CC1

• Detoxification and drug metabolism

  Liver detoxifies nitrogenous waste and protects the body from injurious substances and toxic by-products of metabolism
• Conjugation

  Involved in bilirubin metabolism
• Excretory and secretory function

  Liver excretes bile, bile acids and salts, pigments, and cholesterol
• Liver functions

  • Synthetic function
  • Conjugation
  • Detoxification and drug metabolism
  • Excretory and secretory function
  • Storage function
• Synthetic function

  Liver secretes plasma proteins, carbohydrates, lipids, lipoproteins, clotting factors, ketone bodies, and enzymes
• To abolish liver tissue function, more than 80% of the liver must be destroyed
• Liver

  The chief metabolic organ in the body, receiving 15 ml of blood per minute, composed of hepatocytes and kupffer cells, arranged into lobules, with a unique capacity to regenerate by cell division and hypertrophy
• The liver is the site for protein synthesis, production of fibrinogen, destruction of worn-out erythrocytes, and is the center for fat and carbohydrate metabolism
• Severe loss of hepatic functions of excretion, detoxification, and metabolic activity are reflected in multiple standard and specialized tests
• Bilirubin is a yellowish substance made during the body's process of breaking down old red blood cells, found in bile, and a healthy liver removes most of it from the body
• Test measuring the hepatic synthetic ability is useful for quantitating the severity of hepatic dysfunction, with serum albumin and vitamin K dependent coagulation factors providing useful indices for assessing liver disease severity
• Plasma levels of total protein are about 10% higher in ambulatory individuals
• Storage function

  Liver is the storage site for fat-soluble vitamins and glycogen
• Kjeldahl method is based on the measurement of nitrogen content in proteins
• Total protein determination

  Important in assessing nutritional status and presence of severe diseases involving liver, kidney, and bone marrow
• Biuret Method is the most widely used method for measuring protein concentration in clinical labs
• Reference values for total protein are 6.5-8.3 g/dl
• Folin-Ciocalteu (Lowry) method

  1. Highest analytical sensitivity

  2. Oxidation of phenolic compounds such as tyrosine, tryptophan, and histidine resulting in a deep blue color
• Reagents for Folin-Ciocalteu (Lowry) method

  • Phosphotungstic-molybdic acid or phenol reagent and biuret reagent
• Ultraviolet absorption method

  1. Proteins absorb light at 280nm and at 210nm

  2. Absorption at 280nm is due to tryptophan, tyrosine, and phenylalanine
• End product of H2SO4 (digesting agent) is not provided
• Electrophoresis

  1. Principle: Migration of charged particles in an electric field

  2. Clinical application in serum protein electrophoresis (SPE) is for the identification of monoclonal spikes of immunoglobulins and differentiating them from polyclonal hypergammaglobulinemia
• Reagents for Biuret Method

  • Alkaline copper sulfate, Rochelle salt (NaK Tartrate), NaOH, Potassium Iodide
• Refracometry

  An alternative test to chemical analysis of serum total protein based on the measurement of refractive index due to solutes in serum
• Solubility properties: Albumin is soluble in water and insoluble in saturated salt solution. Globulin is soluble in weak salt solution and insoluble in water
• Turbidimetric and nephelometric methods

  1. Utilize sulfosalicylic acid and/or trichloroacetic acid

  2. Measurement depends on the formation of a uniform fine precipitate which scatters incident light in suspension (nephelometry) or blocks light (turbidimetry)
• Salt fractionation

  1. Globulins can be separated from albumin by salting out procedures using sodium salts

  2. Sodium sulfate is a salt used for analysis (salting out)
• Biuret Method

  1. Most widely used method recommended by IFCC (International Federation of Clinical Chemist)

  2. Extensively used in clinical labs, particularly in automated analyzers where protein concentration can be measured down to 10-15 mg/dl

  3. Requires at least 2 peptide bonds and an alkaline medium

  4. Principle: Cupric ions complex the groups involved in the peptide bond forming a violet-colored chelate which is proportional to the number of peptide bonds present and reflects the total protein level at 545nm
• Other measurements for protein

  • Coomasie brilliant blue dye
  • Ninhydrin
  • Amino acid analysis from ion exchange columns
• Increased total protein is associated with MMmWm. Decreased total protein is associated with HGNS
• Prothrombin Time differentiates intrahepatic disorders (prolonged Protime) from extrahepatic obstructive liver disease (normal Protime)
• Albumin concentration is inversely proportional to the severity of liver disease. Plasma levels decline when severe hepatocellular disease lasts more than 3 weeks. In hepatic circulation disorder, albumin is used because its concentration reflects the shift of protein. Low total protein + low albumin = hepatic cirrhosis and necrotic syndrome
• Anatomy and Physiology of the Liver: Persistent prolongation of Protime despite vitamin K administration indicates loss of hepatic capacity to synthesize proteins. Prolongation of Protime indicates massive cellular damage
• Reference values for serum albumin: 3.5-5.0 g/dL (35-50 g/L). Hyperalbuminemia is increased serum albumin, often seen in severe dehydration or due to prolonged tourniquet application (artifactual hyperalbuminemia). Hypoalbuminemia is decreased serum albumin and denotes a disease process
• Dyes used for measurement

  • BCG – most commonly used dye
  • BCP – most specific/highly sensitive
  • MO
  • HABA (hydroxyazobenene benzoic acid)
• Causes of hypoalbuminemia: Reduced synthesis (chronic liver disease, malabsorption syndrome, malnutrition, muscle wasting disease), increased loss (nephrotic syndrome, massive burns, protein-losing enteropathy, orthostatic albuminuria), increased catabolism (massive burns)
• Thyrotoxicosis is excess thyroid hormone activity
• Increased catabolism breaks down large, complicated molecules into smaller ones
• Bilirubin is the end product of hemoglobin metabolism and the principal pigment of bile
• Nephrotic syndrome results in increased protein secretion when the glomerulus no longer functions to restrict the passage of proteins