Elevation of transamination of branched chain amino acids in brain in acute ammonia toxicity.

The activity levels of leucine, isoleucine and valine aminotransferases were determined in various cerebral regions, liver and muscle of rats injected with a large dose of ammonium acetate and were compared with those of normal animals. In brain the activity levels of both leucine and isoleucine aminotransferases were elevated in both preconvulsive and convulsive states. Valine aminotransferase activity was suppressed in brain stem and corpus striatum and was elevated in cerebellum and hippocampus in preconvulsive states. During convulsions its activity was suppressed in cerebral cortex and hippocampus. Under these conditions, there was a suppression of both leucine and valine aminotransferases in muscle. In liver, however, the activities of these enzymes were elevated. The results suggested that the glutamate required for glutamine formation in hyperammonaemic states in brain might be obtained from branched chain amino acids, especially leucine and isoleucine.