Figure 6.

Comparison of [¹⁴C]FDG uptake with hyperpolarized ¹³C label flux between pyruvate and lactate in EL-4 tumors. (A) Changes in [1-¹³C]pyruvate to [1-¹³C]lactate flux in untreated EL-4 tumors and tumors treated with etoposide for either 16 or 24 hours. Changes in tumor pyruvate and lactate peak intensities were fitted to a two-site exchange model to obtain the rate constant for pyruvate to lactate flux. (B) Uptake of [¹⁴C]FDG in untreated EL-4 tumors and tumors treated with etoposide for either 16 or 24 hours. [¹⁴C]FDG was injected intravenously, and uptake was allowed to proceed for 60 minutes. Tumors were then excised and homogenized. Percentage injected dose per gram of tissue (%ID/g) was determined by liquid scintillation counting. Mean values (n = 6–12) and SEs are shown (*P < .05, **P < .01).