Final- Enzymes

Question 1

when do enzymes pass into plasma?

Answer 1

When tissue is injured or b/c of increased production by cells.
(detection of increased enzyme activity in the serum suggests injury to organ or tissue or increased in the production of the enzyme

Question 2

How are enzymes measured?

Answer 2

They assayed by measured their activities since enzymes catalyze
biochem. Rxns by converting substrate to a product. So it is measured by the disappearance of substrate or formation of a product

Question 3

How is enzyme activity reported?

Answer 3

International units/liter

Question 4

What are leakage enzymes?

Answer 4

May be in the cytosol, organelles, or both. . Escape cell from result of injury to cell membranes or organelles
. Can also result form injury (cell death) or increased cell membrane
permeability

Question 5

What is the significance of being in organelles vs cytoplasm?

Answer 5

If found in cytoplasm- only a small disruption can cause leak of the enzyme. Whereas if in the organelles- need a larger disturbance to cause the leakage.

Question 6

What are the leakage enzymes?

Answer 6

ALT, AST, SDH, GLDH, CK,

They are free in cytoplasm or in organelles

Question 7

What is an induced enzyme?

Answer 7

They are usually attached to membranes and rarely increased
due to cell injur
y. Increase in induced enzymes are due to
increased production
o Drug induced or increase in pressure on liver often
result in induced enzymes (cholestasis!!) can be
extrahhpeatic (obstructive bile duct ) or intraheatpic
(fatty infiltration cuasing intrahepatic bile duct
obsturrction)

Question 8

What are the induced enzymes?

Answer 8

ALP, GGT
• They are attached to membranes
leakage enzymes are neither specific for the cause of liver dz nor predictive of outcome. cant take 2 weeks to decrease after injury

Question 9

What does an increase in enzymes in plasma demonstrate?

Answer 9

Not necessarily mean you have pancreatitis- might simply mean you have enzyme not normally getting eliminated from the body (like w/ dec. glomerular filtration)! amylase and lipase are eliminated through the kidney.

Question 10

What should you consider about the enzymes w/in the body?

Answer 10

Presence or absence of an enzyme in a specific tissue,
concentration of enzyme in the tissue, where the enzyme goes after leakage or secretion, the half life of the enzyme, isoenzymes (same catalytic activity, but other properties differ

Question 11

Remember loss of leakage enzymes can induce

Answer 11

differ

Remember loss of leakage enzymes can induce production and some induced enzymes can rise after acute cell injury!!

Question 12

Where in the cell is alanine transaminase found? (ALT)

Answer 12

liver specific free out in cytoplasm?

Question 13

Where is aspartate transaminase found ? (AST)

Answer 13

More w/in organelles of cells

Question 14

What organ is the most likely source of elevated ALP (Alkaline phosphatase) in the blood?

Answer 14

Liver! remember that the ALP produced by the liver has a half life of about 3 days- other tissue (intestine, placenta and kidney have 1⁄2 life about 6 minutes)

Question 15

Where are cell sources of GGT?

Answer 15

Gamma glyutamyl transferase. • Renal tubules and hepatocytes.

Question 16

If damage to renal tubules (a producer of GGT) will you see an increase in GGt in the serum?

Answer 16

No. the GGT will be put out in the urine filtrate. Not into the plasma. So when you see elevated GGT do not assume the increase is due to renal damage/origin. Most likely source is from the liver hepatocytes

Question 17

What is the significance of the magnitude of enzyme (ALT) activity increase w/ sublethal vs necrosis?

Answer 17

The magnitude of enzyme activity increase does not indicate the severity of damage. w/ leakage enzyme at hepatocytes you can
have very large increase in serum ALT w/ hypoxia or endotoxemia. If focal area of necrosis- may not produce as much ALT than a diffuse are of hypoxia.

Question 18

Where is Creatine kinase found?

Answer 18

It is a leakage enzyme found free in cytoplasm of muscle cells.
(skeletal, cardiac, and smooth muscle) but also found in the
nerves/brain but CNS injury don’t raise serum CK

Question 19

What is AST?

Answer 19

Aspartate aminotransferase- a leakage enzyme from the liver and also found skeletal and cardiac muscle. Found in cytoplasm and organelles.
o Measure the CK levels as well- if elevated, if AST elevated as well may be coming from the muscle more than the liver

Question 20

What is the issue with enzymes that are not tissue specific?

Answer 20

Not a good indicator for identifying the source of the increase enzyme

Question 21

You have a downer cow with increased CK, AST. GTT normal. What is your dx?

Answer 21

CK released from muscle cells w/ necrosis- if down for long time, greater the CK found in plasma. AST can be elevated from increase liver or muscle- rule out liver (GTT normal, GTT only elevated through liver issue) so assume the AST is due to leakage from muscle)

Question 22

what can cause increased serum CK?

Answer 22

Skeletal muscle injury- necrosis, IM injection, trauma, strenuous
exercise, commonly increased in down cow/horses. Cardiac injury,
muscle break down (severely anorexic cats)

Question 23

What is the peak of CK after injury?

Answer 23

6-12 hours, short 1⁄2 life in horses, 4 hrs in cattle can return to normal w/in 24-48 hrs after acute injury

Question 24

why can CK increase w/ anorexic cats?

Answer 24

Malnourishment can lead to muscle breakdown. Decrease

significantly in plasma w/ 48 hours after feeding

Question 25

What is the significance of AST in muscle injury?

Answer 25

AST can be leaked from myocytes slower than CK peaks around 24- 36 hrs after injury and elevated longer. Half life in dogs is 12 hrs vs horses it is 50 hrs. it is not muscle specific like CK is

Question 26

You have a 3 year old FS S cat with highly elevated Ck , ALT, and AST with normal GGT. What is your dx?what is the significance of ALT in this case?

Answer 26

The CK level is way to high to be from anorexia. AST is not nearly as high as the ALT- so probably coming form muscle not the liver. ALT is liver specific but can become increased w/ severe muscle damage. Skeletal muscle 5% of liver ALT activity even though it is liver specific in dogs and cats. So remember, if severe muscle damage, ALT can be increase as well w/ AST and CK

Question 27

you have an 8 year old mixed breed dog w/ normal bilirubin, elevated CK, normal ALP, elevated ALT, AST and normal GGT. How can you rule out liver issue and dx this as a muscle issue?

Answer 27

CK is high, your ALT is liver specific and AST can be produced from muscle and liver. Look at your bilirubin. It is in the reference range so more probably that there is not a liver issue going on as well as looking at your ALP and GGT which are liver specific and those are not increased either). w/ severe muscle damage- CK, ALT and AST can rise.

Question 28

you have a 12 year old Qh gelding. Became stiff and in apparent pain after being ridden. BUN, Creatinine, and Alubmin elevated. CK highly elevated along w/ AST. U/A!red brown urine, cloudy. USG-1.045, 1+ protein, 4+ blood, no RBC or WBC in sediment. What do you think is occurring?

Answer 28

Dehydration, (azotemic w/ increase albumin), and possible muscle damage. b/c no RBC in sediment- rule out fresh blood in urine leaving you w/ myoglobin or hemoglobin. Serum is clear not pink. So w/ lysis of RBC the serum will remain pink. Not the case here. So this is a situation where you have myoglobin in urine due to muscle damage.• Mylogibin is released from dead/dying muscle from
generally severe, acute injury. Low molecular weight, not
protein bound in plasma, and passes through glomerulus
readily and excreted in urine. Does not make serum pink
• w/ urine! hemoglobin and myoglobin stain red/brownish!
look at serum if serum remains pink- then you know it is
hemoglobin not myoglobin.
• Dipstick will be positive for blood/hemoglobin w/ mygolboin
present.

Question 29

What test can you perform in urine to differentiate between Hemoglobin or myoglobin?

Answer 29

ammonium sulfate precipitation test where you add
ammonium sulfate to urine, the ammonium sulfate will precipitate hemoglobin not myoglobin If dipstick remains positive after the test- its is positive for mygolboin. The thing is that
the hemoglobin is precipitated and therefore wont react w/ the dipstick
.

Question 30

What other thing can you look at to test Hgb w/ Mgb?

Answer 30

Anemia would suggest hemoglobin (don’t expect hemoglobinuria w/out an anemia). Increase CK suggests myoglobin, and myoglobin is rapidly cleared so serum not discolored usually.