Serum albumin

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albumin
Identifiers
Symbol(s)	ALB
Entrez	213
OMIM	103600
RefSeq	NM_000477
UniProt	P02768
Other data
Locus	Chr. 4 q13.3

Serum albumin, often referred to simply as albumin, is the most abundant plasma protein in humans and other mammals. Albumin is essential for maintaining the osmotic pressure needed for proper distribution of body fluids between intravascular compartments and body tissues. The human version is human serum albumin. Bovine serum albumin, or BSA, is commonly used in molecular biology laboratories.

Albumin is negatively charged. The glomerular basement membrane is also negatively charged; this prevents the filtration of albumin in the urine. In nephrotic syndrome, this property is lost, and there is more albumin loss in the urine. Nephrotic syndrome patients are given albumin to replace the lost albumin.

Because smaller animals (for example rats) function at a lower blood pressure, they need less oncotic pressure to balance this, and thus need less albumin to maintain proper fluid distribution.

1 Functions of albumin
2 Causes of albumin deficiency (hypoalbuminemia)
3 Testing for albumin loss via the kidneys
4 External links

[edit] Functions of albumin

Maintains osmotic pressure
Transports thyroid hormones
Transports other hormones, particularly fat soluble ones
Transports fatty acids ("free" fatty acids) to the liver
Transports unconjugated bilirubin
Transports many drugs
Competitively binds calcium ions (Ca²⁺)
Buffers pH

[edit] Causes of albumin deficiency (hypoalbuminemia)

Cirrhosis of the liver (most commonly)
Decreased production (as in starvation)
Excess excretion by the kidneys (as in nephrotic syndrome)
Excess loss in bowel (protein losing enteropathy)
Mutation causing analbuminemia (very rare)
Acute disease states (referred to as a negative acute phase protein)

[edit] Testing for albumin loss via the kidneys

In the healthy kidney, albumin's size and negative electric charge exclude it from excretion in the glomerulus. This is not always the case, as in some diseases including diabetic nephropathy, a major complication of uncontrolled diabetes where proteins can cross the glomerulus. The lost albumin can be detected by a simple urine test [1]. Depending on the amount of albumin lost, a patient may have normal renal function, microalbuminuria, or albuminuria.