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Urea production occurs in the liver and is regulated by N-acetylglutamate. Urea is then dissolved into the blood (in the reference range of 2.5 to 6.7 mmol/L) and further transported and excreted by the kidney as a component of urine. In addition, a small amount of urea is excreted (along with sodium chloride and water) in sweat.
Urea produced by the liver is then released into the bloodstream, where it travels to the kidneys and is ultimately excreted in urine. The urea cycle is essential to these organisms, because if the nitrogen or ammonia is not eliminated from the organism it can be very detrimental. [ 5 ]
The resulting L-alanine is shuttled to the liver where the nitrogen enters the urea cycle and the pyruvate is used to make glucose. [4] The Cahill cycle is less productive than the Cori cycle, which uses lactate, since a byproduct of energy production from alanine is production of urea. [5]
The excretion of urea is called ureotelism. Land animals, mainly amphibians and mammals, convert ammonia into urea, a process which occurs in the liver and kidney. These animals are called ureotelic. [3] Urea is a less toxic compound than ammonia; two nitrogen atoms are eliminated through it and less water is needed for its excretion.
In most mammals, two isozymes of this enzyme exist; the first, Arginase I, functions in the urea cycle, and is located primarily in the cytoplasm of hepatocytes (liver cells). The second isozyme, Arginase II, has been implicated in the regulation of intracellular arginine/ornithine levels.
[2] [3] [4] In humans, it is located in the right upper quadrant of the abdomen, below the diaphragm and mostly shielded by the lower right rib cage. Its other metabolic roles include carbohydrate metabolism, the production of hormones, conversion and storage of nutrients such as glucose and glycogen, and the decomposition of red blood cells. [4]
The liver detoxifies and breaks down chemicals, poisons and other toxins that enter the body. For example, the liver transforms ammonia (which is poisonous) into urea in fish, amphibians and mammals, and into uric acid in birds and reptiles. Urea is filtered by the kidney into urine or through the gills in fish and tadpoles. Uric acid is paste ...
For these purposes, hepatocytes are usually isolated from animal or human [8] whole liver or liver tissue by collagenase digestion, which is a two-step process. In the first step, the liver is placed in an isotonic solution, in which calcium is removed to disrupt cell-cell tight junctions by the use of a calcium chelating agent.