Ammonia
Ammonia is recognized as one of the most important factor involved in pathogenesis of hepatic encephalopathy.
Ammonia's chemistry
Ammonia is composed of nitrogen and hydrogen (NH3). When dissolved in solution, it dissociates into NH3 (gas) and NH4+ (ion).
Where come from ammonia?
Proteins need to be hydrolysed in amino acids to be absorbed by organism. ammonia is metabolite which is mostly produced within the gut during protein digestion and deamination. The urea cycle within the liver regulates the concentration ammonia in systemic circulation maintening low blood ammonia levels. Urea, major component of urin, is eliminated by 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, isolating and protecting the brain from the bloodstream and its toxins. Ammonia is neurotoxic and leads to brain dysfunction.
Oxidative stress
Cerveau