Differential up-regulation of ammonia detoxifying enzymes in cerebral cortex, cerebellum, hippocampus, striatum and liver in hyperammonemia.

Abstract

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.