PLASMA PROTEIN Flashcards
WHAT IS PLASMA?
-Blood is withdrawn into tube with an anticoagulant and centrifuged, the cell components are precipitated.
-The supernatant-plasma.
- 55-60% of blood-plasma
WHAT ARE THE COMPOSITION OF PLASMA?
➢Water, 92-93%
➢Electrolytes
➢Metabolites
➢Nutrients
➢Hormones
➢Proteins
WHAT IS SERUM?
Blood is withdrawn into tube without anticoagulant and allowed to clot.
-liquid supernatant- serum.
- lacks coagulation factors-prothrombin and fibrinogen.
PLASMA PROTEINS
protein content of normal plasma= 6-8 g/100mL.
3 major components of plasma proteins:
1. Albumin
2. Globulins
3. Fibrinogen
-Almost all plasma proteins, except immunoglobulins are synthesized in liver.
-generally synthesised on membrane bound polyribosomes.
Most plasma proteins are glycoproteins.
NORMAL LEVELS
total protein = 6-8 g/100mL
1. Albumin- 3.5-5 g/dl
2. Globulins- 2.5-3.5 g/dl
3. Fibrinogen- 200-400 mg/dl
SEPARATION OF PLASMA PROTEINS
- Salting out process
- To separate plasma (serum) proteins into 3 major fraction: Albumin, globulins and fibrinogen. - Electrophoresis
- To separate plasma (serum) proteins into 5 major fractions: Albumin, α1- globulins and α2-globulins, β-globulins, γ-globulins
ELECTROPHORESIS
the movement of charged particles through electrolyte when subjected to an electric field.
- all proteins are negatively charged at pH 8.6,MOVE TOWARDS ANODE
- Albumin have greater charged and low molecular weight, so it move faster to anode and is separated first
- The concentration of fractions can be estimated by a densitometer.
Normal electrophoretic pattern of
plasma proteins
- if plasma used, fibrinogen appears as a distinct band between the beta n gamma region
Abnormal electrophoretic pattern of serum proteins
Nephrotic syndrome
* Thin albumin band due to loss of albumin in urine because of increased permeability of glomerular membrane.
* Prominent a2 band due to an increase in the levels of a2-macroglobulins.
Abnormal electrophoretic pattern of serum proteins
-Cirrhosis of liver
- Thin albumin band due to decreased production by the damaged liver.
- b-g bridging due to markedly raised levels of g-globulins.
Abnormal electrophoretic pattern of serum proteins
-Multiple myeloma
-a plasma cell cancer
-disorder synthesis and secretion of
immunoglobulins.
* These cells synthesize and secrete only the
monoclonal Ig in excess.
* M-band is seen in the γ-
region due to the presence of myeloma protein in serum (monoclonal Ig)
Type of proteins present in each fraction.
a-1
-a1-antitrypsin
a-2
-haptoglobin
-ceruloplasmin
beta
-transferrin
gamma
- immunoglobulins
ALBUMIN
- major part of plasma proteins (~60% with concentration of 3.5-5g/dl)
- Low molecular weight (69 kDa)
- Synthesised by liver. 12g of albumin/day.
- Half-life:20 days.
Functions of albumin
- colloidal osmotic pressure
- transport func
- nutritive func
- buffering func
Colloidal osmotic pressure (oncotic pressure
-Albumin maintain the osmotic pressure in blood vessel (25 mm Hg).
✓Control movement of water into blood vessel and maintains plasma volume.
Low albumin resulting in decrease osmotic
pressure → water filter out into tissue, causing edema.
Transport Functions
▪Albumin is the carrier of various hydrophobic substances in blood circulation.
▪Exp: Bilirubin, fatty acids, minerals, vitamins, steroid hormones & drugs.
Nutritional Function
Serves as source of amino acid for tissue protein synthesis.
Buffering Action
Due to high concentration in blood plasma, albumin has the maximum buffering capacity which contributes to maintain the acid base balance.
Clinical significance of albumin
- Hypo-albuminemia (<2g/dl) will result in tissue edema (swelling) and it can be seen in:
➢Malnutrition (kwashiorkor): Availability of amino acids is reduced, and albumin synthesis is affected.
➢Nephrotic syndrome: Permeability of kidney glomerular membrane defective, so that albumin is excreted in large quantities in urine.
➢Cirrhosis of liver: Albumin synthesis is less, and it escapes into ascitic fluid.
plasma transport proteins
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Transferrin
- of β-globulin fraction of plasma proteins
- Synthesised by the liver.
- Function:
✓Bind to and transport iron through the blood to various tissues.
✓Thus, conserves iron by preventing loss of iron through urine. - High transferrin levels → caused by iron deficiency anaemia.
*Low level of transferrin→liver disease.
ACUTE PHASE PROTEINS
whose plasma concentration may increase 50 to 1000 folds in response to inflammatory and neoplastic conditions.
1. α1-antitrypsin
2. Haptoglobin
3. Ceruloplasmin
4. C-reactive proteins
α1-antitrypsin
Major constituent of α1-globulin fraction
- AKA α-antiproteinase.
* Synthesised in liver.
*Function: inhibits all serine proteases (elastase and collagenase).
*AAT deficiency=
1. Emphysema
2. Nephrotic syndrome
3. Liver disease
EMPHYSEMA
- 5% of emphysema cases are due to the deficiency of α1-AT.
✓associated with lung infections (pneumonia).
✓Macrophage release the active elastase.
✓With no α1-AT, the activity of elastase(its inactive when bind to AAT) increased and causing damage to the lung tissues.
Nephrotic syndrome
AAT molecules are lost in urine, and so AAT deficiency is produced.
Liver disease
AAT deficiency is the most common genetic cause for liver disease in infants and children.
* starts as “neonatal hepatitis syndrome” and may progress to liver failure and cirrhosis.
Haptoglobin
- Is a constituent of α2-globulin fraction of plasma protein.
- Synthesized by the liver.
- Function:
✓Binds to and transport free haemoglobin ( extra-corpuscular haemoglobin) that spills into the plasma due to haemolysis and prevents its excretion in urine.
✓Hp-Hb (MW 155 000) complex cannot pass through glomeruli of kidney, while free Hb (MW 65 000) can.
✓Haptoglobin prevents the loss of free Hb into urine.
Low level indicates haemolysis.
✓The half-life of Hp = 5 days, Hp-Hb complex= 90 mins.
✓In haemolytic anaemia, free Hb in plasma is elevated leading to increased formation of Hp-Hb complex.
✓This complex is rapidly cleared from the plasma resulting in decreased Hp levels.
Ceruloplasmin
- Is a constituent of α2-globulin fraction
- Synthesized by the liver.
- Blue color-high copper.
- Function:
→transport copper in the circulation.
*Increased plasma Cp levels are seen in hepatitis, biliary cirrhosis, inflammatory conditions. - Low level is seen in:
✓Wilson’s disease
✓Malnutrition
✓Nephrosis
✓Cirrhosis
Wilson’s disease
✓Genetic defect that disturbed copper metabolism.
✓Low level of ceruloplasmin, causing free plasma copper is easily enters the tissues (liver, brain,
kidney) and deposited in abnormal amounts.
C-reactive protein (CRP)
reacts with C- polysaccharide of capsule of pneumococci (bacteria).
* Is a β-globulin and MW=115-140 kD. * Synthesised in liver.
* Functions:
*Binds to C-polysaccharide of pneumococci and Stimulate complement activity and macrophage phagocytosis during inflammation – plays an important role in host defense.
* Then, when the inflammation has subsided, CRP quickly falls
Clinical importance of measuring CRP in serum
- Estimation of serum CRP is important for the evaluation of acute phase response – indicator of inflammation
▪ In response to surgery, serum CRP increases and returns to normal level within 7-10 days.
▪ If the recovery is complicated by any infection, it will be reflected by the continuous elevation of CRP which requires further treatment. - Useful for predicting the risk of
coronary heart disease.
✓Increased level of high sensitivity CRP
(hs-CRP), (>3 mg/L) in the circulation has been associated with a high risk of a coronary event.
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- Differences between blood, plasma and serum
- Normal levels of total protein, albumin, globulins and fibrinogen in plasma 3. Functions of albumin
- Plasma transport proteins and their functions.
- Alpha-1 antitrypsin, haptoglobin, Ceruloplasmin, and transferrin
* Site of synthesis
* Electrophoretic band in which it is present
* Function
* Associated disorder - Clinical importance of measuring C- reactive protein in plasma
- The principle of electrophoresis
- Interpret the normal electrophoretic pattern of serum and plasma proteins.
- Abnormal pattern of serum protein electrophoretic in:
* Nephrotic syndrome
* Cirrhosis of liver
* Multiple myeloma
