Practical 6: Investigation of Liver dysfunction

Question 1

Why are certain markers seen in peripheral blood if a patient has liver damage?

Answer 1

These markers leak out of hepatocytes which have become damaged

Question 2

What type of substances are measured in a liver function test?
(4)

Answer 2

Those that are normally produced by the hepatocyte

Those that are known to change when hepatocytes are damaged

Those released from hepatocytes when they are damaged

Those that assess the ability of the liver to perform tasks such as conjugation or detoxification

Question 3

What are the two types of tests that make up a LFT?

Answer 3

Tests of function

Test of hepatocellular damage

Question 4

What are the tests of liver function
(3)

Answer 4

Albumin, bile acids (synthesis)

Total or conjugated bilirubin (excretion)

Ammonia (detoxification)

Question 5

What are the tests of hepatocellular damage?
(4)

Answer 5

Alanine aminotransferase (ALT)

Aspartate aminotransferase (AST)

Alkaline phosphatase (ALP)

y-Glutamyl transferase (GGT)

Question 6

What are considered the two billary tree enzymes

Answer 6

Alkaline phosphatase (ALP)

y-Glutamyl transferase (GGT)

Question 7

What exactly is bilirubin

Answer 7

A hydrophobic breakdown product of haem

Question 8

What is bilirubin conjugation?

Answer 8

The conversion of bilirubin into mono and diglucuronides by the liver

Question 9

What is the function of bilirubin conjugation?

Answer 9

To increase the solubility of the bilirubin molecule

Question 10

What happens to bilirubin once it has been conjugated?
(2)

Answer 10

The majority is secreted into bile

Some leaks out into the plasma

Question 11

How can we determine the type of disease depending on the ratio of conjugated and free bilirubin in circulation?

Answer 11

If bilirubin can be conjugated but not secreted then the levels of conjugated bilirubin will increase in the circulation and the total bilirubin will also be increased

Question 12

What is the principle behind the Bilirubin assay

Answer 12

Bilirubin reacts with diazotised sulphalinic acid to produce azobilirubin which is a reddish-purple colour

Question 13

What does ALT stand for?

Answer 13

Alanine aminotransferase

Question 14

What is ALT

Answer 14

An enzyme involved in amino acid metabolism which is found in the hepatocytes

Question 15

When might ALT be seen in circulation

Answer 15

When there is an injury to the cells which disrupts hepatocyte integrity

Question 16

What is the principle behind the ALT assay
(3)

Answer 16

Based on the ability of ALT to break down alanine to form pyruvate

LDH then converts pyruvate to lactate but with the conversion of NADH to NAD+

This fall in NADH is measured spectrophotometrically