Plasma proteins are proteins that are synthesized in the hepatocytes or liver cells and release in the blood plasma except immunoglobulins.
Plasma proteins plays a vital role in the body metabolism being part of blood,they moves from vessels to organs supplying their functions.Below are the function of plasma protein the body.
Function of plasma proteins
- Maintenance of colloid oncotic pressure and a good example is Albumin
- They help in the transportation of molecules or substances like Lipid transported by apoproteins,cortisols transported by cortisol transporting proteins,Iron by transferrin,drugs and toxic substances by albumin etc.
- They also help in defending the body against foreign organism and particles ( Immunoglobulins and compliments)
- They are involved in blood coagulation or clotting e.g clotting factors such as fibrinogen
- Lastly buffering the Hydrogen ions of blood.
Precaution taking before measuring plasma proteins
- Avoid venous stasis
- Patient should not be in recumbent position or standing
- Avoid collecting samples from a hand containing infusion
- Collect sample in dry tubes
Significance of plasma protein concentration in diseases condition
Diseases may occur when there are defects in some plasma protein catabolism and in situation of dehydration and overhydration.Those plasma proteins involved in these disease conditions include :
Albumin has a low molecular weight and it is the most abundant in blood plasma making it the main protein responsible for the regulation of colloid oncotic pressure of blood plasma.
Albumin is synthesized in the hepatocytes as earlier mention and has a high capillary permeability.
Decrease in albumin concentration of synthesis occurs in :
- Liver disease (only in chronic liver disease)
- Catabolic state especially during injuring or surgery
- Renal diseases especially nephrotic syndrome
2. Pre-albumin and Retinol binding protein
They are mostly present in small quantities and are synthesize by the hepatocytes.Function in transporting Vitamin A and thyroxine.
Fall in their concentration occurs during injury and in both acute and chronic liver disease.They are better markers than albumin to determining nutritional status such as Malnutrition or overnutrition.
Function in the transportation of iron to the bone marrow.The Total iron binding capacity (TIBC) is a measure of the amount of transferrin.
Decrease in the concentration or level of transferrin occurs in protein losing condition,infection and neoplastic disease.
Increase transferrin will occur in iron deficiency state
Haptoglobulin is an Acute phase reactant.It belongs to the Alpha-2 globulin group.
Decrease haptoglobulin occurs in Haemolytic anemi,liver disease and rarely in congenital abnormality.
Increase level of Haptoglobin occurs in acute infection following trauma being an acute phase reactant
This is a copper containing protein which binds about 90% of copper found in the blood plasma.
Decrease occurs in Wilson’s disease ,malnutrition and nephrotic syndrome.
Raise levels occurs during pregnancy and acute infections.
6. Alpha-1 antitrypsin
It is an alpha globulin protein and another Acute phase reactant.Decrease or deficiency occurs during liver diseases while raised level will occur in pregnancy,acute infection that follows trauma
7. Alpha 2 macroglobulin
This is the major alpha 2globulin.It has an antiproteinase activity and decrease levels has not been recorded yet.
8. Alpha 1 fetoprotein (AFP)
Present in tissue and plasma of foetus.This plasma protein rapidly falls after birth but minute amount can be detected in adults.Increase or high level occurs in patients with hepatocellular carcinoma and gonadal neoplasm and in women carrying foetuses with open neural tubes.
9. Carcinoembryonic antigen (CEA)
Normal present in fetal intestinal cells but not measurable in healthy adults.This plasma protein reappears in the cells of intestinal neoplasm in adults.Previously,it was though that the appearance of CEA in the plasma was a diagnostic of intestinal carcinoma in adult like colon cancer.However ,CEA is also released by carcinomas occurring in other sites and from non-carcinomatous lesions of the intestines.Post operatively,plasma CEA provide a means of assessing whether the tumor has been removed that is it should retain to normal within 6 weeks post operation.
10. C-Reactive protein (CRP)
This plasma protein is synthesized by the liver and released into the blood plasma.Small amounts are also made by a subset of êripheral lymphocytes but this remain bound to the surface of the cell.It is the first recognised acute phase reactant.It has a number of immunologic function which include :
- Activation of complements and monocytes
- Initiation of opsonization and phagocytosis
- It is also important in the recognition of necrotic tissues
It’s levels in plasma may increase markedly during acute phase response.
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