The effect of Ca+ free medium on the two different tricarboxylate cycles in the rat brain cortex slices.

The authors studied the effect of calcium-free saline-glucose medium on labelled amino acid and [14C]CO2 synthesis from U-[14C]-glucose and 1-[14C]-acetate in rat brain cortex slices. Respiration was stimulated parallel with increased synthesis of labelled amino acids and of [14C]CO2 from glucose to [to 150 % and 170 % respectively]. Specific glutamate, aspartate and neutral amino acid activity rose, GABA and glutamine were unaffected. Amino acid synthesis from 1-[14C]-acetate was inhibited [58%], while [14C]CO2 release was unchanged. This indicates that oxygen consumption via the tricarboxylase cycle associated with the small glutamate pool [and probably localized in the glia cells] did not alter in calcium-free medium, although conversion to amino acids was impaired.