Abstract
Cerebral phenylalanine (Phe) concentration was measured in vivo by 1H NMR spectroscopy in rabbits made hyperphenylalaninemic by a diet containing 5 % Phe and 0.4 % alpha-methyl Phe. A surface coil and a 4.7 T spectrometer were used with a phase-cycled water-suppressing spin echo sequence optimized at 7.35 ppm. At a total echo delay of 4 msec several resonances were observed at 6.5-8.5 ppm. When brain (Phe) was elevated, subtraction of scaled spectra of control animals from those of test animals left a single broad peak centered at 7.35 ppm, the position of the multiplets arising from aromatic protons of Phe. For determination of brain (Phe), the intensity of this resonance, corrected for T1 and T2 differences, was compared to the creatine+ phosphocreatine resonance at 3.03 ppm, which was assumed to represent 10 mM. Brain (Phe)s determined by NMR and independently by biochemical analysis in 7 rabbits were in excellent agreement (correlation coefficient 0.96), while blood (Phe) correlated less well (0.80). Brain (Phe) above 0.5-1.0 mM was readily detectable. Similar NMR techniques used with large-bore spectrometers should permit non-invasive direct measurement of elevated brain (Phe) in human patients of any age.
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Avison, M., Herschkowitz, N., Novotny, E. et al. 116: MEASUREMENT OF CEREBRAL PHENYLALANINE LEVELS IN VIVO. Pediatr Res 24, 280 (1988). https://doi.org/10.1203/00006450-198808000-00141
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DOI: https://doi.org/10.1203/00006450-198808000-00141