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Proteins. OVERVIEW. 1.Physiological characteristics 2. Measurement: serum protein and electrophoresis 3. Serum protein abnormalities 4. Fibrinogen. Physiological Characteristics. Proteins.

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Presentation Transcript
overview
OVERVIEW

1.Physiological characteristics

2. Measurement: serum protein and electrophoresis

3. Serum protein abnormalities

4. Fibrinogen

proteins4
Proteins

-Fresh serum contains all plasma proteins except those consumed during clot formation (fibrinogen and factors V+ VIII)

-Total proteins comprise ALBUMIN and GLOBULINS

ALBUMIN is synthesised by the liver

GLOBULINS are mainly synthesised by B-Lymphocytes and the liver:  &  fractions and  fractions

N.B. There is one albumin (relative molecular weight of 66) and thousands of globulins (with higher relative molecular weight, i.e. IgG=150)

functions
-Maintenance of oncotic pressure (esp. albumin)

-Buffering capacity (esp albumin)

-Transport of molecules (e.g. drugs, lipids, hormones, metals)

-Coagulation (fibrinogen, etc)

-Immunological functions (globulins)

- Inflammation

Functions
age associated changes
-Total Proteins are low at birth

60-80% of adult values

mainly due to lower globulins

-Increase after colostral absorption

serum protein concentration can assess colostral intake

-Decline over next 1-5 weeks

-Reach adult concentrations in 6-12 months

Age Associated Changes

N.B. Birds have lower reference intervals for total proteins (22-52 g/L) compared to mammals (54-75 g/L)

globulins
Globulins

- and - Globulins:

  • Most are synthesised by the liver
  • Include:
    • Acute phase proteins of inflammation
      • Acute phase proteins (APP) are serum/plasma proteins whose concentrations change during inflammation. Most are increased (positive APP) and some are decreased (negative APP). Examples of APPs are fibrinogen, C-reactive protein (CRP)
    • Transport proteins (e.g. lipoproteins)
    • Some immunoglobulins (IgM, IgA)

-Globulins:

  • Most immunoglobulins secreted by B lymphocytes and plasma cells in many tissues particularly the lymphoid organs
protein measurement
Protein Measurement

-Refractometer

Measures total proteins only

Rapid, easy and reproducible results

Best accuracy between 25-95g/L

Falsely increased values in haemolysed & lipaemic samples

-Spectrophotometric methods

Biuret method (for Total proteins)

Different dyes (for Albumin)

  • Refractometer measurement of total protein is less accurate than spectrophotometry but adequate for routine use.
  • In routine chemistry, globulin is not measured, only estimated (globulin = total protein–albumin)
serum protein electrophoresis
Serum Protein Electrophoresis

Interpretation is based on:

1.the morphology of the electrophoretical profile

2. the concentration of each

fraction calculated from total

proteins

-

+

α1 α2 β1 β2 γ

albumin globulins

serum protein electrophoresis11
Serum Protein Electrophoresis
  • Principle: Proteins migrate in an electrical field at a rate dependent on their net charge & molecular weight
  • Protein electrophoresis should not be performed in plasma because of fibrinogen interference.
  • Globulin fractions and subfractions can vary depending on the species and method used
protein abnormalities
Protein Abnormalities

DYSPROTEINAEMIA: disturbance of the relative or absolute concentrations of proteins

A. HYPERPROTEINAEMIA

( concentration of plasma proteins)

B. HYPOPROTEINAEMIA

( concentration of plasma proteins)

hyperproteinaemia
Hyperproteinaemia

1. Hyperalbuminaemia

- Dehydration is the only cause

2. Hyperglobulinaemia

-Increased  and  globulins

Acute Inflammation

-Increased  and globulins

Chronic inflammation

increased immunoglobulins
Polyclonal gammopathy:

Increase in multiple

immunoglobulins

Monoclonal gammopathy:

Increase in a single immunoglobulin

Increased Immunoglobulins

Alb

Alb

hypoproteinaemia
Hypoproteinaemia

1. Overhydration with intravenous fluids, polydipsia

2. Hypoalbuminaemia

3. Hypoglobulinaemia

N.B. Overhydration with intravenous fluids or polydipsia will cause haemodilution (pseudohypoproteinaemia).

Young animals (< 6-9 months) have lower reference values for proteins than adults

hypoalbuminaemia causes
Hypoalbuminaemia: Causes
  • Inadequate protein intake

Starvation

Malabsorption/maldigestion

Lactation

  • Decreased albumin synthesis:

Hepatic insufficiency

Acute Inflammation

  • Increased albumin loss:

Renal

Gastrointestinal

Haemorrhage / Exudates

hypoalbuminaemia
Hypoalbuminaemia
  • Inflammation can result in hypoalbuminaemia as albumin is a negative acute phase protein (i.e. albumin decreases in response to increased globulin and other acute phase proteins)
  • Renal disease = albumin losing nephropathy (amyloidosis or glomerulonephritis). Globulins not affected
  • Gastrointestinal = protein losing enteropathy (alimentary lymphoma, lymphangectasia, inflammatory bowel disease). Globulins also ↓
  • Chronic haemorrhage. Globulins also ↓
  • Exudates e.g. pyothorax, peritonitis. Globulins may ↑
hypoglobulinaemia causes
Hypoglobulinaemia: Causes
  • Decreased globulin intake

Colostrum deprivation

Failure of passive transfer (neonates)

  • Decreased globulin synthesis

Immunodeficiency diseases (↓ globulins)

Hepatic insufficiency (↓ and  globulins. Albumin also ↓)

  • Increased globulin loss

Gastrointestinal

Haemorrhagic

fibrinogen21
Fibrinogen
  • Consumed during blood clotting

(not part of serum total protein assessment)

  • Produced by liver
  • Important in coagulation
  • Marker of inflammation
fibrinogen abnormalities
Hyperfibrinogenaemia caused by

Inflammation

Dehydration

Hypofibrinogenaemia caused by

Failure of production (Congenital or Severe hepatic insufficiency)

Increased consumption (Disseminated Intravascular Coagulation)

Overhydration

Fibrinogen Abnormalities