4.18. Measurement of Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) Levels

ALT and AST levels in serum were measured by GC Labs (Yongin, Korea), which uses the International Federation of Clinical Chemistry standard method. ALT and AST levels were analyzed using the measured enzymatic colorimetric method with no added pyridoxal phosphate. In a test tube, 1 mL of substrate solution (AST, 2 mmol/L α-ketoglutarate and 200 mmol/L aspartate; ALT, 2 mmol/L α-ketoglutarate and 200 mmol/L alanine) and 0.2 mL of serum were added and incubated at 37 °C for 30 min (ALT) or 1 h (AST). Immediately after the completion of the reaction, 1 mL of a coloring solution (2,4-dinitrophenyl hydrazine, 1 mmol/L) was added, followed by incubation at room temperature for 20 min, and then 10 mL of 0.4 N NaOH was added to measure the absorbance at 520 nm (Modular Analytics, Roche, Germany). Distilled water was used as a blank.