Metabolism of Bilirubin Flashcards
Is unconjugated bilirubin (UCB) water soluble?
No- it is lipid soluble
haemoglobin breaks down into?
- heme
- globin
1a. bilirubin (UCB)
1b. Fe+
which enzyme breaks haemoglobin down?
heme oxygenase bilirubin reductase
what happens to excess globin?
recycled for erythropoiesis.
what can bind to UCB before entering the liver system
- Albumin, most common
- High density lipoproteins
infrequently circulates in blood as UCB
what other than Hb forms bilirubin?
Myoglobin and cytochrome enzymes
UCB enters the liver system- what happens next?
albumin dissociates from the UCB, UCB is taken up by hepatocytes while albumin remains in blood.
by which method is UCB taken into hepatocytes
facilitated diffusion- from area of high to low using a channel protein.
which process does UCB go through in the liver?
glucuronidation
how does glucuronidation change UCB
makes it more water soluble- allows for excretion in urine and feces. forms Conjugated Bilirubin
which enzymes cause glucuronidation?
Uridine 5’-diphospho-glucuronosyltransferase
B- UGT
what percent of bilirubin in small intestine is conjugated?
98%
what is the large intestines effect on the conjugated bilirubin?
bacteria oxidises CB, forming urobilinigens
some urobilinogen’s re-enter the enterohepatic system- what do they colour?
urine
hat do the majoroity of urobilinogens colour?
feces eg stercobilinogens
which type of bilirubin causes jaundice
both UCB and CB
which disorders are associated with UCB jaundice?
non liver dysfunction disorders.
-dyserythropoesis
-extravascular haemolysis
-intravascular haemolysis
-extravasation
-medications
-gilberts syndrome
which disorders are asscoated with CB jaundice
intra hepatic
-hepatitis (all)
-drugs eg steroids
-sepsis
- TPN
Post hepatic
- cholelithiasis (gall bladder stones)
- gall bladder cancer
-pancreatic cancer
initial investigations into jaundice
liver function tests
-AST, ALT- if increased shows liver tissue damage
-GGT, ALP- biliary injury or intrahepatic issues.
if results of LFT are not deranged what does this show
jaundice is caused by UCB, use haemolysis
if results of LFT are deranged what does this show
jaundice is caused by CB
