The formulation of hyperpolarized 13C pyruvate solutions influences the labeling of myocardial metabolites in vivo

In developing an intact rat model for myocardial ischemia using hyperpolarized 13C pyruvate, different compound formulations were evaluated. Infusion of 4-hydroxy-TEMPO-polarized sodium [1-13C]pyruvate was compared to an equivalent dose of buffered trityl radical-polarized [1-13C]pyruvic acid. Whereas higher levels of polarization and MRS signal were obtained with trityl radical, the metabolite signals normalized to total signal were lower. In particular, [1-13C]lactate signal relative to total signal was markedly higher using TEMPO-polarized pyruvate. [13C]bicarbonate and [1-13C]alanine signals were affected to a lesser degree. This study demonstrates the composition of the infused hyperpolarized pyruvate solution can significantly affect its metabolism in vivo.