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Uremia is the condition of having high levels of urea in the blood. Urea is one of the primary components of urine.It can be defined as an excess in the blood of amino acid and protein metabolism end products, such as urea and creatinine, which would normally be excreted in the urine.
Protein toxicity is the effect of the buildup of protein metabolic waste compounds, like urea, uric acid, ammonia, and creatinine.Protein toxicity has many causes, including urea cycle disorders, genetic mutations, excessive protein intake, and insufficient kidney function, such as chronic kidney disease and acute kidney injury.
Measurements of urea and creatinine (Cr) in the blood are used to assess renal function. For historical reasons, the lab test measuring urea is known as "blood urea nitrogen" (BUN) in the US. The BUN:Cr ratio is a useful measure in determining the type of azotemia and will be discussed in each section below.
Glycine toxicity causes hyperammonemia, which manifests as CNS symptoms and nausea. Transient blindness can also occur. [12] Congenital hyperammonemia is usually due to genetic defects in one of the enzymes of the urea cycle, such as ornithine transcarbamylase deficiency, which leads to lower production of urea from ammonia. [citation needed]
Arginosuccinate synthetase is an enzyme in the urea cycle, which removes excess ammonia from the body. When it is deficient, either fully or partially, ammonia can build up and cause the signs and symptoms of CTLN1.
Argininemia is an autosomal recessive urea cycle disorder where a deficiency of the enzyme arginase causes a buildup of arginine and ammonia in the blood.Ammonia, which is formed when proteins are broken down in the body, is toxic if levels become too high; the nervous system is especially sensitive to the effects of excess ammonia.
Ornithine transcarbamylase deficiency also known as OTC deficiency is the most common urea cycle disorder in humans. Ornithine transcarbamylase, the defective enzyme in this disorder, is the final enzyme in the proximal portion of the urea cycle, responsible for converting carbamoyl phosphate and ornithine into citrulline.
The urea cycle converts highly toxic ammonia to urea for excretion. [1] This cycle was the first metabolic cycle to be discovered by Hans Krebs and Kurt Henseleit in 1932, [2] [3] [4] five years before the discovery of the TCA cycle. The urea cycle was described in more detail later on by Ratner and Cohen.