Rate of whole-body protein synthesis in the rat as calculated from fractional oxidation of leucine, valine, or methionine.
Rate of whole-body protein synthesis in the rat as calculated from fractional oxidation of leucine, valine, or methionine.
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根据亮氨酸、缬氨酸或蛋氨酸的氧化分数计算得出的大鼠全身蛋白质合成率。
DOI：
10.1016/0026-0495(88)90177-1
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发表时间：
1988
期刊：
影响因子：
--
通讯作者：
Walser,M
中科院分区：
文献类型：
--
作者：
Imura,K;Walser,M
在稳定状态下，任何必需氨基酸的全身蛋白质合成利用率与其氧化率的比率应与掺入蛋白质的示踪剂剂量的峰值分数（F）与氧化分数（1-F）的比率相同，前提是游离氨基酸库中保留的示踪剂可以忽略不计或在肠道中保持未吸收。总的氨基酸排泄率（C）可由尿中尿素氮（N）加氨态氮（NH3）的排泄率估算。因此，全身蛋白质合成的速率（S）可以用CF（1− F）来估计。本方法并非新方法，但已作如下探索：（1）静脉注射标记亮氨酸后，大鼠全身蛋白质中亮氨酸的放射性在3 - 9小时内达到平台。(2)肠内注射后6小时，标记的亮氨酸、缬氨酸和蛋氨酸在肠道中的残留分数分别为1.2±0.4%（SD）、1.2± 0.4%和7.1± 2.9%;因此，肠内给药的蛋氨酸不能用于此目的。(3)氧化[1-14 C]标记的亮氨酸或缬氨酸，从14 CO2排泄量测量，被发现是相同的，这些同位素是否给予IV或肠内。(4)标记亮氨酸注射后1小时内，血浆游离亮氨酸中的放射性可忽略不计。(5)通过肠内或静脉注射[1- 14 C]标记的亮氨酸或缬氨酸或静脉注射[1 - 14 C]标记的甲硫氨酸后6小时的累积14 CO2排泄量估计全身蛋白质合成率，彼此之间的差异不超过7%。平均S为73 mg 100 g体重/h。这些结果支持该技术用于确定全身蛋白质合成的有效性。
In the steady state, the ratio of the rate of utilization for whole-body protein synthesis of any essential amino acid to its rate of oxidation should be the same as the ratio of the peak fraction of a dose of tracer incorporated into protein (F) to the fraction oxidized (1-F) provided that negligible tracer remains in the free amino acid pool or remains unabsorbed in the gut. The total rate of amino acid catabolism (C) can be estimated from the rate of urinary excretion of urea nitrogen (N) plus ammonia N. Hence the rate of whole-body protein synthesis (S) can be estimated as CF (1− F). This method, which is not new, was explored as follows:(1) Radioactivity in the leucine of whole-body protein of rats after intravenous (IV) injection of labeled leucine was shown to plateau from three to nine hours.(2) The fractions of labeled leucine, valine, and methionine remaining in the gut six hours after enteral injection were 1.2±0.4%(SD), 1.2±0.4%, and 7.1±2.9%, respectively; thus, enterally administered methionine cannot be used for this purpose.(3) Oxidation of [1-14 C]-labeled leucine or valine, measured from 14 CO 2 excretion, was found to be the same whether these isotopes were given IV or enterally.(4) Negligible radioactivity remained in the free leucine of plasma within one hour after injection of labeled leucine.(5) The rates of whole-body protein synthesis, estimated from cumulative 14 CO 2 excretion for six hours after enteral or IV injection of [1-14 C]-labeled leucine or valine, or after IV injection of [1-14 C]-labeled methionine did not differ from one another by more than 7%. Mean S was 73 mg 100 g body wt/h. These results support the validity of this technique for determining whole-body protein synthesis.