Said H M, Chenoweth M, Dunn A
Department of Biological Sciences, University of Southern California, Los Angeles 90089.
Metabolism. 1989 Aug;38(8):718-27. doi: 10.1016/0026-0495(89)90056-5.
Alanine, glutamate and proline labeled with 14C and 3H were infused into fasted normal and adrenalectomized rats. Alanine was administered by the A-V mode (arterial administration-venous sampling), and glutamate and proline by both the A-V and V-A (venous administration-arterial sampling) modes. The kinetics of 14C alanine and 14C glutamate differed markedly from those of the tritium-labeled compounds, but there was little difference in the kinetics of 3H and 14C proline. The replacement rate calculated from the A-V mode for glutamate was about half that obtained in the V-A mode, but there was little difference with proline. The masses of the amino acids (total content of amino acids in the body) were calculated from the washout curves of the tritium-labeled compounds after the infusion of tracer was terminated. The masses for the normal rats were 407 mumol/kg for alanine, 578 mumol/kg for glutamate and 296 mumol/kg for proline. The so-called distribution spaces calculated conventionally from total masses and the amino acid concentrations in plasma are much greater than the volume of the body, reflecting the fact that amino acid concentrations in tissues greatly exceed those in plasma. Adrenalectomy markedly affected the kinetics of the three amino acids, and their replacement rates were greatly reduced. The proline and glutamate masses were reduced by at least one half, while that of alanine was unchanged. Adrenalectomy markedly reduced the conversion of proline to glutamate. The hydrocortisone regimen used in this study restored the metabolism of alanine and glutamate to normal, but had no effect on that of proline.
将用¹⁴C和³H标记的丙氨酸、谷氨酸和脯氨酸注入禁食的正常大鼠和肾上腺切除大鼠体内。丙氨酸通过动静脉模式（动脉给药 - 静脉取样）给药，谷氨酸和脯氨酸则通过动静脉模式和静动脉模式（静脉给药 - 动脉取样）给药。¹⁴C丙氨酸和¹⁴C谷氨酸的动力学与氚标记化合物的动力学明显不同，但³H和¹⁴C脯氨酸的动力学差异不大。从动静脉模式计算的谷氨酸替代率约为静动脉模式下获得的替代率的一半，但脯氨酸的替代率差异不大。在注入示踪剂后，根据氚标记化合物的洗脱曲线计算氨基酸的质量（体内氨基酸的总含量）。正常大鼠的丙氨酸质量为407 μmol/kg，谷氨酸为578 μmol/kg，脯氨酸为296 μmol/kg。传统上根据总质量和血浆中氨基酸浓度计算的所谓分布空间远大于身体体积，这反映了组织中氨基酸浓度大大超过血浆中氨基酸浓度这一事实。肾上腺切除术显著影响这三种氨基酸的动力学，它们的替代率大大降低。脯氨酸和谷氨酸的质量至少减少了一半，而丙氨酸的质量没有变化。肾上腺切除术显著降低了脯氨酸向谷氨酸的转化。本研究中使用的氢化可的松方案使丙氨酸和谷氨酸的代谢恢复正常，但对脯氨酸的代谢没有影响。
