title: Serum versus heparinized plasma for alanine aminotransferase and aspartate aminotransferase of normal individuals.
abstract: The influence of heparin on the estimation of aminotransferases was investigated in a reaction medium containing phosphate or Tris buffer. Heparin scarcely affects the ASAT determination, but the ALAT activity in plasma is about 70% of the activity in serum, when the enzyme determination is carried out in Tris buffer. There exists a lag phase due to which the decrease in absorbance with the incubation time is nonlinear. When the Tris buffer is omitted, the same lag phase is observed in the ALAT determination. This lag phase is not caused by the indicator enzyme LDH. Addition of phosphate to the incubation medium without any buffer abolishes this lag phase. The possibility exists that heparin influences the structure of the proteins present in plasma and that these proteins, in their turn, decrease the enzymatic activity of ALAT.
mesh_terms: D000410:Alanine Transaminase / Q000097:blood*; D001219:Aspartate Aminotransferases / Q000097:blood*; D006493:Heparin / Q000494:pharmacology*; D006801:Humans; D008722:Methods; D010710:Phosphates / Q000494:pharmacology; D010949:Plasma / Q000201:enzymology; D013997:Time Factors; D014325:Tromethamine
chemical_list: D010710:Phosphates; D014325:Tromethamine; D006493:Heparin; D001219:Aspartate Aminotransferases; D000410:Alanine Transaminase