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79 Cards in this Set
- Front
- Back
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The highest activity of AST is found where?
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hepatocytes
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Where in the hepatocyte is AST found?
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intra and extramitochondrially
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What is the half life of cytoplasmic AST?
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17 hrs
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What is the half life of mitochondrial AST?
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87 hrs
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Besides hepatocytes, where else is AST found?
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throughout the body including the heart and muscles
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ALT activity is highest where?
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hepatocytes
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Where within hepatcytes is ALT?
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extramitochondrial only
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Where in the body is ALT found?
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Mainly liver and kidneys
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What is needed for synthesis and enzymatic activity?
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Vit B6 (Pyridoxine)
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HOw can the enzyme changes in hepatic injury be explained?
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By differing hepatic activity levels and the half lives of the enzymes involved
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Tell me about AST and ALT in acute hepatocellular injury (hepatitis).
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-AST will be higher than ALT initially
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Tell me about AST and ALT 24-48 hrs after hepatitis begins.
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-ALT will become higher than AST based on its longer half life
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What form of hepatitis doesn't follow the rules?
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acute alcohol induced hepatocyte injury
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Alcohol induced mitochondrial damage, wich results in what?
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the release of mitochondrial AST
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Alcohol hepatitis results in a disproportionate elevation of what?
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AST over ALT
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What is the DeRitis ratio?
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a ratio of ALT to AST and is is 3-4:1 in alcohol induced liver disease
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In chronic hepatocyte injury (cirrhosis), is AST or ALT more elevated?
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ALT is commonly more elevated than AST
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What happens to ALT and AST as fibrosis progresses in cirrhosis?
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ALT activities decline, and the ratio of AST to ALT gradually increases, so by the time cirrhosis is present AST of often higher than ALT
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Why are enzymes low in end stage cirrhosis?
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due to massive tissue destruction
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Overall, what enzyme is more specific for detecting liver disease in nonalcoholic, asymptomatic patient?
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ALT
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ALT is mildly elevated in what?
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hep C
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What enzyme is used for monitoring therapy with potentially hepatotoxic drugs?
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AST
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What does LD do?
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catalyzes the reversible oxidation of lactate to pyruvate.
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How many types of LD are there?
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5
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Of the 5 isoenzymes that exist for LD, there are tetramers of two forms, what are they?
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H and M
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The H form has a high affinity for what?
M form? |
-H for lactate
-M for pyruvate |
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LD1 and LD2 are predominate where?
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-cardiac
-kidney -erythrocytes |
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LD 4 and LD5 are found where?
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-liver
-skeletal muscle |
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Increases in LD in hepatitis is often what?
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transient and returns to normal by the time of presentation
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Large increases of LD are usually associated with what?
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space-occupying lesions of the liver
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ALP is present where in the boyd?
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-liver
-bone -kidney -intestine -placenta |
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Each organs contains distinct isoenzymes for ALP that can be separated how?
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electrophoresis
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ALP in the liver has a half life of how long?
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3 days
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Where in the liver is ALP found?
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canalicular surface
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Because ALP is on the canalicular surface, it is a marker for what?
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biliary dysfunction
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The bulk of ALP in the serum is make up of what types of ALP?
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liver and bone ALP
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Why does obstruction or inflammation of the biliary cause ALP to rise?
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because there is an increased synthesis and decrease excretion
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In obstruction or inflammation of the biliary tract, ALP most commonly rises how much?
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twice the upper limit of normal in parellel with the rise in bilirubin
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What does GGT do?
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Regulates the transport of amino acids across cell membranes
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What is the majore use of GGT?
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to discriminate the source of elevated ALP
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IF ALP is elevated and GGT is also elevated, then what is the source of the ALP?
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biliary tract
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GGT is often elevated in what people?
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those who chronically abuse alcohol with a rought correlation between amount of alcohol intake and GGT activity
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All acute injuries and or necrotic lesions in the liver primarily cause a marked riske in what?
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AST and ALT
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Cell injury and necrosis cause a rise in what?
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LD
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What are some things that cause a rise in LD?
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-acute hepatitis
-infarction -trauma |
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Because of biliary tract injury, the enxyme ALP rises along with what?
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GTT and 5'-N
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Because hepatocyte injury causes loss of conjugation of trasported bilirubin, what also happens?
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-unconjugated or indirect bilirubin also rises
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In hepatitis, what levels tend to remain normal?
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-total protein
-albumin -ammonia |
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Cirrhosis is the reverse pattern of what disease?
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hepatitis
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What levels tend to be normal in cirrhosis?
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-AST
-ALT -LD |
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How are the total protein and albumin levels in cirrhosis?
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abnormally low
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How is the ammonia level in cirrhosis?
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elevated
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Why in cirrhosis is both the indirect and direct bilirubin elevated?
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because there is insufficient viable liver tissue remaining, and because fibrosis destroys the cholangioles
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Acute biliary obstruction results in the elevation of what?
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-direct bilirubin
-biliary tract ALP -GGT -5'-N *****ALL OTHER LIVER TESTS ARE NORMAL***** |
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Space-occupying lesions are characterized by isolated elevations of what enzymes?
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ALP and LD
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What is the most common cause of space occupying lesions of the liver?
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Metastatis carcinoma to the liver
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How is passive congestions of the liver characterized?
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Mild elevation of ALT, AST, and LD
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In more severe cases of passive congestion of the liver, what is also elevated?
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total bilirubin and ALP
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The pattern of liver function that is seen in passive congestion of the liver is also seen in what infectious disease?
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Mono
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In total liver failure appears as what on liver tests?
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a combo of hepatitis and cirrhosis
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Tell me about AST and ALT in liver failure.
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Reach very high levels, of then >10,000
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Tell me about total protein and albumin in total liver failure.
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they are reduced
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In total liver failure, ammonia levels are what?
What does this cause? |
-ammonia levels are elevated, which causes hepatic encephalopathy
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In total liver failure, LD, ALP, and bilirubin are what?
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elevated
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A disproportional rise in what helps to confirm the dx of liver failure?
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rise of AST over ALT
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In severe liver failure, it is not uncommon to find abnormalities where?
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In lytes and renal function tests and coagulation profile
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Patients with severe liver failure also tend to have ascites with what?
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marked third space fluid loss
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As the result of marked third space fluid loss, there are increases in what to retain intravascular water?
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ADH and aldosterone
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Severe liver failure can also cause what?
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hepatorenal syndrome, or renal dysfunction 2nd to hepatic failure
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Renal failure results in elevations in what?
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BUN and creatinine with a 10-20:1 ratio, which indicated renal failure
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Uosm/Posm ratio of <1:2:1 is indicative of what?
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tubular dysfunction
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DIC can accompany what?
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liver failure
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DIC must be distinguished from what?
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Low coagulation factor production combined with hepatosplenomegaly due to protal hypertension as in cirrhosis
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How come splenomegaly can be mistaken for DIC?
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Because splenomegaly may result in sequestration of platelets, so the overall pattern resembles DIC, but it is NOT ture DIC
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To clinch the dx of DIC, what must be seen?
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Elevations of both D-dimer and fibrin split product levels
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What may be seen on peripheral blood smear in severe liver failure?
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-abnormal red cell forms called target cells
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Patients with cirrhosis and acute fulminant hepatic failure tend to be what?
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immunocompromised
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May pts iwth cirrhosis and acute fulminant liver failure have defective what?
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T cell function and produce an excess of ineffective immunoglobulin
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Because of the excess of ineffective immunoglobulins, what is seen in these pts?
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low serum albumin levels from diminished albumin synthesis but elevated serum immunoglobulins
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