Ammonia
Ammonia is recognized as one of the most important factors involved in the pathogenesis of hepatic encephalopathy.
The Chemistry of Ammonia
Ammonia is composed of nitrogen and hydrogen (NH3). When dissolved in a solution, it separates into NH3 (gas) and NH4+ (ion).
Where does Ammonia come from?
Proteins need to be hydrolysed in amino acids in order to be absorbed by the organism. ammonia is a metabolite that is mostly produced in the gut during protein digestion and deamination. The urea cycle within the liver regulates the concentration of ammonia in the systemic circulation, maintaining low blood ammonia levels. Urea, a major component of urine, is eliminated by the kidneys.
In Hepatic Encephalopathy
Liver failure leads to an increase in blood ammonia, called hyperammonemia.
Both NH3 (gas) and NH4+ (ion) are capable of crossing cell membranes, and therefore can easily enter the brain through the blood-brain barrier that isolates and protects the brain from the bloodstream and its toxins. Ammonia is neurotoxic and leads to brain dysfunction.
Oxidative stress
Brain