Albumin is a class of proteins that are very common in nature, being part of numerous plant and animal species. Probably the best known type is the one found in the white part of eggs but another albumin is a key part of human blood and it can be found in many places. Albumins play a critical role in the health of living organisms, being one of the major types of protein.
Albumin is extremely important in the human body, which can't function without it. Its main role if as a component of the blood, it is responsible for the transport of essential fatty acids from the fat deposit to the muscle cells, where the fats are burned in order to generate energy. It also carries numerous other compounds through the blood stream, like natural hormones or chemical drugs and it helps regulate osmosis. Lack of albumin can lead to critical health problems and it is one of the standard tests required by doctors when evaluating a sick person.
In general, albumins are a type of protein with a globular structure. The human blood actually has several closely related albumins, all of them used in the transport of nutrients, examples include alpha-fetoprotein, afamin, vitamin D-binding protein and especially serum albumin. Serum albumins are by far the most commonly found. All of these types are soluble in water and partly soluble in salty concentrates, unlike other blood proteins they are not glycosylated. They are one of the main components of blood plasma and decompose at high temperatures. Albuminoids is an umbrella term for substances with a content of albumin.
Ovalbumin is the name of the specific variety of albumin found in the white part of eggs. Ovalbumin actually makes up more than half of the total quantity of protein in the egg whites. It is often confused with albumen, which is a general name for egg white, of course the two terms don't mean the same thing.
Albumin coagulates when heated, a property common among proteins and easy to observe in eggs. It is very handy in cooking and makes eggs a vital ingredient in baking and many other recipes. By coagulating, albumin maintains the structure of food, especially in bakery products. The egg white is also added in order to improve soups and other dishes. Proteins bind with toxins, which makes albumin an effective counter in poisoning cases. It traps and neutralizes other impurities as well and can serve as a general detoxification and purification agent.
When heated in the process of cooking, proteins change their structure and combine into a new one. A side effect of this process is that their color changes as well, egg white for example turns from transparent to opaque and white. Ovalbumin loosens and expands when beaten, becoming a foam mixed with air particles. As every experienced cook knows, beating the eggs too much destroys their structure completely. Due to its coagulation property and the air trapped inside, egg albumin can expand when cooked but retain its original shape, which produces food with a nice soft texture.
In addition to other roles, albumins regulate the level of fluids in the body, acting in every cell. Basically, albumin balances the amount of water inside the cell, allowing more water to come in and releasing some of it, as needed. Cells need constant filling and refilling with fluids but the actual level has to be regulated very precisely. Too much water can cause the cells to blow up. This is what happens when the body doesn't have enough albumin, the excess fluids will swell and inflame nearby tissues when they leak out of cells.
In the blood stream, albumin mainly acts like a transport agent. It ships around numerous different compounds, the most important are hormones, drugs but also essential minerals such as calcium. Lack of albumin severely disrupts the transport of bilirubin. This compound is produced in the liver as a by-product of bile and has a yellow color. Bilirubin deficiency can lead to serious problems starting from lack of energy and weight loss to jaundice.
A poor diet that doesn't provide enough proteins will hamper the liver's ability to produce albumin and cause severe issues. A lack of albumin initially leads to swelling, because of its role in fluid exchange and the transport of nutrients. However, low albumin levels can also be caused by liver diseases, since the production output is decreased. Another possible cause is a kidney disease because this organ also plays a role in the metabolism of proteins.
Too much albumin is also bad for health. This usually happens as an effect of certain drugs, the most common are androgen hormones, growth hormones, insulin and anabolic steroids. In this case, the cells are forced to absorb more fluids than normal, which causes dehydration.
Albumin is the most important protein found in the blood. Blood proteins have a number of roles and all of them are critical for a healthy life. Low levels of albumin have severe consequences and doctors will measure blood albumin as part of the standard package of tests. If a blood test reveals insufficient albumin, modern medicine has several effective treatments able to correct this problem.
Albumin is present in many parts of the human body but the highest concentration, about 30 or 40% of the total, is found in plasma. The rest is spread all around tissues, in particular in the interstitial and intracellular spaces. It is present everywhere, in the muscles and skin but also in internal organs such as lung, heart, kidneys, liver or spleen. A small part of the interstitial albumin, around 10% of it, is permanently bound to tissues. The rest circulates permanently and gets pumped back into the system by the cranial vena cava, after lymphatic drainage.
As a critical protein, albumin serves in a number of different metabolic functions. It binds with toxins and impurities, providing relief in cases of poisoning. It plays an important role in osmosis, especially the colloid osmotic pressure (COP), and contributes to healing by transporting drugs through the blood stream. It can neutralize toxic by-products of our body as well, for example the excess hypochlorite synthesized in the human metabolism, which would otherwise turn into dangerous hydroxyl radicals. Albumin is also an antioxidant compound.
The loss of albumin can have dramatic effects. For example, nephrotic syndrome causes a glomerular loss of albumin. This increases the quantity of arachidonic acid in the blood, making a larger amount available for metabolism to prostaglandins. Apparently, this further translates into thrombosis and higher platelet aggregation. Platelet aggregation can also happen through a similar mechanism after long periods of high glycaemia or severe cases of diabetes mellitus. Conditions such as hypoalbuminemia, nephrotic syndrome or untreated diabetes might develop into the even more serious coagulopathy, this is because albumin is known to increase the effects of antithrombin III, similar to the way heparin does.
Lung interstitial tissues concentrate almost 70% of the entire content of albumin in plasma. This is not usually a problem, since the lymphatic system of the lungs routinely drains the albumin from the tissues. However, some diseases can break this mechanism. Hypoproteinemia is a condition that makes blood hypoosmotic and disturbs the balance of albumin, since the higher flow of lymph in the lungs removes too much albumin from lung interstitial tissues. This can break the entire osmotic balance of the body.
The opposite effect is also possible, since higher levels of serum COP boost the osmotic balance. What actually happens if that more fluids than normal are released by the cells in the intravascular space and the lungs of shocked patients become dry as a result. Doctors have to react quickly to this problem and counter the symptoms of shock. If the osmotic balance is not back to normal, the situation can evolve into pulmonary edema and acute respiratory distress syndrome (ARDS) due to a lack in the amount of plasma and the imbalance of fluids. ARDS is the severe inflammation of dry lungs and can be fatal. It can lead to respiratory failure, because the lungs are destroyed internally by pulmonary edema and damaged capillaries. The high amount of fluid and transcapillary escape eventually breaks the lymphoid function as well, this can be critical to people with heart failure and lead to other even more severe conditions.