RBC destruction and Bilirubin Processing in Health

Question 1

Bilirubin Processing in Health

Answer 1

• Product of hemoglobin breakdown
• Senescent red cells are phagocytized by marcorphages
• Hemoglobin → heme and globin
  
  • Globin → aa
  • Heme → Fe and protoporphyrin → biliverdin → bilirubin
• Bilirubin released form macrophages, binds to plasma proteins, transported to liver
• Taken up by hepatocytes via membrane carriers
• Attaches to a binding protien - ligandin - in hepatocyte cytoplasm - prevents efflux back into blood
• Conjugated with glucuronic acid - now water soluble
  
  • in horses
• Secreted into biliary system, stored in gall bladder
  
  • most species
• Excreted into small intestine as part of bile
  
  • Bacterial reduction → urobilinogen which can be passively absorbed and recirculate to be excreted in bile or urine
  • some degredated to stercobilinogen and excreted in feces

Question 2

RBC destruction and Bilirubin metabolism Pathway

Answer 2