What is the primary source of plasma ammonia?

The primary source of plasma ammonia is indeed produced in the intestines from the breakdown of proteins by bacterial enzymes. In the human digestive system, dietary proteins are broken down into amino acids and other nitrogenous compounds. The bacteria present in the intestines further metabolize these proteins, resulting in the production of ammonia as a byproduct, which is then absorbed into the bloodstream.

This ammonia can contribute to various metabolic processes and is particularly important to consider in clinical settings, as elevated levels might indicate liver dysfunction or issues with the urea cycle. The liver typically converts ammonia into urea, which is then excreted by the kidneys. Therefore, ammonia levels in the blood can provide valuable insights into both hepatic function and protein metabolism.

The other sources mentioned—such as the liver, kidneys, and muscles—do participate in ammonia production, but the contribution from intestinal bacteria is the most significant in terms of the primary source that influences plasma ammonia concentrations in a healthy individual.