Liver Serum Enzyme Tests - Dahms

Question 1

What is cholestasis?

Give some examples of extrahepatic cholestasis, intrahepatic colestasis, and medications that might cause cholestasis

Answer 1

Any condition in which the flow of bile from the liver is inhibited or blocked

extrahepatic

• strictures
• stones in the common bile duct
• pancreatitis
• primary sclerosis cholangitis
• cysts and tumors

intrahepatic

• alcoholic liver disease
• primary biliary cirrhosis
• viral hepatitis

medications

• antibiotics
• anabolic steroids
• birth control pills

Question 2

Name the two isoforms of AST and describe where each is found in the cell

What is a required co-factor for both?

Which is responsible for the most activity in the human liver?

Answer 2

AST isoforms:

GOT1 = cytoplasmic form

GOT2 = mitochondrial form

Co-factor: PLP

Isoform GOT2 is responsible for ~80% of AST activity in the human liver

Question 3

Where is ALT found in the cell? In what tissue?

What is a required co-factor?

Answer 3

Liver, cytoplasmic

PLP is a required co-factor

Question 4

Which is more sensitive to PLP deficiency, AST or ALT? Why is this important?

Answer 4

ALT is more sensitive to PLP deficiency

PLP deficiency underlies the AST:ALT (>2:1) ratio seen in alcholoic hepatitis

Question 5

Name the four (4) isoenzymes of Alkaline Phosphatase (ALK PHOS)

Answer 5

• non-specific liver/bone/kidney
• intestinal
• placental
• germ cell

Question 6

Where is 5’-nucleotidase found in the liver?

Why is it useful?

Answer 6

Associated primarily with canalicular and sinusoidal plasma membranes

Useful because 5’-nucleotidase is not elevated in bone disease or pregnancy (unlike ALK PHOS) -> more specific to the liver in the setting of elevated ALK PHOS

Question 7

Other than diseases of the liver, biliary tract, and pancreas, what else might cause an elevated GGT?

Answer 7

alcohol abuse (increases hepatic microsomal GGT –> increased serum GGT)

medications (barbiturates, anticonvulsants)