The Liver Flashcards
what are the functions of the liver?
- Carbohydrate Metabolism
- Fat Metabolism
- Protein Metabolism
- Hormone Metabolism
- Drugs and Foreign Compounds
- Storage
- Metabolism and Excretion of Bilirubin
what kind of specimen is required for a bilirubin assay?
fasting serum specimen refrigerated and kept away from sunlight
what is the Evelyn Malloy procedure based upon?
(1) conjugated bilirubin is water soluble and therefore, will react with the diazo reagent in a water solution.
(2) unconjugated bilirubin is not water soluble, therefore, alcohol is necessary to put the unconjugated bilirubin in solution so that it can react with the diazo reaction.
how is bilirubin measured?
the Evelyn Malloy procedure:
Bilirubin and the diazo reagent form an azobilirubin complex, which can be measured colorimetrically. The colour of the azobilirubin varies with pH
what is the Jendrassik-Grof Procedure
(1) Total bilirubin forms a coloured complex with diazo reagent in the presence of a catalyst (caffeine benzoate)
(2) Ascorbic acid is added, which destroys the excess diazo reagent (terminates the reaction)
(3) Alkaline tartrate is added, which converts the medium to an alkaline pH (13) The red-purple azobilirubin is converted to a blue azobilirubin.
what are the most commonly used markers of hepatocyte injury?
aspartate aminotransferase (AST) and alanine aminotransaminase (ALT)
why do AST and ALT lack specificity?
- enzymes can leak into circulation due to hepatic necrosis
- Levels can rise to several times normal after severe muscular exertion or other muscle injury
why are AST and ALT values are higher in obese patients?
they have a fatty liver
what causes a high AST to ALT ratio,
viral or toxic liver injury often due to alcoholism
how is an AST assay performed?
With the coenzyme P-5-P, AST transfers an amino group from aspartic acid to alpha-ketoglutaric acid to form oxalacetic acid and glutamic acid.
A kinetic method enzyme, malate dehydrogenase (MDH) is a reagent.
The reaction at 340nm the decrease in abs per time is directly proportional to AST activity.
how is an ALT assay performed?
coenzyme:P-5P, ALT transfers amino group from alanine to alpha ketoglutaric acid to form pyruvic acid and glutamic acid
pyruvic acid coupled with dinitrophenylhydrazine to form a coloured hydrazone.
The enzyme LDH is used as a reagent:
what is cholestasis?
lack of bile flow
what is a cause of cholestasis?
the blockage of bile ducts or from a disease that impairs bile formation in the liver itself
what is a sign of cholestasis?
AP and gamma-glutamyltransferase (GGT) levels typically rise to several times normal level
