Fig. 1.

Time-averaged ¹³C signals from rat skeletal muscle after injection of 40 mmol l⁻¹ hyperpolarized [1-¹³C]lactate. (A) Control. (B) 1 h after DCA infusion. Each spectrum is normalized to the corresponding [1-¹³C]lactate peak intensity and time averaged for 0–2 min. Relative to the signal intensity of [1-¹³C]lactate, the DCA stimulation of PDH produces a marked change in ¹³C spectra, as noted in intensity changes of the alanine, pyruvate, HCO₃⁻ and CO₂ signals. Scaling all signals to the initial lactate signal intensity corrects for variation in ¹³C polarization.