Chemically, urate is the salt of uric acid. Urate and uric acid are different forms of the same thing, and which form it occurs in depends on the acidity of the fluid in which it is dissolved. In most body fluids, which are slightly alkaline, urate is in the form of sodium urate. Urate is thus the principal form in the body and is the more correct term. However, in the urine, as it becomes increasingly acid, more is in the form of uric acid.
Uric acid is the more commonly used term, but the two terms can be regarded as being interchangeable. Thus the serum or plasma urate concentration has the same meaning as the serum or plasma uric acid. Urate (which is more correct) is used in this site – http://www.mygoutdietfoods.com – in relation to body fluids. In relation to the urine, however, uric acid is used for the same reason.
In blood, urate is principally present in the plasma and is always measured in the plasma or serum rather than in the whole blood. (The main difference between serum and plasma is that the clotting factors are removed from plasma to give serum.)
What are purines?
You will often find urate referred to as a purine. This refers to its chemical structure, a molecule with two rings, which is of the same type as some essential chemical components of the body.
These purines have two indispensable functions. First, the nucleic acids (DNA and RNA) that control the cell machinery in the body are made up of equal numbers of purine and pyrimidine nucleotides. The purines adenine (Ad) or guanine (G), in the form of adenine monophosphate and guanine monophosphate (AMP and GMP), are thus building blocks of nucleic acid. Any purine bases not used as AMP or GMP are broken down (degraded) to uric acid.
The purine base adenine has a second function: to provide energy for body functions. Adenine, in the form of adenosine triphosphate (ATP), stores chemical energy and is the main high-energy source for the metabolic processes of cells. The provision of cell energy is vital for the function of all tissues.
Urate is not broken down in human body tissues, although some animals contain an enzyme, uricase, which can degrade urate to form the more soluble substance, allantoin. However, many micro-organisms, such as the bacteria in the colon, can degrade uric acid. This means it is important to avoid bacterial or faecal contamination of the urine if the uric acid content of urine is being measured.
What determines urate concentrations in the body?
The concentration of urate in the body is a balance between the amount which is produced and the amount which is eliminated.