Selection of endogenous 13C substrates for observation of intracellular metabolism using the dynamic nuclear polarization technique.

PURPOSE

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.

MATERIALS AND 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.

CONCLUSION

The DNP technique is useful for evaluating intracellular metabolism. However, Glc is not suitable for use with the DNP technique.