Recycling of an amino acid label with prolonged isotope infusion: implications for kinetic studies.
Recycling of an amino acid label with prolonged isotope infusion: implications for kinetic studies.
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延长同位素输注的氨基酸标记的回收：对动力学研究的影响。
DOI：
10.1152/ajpendo.1985.248.4.e482
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发表时间：
1985
期刊：
影响因子：
--
通讯作者：
Haymond,MW
中科院分区：
文献类型：
--
作者：
Schwenk,WF;Tsalikian,E;Beaufrere,B;Haymond,MW
为了研究输注 24 小时后是否会发生标记氨基酸的再循环，两组正常志愿者分别输注 [3H]亮氨酸和 α-[14C]-酮异己酸 4 小时，以及输注 [2H3]亮氨酸 4 或 24 小时（分别为 I 组和 II 组）。 [2H3)亮氨酸在稳态下进入血浆空间与其 I 组的输注速率没有区别，但比 II 组的输注速率高 30%（P 小于 0.001），表明标记的显着回收。停止输注后，追踪同位素从血浆空间消失2小时。两组的 3H 和 14C 衰变数据表明血浆亮氨酸和 α-酮异己酸源自吸收后状态的单个细胞内库。在第一组中，3H 和 2H 标记的衰减相同；而在第 II 组中，[2H3]-亮氨酸和 α-[2H3]酮异己酸的衰变比 [3H]亮氨酸和 α-[3H]酮异己酸的衰变慢（P 小于 0.01），这证实了输注 24 小时后标签的重新进入。因此，假设标记氨基酸不循环利用的模型计算出的动力学值很可能不是定量的，并且当通量不改变或减少时必须小心解释。
To investigate whether recycling of a labeled amino acid would occur after 24 h of infusion, two groups of normal volunteers were infused with [3H]leucine and alpha-[14C]-ketoisocaproate for 4 h and [2H3]leucine for either 4 or 24 h (groups I and II, respectively). Entry of [2H3 )leucine at steady state into the plasma space was indistinguishable from its infusion rate for group I but 30% higher (P less than 0.001) than this rate for group II, demonstrating significant recycling of label. After discontinuation of the infusions, isotope disappearance from the plasma space was followed for 2 h. The 3H and 14C decay data for both groups suggest that plasma leucine and alpha-ketoisocaproate are derived from a single intracellular pool in the postabsorptive state. In group I, the 3H and 2H labels decayed identically; whereas, in group II, the decay of [2H3]-leucine and alpha-[2H3]ketoisocaproate was slower (P less than 0.01) than the decay of [3H]leucine and alpha-[3H]ketoisocaproate, confirming re-entry of label after a 24-h infusion. Therefore kinetic values calculated from models assuming no recycling of labeled amino acids are most likely not quantitative and must be interpreted with care when flux does not change or decreases.