Figure 4

Representative time evolution of the ¹³C MR spectrum detected after the injection of HP [1-¹³C]pyruvate solution in resting (A) and activated (B) T cells. The delay between each acquisition was set to 4 s, starting 2 s after the beginning of the injection. The sum of the 1^st to 15^th spectra is displayed on the top. Along with the substrate resonance at 171.1 ppm, two products were detected: [1-¹³C]pyruvate hydrate at 179.5 ppm and [1-¹³C]lactate at 183.2 ppm. The impurity signal (marked with a star) overlapping with the lactate peak was subtracted from the spectra prior to quantification of the lactate signal.