Used at low concentration in DNP sample preparations, radicals are typically chemically highly reactive species that could potentially interfere with the biochemical processes assessed in HP MR experiments. In this work, we investigate the influence of the nitroxyl radical TEMPOL on the cerebral metabolic response to a bolus of hyperpolarized [1- C]lactate in a mouse model of transient ischemic stroke. Our results show that TEMPOL, administered at the same dose as when used as a polarizing agent for DNP, alters substantially the metabolic outcome of the experiment and notably results in a significantly different pyruvate labelling after hyperpolarized lactate infusion.