Lecture 1 Flashcards
(54 cards)
What three things must happen for an enzyme to be able to accumulate in the blood?
The enzymatic activity in the target cell must be greater than in the blood
It must have a long enough half life that it can accumulate in the blood
It must have access to the blood stream directly or through lymphatics
Why would an enzyme increase in the blood?
Leakage from damaged cells
Increased synthesis of the enzyme
Decreased inactivation or clearance
Absorption of maternal enzymes in colostrum
What does a high sensitivity mean?
Specificity?
High true positives and low false negatives
High true negatives and low false positives
When would increased enzymes be significant?
When it is 2 to 3 fold increase over upper RI
2-3= mild 3-6= moderate >6= marked
What are the exceptions to the “>2-3x RI” rule?
ALP in cats, GGT, and SDH
Low-grade inflammatory lesion
Decreased number of target cells due to necrosis or fibrosis
Inhibitors of enzyme activity
What does low enzymes mean?
Not clinically significant
What type of enzymes come from muscles?
Only leakage
CK, AST, LDH
What do muscle enzymes tell you?
Correlates with number of injured cells, not injury type
Can you determine the cause of a myopathy from a chem panel?
No
What type of enzyme is CK? Where does it come?
Muscle leakage
Skeletal muscle mainly
Describe the half life of CK
Very short- goes up and comes down quickly following muscle injury
What might cause interference in measuring CK?
Hemolysis
Difficult blood draw
Young animals, post exercise
What type of enzyme is AST? Where does it come from?
Leakage
Muscle, hepatocytes, other cells
Describe the half life of AST in comparison with CK?
Much longer than CK
ALT in muscle damage?
May see mild elevation in dogs and cats, but not usually the main cause
may see in young dogs and cat with muscular dystrophy
What blood changes might you see with MASSIVE rhabdomyolysis
Hyperkalemia
Hyperphosphatemia
Increased creatinine
Other than chem panel, what else might you see with a myelopathy?
Myoglobin in the urine
What type of enzyme is AST?
Where does it come from?
Leakage from skeletal muscle and hepatocytes
*low sensitivity
What type of enzyme is ALT?
Where does it come from?
Who is it not used in?
What artifactually increases the values?
Leakage from hepatocytes
Not used in large animals
Hemolysis increases the value in cats and pigs
What type of enzyme is SDH?
Where does it come from?
Who is it used in?
Leakage from hepatocytes
Horses, pigs, ruminants
What leakage enzymes increase in myopathies?
Liver injury? Both?
Myopathies- CK
Liver injury- ALT, SDH
Both- AST
What enzymes are inducible in the liver?
ALP, GGT
What is cholestasis? What enzymes are markers of cholestasis?
Impaired biliary flow
ALP and GGT
What are other markers besides enzymes of cholestasis?
Tbili, cholesterol, bile acids
