Acute effects of ammonia on the enzymes of citric acid cycle in rat brain

Activities of the enzymes of citric acid cycle were determined along with aspartate and alanine aminotransferases and NADP +-isocitrate dehydrogenase in the brains of rats treated with an acute dose of ammonium acetate and compared with those of normal animals. Elevation in the activities of pyruvate, α-ketoglutarate and succinate dehydrogenases and citrate synthase was observed in hyperammonemic animals. The activities of malate, NADP +-isocitrate dehydrogenases and aminotransferases decreased under these conditions. The results suggest that ammonia toxicity might not be due to the depletion of α-ketoglutarate from citric acid cycle.