Calculation of substrate turnover rate in stable isotope tracer studies.
Calculation of substrate turnover rate in stable isotope tracer studies.
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稳定同位素示踪剂研究中底物周转率的计算。
DOI：
10.1152/ajpendo.1983.245.3.e308
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发表时间：
1983
期刊：
影响因子：
--
通讯作者：
Kalhan,SC
中科院分区：
文献类型：
--
作者：
Tserng,KY;Kalhan,SC
用稳定同位素标记的化合物测定底物周转率具有安全性好的优点，适用于儿童和孕妇的研究。目前，这些研究中的大多数都是通过启动恒速输注技术进行的。通过气相色谱-质谱法（GCMS）测量等离子体中底物的同位素富集。然后根据稳态动力学计算周转率。为此目的，不同的研究人员使用了许多不同的方程。基于理论考虑和实验数据，得出的结论是，正确的周转率计算应使用方程 P = [(1/E) - 1] I 或 P = (y/x) I，其中 P 为周转率，单位为 mumol X kg-1，E 为同位素富集度，I 为输注率，单位为 mumol X kg-1 X min-1，y/x 为痕量与示踪剂的摩尔比。前一个方程应使用根据同位素富集与同位素峰丰度构建的 GCMS 标准曲线，而后一个方程应使用根据摩尔比 (x/y) 与同位素比构建的标准曲线。标准曲线的互换或使用其他方程将产生错误的周转率。当使用低富集同位素标记化合物作为示踪剂时，这一点尤其重要。
The determination of substrate turnover rate with stable isotope-labeled compounds has advantages of being safe and applicable in the study of children and pregnant women. Currently, a majority of these studies has been performed with primed constant-rate infusion technique. The isotope enrichment of the substrate in the plasma is measured by gas chromatography-mass spectrometry (GCMS). The turnover rate is then calculated from steady-state kinetics. A number of different equations have been used by various investigators for this purpose. Based on theoretical consideration and experimental data, it is concluded that the equation P = [(1/E) - 1] I or P = (y/x) I should be used for a correct turnover rate calculation, where P is turnover rate in mumol X kg-1, E the isotope enrichment, I the infusion rate in mumol X kg-1 X min-1, and y/x the mole ratio of tracee to tracers. A GCMS standard curve constructed from isotope enrichment versus isotope peak abundance should be used for the former equation, whereas a standard curve constructed from mole ratio (x/y) versus isotope ratio should be used for the latter equation. Interchange of standard curves or use of other equations will produce erroneous turnover rate. This is especially significant when a low enriched isotope-labeled compound is used as a tracer.