Parameters of hepatocyte damage

• Membrane permeability and integrity tests.

Aminotransferases

 For more information see Aminotransferases.

• The most sensitive and the fastest telling.

Aspartate aminotrasferase (AST)

• Transfers an amino group from aspartate to oxoglutarate to form glutamate and oxalacetate.
• It is present not only in liver cells, but also elsewhere (muscles, kidneys, pancreas and in erythrocytes − during hemolysis the activity of AST in the blood increases).
• Two forms - one is in mitochondria and the other is in cytosol (35 %).
• S-AST' = 0.66 µcat/l.

Transamination reaction.

Alanine aminotransferase (ALT)

• Catalyzes the transfer of an amino group from alanine to oxoglutarate, resulting in glutamate and pyruvate.
• It is in the highest concentration in the liver and kidneys.
• Present only in the cytoplasm.
• The half-life of ALT is about 48  hours, the coenzyme is pyridoxal phosphate − when determining enzyme activity, its amount is limiting.
• That is why we mostly measure turbidity (change in absorbance of NADH).
• S-ALT' = 0.73 µcat/l.

Transamination reaction.

• For interpretation, ALT is a sensitive indicator of membrane damage, a greater rise in AST occurs only after cell necrosis.
• ALT - sensitivity (83 %), specificity towards individuals with the disease (84 %), AST - about 70 %.
• The so-called de Ritis coefficient − AST/ALT ratio, prognostically more serious at a value greater than 0.7–1.
• Highest values of transferases - viral hepatitis (prodromal stage - 2x, after two weeks up to 50x increased, around the 8th week they normalize).
• Rapid rise (approx. 30×) − toxic liver damage.
• Drug and alcohol intoxication - a slight increase.

Glutamate dehydrogenase (GMD)

• Relatively specific for the liver (about 10x more in the liver than elsewhere).
• GMD is a mitochondrial enzyme, also found in muscles, brain and leukocytes.
• Converts glutamate to oxoglutarate.

S-GMD = 0.123 cat/l (male); 0.088 cat/l (women).

• A massive increase in GMD is a manifestation of liver necrosis or neoplasia.
• With obstructions and cholestasis, the values increase up to 10x (induction of enzyme formation in cells).
• However, the sensitivity is below 50 %.

Lactate dehydrogenase (LDH)

• Lactate dehydrogenase is of rather limited importance for the examination of the liver - it is a cytosolic enzyme that occurs in practically all cells.
• Half-life of isoenzymes with liver subunits (LDH₅ and LDH₄) − short half-life (10 h).
• Cardiac subunits predominate - LDH₁ and LDH₂, which circulate longer.

S-LDH = 2.5–7.7 µcat/l.

• Information on total LDH is non-specific.
• From liver disorders - the biggest rise in acute liver failure or toxic lesions, also in hepatitis, liver metastases; it tends to be low for obstructions.
• Examination of isoenzymes by electrophoresis − the most significant is the rise of LDH₃ − infectious mononucleosis (from disintegrated monocytes), or pulmonary embolism (from  platelets).

Glutathione-S-transferase (GST)

• Normally penetrates minimally;
• sensitive indicator;
• increases mainly with intoxication and drug damage, also with chronic hepatitis and hepatocellular carcinoma.

Links

Related Articles

• Biochemical tests of the liver
• Liver function tests

References

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