The Lactate/Pyruvate Ratios of Cerebrospinal Fluid of Rats and Cats Related to the Lactate/Pyruvate, the ATP/ADP, and the Phosphocreatine/Creatine Ratios of Brain Tissue

Abstract

Abstract The CSF and brain tissue concentrations of lactate and pyruvate were measured in cats and rats, and related to the corresponding tissue concentrations of ATP, ADP, phosphocreatine and creatine. A comparison between superficial and deep phenobarbital anaesthesia, and nitrous oxide anaesthesia, showed that the type of anaesthesia had a marked effect on the tissue metabolites with a differential influence on the lactate/pyruvate, and on the ATP/ADP and the phosphocreatine/creatine ratios. Optimal conditions for freezing and extracting the tissue were sought and were found to include freezing of the head in such a way that the ventilation and the circulation of the animals were upheld during the freezing, as well as extraction of the tissue at −15 to −20° C. The distribution of lactate and pyruvate between extra‐ and intracellular phases was investigated in both rats and cats. In all groups studied lactate and pyruvate were found in higher concentrations in CSF than in the tissue, suggesting a pH‐dependent distribution of the weak acids. In the cat, the CSF pyruvate occurred in a relatively higher concentration than lactate, indicating a specific transport mechanism for pyruvic acid.