Endogenous respiration and ammonia formation in brain slices

• 1.1. Ammonia formation in brain cortex slices of guinea pig respiring in a glucose-free medium was analyzed.
• 2.2. The formation of ammonia was accompanied with a decrease of glutamic acid content, and an appreciable oxygen consumption. In the presence of oxidizable substrates, ammonia formation and the decrease of glutamic acid content in brain slices were suppressed. Therefore, it was thought that glucose or other oxidizable substrates depressed ammonia formation through the inhibition of an appreciable part of the endogenous metabolism in brain slices.
• 3.3. More than half of the endogenous oxygen consumption could be related to a decrease of glutamic acid content, and the remaining part to the carbohydrate and lactic acid consumption in brain slices.
• 4.4. It was thought that ammonia formation in brain slices had two components, one of them being presumably autolytic, the other depending upon the oxidation of glutamic acid.
• 5.5. The effect of certain metabolic inhibitors on ammonia formation and endogenous oxygen uptake was studied. Generally, inhibitors which inhibited the oxygen uptake also inhibited the ammonia formation, and those which did not inhibit the former did not affect the latter.
• 6.6. The relations between the ammonia formation in brain slices in vitro and the increase of ammonia in living brain in excited conditions were discussed.