liver diseases and enzymes

Question 1

what are the membrane bound vs cytoplasmic enzymes

Answer 1

membrane = alkaline phosphatase (ALP), gamma-glutamyltransferase (GGT)

cytoplasmic = alanine transferase (ALT), aspartate aminotranferase (AST), sorbitol dehydrogenase (SDH), glutamate dehydrogenase (GLDH)

Question 2

which enzyme can be a sign of normal function and not liver disease

Answer 2

• membrane bound enzymes - ALP

Question 3

what enzymes are associated with cell damage vs disease

Answer 3

cytoplasmic = cell damage
membrane bound (inducible) = disease

for cytoplasmic enzymes -> magnitude of serum levels relate to degree of damage

Question 4

what is alanine aminotransaminase and its role/significance

Answer 4

• cytoplasmic enzyme
• transfers amino group form alanine tto alpha-keetogultarate in alanine cycle to form pyruvate and glutamate
• non-specific -> indicates myocyte injury (damaged cells)
• very present in dogs (x4)

Question 5

what is Aspartatte aminotransferase (AST)?

Answer 5

• cytoplasmic
• transfers an amino acid between aspartate and glutamate
• poor specificity but highly sensitive
• if accompanid by high SDH activity = chronic hepatic injury
• used for LARGE animals

Question 6

what is sorbitl dehydrogenase (SDH)

Answer 6

• cytoplasmic
  *MOST specific in all species!!!
• specific indicator for ALL species -> especially large
• very short half life
• ALT favoured but SDH useful if ALT and CK elevated SOD = concurrent hepatic injury
• SDH also useful when SDH and ALT are elevated together = peristent hepatocellular injury

Question 7

what is Glutamate dehydrogenase (GLDH)

Answer 7

• cytoplasmic
  if this is in the cytoplasm it signifies irriversible cell damage -> because its from the mito
• mitochondrail leakage enzyme in cytoplasm when injured
• specific
• commonly used in large animals

Question 8

what is gamma glutamyl transferase (GGT)

Answer 8

• membrane-bound
• serum GGT can ONLY come from the liver!!!
• signifies cholestasis
• evaluated with ALP
• GGT only from liver, ALP can be from from skeletal muscles etc
• low GGT and high ALP indicates it is NOT liver disease (should change together) -> skeletal muscle disease

Question 9

what is alkaline phosphatase? (ALP)

Answer 9

• membrane bound
• may be increased by coritosteroids in dogs (C-ALP)
• L-ALP found in serum
• *NOT useful for large animals and insensitive for cats

Question 10

which enzyme is most specific for large animals

Answer 10

• SDH -> short half life (very liver specific)
• then GLDH

Question 11

which enzyme is least specific for large animals

Answer 11

• ALT
• very useful in dogs and cats