, Volume 314, Issue 4, pp 292-311

Effects of carbon dioxide, bicarbonate and pH on lactate and pyruvate in the brain of rats

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The influence of acute changes inPa CO 2on lactate concentration in brain and blood was studied in hypercapnic and hypocapnic rats. Lactate in brain increases markedly whenP CO 2is acutely decreased by severe hyperventilation. Compared with the observations in normal rats, the lactate response to an intense hypocapnia was decreased in animals maintained 24 hours in hypoxic alkalosis and increased after 24 hours hypercapnia. The results are discussed in relation to the hypothesis that the lactate concentration response in brain in these conditions is related to local pH. Incubation studies of brain tissue, in whichP CO 2or (and) [HCO3 ] were varied, show that lactate and pyruvate concentration and glucose consumption increase while the lactate/pyruvate ratio decreases when the pH of the incubation fluid is augmented. In an iso-pH system, lactate and pyruvate concentration, glucose consumption and L/P ratio increase with increasing [HCO3 ]. The possible mechanisms and the possible importance of these metabolic variations are discussed.