Differential Up-Regulation of Ammonia Detoxifying Enzymes in Cerebral Cortex, Cerebellum, Hippocampus, Striatum and Liver in Hyperammonemia

In order to gain insight into the ammonia-detoxification mechanisms in the brain and liver tissues, we have investigated the effects of hyperammonemia in rats, in vivo, on the activity levels of a number of ammonia- and glutamate-metabolizing enzymes in mitochondria and the cytosolic fractions of the cerebral cortex, cerebellum, hippocampus, striatum and liver. In general, the ammonia metabolizing enzymes – glutaminase, glutamine synthetase, glutamate dehydrogenase, AMP deaminase, adenosine deaminase, as well as aspartate aminotransferase and alanine aminotransferase – are differentially upregulated in various brain and liver regions of the hyperammonemic rats, indicating that divergent ammonia-detoxification mechanisms are involved in the various brain regions and liver in acute hyperammonemia.