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MLAB 2401: Clinical Chemistry Keri Brophy-Martinez
Plasma Proteins
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Plasma Proteins Two groups Albumin Globulins
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Prealbumin Synthesized mainly in the liver
Migrates ahead of albumin on electrophoresis Transport protein for thyroid hormones and retinol(Vitamin A)
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Prealbumin Increased Levels Decreased Levels Hepatic damage
Acute-phase inflammatory responses Tissue necrosis Poor nutrition Steroid therapy Alcoholism Chronic renal failure Prealbumin
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Albumin Synthesized in the liver
Protein present in the highest concentration in the plasma Functions Maintenance of colloid osmotic pressure Buffers pH Negative acute phase reactant Binds substances in the blood
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Albumin Decreased Levels Increased Levels Dehydration
Malnutrition/Malabsorption Inadequate intake of amino acids Liver disease GI loss Loss of fluids Renal disease Excreted excessively Dilution by excess IV fluids, polydipsia Dehydration Excessive albumin infusion Albumin
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Globulins Group consisting of α1, β, α2, and gamma fractions
Focus will be on globulins most often encountered in the lab
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α1- Globulins Globulin Function Increased Decreased α1-Antitrypsin
Acute phase reactant Inflammatory reactions, pregnancy, contraceptive use Neonatal Emphysema α1-Fetoprotein Principal fetal protein Spina bifida Anencephaly Fetal Distress
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α2- Globulins Globulin Function Increased Decreased Haptoglobin
Acute phase reactant Binds hemoglobin Inflammatory diseases Rheumatic disease Hemolytic anemia Liver disease Ceruloplasmin Redox activity 90% copper found here Inflammation Severe infection Tissue damage Pregnancy Others Wilson’s disease Malnutrition/Malabsorption Severe liver disease α2-Macroglobulin Inhibits proteases Nephrosis Diabetes
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β- Globulins Globulin Function Increased Decreased Transferrin
Transports iron Prevents iron loss Negative acute phase reactant IDA Liver disease Nephrotic syndrome Malnutrition Hemopexin Acute phase reactant Binds free heme Inflammation Diabetes melllitus Melanoma Hemolytic anemia Lipoprotein Transports lipids, mainly LDL Atherosclerosis Heart disease Diabetes mellitus Hypothyroidism
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ß- Globulins (con’t) Globulin Function Increased Decreased Fibrinogen
Precursor of fibrin clot Acute phase of inflammatory processes Pregnancy Oral contraceptives Excessive coagulation Complement Immune response Inflammation Malnutrition Hemolytic anemia CRP Acute phase reactant Tissue necrosis Cardiac disease
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γ- Globulins: Immunoglobulins
Function Increased Decreased IgG Antibodies Liver disease Infections Parasitic disease Others Immunodeficiency IgA Antibodies in secretions Autoimmune disease Decreased protein synthesis IgM Antibodies: early response Toxoplasmosis Hereditary immunodeficiency IgD IgE Antibodies: allergies Not diagnostic
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Other Noteworthy Proteins
Myoglobin Troponin Heart marker for MI BNP Distinguishes between MI and CHF Fibronectin Glycoprotein used to predict the short term risk of premature delivery
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Do you feel like this? If the answer is “Yes” take a break!
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Protein Abnormalities
Total protein measures all of the proteins in plasma Measurements reflect Nutritional status Kidney disease Liver disease Other
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Hypoproteinemia Total protein level <6.4 g/dL
Due to a negative nitrogen balance Causes Excessive loss renal disease, blood loss, burns Decreased intake Malnutrition, intestinal malabsorption Decreased synthesis Liver disease, inherited immunodeficiency Acceleration of catabolism of proteins Burns, trauma
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Hyperproteinemia Total protein level > 8.3 g/dL Causes Dehydration
Excess water loss leads to the increased concentration of proteins Examples: vomiting, diarrhea, diabetic acidosis, hypoaldosteronism Excessive Production of gamma globulins Examples: multiple myeloma, Waldenstrom’s macroglobulinemia
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Summary of Protein Levels
Total Protein Albumin Globulin Disease N, D D I Hepatic damage, Burns, trauma, Infections N Malabsorption, Inadequate diet, nephroticsyndrome Immunodeficiency syndromes Dehydration Multiple myeloma, monoclonal and polyclonal gammopathies N= normal I=increased D=decreased
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References Bishop, M., Fody, E., & Schoeff, l. (2010). Clinical Chemistry: Techniques, principles, Correlations. Baltimore: Wolters Kluwer Lippincott Williams & Wilkins. Sunheimer, R., & Graves, L. (2010). Clinical Laboratory Chemistry. Upper Saddle River: Pearson. -break/
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