Formation of glutamine from glutamate, by glutamine synthetase
, in the liver and brain is another means of detoxifying ammonia
. Impaired liver function, shunting of blood around the liver, and increased muscle wasting all lead to increased serum ammonia levels in cirrhotic patients.
Ammonia interferes with brain function at many sites. Ammonia crosses the blood-brain barrier and directly depresses the central nervous system.