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Proteins

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

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Proteins

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  1. Proteins

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

  3. Physiological Characteristics

  4. 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)

  5. -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

  6. -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)

  7. 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

  8. Measurements: Serum Protein & Electrophoresis

  9. 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)

  10. 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

  11. 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

  12. Serum Protein Abnormalities

  13. Protein Abnormalities DYSPROTEINAEMIA: disturbance of the relative or absolute concentrations of proteins A. HYPERPROTEINAEMIA ( concentration of plasma proteins) B. HYPOPROTEINAEMIA ( concentration of plasma proteins)

  14. Hyperproteinaemia 1. Hyperalbuminaemia - Dehydration is the only cause 2. Hyperglobulinaemia -Increased  and  globulins Acute Inflammation -Increased  and globulins Chronic inflammation

  15. Polyclonal gammopathy: Increase in multiple immunoglobulins Monoclonal gammopathy: Increase in a single immunoglobulin Increased Immunoglobulins Alb Alb

  16. 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

  17. Hypoalbuminaemia: Causes • Inadequate protein intake Starvation Malabsorption/maldigestion Lactation • Decreased albumin synthesis: Hepatic insufficiency Acute Inflammation • Increased albumin loss: Renal Gastrointestinal Haemorrhage / Exudates

  18. 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 ↑

  19. 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

  20. Fibrinogen

  21. Fibrinogen • Consumed during blood clotting (not part of serum total protein assessment) • Produced by liver • Important in coagulation • Marker of inflammation

  22. Hyperfibrinogenaemia caused by Inflammation Dehydration Hypofibrinogenaemia caused by Failure of production (Congenital or Severe hepatic insufficiency) Increased consumption (Disseminated Intravascular Coagulation) Overhydration Fibrinogen Abnormalities

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