Analysis of 13 C and 14 C labeling in pyruvate and lactate in tumor and blood of lymphoma-bearing mice injected with 13 C- and 14 C-labeled pyruvate

Measurements of hyperpolarized C label exchange between injected [1- C]pyruvate and the endogenous tumor lactate pool can give an apparent first-order rate constant for the exchange. The determination of the isotope flux, however, requires an estimate of the labeled pyruvate concentration in the tumor. This was achieved here by measurement of the tumor uptake of [1- C]pyruvate, which showed that