Application of albumin
Introduction to albumin
Albumin is the most important protein in human plasma and plays an important role in maintaining blood volume and body fluid balance. It is a spherical simple protein soluble in water and coagulated with heat. Its molecular structure was clarified in 1975. It is a single-chain polypeptide with 585 amino acid residues, and its molecular shape is oval. In the environment of pH 7.4 of body fluid, it behaves as negative ions, and each molecule carries more than 200 negative charges, which plays a certain role in buffering the disorder of acid-base balance.
Albumin is the most important carrier in plasma. Many substances with poor water solubility can be transported by combining with albumin, including bilirubin, long-chain fatty acids (each albumin molecule can bind 4-6 fatty acid molecules), bile salts, prostaglandins, steroid hormones, metal ions (such as Cu2+, Ni+, Ca2+), drugs (such as aspirin, penicillin), etc.
Physiological function of albumin
1. Maintain plasma colloid osmotic pressure
The plasma colloid osmotic pressure is the main power to make the interstitial fluid at the venous end return to the blood vessel, and the colloid osmotic pressure is mainly produced by albumin. When the concentration of plasma albumin decreases, the plasma colloid osmotic pressure decreases, which can lead to excessive blood water entering the interstitial fluid and edema.
2. Transportation function
Plasma albumin can reversibly combine with many insoluble small molecular organic substances and inorganic ions in the body to form soluble complex, and become the transport form of these substances in the blood circulation. It can be seen that albumin is a non-specific transport protein with important physiological significance and is closely related to human health.
3. Stabilization of globulin
The content of plasma albumin is much more than globulin, and the hydrophilicity is greater than globulin, which plays a colloid protective and stabilizing role on globulin. The obvious decrease of albumin concentration can make the plasma globulin lose its colloidal protective effect, and its stability will decline. The decrease of the stability of plasma globulin will lead to the increase of erythrocyte sedimentation rate (ESR), which is easy to cause microcirculation disturbance and thrombosis.
4. Nutrition
Albumin is an important nutrient of human body. Albumin is constantly metabolized in plasma and decomposed to produce amino acids, which can be used to synthesize tissue protein; It can also be oxidized to provide energy or converted into other nitrogen-containing substances.
5. Acid-base buffer effect
In the environment of body fluid pH 7.4, albumin is a negative ion, with more than 200 negative charges per molecule, which has a certain buffer effect on acid-base balance disorder, among which the buffer effect of acidosis is stronger.
6. Regulate the activity of substances in plasma
When active hormones or drugs are combined with albumin, they may not show their activity but be stored.Because of the reversibility and dynamic balance of this binding, albumin is of great significance in regulating the metabolism of these hormones and drugs.
7. Protection
Albumin is a viscous and colloidal substance. When heavy metal ions are encountered in the human body, it will automatically combine with it and be discharged from the body by the excretory system to play a detoxification role. Therefore, the absorption of heavy metal ions can be avoided by eating foods rich in albumin. Albumin also has protective effect on gastric wall.
Inspection of albumin
1. Increased albumin concentration
It is mainly seen in blood concentration, such as severe dehydration and shock, severe burns, acute hemorrhage, and chronic adrenal cortical dysfunction; When diarrhea, vomiting and high fever occur, rapid dehydration can also lead to an increase in serum albumin concentration.
2. Decrease of albumin concentration
It can be seen in insufficient synthesis, enhanced catabolism plus or increased exudation, and is common in chronic consumptive diseases; Diseases with increased capillary permeability, such as acute lung injury, trauma, surgery, and critical illness; Liver diseases, such as cirrhosis, ascites, acute liver necrosis, toxic hepatitis; Diabetes; Serious renal diseases, such as nephrotic syndrome, severe nephritis, renal insufficiency, etc. Edema is easy to occur when albumin is reduced to below 25g/L. Gastrointestinal diseases can not be well digested and absorbed, and lack of raw materials for protein production, such as stomach cancer, colon cancer and liver cancer.
Five misunderstandings in the use of human serum albumin
Improve immunity:
Some people believe that injection of human serum albumin can strengthen the constitution, improve immunity, delay aging, etc. Therefore, more and more healthy people actively require injection of albumin. However, globulin, not albumin, is involved in the formation of human immune mechanism. Large dose of albumin infusion can not only improve immunity, but may cause the decline of immune function. This is because the albumin preparation contains some biologically active substances, such as trace endotoxin, vasodilator, trace α1-Acid glycoprotein and other substances may have "interference" effect on human immune function.
As a nutritional supplement for healthy people:
In fact, albumin, as a nitrogen source, is slow to synthesize protein, and its half-life is as long as 16~21 days. After it is imported into the human body, it needs to be decomposed into free amino acids for a period of time before it can synthesize the protein needed by the body itself. Therefore, the white protein imported on the same day cannot play a nutritional role very quickly. Moreover, the study found that the proportion of essential amino acids contained in albumin is very uneven, especially the lack of tryptophan, one of the important amino acids used to synthesize other proteins, its nutritional value is low, and its cost-benefit ratio is far lower than that of balanced amino acid preparations, so albumin is not suitable as a nutritional supplement.
Serum protein concentration was not tested before use:
The important reference index for clinical use of human serum albumin is the concentration of serum albumin, whose normal concentration range is 35~50g/L. In actual clinical practice, patients with serum albumin concentration in the normal range, or patients without serum albumin concentration detection, are given human serum albumin infusion, both of which are non-indicated drugs. Generally speaking, the concentration of serum albumin is lower than 25g/L, which indicates the use of human serum albumin.
Albumin may spread infectious diseases such as hepatitis B:
Although theoretically, this possibility cannot be completely denied. However, the human serum albumin currently used is used to inactivate the disease for 10 hours after heating at 60 ℃ when there is a stabilizer. Under this condition, HBV, HCV, HIV and other viruses have lost their infectivity, and albumin has no antigenicity, and can be repeatedly infused. Therefore, albumin infusion is much safer than plasma or whole blood infusion. Of course, the possibility of infection cannot be completely ruled out.
Albumin is safe and has no side effects. Anyone can use it:
Medicine is a double-edged sword, which has both therapeutic effects and may lead to side effects. Albumin is also the same. Some patients have allergic reactions to albumin. Therefore, albumin should be banned for those with allergic reactions to albumin. In addition, it is also prohibited for patients with severe anemia and heart failure. Occasionally, nausea, vomiting, fever, headache, chills, urticaria, tachycardia and other adverse reactions may occur after albumin infusion. For anaphylactic shock, it may endanger life and should be treated in time.