Lab 10 - Hepatic Enzymes

Question 1

Liver FUNCTION tests, ⬆️⬇️ eg pss no damage, chirrosis - hepatpcytes struggeling, enzymes may not!)

Answer 1

🔺 non-specific parameters:
PROTEIN
⬇️ albumin
⬇️ TT, fibrinogen
⬇️ apolipoproteins
⬆️ PT, APTT

CARBS
⬇️ glucose (in first 24h)
⬇️ fructosamine

FATS
⬇️ Tcholesterol
⬆️ FFA - most useful in herb
⬆️ TG - most useful in car

🔺Most specific group:
1️⃣ TBr (into direct) post/hep/prehepatoc jaundice
2️⃣ NH3 (into urea) in car, (GI in herb)
3️⃣ Tbile acids - very important, hepatic, posthepatic
(4️⃣ BSP. ICG)

Question 2

When is determination of ammonia concentration in the blood required?

Answer 2

1️⃣ carnivores: diagnose severe decrease of liver function (i.e. cirrhosis) or pss (where blood bypasses liver and NH3 is not detoxified),
2️⃣ ruminants: consequence of ruminal alkalosis, or decomposition of ruminal fluid severe systemic alkalosis can be developed due to hyperammoniaemia,
3️⃣ horse, rabbit: pathologic breakdown of ingest in the colon or caecum or in case of liver failure

Question 3

Why do we use ammonia as a parameter of liver function?

Answer 3

Bacteria produce NH3 in the intestines, which is tp by the portal vein to the liver for detoxification. So the liver must function for this detox to work, if not there will be incr. NH3 in the blood.

Question 4

Prep for ammonia conc measurement

Answer 4

animals should starve for 24 hours

Question 5

🍏Ammonia measurement sample when measuring conc, who needs the test?

Answer 5

• FRESH blood samples to tubes that contain EDTA or citrate as an anticoagulant, tp dog rather that blood!

CNS symptoms are the no.1 candiate for this test! PSS

Question 6

🍏Ammonia sample handling when measuring conc

Answer 6

1️⃣ avoiding air - contamination of them (“Astrup-samples”), because NH3 gas may evaporate from the sample to the air, or it can be dissolved in the sample from the air
2️⃣ Determination should be performed right after sampling
3️⃣ plan B: Blood samples can be stored in ice baths for max. 20 minutes, or plasma samples can be stored deep frozen (-20 C°) for 2 days

Question 7

🍏Ammonia normal value

Answer 7

She said below 60 μmol/l

(26,4-70,5 μmol/l (dog)

17,6-58,7 μmol/l(cat))

Question 8

🍏Methods of NH3 conc measurement

Answer 8

1️⃣ standard method: spectrophotometryof a reaction where the absorbancy is DECREASED. (See manual for reaction) - PLASMA sample

2️⃣ “portible ammonia checker”: light refraction method is more frequently used as it has fewer problems. WHOLE BLOOD

Question 9

🍏When do we need an Ammonia tolerance test

Answer 9

when basal NH3-concentration values do not show alteration and the suspect of portosystemic shunt is strong. (If both NH3 and bile acids are incr indicates PSS!)

Never do if ammonia toxicosis or CNS symptoms!! NH3 is toxic, be ready with treatment, large int flushing

Question 10

🍏Ammonia tolerance test method: prep

Answer 10

24 hours starvation and pretreatment with neomycin (in order to reduce bacterial NH3 production in the intestines)

Question 11

🍏Ammonia tolerance test method, whats the normal result?

Answer 11

🔺we take a basal blood sample, and give NH4Cl in 5%-water solution PO or rectally
🔺 blood samples are taken 30 or 45 minutes after treatment.
🔺If liver function is normal, ammonia concentration is <120 μmol/l in dogs, and <175 μmol/l in cats.

If ⬆️ NH3 and bile acids PSS is indicated!

Question 12

🍏Causes of increased NH3.concentration in the blood, or positive ammonia tolerance test results:

Answer 12

1️⃣Impaired liver function - decreased production of urea in case of peracute liver failure, liver cirrhosis, or
neoplasia, portosystemic shunt, hepatic lipidosis, lipid mobilisation disease in RU and EQ, car liver can coap and prod urea.
2️⃣ Ruminal alkalosis or ammonia toxicosis - due to absolute or relative protein overload (with the feed), or the
intake of rotten feed/ rumen stasis
3️⃣ 👇 results in Intestinal overgrowth of ammonia producing bacteria - in ruminants, horses, rabbits, swine or
carnivores
4️⃣ Congenital enzymopathies - decreased activity of i.e. OCT (ornithine-carbamoyl transferase)
5️⃣ PSS
6️⃣ anorexia, starvation
7️⃣ carb deficiancy

Question 13

🍏Types of liver cell/parenchymal enzymes and when they will increase

Answer 13

Mitochondrial and cytoplasmic enzymes: elevated conc depends on the severity of the cell damage, as it takes a mild injury to incr cytoplasmic enzymes, while a more severe liver cell damage is needed for incr mitochondrial enzyme conc

Question 14

🍏List the parenchymal(cell) enzymes

Answer 14

Mitochondrial: Aspartate-aminotransferase, glutamate-dehydrogenase

Cytoplasmic: Alanine-aminotranferase

Question 15

🍏AST (Aspartate-aminotransferase): where is it found and specific for which animals

Answer 15

🔺 mitochonria of liver cells, all muscle types, RBC

🔺 liver specific in herbivores(ru, eq, su)

Question 16

AST (Aspartate-aminotransferase) - how is it measured?

Answer 16

Spectrophotometric method: result of enzyme function is NAD formation that causes discoloration of a chromophor. (Decr absorbancy)

Question 17

🍏AST (Aspartate-aminotransferase) causes of decreased activity

Answer 17

1️⃣ metronidasol (an antimicrobial drug, which can cause liver function problems)
2️⃣ vitamin B6 deficiency, (practically there is no diagnostic importance of this)

Question 18

ALT (Alanine-aminotranferase) metod of measurement

Answer 18

Spectrophotometric method: result of enzyme function is NAD formation that causes discoloration of a chromophor. (Decr absorbancy)

Question 19

🍏Causes of ⬆️ activity of ALT (Alanine-aminotranferase)

Answer 19

(Cytoplasmic enzyme!)
1️⃣liver cell damage (especially in carnivores)
2️⃣ pancreatitis
3️⃣ septicaemia
4️⃣ cirrhosis,
5️⃣ bile duct obstruction,
6️⃣ liver neoplasm 
7️⃣ some hepatitis types
8️⃣ hepatic lipidosis
9️⃣drugs: barbiturates, glucocorticoids
as a result of cell damage
copper storage disorder: Doberman pincher,
West highland white and Bedlingtone terrier !

Question 20

GLDH (glutamate-dehydrogenase) Location and liver specific for which animal

Answer 20

🔺liver, small amount is found in nerves and muscles in mitochondria
🔺Liver specific in ruminants, horses and dogs.
.

Question 21

🍏ALT (Alanine-aminotranferase)

Location and liver specificity for which animals

Answer 21

🔺in the cytoplasm of liver cells, and red blood cells

🔺 in carnivores liver specific

Question 21

🍏List the bile duct obstruction enzymes

Answer 21

1️⃣AP-Alkaline-phosphatase - very sensitive, dog
2️⃣ GGT - gamma glutamyl-transferase, not so sensitive

Found at surface of bile duct endothelial cells -> into blood -> excreted in urine (=tubular cell obstruction cause incr activity of these in urine!)

Question 22

Parenchyma enzymes increase

Answer 22

Liver - AST, ALT, GLDH
1️⃣ hepatits
2️⃣ trauma
3️⃣ necrosis
4️⃣ FHL (fe hepatic lipidosis)
5️⃣ severe lipotic degener. In car
7️⃣ tumor in liver
RBC - AST, ALT
1️⃣ hemolysis ➡️ lab error
Toxin liver - AST
1️⃣ethanol, NSAIDS, GC, Barbiturates
Muscle - AST
1️⃣ necrosis
2️⃣ exercise, injection, other trauma
3️⃣ myositis
4️⃣ rhabdomyosarcoma
5️⃣ rhabdomyolysis
6️⃣ myocarditis

Question 23

ALKP (AP-Alkaline-phosphatase)

Location and liver specificity

Answer 23

potentially appears in every cell membrane, but only hepatic and bone ALKP appears in the blood. (urine if tubukar damage)

In cats not liver specific (used mostly in dog)

Question 24

ALKP (AP-Alkaline-phosphatase) isoenzymes: which are there and how are they differentiated?

Answer 24

SIAP and ALKP from liver are heat stabile, eg. ALKP from bone is heat labile - so we differentiate them by heating plasma to 65˚C for 5mins

Isoenzymes can be differentiated by many methods: electrophoreis, specific blocking (L-fenilalanine, ELISA, chromatographic).

Question 25

Function of ALKP (AP-Alkaline-phosphatase)

Answer 25

Only active in pH 10, so not active in living organism!

They are phosphotransferases and not phosphatases.

Question 26

ALKP (AP-Alkaline-phosphatase) Causes of ⬇️ activity:

Answer 26

Decreased activity: very severe cirrhosis (decreased synthesis) (Ypractically there is no diagnostic importance)

Question 27

GGT (gamma glutamyl-transferase) location

Answer 27

🔺produced by different organs, endothelial cells of bile duct concentrates it. GGT of liver origin appears in the blood.
🔺Liver specific in horses and cats

Question 28

Decreased activity: GGT (gamma glutamyl-transferase)

Answer 28

cirrhosis,

practically there is no diagnostic importance.

Question 30

Bile duct obstruction enzymes increase

Answer 30

Bile duct - ALKP, GGT
1️⃣ pancreatitis
2️⃣ cholangitis
3️⃣ bile duct carcinoma
4️⃣ chirrosis
5️⃣ paraneoplastic disease
6️⃣ barbiturates(!)
7️⃣ alcohol
8️⃣ bile stones
Bone - ALKP
1️⃣ osteosarcoma
2️⃣ osteomyelitis
3️⃣ young animals, pregnant animals
4️⃣ trauma: fracture
SIAP - ALKP
1️⃣ hyperadrenocorticism
2️⃣ Cushings disease
3️⃣ GC therapy, 
4️⃣ chronic stress 
5️⃣ chronic inflammation
(Gc induce siap)
liver - ALKP
1️⃣hepatitis
2️⃣ ncrosis
3️⃣ feline hepatic lipidosis

Very sensitive to lab error!!

Question 31

🍏What are the routine liver parameters used in dog and cat?

Answer 31

Dog: ALT, ALKP, GGT
Cat: ALT, GGT

Question 33

🍏What are the the liver parameters used in horse and swine?

Answer 33

AST, GGT

ALKP, OCT, SDH too in su

Question 34

🍏What are the the liver parameters used in RU?

Answer 34

Routinely only the liver mitochondrial enzymes (AST, GLDH)

Question 35

what parameters change in portosystemic shunt and why

Answer 35

1️⃣decreased hepatic perfusion
the shunt redirect part of the blood flow away from liver
2️⃣increased bile acids in blood
absorbed bile acids bypass liver tissue
3️⃣decreased urea concentration in blood
nh3 dont reach liver, no urea synthesis
4️⃣increased NH3 in blood
5️⃣microcytosis, hyperchromasia
6️⃣decreased MCV, decreased MCHC