Küstermann E, Seelig J, Künnecke B
Biocenter of the University, Basel, Switzerland.
Am J Physiol. 1998 Jan;274(1):E65-71. doi: 10.1152/ajpendo.1998.274.1.E65.
The first in vivo detection of a vitamin with nuclear magnetic resonance (NMR) is reported for mammalian liver. Vitamin C, also known as ascorbic acid, was monitored noninvasively in rat liver by "whole body" 13C NMR spectroscopy at high field after infusion of [1,2-13C2]glucose into anesthetized rats. Generally, the carbon resonances of ascorbic acid overlap with those of other highly abundant cellular metabolites, thus precluding their observation in situ. This problem was resolved by taking advantage of the 13C-13C spin couplings introduced by the two covalently bound 13C nuclei in [1,2-13C2]glucose. During glucose metabolism, [5,6-13C2]ascorbic acid was synthesized, which also exhibited characteristic 13C homonuclear spin couplings. This feature enabled the spectral discrimination of ascorbic acid from overlapping singlet resonances of other metabolites. Quantitative analysis of the spin-coupling patterns provided an estimate of the turnover rate of hepatic ascorbic acid in vivo (1.9 +/- 0.4 nmol.min-1.g-1) and a novel approach toward a better understanding of optimal ascorbic acid requirements in humans. The results obtained in vivo were confirmed with high-resolution proton and 13C NMR spectroscopy of liver extracts.
据报道，首次利用核磁共振（NMR）在活体中对哺乳动物肝脏中的一种维生素进行了检测。在给麻醉大鼠输注[1,2-¹³C₂]葡萄糖后，通过高场“全身”¹³C NMR光谱对大鼠肝脏中的维生素C（也称为抗坏血酸）进行了非侵入性监测。一般来说，抗坏血酸的碳共振与其他高丰度细胞代谢物的碳共振重叠，因此无法在原位观察到它们。通过利用[1,2-¹³C₂]葡萄糖中两个共价结合的¹³C核引入的¹³C-¹³C自旋耦合解决了这个问题。在葡萄糖代谢过程中，合成了[5,6-¹³C₂]抗坏血酸，其也表现出特征性的¹³C同核自旋耦合。这一特性使得能够从其他代谢物的重叠单重态共振中光谱鉴别抗坏血酸。对自旋耦合模式的定量分析提供了体内肝脏抗坏血酸周转率的估计值（1.9±0.4 nmol·min⁻¹·g⁻¹），并为更好地理解人类对抗坏血酸的最佳需求提供了一种新方法。体内获得的结果通过肝脏提取物的高分辨率质子和¹³C NMR光谱得到了证实。
