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，使得在体外区分组织或器官中的细胞内和细胞外离子成为可能。然而，在体内器官中的这种测量尚未报道。在目前的研究中，我们尝试<23>使用位移试剂三乙烯四胺六乙酸镝（Dy（TTHA）^），通过核磁共振光谱测量沙土鼠脑和骨骼肌中体内和细胞外的^ Na和^1H<3->。在没有Dy（TTHA）^的情况下<3->，^<23>Na和^1H信号仅被视为单峰。逐渐静脉输注300 mM DY（TTHA），<3->血压几乎没有降低，脑电图也没有变化，脑电图与NMR光谱同时记录。输注DY（TTHA）^2小时后<3->，^<23>Na和^1H信号分别出现两个峰。未移动的峰反映了细胞内的^<23>Na和^1H信号，而移动的峰反映了细胞外的信号。在脑光谱中，检测到一个额外的小峰，代表血管内信号，注射盐酸罂粟碱后其强度增加。本方法优于微电极技术，因为它具有非破坏性，并且能够从^1H光谱的测量中获得细胞内和细胞外的体积信息，其峰值反映了细胞内和细胞外的水量。该技术显然可用于器官的生理学和病理生理学研究。

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.