Transaminases in serum – general information, principles of analytical methods, sources of errors, indications for analysis, biological material, reference ranges, interpretation of results.
Aspartate aminotransferase (ASAT) and Alanine aminotransferase (ALAT). They are two transferases and catalyse ammine group transfer between α-ammine acids and β-keto acids. Both aminotransferases are highly concentrated in the liver. ASAT is also diffusely represented in the heart, skeletal muscle, kidneys, brain and red blood cells, and ALAT has low concentrations in skeletal muscle and kidney; an increase in ALT serum levels is, therefore, more specific for liver damage. AST has 2 isoforms - cytoplasmic (cASAT) and mitochondrial forms (m ASAT).
- Aspartate aminotransferase is a transaminase enzyme that catalyses the conversion of aspartate and alpha-ketoglutarate to oxaloacetate and glutamate. Cell localization of ALAT is entirely in cytoplasm.
- Alanine aminotransferase catalyses the transfer of an amino group from alanine to alpha-ketoglutarate in the alanine cycle to form pyruvate and glutamate.
Principles of analytical methods: kinetic enzymatic. Principle –the decrease of optic density within the UV spectrum is assayed (A at 340 nm/min using the NADH oxidation reaction.
Sources of errors: false positive results in artificial haemolysis. A shot or injection of medicine into the muscle tissue, or strenuous exercise, may increase AST and ALT levels. Many drugs may cause positive analytical or pharmacological interference drugs such as corticosteroids and anticonvulsants appear to induce ALT production
Indication for analysis: parenchymal liver damages, confirming of the clinical and ECG data of myocardial infarction and Skeletal muscle disorders.
Reference range: ASAT 0 – 36 U/l ALAT Male. 0 – 49 U/l; Female. 0 – 33 U/l
0 - 36 0 - 49 0 - 33
Interpretation of results:
- Increased activity: Very high levels of AST (more than 10 times) are usually due to acute hepatitis, often due to a virus infection.
- Increase between 5 and 10 times in acute myocardial infarction, Surgical and other muscular traumas, diseases of skeletal muscles;
- Increase to 5 times above the upper reference limit: newborns, hepatic diseases (with hepatic cytolysis), pancreatitis, hemolysis.