Fate of hemoglobin when red blood cells are destroyed?

Answer 1

Fate of haemoglobin

When RBC, become old they receptured mostly in spleen (as well as in the liver & bone marrow ) . The Hb is liberated from the ruptured RBC & phagocytozed by the phagocytes of RE system. Within the phagocytes the tetrapyrrole ring is opened up that is heam is converted into a compond where 4 pyrrole ring are lie side by side. The iron is still attached with the tetrapyrrole straight chain compound and probabily the globin also remains attached with it . Susequently both globin and iron are removed . The terapyrrole straight chain compound thus formed (free iron and globin) is called biliverdin. Biliverdin is Oxidized to form bilirubin . All these changes occur within the phagocyte of RE system. Bilirubin now comes out of the phagocyte and in plasma combine with albumin and is transported in the plasma as bilirubin- albumin complx. This complex is frequently called free bilirubin; The free bilirubin ultimately enters the liver and here the albumin is removed from the free bilirubin and the bilirubin is conjugated with glucornicacid a derivative of glucose) to form bilirubin gluccoronides, which is water soluble.

A small amount of bilirobin is conjugated with sulphate radicals to form bilirubin sulphate. The conjugated water soluble bilirabin is called "conjugated bilirubin". Glucoronyl transferase activity can be increased by the drug phenobarbitone, Hyperbilirubinaemia and kernicterus in the neonates can thus be sucessfully treated by phenobarbitone. All conditions which produce execusion erythrocyte destruction eg: malaria, mismatched blood transfusion, erythroblastosis faetalis, bites by some types of poisonous snakes thus leads to excessive free bilirubinn formation & jauadice clinically called haemdytic jauxdice, develops. But the urine doesnot contain free bilirutrin in heamolytic jaundice, as the compound cannot pass the renal filter. Instead the urine contains excessive urobilinogen. The normal bilirubin concentration in plasma is below 0.5-1.0mg/100l, which rises greatly in haemolytic jaundice.