Protein Flashcards
Plasma Proteins Background
Most abundant components
Chains of amino acids, most proteins are combined with ohter substances
Plasma Protein Functions
Blood coagulation (Fibrinogen, Coagulaition factors)
Maintaining oncotiv presure (Albumin)
Host defense ( immunoglobulins, complement)
Transport of substances ( albumin, transferrin)
Provide mitrogen balance for nutrition ( albumin)
Regulation of cellular metabolism (hormones)
Prevention of proteolysis (a-1 antitrypsin)
Two major categories of Plasma Proteins:
Albumin
Globulins
Albumin
One of the smallest proteins
Single most abundant protein
Synthesized in the liver
Accounts for 75% of colloidal osmotic pressure
Important carrier molecule
Transports FFA, bile acids, bilirubin, calcium, hormones, drugs
Acute Phase Response
- Time Course:
- major Apps:
- Increase rapidly within 2-24 hrs, and decrease rapidly
- Moderate APPs:
- increase over several days and decrease more slowly
- Species differences in major and moderate APPs
- increase over several days and decrease more slowly
- APPs often increased prior to presence of inflammatory leukogram
- Persist until insult resolved
- May be useful for disease monitoring in the future
- major Apps:
Globulins
- All non-albumin Proteins:
- immunoglobulins
- Acute phase proteins
- Complement proteins
- Lipoproteins
- Over 1000 different proteins characterized, very heterogenous group
- about 10 of these contribute significantly to globulin concentration
- Multitude of functions
- most combined with other substances
- lipid, carbohydrate
- Most synthesized in Liver
- except immunoglobulins, which are secreted by plasma cells and B lymphocytes
Acute Phase Proteins
Proteins that change concentration by >25% in response to inflammatory cytokines
Postive AAPs → increase in concentration
Negative AAPs → decrease in concentration
Plasma
liquid portion of unclotted blood
Contails all proteins,
Mst be collected with anticoagulant
Serum
liquid portion of clotted blood
Serum contains all protien exceopt fibrinogen (Consumed during clotting)
Analytical Principles:
Total Protein Refractometry
- TP b refractometer
- estimation of protein in plasma
- reported as part of the hemogram
- Light refraction proportional to solids in solution
- Calibration Scales
- [total solids] = proteins + glucose + electrolytes
- [total protein] = proteins (albumin, globulins)
- Assumes concentrations of glucose, electrolytes, urea, and lipids are normal
- Interferences for [TPref]
- hyperglycemia
- increaed urea
- hypercholesterolemia
- lipemia
- excess EDTA in blood
- Hyperbilirubinemia and hemolysis do not interfere with the refractive index, however they may make the demarcation difficult to read
Analytical Principles:
Measurement of Fibrinogen
- [fibrenogen] by heat percipitation
- crude measurement used in large animal species
- Often more sensitive to inflammation than leukogram changes in LA
- Reported on the hemogram
- [TPref] measured → plasma heated for 3 min at 56C → [TPref] re-measured after centrifugation
Analytical Principles:
Total Protein Spectrometry
- Total protein via spectrophotometry - Biuret reaction
- detects peptide bonds in proteins
- Most common method to measure TP in serum
- Reported on the serum chemistry profile
- TPref usually > then TP biuret
- non-protien solids measured by refractometry
- Fibrinogen in plasma not found in serum
- Biuret Reaction:
- Cu binding to peptide binds → creates voilet complex
- color change read spectrophotometrically
- Interferences:
- hemolysis: + interference in some assays
Analytical Principles:
Albumin Measurements
- Bromocresol Green dye-binding
- Bromcresol Green dye perferentially binds to albumin, causes color change, read spectrphotopmetrically
- Reported on the serum chemistry profile
- Interferences:
- will bind to some globulins, esp if albumin is low
- Leads to falsely increaesd albumin
- Hemolysis + intergerence in some assays
- Inaccurate for measurement in rabbits and old world monkeys
- Unrelianle in most species of bird
- Obtain [TPbiuret] then measure albumin via serum protein eletrophoresis
Analytical principles:
Globulins Measurement
Indirect (calculated) measurement on serum chemistry profile
[TP] - [albumin] = [globulins]
Gractionate globulins
Serum protein electrophoresis (SPE)
Indications: hyperglobulinemia
Inflammatory vs. neoplasia
Analytical Principles:
Serum Protein Electrophoresis
serum is applied to an agarose gel and proteins migrate either towards the cathode or the anode
Separates proteins based on size, shape and charge
- Densitometer translates bands into peaks
- area under each peak is proportional to the % of the fraction in serum
- Absolute quantity of each fraction = [TP] x %
- Acute phase proteins
- alpha and beta globulin
- Immunoglobulins
- gamma globulin
- Occasional beta globulin
Analytical Principles:
Summary:
CBC
[TPref] → estimate of albumin + globulins via reftractometry
[Fibrinogen] → large animla cbc by heat precipitation
Analytical Principles:
Summary
Chemistry Profile
[TPbiuret] → measurement of albumin + globulims by spectrophotometry.
No fibrinogen → removed during clotting process
{Albumin] → measures by BCG
unreliable in birds, rabbits, and old world monkeys
[Globulin] → calculated by [TPbiuret] - [Albumin]
Analytical Principles:
Summary:
Ancillary Tests
Serum protien electrophoesis
Fractionate globulins
Quantify albumin in birds
Dysproteinemia
Presence of normal protein at abnormal concentrations, or abnormal protein in blood
Hypoalbumenimia
Hyperalbumemia
Hypoglobinemia
Hyperglobinemia
Major Mechanisms:
Decreased production, increased production, loss, relative (Shifting of water)
Abnormal proteins, and abnormal protein concentrations
TP, albumin, Globulin concentrations should increase together
Patterns are important
Nonselective: both albumin and globulin affected. Panhypoprteinemia
Selective: only albumin or globulin affected
Interpret in context of relevant history, physical exam findings, CBC results etc.
Nonselective Hyperproteinemia:
Dehydration
increased [TP], concurrent increased in [albumin] and [globulin] usually due to dehydration
Usually accompanied by increased Hct
Loss of plasma water results in relatve increase in albumin and globulins
Nonselective Hypoproteinemia:
Overhydration
Panhypoproteinimaia: Concurrent hypoalbuminemia and Hypoglobulinemia
Overhydration or hemodilution
Uncommon causes of hypoproteinemia
Iatrogenic: excess administration of IV fluids
Edematous Disorders
congestive heart failure, cirrhosis, nephrotic syndrome
Excess ADH secretions: SIDH
Nonselective Hypoproteinemia:
Blood Loss
Hemorrhage
decreased blood volume
Fluid shifts from extravascular space to intravascular
Hemodilution
Hypoprotenemia and anemia
Nonselective Hypoproteinemia:
Protein losing enteropathy
- Protein rich intestinal secretions typically are digested into amino acids and absorbed in the small intestine, then transported to the portal system and lymphatic vessels
- When intestinal disease prohibits absorption or transport of the proteins, the proteins are lost in feces
- When the rate of protein loss exceeds ability of the livere and B lymphocytes to produce proteins, Hypoproteinemia occurs
Nonselectie hypoproteinemia:
Protein losing dermatopathy
- Thermal/chemical burn
- Plasma proteins oozing out of vessels
- globulins may be increased with inflammation
- Early:
- nonselective hypoproteinemia
- Late:
- nonselective hypoproteinemia masked by inflammation
Nonselective Hypoproteinemia:
Effusive Disease
- Pleuritis and Peritonitis:
- extravasation of plasma proteins into pleural and peritoneal cavities
- Vasculitis:
- extravasation of proteins into interstital space
Hypoalbuminemia:
Decreased Productin:
Inflammation
- Albumin is the major negative acute phase protein
- changes in production occur soon after onset of inflammation
- changes can be detected within hours to days
- Increased production of Positive Acute Phase Proteins necessitates decreased albumin production to conserve amino acids for upregulated production of positive acute phase proteins
- Often accompanied by Increase in globulins
- Inflammatory dysproteinemia = Increased [globulin] + decreased [albumin]
- [TP] may be WRI
- Often accompanied by inflammatory Leukogram
- The most common dysproteinemia you will see
Hypoalbuminemia:
Decreased Production:
Hepatic Failure
- 60-80% of functional liver lost before hypoproteinemia occurs
- Albumins and globulin production may both me decreased, however immunoglobulin is not decreased; therefore globulins are often normal
- Other signs of hepatic failure present
- decreased UN, glucose, cholesterol etc)
Hypoalbuminemia:
Decreased Production:
Starvation / Cachexia
- Starvation or cachetic states
- decrease intake of nutrients
- decrease protein production
- Increase protein degradation
- Hypoproteinemia dut to hypoablunemia
- hypoglobulinemai rarely occurs
- decrease intake of nutrients
Hypoalbuminemia:
Decreased Production:
Malabsorption / maldigestion
Malabsorption or maldigestion
decreased intake of nutrients = to few amino acids for protein production
Most commonly a selective hypoalbuminemia; rarely accompanied by hypoglobulinemia
Hypoalbuminemia:
increased loss
Protein-losing nephropathy
- Albumin:
- small – therefore passes more readily than most globulins through damaged glomerular membranes
- Expect concurrent proteinuria and increased urine protein / creatininie ratio
- Hypoglobulinemia may occur in severe cases
- Might be evidence of renal insufficiency – depends on number of functional nephrons
Selective Hypoglobinemia
Generally due to decreased beta or gamma globulin
Usually due to:
Failure of transfer of passive immunity
Inherited or acquired immune deficiency
Selective Hyperglobinemia
Increased [globulin] without concurrent increase in albumin
Inflammation: acute response, delayed response, accompanied by decreased albuminand often an inflammatory leukogram
Antigenic stimulaitons
B-lymphocyte neoplasia
Multiple myeloma, extramedullary plasmacytoma, lymphosarcoma, chronic lymphocytic leukemia
Serum prtien electrophoresis: investigate hyperglobulinemia pathophysiology
