Albumin 'Key Points'

What is albumin?

Albumin is an important intravascular and extravascular protein; it contributes strongly to the maintenance of colloid osmotic pressure.

Why is it important?

Binding and transport, osmotic pressure, free radical scavenging, platelet function inhibition and antithrombotic effects.

What causes serum albumin to decrease?

Decreased synthesis, increased catabolism, increased loss & redistribution.

* Consequences of decreased plasma albumin

1. Decreased ligand binding.

2. Decreased plasma colliod pressure

* Disease processes associated with Hypoalbuminaemia

In critical illness, there is a stronger correlation between colloid oncotic pressure and Total protein than with albumin.

Albumin decreases in burns, liver disease, renal disease, pre-eclampsia, stress and sepsis.

* Albumin as a prognostic index

Serum albumin concentration in critical illness is inversely related to the risk of death.

* Correcting Hypoalbuminaemia

The "normalisation" of plasma albumin concentrations has nor been shown to improve outcome in critical illness and in many of the traditional theraputic roles of albumin

* The recent fuss about albumin

The Cochrane report in the BMJ in July 1998 suggested that treatment with albumin was related to a 6% excess of deaths above control. Although this study was flawed in many ways, it has illustrated what many have believed for some time: that theraputic albumin therapy has little role in the management of most patients. Nevertheless, where albumin's use is well defined - in paediatrics / burns, it's abandonment does not appear justified at this time.

Why is albumin important?

1. Binding and transport.
2. Maintenance of colloid osmotic pressure.
3. Free radical scavenging.
4. Platelet function inhibition and antithrombotic effects.
5. Effects on vascular permeability.

Binding and transport
There are actually four binding sites on albumin and these have varying specificity for different substances.
Competitive binding of drugs may occur at the same sit or at different sites (conformational changes) [eg. warfarin and diazepam].
The drugs that are important for albumin binding are: warfarin, digoxin, NSAIDS, midazolam, thiopentone.
The relevence of a low albumin and drug binding is unknown.

Osmotic pressure
Albumin is responsible for 75 - 80 % of osmotic pressure.
Starling's equation: Transcapillary Flow = k [(Pcap + p i) - (Pi + p cap )]
Remember that albumin is the main protein both in the plasma and in the interstitium and it is the COP gradient rather than the absolute plasma value that is important: this is what distinguishes hypoalbuminaemia derived from redistribution (capillary leak) from that of pure full body deficiency.

Free Radicals
Albumin is a major source of sulphydryl groups, these "thiols" scavenge free radicals (nitrogen and oxygen species).
Albumin may be an important free radical scavenger in sepsis.

Anticoagulant effects
The anticoagulant and antithrombotic effects of albumin are poorly understood this may be due to binding nitric oxide radicals inhibiting inactivation and permitting a more prolonged antiaggregatory effect.
In diabetes, glycosylated albumin may increase the incidence of thrombotic events and atherosclerosis.

Capillary Membrane Permeability
In sepsis there is an increased rate of albumin loss into the tissues - this is probably related to increased capillary membrane permeability.

Source: 4um.com

What Is Albumin?

Albumin is an umbrella term for a type of protein which is water soluble. Numerous types of albumin can be found all over the natural world, and two of the most familiar examples of albumin can be found in egg whites and in human blood. Albumins are an important class of protein, and they are vitally important to health and well being for many organisms. Many plants and animals contain or secrete albumin.

A protein classified as albumin is globular, meaning that it is soluble in water. Globular proteins also have a roughly spherical structure. When combined with water, albumin and other globular proteins form a colloid, a solution which appears homogeneous although it actually contains multiple substances. The other type of protein, fibrous protein, such as that found in muscles, is not water soluble, and it has a different basic structure.

Source: wisegeek.com

Albumin 'Wiki'

Albumin (Latin: albus, white) refers generally to any protein that is water soluble, which is moderately soluble in concentrated salt solutions, and experiences heat coagulation (protein denaturation). Substances containing albumin, such as egg white, are called albuminoids.
A number of serum transport proteins are known to be evolutionarily related, including serum albumin, alpha-fetoprotein, vitamin D-blinding protein, and afamin.

Source: Wikipedia.