Cerebral Lactate Turnover after Electroshock: In vivo Measurements by 1 H/ 13 C Magnetic Resonance Spectroscopy

We reported earlier that brain activation by 10 s of cortical electroshock caused prolonged elevation of brain lactate without significant change in intracellular pH, brain high-energy phosphorylated metabolites, or blood gases. The metabolic state of the elevated lactate has been investigated in further experiments using combined, in vivo ¹H-observed ¹³C-edited nuclear magnetic resonance spectroscopy (NMRS), homonuclear J-edited ¹H-NMRS, and high-resolution ¹H-NMRS of perchloric acid extracts to monitor concentrations and ¹³C-isotopic fractions of brain and blood lactate and glucose. We now report that electroshock-elevated lactate pool in rabbit brain approaches equilibrium with blood glucose within 1 h. There was nearly complete turnover of the raised lactate pool in brain; any pool of metabolically inactive lactate could not have been >5% of the total. In the same experiments, blood lactate underwent <50% turnover in 1 h. The new ¹H-spectroscopic methods used for these experiments are readily adaptable for the study of human brain and may be useful in characterizing the metabolic state of elevated lactate pools associated with epilepsy, stroke, trauma, tumors, and other pathological conditions.