Figure 2

(A) In vivo cardiac ¹³C spectrum recorded after the injection and metabolism of hyperpolarized [1-¹³C]pyruvate in the fed state (n=5 in both groups). Signal ratios of lactate (B, F), bicarbonate (C,G) and acetylcarnitine (E) relative to pyruvate and alanine in all 4 experimental groups where hyperpolarized [1-¹³C]pyruvate was either injected separately or co-injected with hyperpolarized [1-¹³C]butyrate in both fed and fasted animals. Note the nearly constant fraction of alanine, which justifies its use as normalization factor for the other metabolites as was shown previously in perfused heart. Error bars indicate +/- SEM.