ESTIMATION OF CEREBRAL INTRA- AND EXTRACELLULAR Na^+ CONCENTRATION BY IN VIVO MAGNETIC RESONANCE SPECTROSCOPY WITH SHIFT REAGENT

在核磁共振（NMR）方法中引入新的顺磁位移试剂，使得在体外组织或器官中区分细胞内和细胞外离子成为可能。然而，这种在体内器官的测量还没有报道。在本研究中，我们尝试使用移位试剂，三乙烯四胺六乙酸镝，Dy(TTHA)^<3->，通过核磁共振波谱法测量沙鼠大脑和骨骼肌体内细胞内和细胞外^<23>的Na和^1H。在没有Dy(TTHA)^<3->的情况下，^<23>的Na和^1H信号仅为单峰。逐渐静脉输注300 mM DY(TTHA)^<3->，血压下降不大，脑电图无变化，同时记录核磁共振波谱。DY(TTHA)^<3->输注2小时后，^<23>Na和^1H信号分别出现两个峰。未移位的峰反映细胞内的^<23>Na和^1H信号，而移位的峰反映细胞外信号。在脑光谱中，检测到一个额外的小峰，代表血管内信号，并且注射盐酸罂粟碱后其强度增加。该方法优于微电极技术，因为它具有非破坏性，并且能够从测量的^1H光谱中获得细胞内和细胞外的体积信息，其峰反映了细胞内和细胞外的水量。这项技术显然可用于器官的生理和病理生理研究。

The introduction of new paramagnetic shift reagent in the nuclear magnetic resonance (NMR) method has made it possible to distinguish intra- and extracellular ions in tissues or organs in vitro. However, such measurements in organs in vivo have not yet been reported. In the present investigation, we attempted to measure the intra- and extracellular ^<23>Na and ^1H in vivo in the gerbil brain and skeletal muscle by NMR spectroscopy employing the shift reagent, dysprosium triethylenetetraminehexaacetate, Dy(TTHA)^<3->. Without Dy(TTHA)^<3->, the ^<23>Na and ^1H signals were seen only as single peaks. Gradual intravenous infusion of 300 mM DY(TTHA)^<3-> caused little blood pressure reduction and no change in electroencephalogram which was recorded simultaneously with the NMR spectroscopy. After 2 hours of DY(TTHA)^<3-> infusion, the ^<23>Na and ^1H signals were into two peaks, respectively. The unshifted peaks reflected the intracellular ^<23>Na and ^1H signals, whereas the shifted peaks reflected the extracellular signals. In the brain spectra, an additional small peak, which represented intravascular signals, was detected, and its intensity increased after injection of papaverine hydrochloride. The present method is advantageous over the microelectrode technique because of its nondestructiveness and its capability for obtaining intra- and extracellular volume information from measurements of the ^1H spectra, the peaks of which reflect the intra- and extracellular water amounts. The technique is clearly of use for physiological and pathophysiological studies of organs.