Tricarboxylic acid-cycle metabolism in brain. Effect of fluoroacetate and fluorocitrate on the labelling of glutamate, aspartate, glutamine and gamma-aminobutyrate.

1. The effect of fluoroacetate and fluorocitrate on the compartmentation of the glutamate-glutamine system was studied in brain slices with l-[U-(14)C]glutamate, l-[U-(14)C]aspartate, [1-(14)C]acetate and gamma-amino[1-(14)C]butyrate as precursors and in homogenates of brain tissue with [1-(14)C]acetate. The effect of fluoroacetate was also studied in vivo in mouse brain with [1-(14)C]acetate as precursor. 2. Fluoroacetate and fluorocitrate inhibit the labelling of glutamine from all precursors but affect the labelling of glutamate to a much lesser extent. This effect is not due to inhibition of glutamine synthetase. It is interpreted as being due to selective inhibition of the metabolism of a small pool of glutamate that preferentially labels glutamine.