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16 Cards in this Set

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What is diagnostic enzymology?
a means of locating where tissue injury or stimulation of increased production has occurred

serum enzyme activities are helpful in understanding the disease process and in making a diagnosis
How are enzymes measured?
by their activities

enzymes catalyze biochemical reactions by converting a substrate into a product

activity is measure by either disappearance of substrate or formation of product

enzyme activity reported in international units/liter
What are leakage enzymes?
maybe in cytosol, organelles or both

enzymes escape from the cell as a result of injury to cell membranes or organelles

injury may be as severe as cell death or maybe as mild as increased cell membrane permeability

examples: AST,ALT CK (seen with muscle damage)
What are induced enzymes?
usually attached to membranes, rarely increased due to cell injury

increases are usually due to increased production
What happens to enzymes when the are released from tissue?
enzymes are degraded or excreted from the body

they may persist, but they lose their activity over time

the rate of degradation or loss is quite variable depending on the enzyme
What are some considerations when look at enzymes?
the presence or absence of an enzyme in a specific tissue

the concentration of enzyme in the tissue

where the enzyme does after leakage or secretion

the half life of the enzyme

isoenzymes (same catalytic activity, but other properties differ)
ALP has the longest half life in what organ? Shortest?
Liver- 3 days
Intestine, placenta, kidney- 6 minutes
Does magnitude of ALT increase equal the severity of injury?
no,needs to be 2-3 times RI
What lab values indicate muscle injury?
AST, CK, Urine Mb
Where is creatine kinase found at highest concentration?
free in the cytoplasm of muscle cells
-skeletal
-cardiac
-smooth muscle
-CNS injury does not raise serum serum CK but may increase in cerebral spinal fluidQ
Where is apartate aminotransferase found in highest concentration?
cytoplasmic associated with organelles

highest activity
-skeletal muscle and cardiac mucles
-hepatocytes

***not muscle specific**
What can causes increases in serum creatine kinase?
skeletal muscle injury due to:
-necrosis
-IM injectious
-trauma
-strenuous exercise

Cardiac muscle injury

muscle breakdown
-severely anorexic cats
How long does it take for CK to show up and then return to normal after being elevated?
Increases rapidly after injury 6-12 hours

very short half life

can return to normal within 48 hours after an acute injury
What is ALT?
liver specific enzyme in dogs and cats

can be increased with severe muscle damage
What is myoglobin?
released from dead/dying muscle
-generally severe, acute injury

low molecular weight

not protein blood in blood
-passes glomerulus readily and excreted in urine
How do you distinguish hemoglobin vs myoglobin?
supporting laboratory data

anemia suggestes hemoglobin
increased CK suggest myoglobin
Myoglobin is rapidly cleared so serum usual not discolored

can distinguish the two with ammonium sulfate precipitation test (precipitates hemoglobin not myoglobin)
dipstick is + if it is myoglobin

extreme hemoglobinuria may not all precipitate = false positive