
