Clin path 2 enzymology Flashcards
1
Q
define leakage enzyme?
A
• May be 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 may be as mild as increased cell membrane permeability.
2
Q
what are induced enzymes?
A
• Usually attached to membranes, rarely
increase due to cell injury.
• Increases are usually due to increased
production
3
Q
what are the leakage enzymes?
A
ALT AST SDH GLDH CK
4
Q
which are the induced enzymes
A
ALP
GGT
5
Q
creatinine kinase
A
• Free in the cytoplasm of muscle cells – Skeletal, cardiac and smooth muscle – Muscle specific • Also in nerves/brain – CNS injuries do not raise serum CK –May increase in cerebral spinal fluid
6
Q
aspartate aminotranferase
A
• Cytoplasmic and associated with organelles • Highest activity: – Skeletal and cardiac muscle – Hepatocytes
7
Q
serum CK
A
• Skeletal muscle injury –Necrosis, IM injections, trauma, strenuous exercise –Commonly increased in “down” cows/horses • Cardiac muscle injury • Muscle break down (catabolism) –Severely anorexic cats
8
Q
CK kinetics
A
• Increases rapidly after injury –Peaks in 6-12 hours • Very short half-life – < 2 hrs in horses, 4 hrs in cattle • Can return to normal within 24 - 48 hrs after an acute injury
9
Q
CK in anorexic cats
A
• Malnourishment can lead to muscle breakdown • One study from AMC*: – Anorexic cats: Mean CK 2,529 U/L – Control Group: Mean CK 175 U/L • Decreased significantly within 48 hrs of re-feeding
10
Q
AST in muscle injury
A
• Increases more slowly than CK –Peaks around 24 - 36 hrs post-injury –Stays elevated longer –Half-life: 12 hrs in dogs, 50 hrs in horses • NOT muscle specific
11
Q
ALT in liver injury
A
• “Liver specific” in dogs, cats • Yet can be increased with severe muscle damage – Skeletal muscle - 5% of liver ALT activity – Larger volume of muscle
12
Q
myoglobin
A
• Released from dead/dying muscle –Generally severe, acute injury • Low molecular weight • Not protein bound in blood –Passes glomerulus readily –Excreted in urine
13
Q
ammonium sulfate precipitation test
A
– Add ammonium sulfate to urine – Precipitates hemoglobin, not myoglobin – Dipstick remains + if it is myoglobin – Extreme hemoglobinuria may not all precipitate (false positive result)
