serum enzyme tests Flashcards
Liver panel/ liver biochemistries abbreviations
AST (SGOT)- Aspartate aminotransferase, serum glutamic oxaloacetic transaminase)
ALT (SGPT)- Alanine aminotransferase, serum glutamic pyruvic transaminase
ALK PHOS- alkaline phosphatase
GGT- gamma glutamyl transpeptidase
Bili- bilirubin
PT- prothrombin time (INR)
Transaminases
ALT and AST
Both located in the hepatocyts
AST in cytoplasm and Mitochondrila
ALT in just cytoplasm
Elevation usually indicates hepatocyte injury
ALT is more specific to the liver than AST (Sk and card muscle injury can increase AST )
Alkaline phosphatase
An enzyme on the surface of liver cells that is adjacent to the bile canaliculi
Usually elevated with biliary obstruction or cholestatic process
Present in Liver, bone, intestine, placenta
If not sure about hepatic origin check Isoenzyme 5’nucleotidase, GGT (all biliary)
bilirubin
the product of RBC breakdown, first water insoluble (unconjugated/indirect) then liver cells conjugate indirect bilirubin theu the action of UDPglucuronytransferase (UDP1A1), and make it water soluble (conjugated/direct) allowing it to be secreted in bile
Increased direct (conjugated) bilirubin- liver injury, bile duct problems, rare metabolic problems
Increased indirect (unconjugaed) bilirubin- hemolysis, Gilberts
tests of synthetic function: albumin and INR
Both are good indicators of liver synthetic function,
both can be affected by poor intake and severe infections,
Replacement of vit K corrects the INR if due to nutritional causes but not if due to hepatic dysfunction, proteinuria and GI loss can decrease albumin levels
infiltrative liver disease
space occupying lesion, alkaline phosphatase elevation, occasional bilirubin elevation
Ex: tumors amyloid and sarcoid
Liver biochemistry
Bilirubin Helpful/unhelpful
GGT Sepcific or/ Unspecific
ALT
- Bilirubin is not helpful in determining type of injury (can be hi for hepatic and non hepatic, hepatocellular, cholestatic and infiltrative)
- GGT is non specific (only helpful if AlkPhos is high to tell you its a biliary tree problem)
- ALT>500= Hep A, Hep B, AI hepatitis, meds, ischemia (not stones)
- Alcoholic liver disease typically ALT/AST<300
AST:ALT> 2:1 is usually alcoholic liver disease
Acute vs chronic
INR!, albumin (protein)
Serum enzymes review
AST and ALT are inside cells, indicative of hepatocellular injury
On cell surface: ALP, 5NT, GGT: associated with cells adjacent to bile canaliculi, can be indicative of cholestasis
Transaminase AST SGOT
2 isoforms, GOT1- cytoplasmic form, GOT2- mitochondria form
Both isoforms require pyridoxal phosphate (PLP) as a cofactor, broad tissue distribution : liver cardiac muscle, skeletal muscle, kidney, brain, pancreas, lung, leukocytes, erythrocytes
80% of AST activity in human liver is due to GOT2 mitochondrial form
Makes glutamate and oxaloacetate–> malate
ALT/ SGPT
Present only in cytoplasm requires PLP, found only in the Liver
Makes glutamate and pyruvate–> lactate
Transaminases AST and ALT liver cell necrosis
ALT> AST= viral hepatitis
AST> ALT = alcoholic hepatitis
Cholestasis
any conditions in which the flow of bile from the liver is inhibited or blocked- obstructive Extrahepatic cholestasis (occurs outside the liver)- Strictures (narrowing of bile duct), stones in common duct, pancreatitis, primary sclerosing cysts, tumors
Intrahepatic- occurs inside the liver- alcoholic liver disease, primary biliary cirrhosis, viral hepatitis
Meds-Abx, Anaboid steroids, birth control pills
Alkaline Phosphatase
Membrane bound metalloenzymes which catalyzes the hydrolysis of phosphomonoesters at an alkaline pH
in several places (bone liver kidney), placental and germcells, elevated in increased osteoblastic activity, and normally during growth and pregnancy
5 NT
purine catabolism , broad tissue distribution but not in growth and pregnancy
