What happens to old RBCs after approximately 120 days in the circulation?
- After approximately 120 days in the circulation, old RBCs are taken up and degraded by the reticuloendothelial system (macrophages) particularly in the liver, spleen and bone marrow.
- The globin is degraded to amino acids β reutilized by the body. β’ Heme releases:
- iron β returns to the bodyβs iron stores.
- tetrapyrrole component β converted to biliverdin, then to bilirubin.
How is bilirubin carried in blood?
“Bilirubin is lipid soluble”
- Carried in the blood by albumin β unconjugated (indirect) bilirubin.
Where is bilirubin uptakin and conjugated?
“With glocuronic acid”
- Uptaken & conjugated in the liver β conjugated (direct) bilirubin.
Where is bilirubin excreted?
- Excreted in the bile.
What is jaundice?
- Jaundice is a yellow discoloration of membrane due to an increase in the level of blood bilirubin (hyperbilirubinemia) beyond normal level.
What are the normal levels for total bilirubin and direct bilirubin?
β Normal total bilirubin β up to 1 mg/dl. βToo lowβ
β Normal direct bilirubin β up to 0.25 mg/dl.
What are the types of jaundice?
Hemolytic (Prehepatic) jaundice
Hepatocellular (Hepatic) jaundice
Obstructive (Posthepatic) jaundice
What is the biochemical basis of hemolytic (prehepatic) jaundice?
“Due to excess hemolysis of RBCs”
- Excess production of bilirubin exceeding the capacity of hepatocytes for uptake, conjugation and excretion
What is the type of raised bilirubin in hemolytic jaundice?
Unconjugated (indirect)
What are the causes of hemolytic jaundice?
- G-6-P-D deficiency
- Sickle cell anemia
- Incompatible blood transfusion
What is the biochemical basis of hepatocellular (hepatic) jaundice?
- Hepatocyte dysfunction β impaired hepatic uptake, conjugation or secretion of bilirubin
What is the type of raised bilirubin in Hepatocellular (Hepatic) jaundice?
- Both unconjugated & conjugated (direct & indirect)
What are the causes of Hepatocellular (Hepatic) jaundice?
- Infection (viral hepatitis)
- Liver cirrhosis
What is the biochemical basis of Obstructive (Posthepatic) jaundice?
- obstruction in the passage of conjugated bilirubin from the liver to the intestine β regurgitation of bilirubin to blood
What is the type of raised bilirubin in Obstructive (Posthepatic) jaundice?
Conjugated (direct)
What are the causes of Obstructive (Posthepatic) jaundice?
- Tumor “pancreas cancer”
- Bile stones
What is the importance of estimation of Bilirubin levels?
β Used to assess presence of jaundice and to detect type of jaundice
β One of liver function laboratory tests ( used to assess excretory function of the liver
What are liver function laboratory tests?
β TOTAL PROTEIN
β ALBUMIN
β BILIRUBIN - TOTAL/DIRECT/INDIRECT
β LIVER ENZYMES β SGOT (AST) βSGPT(ALT) “their presence in plasma indicates problems”
What is the principle of colorimetric estimation of bilirubin Level
- Bilirubin reacts with diazotized sulfanilic acid to form a red colored azobilirubin.
- The intensity of the color produced is directly proportional to the concentration of bilirubin in the sample.
How is reading of colorimetric estimation of total bilirubin level done?
- Measure the absorbance of sample against blank at wave length 578 nm (560-600 nm).
How is total bilirubin concentration calculated?
- Total bilirubin concentration (mg/dl) = A(sample) Γ 10.8
How is reading of colorimetric estimation of direct bilirubin level done?
- Measure the absorbance of sample against blank at wave length 546 nm (530-555 nm).
How is direct bilirubin concentration calculated?
- Direct bilirubin concentration (mg/dl) = A(sample) Γ 14.4
What does indirect bilirubin concentration equal?
- Indirect bilirubin can be calculated by subtracting direct bilirubin from total bilirubin.
