Selection of endogenous 13C substrates for observation of intracellular metabolism using the dynamic nuclear polarization technique.
OBJECTIVE
The aim of this study was to select a suitable substrate candidate for dynamic nuclear polarization (DNP) studies and demonstrate its utility for evaluating intracellular metabolism.


METHODS
Hyperpolarized substances included 1-(13)C-pyruvate (Pyr), 1-(13)C-glucose (Glc), and 1-(13)C-acetate. A DNP polarizer and a 600-MHz vertical small-bore scanner were used for (13)C-MR spectroscopic measurements. After polarization for 1 h, the dissolved solution was injected via a capillary line into the nuclear magnetic resonance tube in the scanner. The sequential spectra of the hyperpolarized (13)C-labeled substrates were acquired in durations of more than 120 s, and a thermal spectrum was obtained more than 1 h thereafter. FM3A cancer cells of mammary tumors were cultured for intracellular detection of the hyperpolarized (13)C-substances.


RESULTS
The greatest sensitivity was found using Pyr with the longest T1 decay (51.5 s); and remarkably, the least sensitivity was observed using Glc with a signal decay of less than 2 s. An effective increase in sensitivity was shown using the other substances. The hyperpolarized intracellular study using (13)C-Pyr showed distinct elevation of lactate levels.


CONCLUSIONS
The DNP technique is useful for evaluating intracellular metabolism. However, Glc is not suitable for use with the DNP technique.
Harada
Masafumi
M
Department of Medical Imaging, Institute of Health Biosciences, University of Tokushima Graduate School, Tokushima, Japan. masafumi@medsci.tokushima-u.ac.jp
Kubo
Hitoshi
H
Abe
Takamasa
T
Maezawa
Hiroshi
H
Otsuka
Hideki
H
D000085:Acetates / Q000378:metabolism*; D000818:Animals; D014408:Biomarkers, Tumor / Q000378:metabolism; D002247:Carbon Isotopes / Q000378:metabolism*; D045744:Cell Line, Tumor / Q000378:metabolism; D002478:Cells, Cultured; D005260:Female; D005947:Glucose / Q000378:metabolism*; D007089:Image Enhancement / Q000379:methods; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D008325:Mammary Neoplasms, Experimental / Q000378:metabolism*; D051379:Mice; D008809:Mice, Inbred C3H; D019289:Pyruvic Acid / Q000378:metabolism*; D012680:Sensitivity and Specificity
D000085:Acetates; D014408:Biomarkers, Tumor; D002247:Carbon Isotopes; D019289:Pyruvic Acid; D005947:Glucose